1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98
T. Higuchia,c, H. Yabub,c,d, M. Shimomurab,c,d
aGraduate School of Science, Hokkaido University, Japan (higuchi / poly.es.hokudai.ac.jp)
bIMRAM, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
cFrontier Research System, RIKEN, Japan
dCREST, Japan Science and Technology Agency, Japan
It is well known
that block copolymers form many kinds of micro-phase separation
structures in their films. We have reported that the block
copolymer nanoparticles with micro-phase separation structures
can be prepared by evaporation of THF from the THF/water mixing
solution of the block copolymer [1]. In this study, nanowire and nanodisks
are prepared from the block copolymer nanoparticles by using
selective immobilization and selective elution (SISE) method,
which includes cross-linking of one polymer segment and
consequently dissolving the other polymer segment in a
good solvent .
Nanoparticles were prepared from two kinds of diblock copolymers of polystyrene (PSt) and polyisoprene (PI) segments (molecular weights and molecular ratios are shown in the figure). Nanoparticles were observed by scanning transmission electron microscope (STEM) after staining and cross-linking with OsO4, whichselectively reacts with polyisoprene moieties. As shown in Fig. a) and b), nanoparticles with hcp cylinders and lamellar structures were obtained, respectively. Furthermore, by elution of polystyrene moieties after dispersed in THF, nanowire (Fig. c) and nanodisks (Fig. d) were formed from these block copolymer nanoparticles.
[1] H. Yabu, T. Higuchi, M. Shimomura, Adv.
Mater., 17, 2062 (2005)
I. Hussain
aV& PO Dobian Distt.Swabi NWFP PAKISTAN
Block copolymer ionomer template; Sol-gel reactions; Ionomer/silicate nanocomposite
Silicate structures were inserted along the cylindrical polystyrene (PS) domains in an ionomer form of elastomeric poly (styrene-b-isobutylene-b-styrene) tri-block copolymers, via in situ sol-gel reactions. Environmental scanning electron microscopy/energy dispersive X-ray spectroscopy studies indicated that silicate structures do in fact grow within the interior of ca. 0.8 mm thick films rather than forming undesirable silica precipitates on the surface. The combination of a domain-selective swelling solvent (DMAc) and the attachment of large organic counterions (benzyltrimethylammonium) along the styrene blocks facilitated the preferential migration of hydrolyzed Si (OEt) 4 monomers to these ionic domains where the sol-gel reactions are apparently seeded. Differential scanning calorimetry and dynamic mechanical studies indicated that Tg for the polyisobutylene (PIB) phase is essentially unaffected, but the PS phase Tg shifts to higher values with ionomer formation, and to even higher values with subsequent silicate phase insertion. These two methods provide indirect evidence that the silicate component is mainly incorporated in the PS rather than PIB domains. Combined with the results of earlier atomic force microscopy studies that demonstrated that the basic morphology of the unmodified block copolymer is unchanged despite the insertion of a silicate phase, the data presented here reinforce the concept of a robust sol-gel reaction template. Also, the rubbery plateau storage modulus was elevated as a result of ionomer formation and more so after the ionomer was imparted with a silicate phase, which illustrates mechanical reinforcement
a Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovského nám. 2, CZ-162 06 Praha 6, Czech Republic (holou / imc.cas.cz)
b Argonne National Laboratory, Argonne, IL 60439-4814, USA (jlal / anl.gov)
Self assembly of block copolymers or functionalized nanostructures can generate a rich variety of nanomorphologies (lamellar, cylindrical, gyroid, various cubic etc.)
Phenomena associated with the order-disorder transition (ODT), microdomain morphology and phase behaviour of three block copolymer systems have been studied by small-angle X-ray scattering (SAXS), small-angle neutron scattering (SANS) and transmision electron microscopy (TEM).
1) The microdomain morphology and phase behaviour in copolymer blends of A-b-B/A-b-C i.e. with one block in common (deuterated PS-b-PMMA / deuterated PS-b-PI) were investigated. The studied almost symmetric copolymers differ essentially in microdomain morphology. One of them is in disordered microdomain state, while the other displays lamellar morphology at ordinary temperatures. Self-assembled structures in blends were investigated as a function of concentration of the added microphase-separated copolymer and temperature.
2) Self-assembled structures in binary mixtures of A-b-B/A (deuterated PS-b-PMMA/PS homopolymer) were studied as a function of molecular weight and concentration of the added polymer. A criterion for "wet and dry brush" behaviour respecting different solubilization of the homopolymer in microdomain morphology has been applied to explain the changes in microdomain morphology.
3) ) The microdomain morphology in copolymer blends of (A-b-B)1/A-b-B)2 type i.e. differing in molecular weight of blocks (deuterated PS-b-PMMA)1 / deuterated PS-b-PMMA)2 were investigated.
M. Milnera a, M. Štěpánek a, L. Billon b, O. Borisov b, K. Procházka a
aCharles University Prague, Faculty of Science, Department of Physical and Macromolecular Chemistry, Hlavova 8, CZ-12843 Prague 2, Czech Republic, (milnera / gmx.net, http://www.natur.cuni.cz/ )
bUniversité de Pau et des Pays de l'Adour, Laboratoire de Physico-Chimie des Polymères, Hélioparc, 2 Avenue du Président Angot, 64053 Pau Cedex, France
Studies of the self-assembly of poly(acrylic acid)-block-poly(acrylic acid-grad-styrene) synthesised at the University in Pau in aqueous media by quasi elastic light scattering (QELS) indicate the presence of several types of particles in solutions with changing pH. Two distinct modes in spectra of relaxation times reflect the diffusion of scatterers with hydrodynamic radii 4 and 100 nm. The former type of scatterers can be either unimer or a very small associate, while the latter type of scatterers corresponds presumably to large multimolecular micelles. The presence of large associates in basic solutions is very surprising and also the changes of fractions of individual species with pH are surprising. We applied a number of different techniques (AFM, capillary zone electrophoresis, ultracentrifugation, etc.) in order to investigate this unexpected behaviour in detail. Here we report on the capillary zone electrophoresis (CZE) measurements. The mobility (in units 10-9 m2/Vs) of the faster migrating peak ranges from -31.3 to -34.7 in a broader region of pH from 5.9 to 9.1. The slower peak is not well separated from the faster one and does not differ much in the mobility (ca. -31.3 to -32.3). The shape of the electrophoretic curves suggests that there could be a mobile equilibrium between the two types of scatterers (and fast exchange of unimers between micelles), but further investigations are needed in order to understand the behaviour of the system at different pH. Various experiments together with computer modelling are in progress.
M. Przybyszewskaa, M. Zaborskia
aTechnical University of Lodz, Institute of Polymer and Dye Technology, Stefanowskiego 12/16 Lodz 90-924, Poland (magdalena.przybyszewska / p.lodz.pl)
During peroxide vulcanization coagents become incorporated in the polymer network by covulcanization of coagent domains with elastomer matrix. As a result coagents affect the crosslink structures and the network topology of vulcanizate, resulting in strength properties improvement and increase crosslinking efficiency.
In order to study the effect of new coagents in peroxide vulcanization of hydrogenated butadiene-acrylonitrile elastomer (Therban A3407), various coagents based on nanostructured zinc oxide modified with unsaturated acid and esters (itaconic acid, acrylic acid, monoallyl maleate respectively) were synthesized.
From zeta potential measurements the isoelectric point of nanostructured zinc oxide that was about pH 3,7 was determined. Surface modification of ZnO shifted the isoelectric point towards pH about 11 and made the ZnO surface basic.
The stress at elongation (i.e. modulus) of the vulcanizates crosslinked in presence of coagent was much higher in the comparison with vulcanizates without modified ZnO. The highest mechanical properties exhibited vulcanizates containing nanostructured ZnO modified with itaconic acid. Considering the results of tensile tests it should be noticed that the tensile strength of these vulcanizates was six times higher compared with vulcanizates without coagent. Nanostructured zinc oxide with surface modified unsaturated acid and esters applied in HNBR crosslinking caused the increase of crosslinking density in comparison with vulcanizates without coagent. The highest crosslinking density had the vulcanizates containing nanostructured ZnO modified with itaconic acid.
From these studies it follows that addition of these coagents to a HNBR and DCP mixture provide considerable improvement in crosslinking density and mechanical properties of vulcanizates. The most effective coagent in peroxide vulcanization of HNBR seems to be nanostructured zinc oxide modified with itaconic acid. The application of this coagent to synthetic rubbers improves the crosslinking efficiency and increase the tensile strength of rubber material as well. This observation seems to be more important if we assume that application of coagents based on nanostructured zinc oxide is a very good way to eliminate the main disadvantages of peroxide vulcanization of saturated elastomers.
A. Gugliuzzaa, M.C. Acetoa, E. Driolia,b
a Research Institute on Membrane Technology, ITM-CNR,
Via Pietro Bucci 17/C, I-87030 Rende, Italy,
bDepartment of Chemical Engineering and Materials, University of Calabria,
Highly ordered structures with mono-dispersed pore size represent an attractive challenge for the membrane technology, due to the strategic role of the membrane morphology in the separation process. With this regard, the self-assembling method appears an innovative manufacturing technique for tailoring porous and ordered structures with submicron- and nanometer scales. Until now, this approach has not been fully exploited to form porous films easily removable from the support and such to be used as membranes. In this work self-assembled microporous PEEK-WC films are proposed as ideal interfaces for advanced membrane processes. Although the PEEK-WC is a poly(etheretherketone) largely used in the membrane processes, traditional phase inversion techniques did not allow achieving regular and controlled morphologies. In this work, self-organised patterns have been fabricated by templating action of condensed water droplets, forming pores with regular size and shape. Kinetic and thermodynamic process parameters have been modulated in order to control the nucleation and the growth of water droplets on the casting solution surface, evaluating the related effects on the final membrane morphology. Structure-property relationships have been found, providing important insights into the design of a new class of regular porous PEEK-WC membranes.
Acknowledgment
The "Ministero dell'Istruzione dell'Università e della Ricerca Fondo Investimenti per la Ricerca di Base (FIRB)" is gratefully acknowledged for the financial support for the project CAMERE.
C.M. de las Heras Alarcón,1 A. Lopez,2 M.J. Barandiaran,2 J. M. Asua,2 J.L. Keddie1
1. Department of Physics, University of Surrey, Guildford, Surrey GU2 7XH, UK (c.heras / surrey.ac.uk, j.keddie / surrey.ac.uk)
2. Institute for Polymer Materials, University of the Basque Country, 20018 Donostia-San Sebastian, Spain
Waterborne nanocomposite films of alkyd resin and acrylic polymers have attractive properties useful for coatings, but previous work has revealed that phase separation can occur upon film formation (1). Miniemulsion polymerisation(2) has been proven to be an effective way to create nanocomposite particles of acrylics and alkyd resin, but questions remain about the phase distribution in the final film. Our aim in this work is to use fluorescent confocal microscopy to determine the level of heterogeneity in nanocomposite films, as it is affected by the interdiffusion of miscible acrylic phases and the phase separation of alkyd and acrylic phases. A fluorescently-labelled acrylic monomer(3) was used in the miniemulsion polymerization of acrylic nanoparticle and also alkyd/acrylic nanocomposite particles. Confocal microscopy was used to determine the acrylic distribution in films made from various combinations of particles. The continuous phase is made up of either acrylic or alkyd/acrylic particles, whereas either acrylic or alkyd/acrylic particles are dispersed as a minority phase. It was found that physical blends of acrylic particles are able to interdiffuse to make a homogeneous film, but when acrylic is blended with acrylic/alkyd nanocomposite particles, the extent of acrylic interdiffusion is reduced. The extent of interdiffusion is reduced further as the concentration of alkyd in the matrix is increased. One explanation is that the number of acrylic/acrylic "contact points" is reduced in the nanocomposites. Atomic force microscopy (AFM) phase images have been successfully obtained from cross-sections of nanocomposite films. Two components (attributed to alkyd and acrylic phases) are observed in the nanocomposite films. Two components are likewise observed at the air interface. Increasing water contact angles with increasing alkyd content indicates that there is alkyd present at the film surface, which is consistent with the interpretation of the AFM images.
(1) Van Hamersveld E.M.S. et al., Progr. Org. Coat., 1999; 35, p. 235.
(2) Wang S.T., et al. J. Appl. Polym. Sci., 1996; 60, p. 2069.
(3) Tronc F. et al., J. Polym. Sci., Part A-Polym. Chem., 2003; 41 (6), p. 766.
R.-Y. Lin, S.-Y. Suen*
Department of Chemical Engineering, National Chung Hsing University, Taichung, Taiwan 402 (sysuen / nchu.edu.tw)
Sodium montmorillonite (Na+MMT) is one of the most widely used inorganic fillers in polymer matrices for improving the associated mechanical and thermal properties. With the characteristics of cation exchange and intercalation of molecules, Na+MMT could be incorporated into polymer matrices through two possible mechanisms: either the extended polymer chains are inserted into interlayer spaces of this layered clay, or the clay layers are dispersed into the polymer matrix. In previous studies, most clay particles-filled hybrid membranes are prepared and developed for common pervaporation or filtration technologies. However, their potential application as cation-exchange membranes has so far been overlooked.
In this study, the poly(methyl methacrylate) (PMMA)/Na+MMT composite materials were synthesized by emulsion polymerization of MMA and Na+MMT at different ratios with sodium dodecyl sulfate as emulsifier, followed by the preparation of porous membranes via phase inversion. Membrane morphology was characterized by scanning electron microscope and optical microscope, and the uniform distribution of Na+MMT particles on frontal membrane surface was only observed for the feed Na+MMT/MMA (w/w) ratio ≤ 0.5. Moreover, the X-ray diffractograms exhibited the larger interlayer spacing of Na+MMT in the PMMA/Na+MMT composite membranes, while the thermogravimetric analysis verified the near complete incorporation of Na+MMT on the composite membranes. An optimal feed Na+MMT/MMA ratio was thus selected as 0.5 (about 33 wt% Na+MMT) for the preparation of Na+MMT-filled composite membrane, which showed a cation-exchange capacity of 354 μeq/cm3. To further investigate the cation-exchange performance of these PMMA/Na+MMT membranes, the time course of cationic dye Methyl violet 2B adsorption (initial concentration of 0.05 g/L) was recorded. The best dye adsorption performance was achieved by the composite membrane prepared under the optimal feed ratio (Na+MMT/MMA = 0.5), where about 97% dye adsorption was attained in two hours.
Ionel Mangalagiu1*, Dorina, Mantu,1 Rodinel Ardeleanu,2 Gabriela Sacarescu,2 Mihaela Simionescu2 and Liviu Sacarescu2
1. 1. "Al. I. Cuza" University of Iasi, Organic and Biochemistry Department, Bd. Carol 11, 700506 Iasi, Romania; e-mail: ionelm / uaic.ro
2. 2. Institute of Macromolecular Chemistry "Petru Poni", Aleea Grigore Ghica Voda 41A, 700487 Iasi, Romania; e-mail: livius / icmpp.tuiasi.ro
Oligo- and polysilanes form a specific class of materials, which have been subjected to many investigations during the last decades.[1,2 Some of their intriguing electrical properties are related to the specific σ-electron delocalization which endow polysilanes directional conductivity, strongest along the axis of the chain.[3,4 Among these, polyhydrosilanes are a relatively new class with specific properties.[5,6Recently[7] our group discover a new class of hybrid polysilanes with N-allyl-cycloimmonium salt skeleton.
This work describes the first synthesis of a new polymer poly[methyl(H)-co-methylphenylsilane] with pendant diazine heterocyle. These material was obtained by catalytic addition of Si-H groups within a poly[methyl(H)-co-methylphenylsilane] backbone to the N-heterocycle. This hybrid polymer was characterized by spectral analysis, thermogravimetric analysis and gel permeation chromatography (GPC).
References
[1] J. P. Wesson, T. C. Williams, J. Polym. Sci., Part A; Polym. Chem. Ed. 1979, 17, 2833.
[2] R. West, L. David, P. I. Djurovich, K. L. Stearly, K. S. Srinivasan, H. J. Yu, J. Am. Chem. Soc. 1981, 103, 7352.
[3] A. Herman, B. Dreczewski, W. Wojnowski, Chem. Phys. 1985, 98, 475.
[4] J. Roncali, Chem. Rev. 1992, 92, 711.
[5] G. Sacarescu, R. Ardeleanu, L. Sacarescu, M. Simionescu, J. Organomet. Chem. 2003, 685, 202-206.
[6] J. E. Frommer, R. R. Chance, "Encyclopedia of Polymer Science and Engineering",J. Wiley & Sons, New York 1986, Vol. 5.
[7] R. Ardeleanu, I. Mangalagiu, G. Sacarescu, M. Simionescu, L. Sacarescu, Macromol. Rapid Commun. 2004, 25, 1231.
J. Jaczewskaa, A. Budkowskia, J. Raczkowskaa, I. Raptisb, D. Goustouridisb
aM. Smoluchowski Institute of PhysicsJagellonian University, Reymonta 4, 30-059 Kraków, Poland (www.if.uj.edu.pl/pl/ZINM/polyfilms)
bInstitute of Microelectronics, NCSR 'Demokritos', 15310 Aghia Paraskevi, Athens, Greece
White light interferometry was used to determine swelling of poly(3-alkylthiophene)s, P3ATs with varied head-to-tail regioregularity and alkyl chain length, exposed to different volatile compounds VCs: humidity, cyclohexanone, tetrahydrofuran and chloroform. The data have shown that film expansion increases always in the following order: (regioregular) R-P3DDT < R-P3HT < (regiorandom) P3BT < P3DDT.
Regular solution approach was applied to determine Flory-Huggins interaction parameter cbetween P3ATs and VCs. Evaluated sequence of polymer solubility parameters dP(increasing from P3DDT and P3BT to R-P3HT and R-P3DDT) is attributed to steric interactions of alkyl chains, present in regiorandom but absent in regioregular P3ATs.
Fig.1. Relative expansion d/d0 of poly(3-alkylthiophene) films exposed to the sequence of N2 fluxes carrying THF.
J. Jaczewskaa, A. Budkowskia, J. Rysza, A. Bernasikb
aM. Smoluchowski Institute of Physics Jagellonian University, Reymonta 4, 30-059 Kraków, Poland (www.if.uj.edu.pl/pl/ZINM/polyfilms)
bFaculty of Physics and Applied Computer Science, AGH-University of Science and Technology, Mickiewicza 30, 30-059 Kraków, Poland
From application view-point spin-coating of polymer blends is one-step process to deposit and align domains rich in different polymers. Resulting lamellar and lateral structures can be used in potential hi-tech devices e.g. in FETs and submicron size LEDs, respectively.
We present here systematic morphological studies on thin films of PS, blended with regioregular (R-P3DDT, R-P3HT) or regiorandom (P3BT, P3DDT) poly(3-alkylthiophenes) (P3AT), spin-cast onto various substrates (Si, Au, self-assembled monolayer) from few common solvents. Film structures were determined with Atomic and Lateral Force Microscopy (AFM/ LFM); depth profiling and mapping modes of dynamic Secondary Ion Mass Spectroscopy; and Near Field Optical Microscopy.
The data indicate some general trends governing the PS-P3AT film morphology: i) Decrease in P3AT solubility parameter or increase in solvent solubility parameter results in morphological transition from lamellar to lateral structure. ii) Larger solvent cohesion energy stabilizes the PS-P3DDT films against dewetting. In addition substrate effects were observed.
Fig.1. AFM and LFM surface images collected for P3AT-PS blends spin-cast from chloroform.
Study of conformational composition and small-scale mobility of glassy polymers by methods of FTIR-spectroscopy and quantum chemistry
J. Kostinaa, G. Bondarenkoa, A. Alentievb, M. Yablokovac, A. Fadeev
a Topchiev Institute of petrochemical synthesis Russian Academy of Sciences, GSP-2, Leninskii pr, 29, 119991, Moscow, Russia
b Lomonosov Moscow state university, GSP-2, Leninskie Gory, Moscow, 119992, Russian Federation
c Institute of synthetic polymer matherials Russian Academy of Sciences, Profsoyuznaya ul.70, Moscow, 117393, Russia
Physicochemical, mechanical, optical and membrane properties of glassy polymers depend on mobility of chain fragments, structure and packing of macromolecules in a polymeric material and, hence, on ability of conformational changes in polymer chain. The combination of theoretical and experimental methods of vibration spectroscopy is the most informative in study of conformational structure and mobility of polymer which depend on various factors (a method and time of sample formation, temperature, interaction with low molecular weight substances, etc). By method high-temperature FTIR- spectroscopy it is shown, that the choice of solvent and treatment of obtained polymer films by various methods lead to changes of its optical and membrane properties. It was demonstrated that the reason of these properties changes is modification of polymer chain conformational set.
For the group of polyetherimides it was shown that the hydrogen bond complex formation between oxygen-atom of ether-group of polymeric chain and hydrogen-atom of solvent or sorbate (chloroform or aliphatic alcohol) leads to ordering of conformational composition in Ph-O-Ph-units of polymer. Conformational ordering of polymer chains results in increase of polyimide films permselectivity.
For the series of comb-shaped mesomorphic acrylic polymers it was shown that at temperature of the first order transition there is a change of conformational composition in an ester group of a side chain. The temperature treatment of mesomorphic acrylic polymers leads to the same results. Such conformational modifications result in changes of optical and pervaporation properties of polymers.
By the example thermocyclization of the polyamic acid in polyimide was shown, that the choice of solvent (dimethylformamide or dimethylacetamide) determines various conditions of synthesis of polyamic acids, process its imidization and film-forming properties.
P. Sysel, V. Šindelář, R. Čechová, R. Hobzová, M. Fryčová
Department of Polymers, Institute of Chemical Technology, Technická 5,
CZ-166 28 Prague 6, Czech Republic (Petr.Sysel / vscht.cz, http://www.vscht.cz)
The thermal stability, dielectric and mechanical properties and chemical resistance make the linear and crosslinked aromatic polyimides suited for applications in (micro)electronics, aircraft industry, space exploration and membrane separations. The considerable disadvantage of classic linear polyimides is their insolubility and infusibility, and thus poor processability. Therefore, polyimides are often prepared by thermal solid-state imidization of polyimide precursors, polyamic acids [1]. The insolubility of polyimides can be reduced by introducing kinks into the polymer backbone and/or bulky substituents that will inhibit chain-chain interactions [1]. Can a hyperbranched structure also contribute to the solubility of polyimides?
In the field of synthetic polymers the dendritic topology has recently been recognized as a new class of macromolecular architecture. Dendrimers and also hyperbranched polymers are expected to play a key role as enabling building blocks for nanotechnology during the 21st century [2]. Highly branched structure and large number of terminal functional groups of hyperbranched polymers bring some different properties, e.g. increased solubility, in comparison with linear analogues.
In this work the hyperbranched polyimides based on 4,4´,4´´-triaminotriphenylmethane or 2,4,6-triaminopyrimidine and various dianhydrides were prepared. The solubility and other properties of these polymeric materials were studied in the dependence on their chemical composition. Their (?nano?)structure was monitored by using DMA, SEM, iodine indicator and PALS techniques.
Acknowledgement: MSM 6046137302, GA CŘ 203/06/1086
1 Hergenrother P. M.: High Perform. Polym.: 15, 3 (2003).
2 Tomalia D. A.: Aldrichimica ACTA 37(2), 39 (2004).
Z. Sedlákováa, K. Jeništováa, J. Baldriana, J. Pleštila, J. Nedbalb, I. Krakovskýb, M. Ilavskýa,b
aInstituteof Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovského nám. 2, CZ-162 06 Praha 6, Czech Republic (sedlakova / imc.cas.cz, https://www.imc.cas.cz/)
bFacultyof Mathematics and Physics, Charles University, Ke Karlovu 3, CZ-121 16 Praha 8, Czech Republic (http://www.mff.cuni.cz/)
Organic-inorganic hybrids with well defined morphology and structure controlled at the nanometric scale represent a very interesting class of materials. They find use in a broad range of advanced technology as well as in more conventional application fields. Emulsion polymer suppliers, as well as many other material and product suppliers, have been practicing nanotechnology for decades. Common small-sized emulsion polymers can be described in terms of nanotechnology. In contrast to emulsion polymer nanostructures, or to conventional composites, polymer/clay nanocomposites ranks among the emerging new nanocomposites.
We have investigated the properties of the polymer/organically modified montmorillonite (MMT) latexes prepared via in-situ emulsion free radical copolymerization. Organoclays (Cloisite, Nanocor) were obtained by cationic exchange of MMT with [2-(acryloyloxy)ethyl]-trimethylammonium chloride, [2-(methacryloyloxy)ethyl]-dimethyloctylammonium bromide and [2-(methacryl-oyloxy)ethyl]-dimethyloctadecylammonium bromide. The intercalated anchoring monomers were used for copolymerization with styrene and butylmethacrylate.
The structure and physical properties of the prepared aqueous polymer dispersions were studied by WAXS, SAXS, DSC and mechanical and dielectric spectroscopy. X-ray diffraction studies showed that all systems were swollen after monomer intercalation and the increase of interlayer d-spacing for monomer and polymer was dependent on the monomer composition.
Acknowledgements. Financial support of Academy of Sciences of the Czech Republic (Project No KAN 100500651) is gratefully acknowledged.
B. Mossety-Leszczaka, H. Galinaa, M. Włodarskab, G.W. Bąkb
aDepartment of Industrial and Materials Chemistry, Rzeszów University of Technology, W. Pola 2, 35-959 Rzeszów, Poland (mossety / prz.edu.pl, hgal / prz.edu.pl, http://www.prz.edu.pl)
bInstitute of Physics, Technical University of Łódź, Wólczańska 119, 90-924 Łódź, Poland (mwlodarska / p.lodz.pl, gwbak / p.lodz.pl, http://www.p.lodz.pl)
Highly anisotropic polymer networks with ordering on molecular level can be prepared by aligning the mesophase of the liquid crystalline precursors during the curing process, particularly under the influence of an external (e. g. magnetic) field. These materials can be used as matrices in advanced composites, e.g. nanocomposites and as new materials for non-linear optics.
A series of networks based on aromatic mesogenic epoxy precursors were prepared and characterized. The change in liquid crystalline order during crosslinking reaction with selected curing agents was the focal point of the study. The properties of the liquid crystalline polymer networks in relation to the structure of reagents, mechanism of curing reaction (polyaddition, anionic polymerization) and presence of magnetic field are to be discussed. The stability of liquid crystalline alignment upon heating above glass transition will also be reported.
Acknowledgment
Part of this work was supported by grant N205 060 31/2543.
J. Nedbala, A. Jigounova, Z. Sedlákováb , J. Spěváčekb, M. Ilavský a,b
aFaculty of Mathematics and Physics, Charles University, 180 00 Prague 8, Czech Republic, (nedbal / kmf.troja.mff.cuni.cz)
bInstitute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, 162 06 Prague 6, Czech Republic
Liquid-crystalline polybutadiene-diols (LCPBDs) with the comb-like architecture were synthesized by reaction of the SH groups of the LC thiol:
with the double bonds of telechelic HO-terminated polybutadiene (PBD); LCPBDs were prepared with various initial molar ratios of thiol to double bonds of PBD by the radical reaction at temperature 60°C for 48 h (initial ratio R0 = [double bonds]/[SH] has changed in the range from 0.15 to 1). The experimentally obtained degree of modification, Re, after the reaction and purification, was determined from elemental analysis - from the amount of sulphur bounded in LCPBDs, GPC and from 1H NMR spectra. The physical properties were investigated by DSC, polarizing microscopy and dielectric and dynamic mechanical spectroscopy. With increasing Re the glass transition temperature of LCPBDs, Tg, increases from ~ -45 °C (neat PBD) to ~20 °C (Re~0.5). LC transition starts at Re~0.27 (the transition temperature Tm~27 °C). With increasing Re temperature Tm increases and for Re ~ 0.5 reaches the value Tm~74 °C, at the same time also the change in enthalpy at LC transition increases. The LC transition could be detected also by the dielectric and dynamic mechanical spectroscopy; especially shape and position of mechanical and dielectric functions on frequency and temperature strongly depend on degree of modification.
Acknowledgements. Financial support of the Grant Agency the Academy of Sciences of the Czech Republic (grant No. IAA4112401) and of the Ministry of Education, Youth and Sports of the Czech Republic (grant MSM 0021620835) is gratefully acknowledged.
A. Bukowskaa, W. Bukowskia, J. Noworóla, A. Drelinkiewiczb, A. Kozakb, A. Waksmundzka-Górab
aFaculty of Chemistry, Rzeszów University of Technology, 35-959 Rzeszów, al. Powstańców W-wy 6, Poland (wbuk / prz.edu.pl)
bInstitute of Catalysis and Surface Chemistry, Polish Academy of Sciences, 30-239 Kraków, Niezapominajek 8, Poland
Methacrylicgel-type terpolymers, obtained as microbeads (75-150 mm) by suspension copolymerization of 2-hydroxyethyl methacrylate (HEMA, 20 mol.-%) with styrene (77 mol.-%) and diethylene glycol dimethacrylate (3 mol.-%), were utilized as supports for transition metal catalysts. To produce polymer catalysts, HEMA resins were firstly treated with an excess of glutaric anhydride or 4-nitrophenyl chloroformate in methylene chloride. Polymer-bound glutarate was used to immobilize Pd particles or it was reacted with hydroxyl substituted salen ligand and then applied to cobalt ions complexing. X-ray diffraction (XRD) and electron microscopic studies (SEM, TEM) showed the presence of Pd nanoparticles located through the bulk of spherical grains of catalysts. IR and UV-Vis spectroscopies and DSC analysis were applied to study of the resins nature. The swelling ability of catalysts and supports in a series of solvents were also examined.
Pd catalysts were tested in the hydrogenation of several reactants with unsaturated CºC and C=C bonds. Performance of catalysts in terms of activity and selectivity was found to critically depend on cross-linking degree of the resin and Pd loading in catalysts, factors that remarkably affected the swelling ability of polymer. Expanded state of catalyst grains under catalytic reaction provided conditions that facilitated almost selective hydrogenation of CºC to C=C in alkyne reactants (phenylacetylene, 3-hexyne, 2-butyne-1,4-diol) thus giving the corresponding alkene products at yield near to 100%.
Cobalt salen catalysts were tested in the ring opening reactions of terminal epoxides. It was found that polymer-bound salen catalysts were characterized by the comparable activity to soluble Co(III)Ac salen complex. Recycling of the catalysts was possible without sufficient decreasing their catalytic activity.
Acknowledgements
This work was partially founded by grants no. PBZ-KBN-116/T09/2004 and N205 001 31/0012 of Polish Ministry of Scientific and Higher Education.
A.V. Krekoten, Y.A. Shchipunov
Institute of Chemistry, Far East Department, Russian Academy of Sciences
690022 Vladivostok, Russia (krekoten / ich.dvo.ru)
Jellification of aqueous solutions of alkyl polyglucoside (APG) has been observed when a silica precursor, tetrakis(2-hydroxyethyl) orthosilicate (THEOS), was used. The hydrogel formation occurred beginning with 10 wt.% of THEOS. The APG concentration in solutions was varied in the range of 0.1 to 50 wt.% in which the surfactant was aggregated as spherical micelles.
It was found that the surfactant had a catalytic effect on the sol-gel processes. This allowed performing them in the neutral region in which the jellification was not observed in the absence of APG.
The mechanical properties of synthesized hydrogels examined by a dynamic rheology depended on the silica content. With increasing the THEOS amount in initial solution, one could observe an increase in the mechanical strength. The variation of APG concentration did not influence notably the mechanical properties.
Hybrid APG-silica hydrogels were dried at the supercritical conditions to prepare aerogels. A scanning electron microscopy was applied to study their morphology. It was demonstrated that there are mesoporous materials consisting of a three-dimensional network of cross-linked silica nanoparticles. According to a suggested mechanism, products of precursor hydrolysis nucleate on the surface of micellar aggregates through hydrogen bonds formed between sylanol groups and hydroxyl groups of glucose residues in APG molecules. Therefore, the micelles serve as a template for silica generated in situ. The silica in its turn provides the cross-linking that leads to formation of three-dimensional network bringing about the jellification.
E.M. Leea, B.C. Jia, H.W. Leea, M.H. Hwanga, J.D. Yunb, J.H. Parkb, J.H. Yeumb
aDepartment of Advanced Organic Materials Science and Engineering, Kyungpook National University, Daegu 702-701, Republic of Korea
bDepartment of Natural Fiber Science, Kyungpook National University, Daegu 702-701, Republic of Korea (jhyeum / knu.ac.kr)
Nanoscale materials design and synthesis is important in the fabrication of advanced devices for optics, electronics, and biotechnology. Hollow latex particles enhance the performance of industrial coatings and potentially are useful in other technologies such as microencapsulation and controlled release.
In this study, atactic poly(vinyl alcohol)/silver (PVA/Ag) nanocomposite microparticles with hollow structure were prepared via a low temperature W/O/W emulsion polymerization in the presence of Ag nanoparticles and heterogeneous saponification. It was found that a high yield and high molecular weigh PVA/Ag could be obtained even using a low-temperature initiator. In the case of presence of Ag nanoparticles, the rate of polymerization was slightly slower than that without Ag.
In the preservation test, the PVA/Ag nanocomposite microparticles showed a powerful antibacterial effect.
M. Kanesato, S. Ishibe, K. Nagahara Y. Kikkawa, E. Koyama, H. Tokuhisa
Nanoarchitectonics Rsearch Center (NARC), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8562, Japan
(m. kanesato / aist. go. jp, http://unit.aist.go.jp/narc/e/index_e.html)
The design and synthesis of artificial receptor molecules are fascinating areas of research because oftheir importance in basic and applied chemistry. Organic multidentate ligands able to recognize metal ions will make them valuable for the development of applications such as chemical sensors, the selective extraction of metal cations, optical materials, and catalysts of organic reactions. We have reported dinuclear lanthanide cryptates and dinuclear lanthanide complexes of bis-macrocyclic ligands and their host-guest reactions.1)
Here we report the preparation and characterization of metal complexes of heptadentate ligands and their recognition of alkali metal ions. We also report the preparation and characterization of organic/inorganic hybrid materials composed of metal complexes and organic polymers and their recognition of fluoride ion.
The lanthanide complexes of heptadentate ligand trensal, tris[2-(salicylideneamino)ethyl]amine (H3L1) and its derivatives which has a tert-butyl group at the 3-position (H3L2) of the salicylidene group were prepared by the procedure described elsewhere.2) [LnL2] possesses a space which is surrounded by the central metal ion, three oxygens, and three tert-butyl groups. [LnL2] was found to be a host for lithium ion.
The lanthanide complexes of the heptadentate ligand containing phosphonomethylamino group were found to be hosts for fluoride ion. Selective adsorption of fluoride ion by organic/inorganic hybrid materials with metal complexes will be discussed.
1) M. Kanesato, H. Houjou, Y. Nagawa, K. Hiratani, Inorg. Chem. Commun., 2002, 5, 984-988.
2) S. Mizukami, H. Houjou, M. Kanesato, K. Hiratani, Chem. Eur. J., 2003, 9, 1521-1528.
V. Samaryk, S. Varvarenko, I. Tarnavchyk, N. Nosova, N. Puzko, S. Voronov
Lviv Polytechnic National University, 12 Bandera str, Lviv 79013 Ukraine
Nature and structure of thin polymer films is of essential value in a lot of technological processes: microelectronics, paint production, application of lubricants, and at creation of biocompatible surfaces for medicine.
In the recent years, such the films have been formed mainly via graft-polymerization of corresponding monomers from polymer surfaces activated by ozonization, irradiation with high energy particles including gas plasma, corona discharge, UV etc.
Application of peroxide-containing copolymers of peroxide monomers with acrylate monomers as activating agents for low energetic surfaces (polyethylene, polypropylene) allows to provide a covalent grafting of peroxide groups from copolymer composition to these surfaces at the expense of the free radical reactions mentioned.
Utilization of the part of peroxide groups only from the copolymer composition at polymer surface activation allows to perform following modification at the expense of covalent grafting of the next modifying layer or initiation of graft-polymerization of monomers from the surface. The techniques elaborated provide the possibility of incorporating hydroperoxide, perester, ditertiary peroxide groups to mentioned copolymers allowing the precise control of initiation and proceeding of free radical processes at known rate of free radical generation at different thermal and RedOx conditions, and ability of the majority of polymer materials to participate the radical processes makes our route highly universal.
Grafting of polyperoxide, and then, dextran, dextran sulfate, heparin and polyacrylic acid to low energetic surfaces has been performed.
Grafting process was controlled by changes of surface energy by measurements of contact angles for two liquids, AFM, FTIR- and FTIR-ATR-spectroscopy, ellipsometry and ellipsometric mapping.
REINFORCED ELASTOMERIC NETWORKS
B. Meissner, L. Matějka
Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovského nám. 2, CZ-162 06 Praha 6, Czech Republic (meissner / imc.cas.cz, matejka / imc.cas.cz)
Recently, we have proposed a structure-based constitutive equation for filler-reinforced elastomeric networks. It is composed of a connectivity term based on Langevin statistics and a constraint term based on tube theories; the effect of filler is described using the concept of a strain-dependent strain-amplification factor. The equation has been shown to offer a very good description, up to high strains, of stress-strain dependences in all deformation modes of virgin and strain-softened carbon-black-reinforced networks of natural and styrene-butadiene rubber (Polymer 2006;47:7997).
The same equation is now shown to give a very good description of the whole set of experimental data measured by Wang, Xu, Mark (Rubber Chem Technol 1991) on in-situ sol-gel silica-reinforced poly(dimethyl siloxane) networks in different deformation modes (uniaxial and biaxial extension, pure and simple shear).
Reduced stress vs reciprocal stretch ratio. Uniaxial extension, virgin ○; after prestrain ∆; uniaxial compression □. Curves fitted to data. Networks W10,W23 contain 10 and 23 phr silica.
Parameters of the equation were
determined by curve-fitting and
their relation to structure is
discussed.
A reasonable interpretation of the pronounced - so far not well understood - minima and maxima
in the isotherms is offered. Strain-softening (curve b) has similar features as that observed in carbon-black reinforced hydrocarbon rubbers.
A plausible insight into the problem of filler-reinforcement in elastomers seems to emerge.
K. Charmuszko, D. Gront, A. Sikorski*
Department of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warszawa, Poland (sikorski / chem.uw.edu.pl)
A lattice model of branched polymer [as1] [as2] chains was designed and studied. The chains consisted of united atoms (segments) which positions were restricted to a [310] type lattice. The model macromolecules were star-branched chains consisting of two kinds of polymer segments defined as hydrophilic and hydrophobic. The force field used consisted of the long-range contact potential between a pair of non-bonded segments and of a local stiffness. In order to study the static and thermodynamic properties of the model chain we used a variant of the Monte Carlo method called pruned-enriched Rosenbluth method (PERM). The static properties and the structure of model chains in a wide range of solvent conditions were studied. The influence of the number of arms on the process of their self-assembly was shown and discussed.
M. Walczak*, J.B. Lechowicz, H. Galina
Rzeszów University of Technology, Faculty of Chemistry, Department of Industrial and Materials Chemistry, ul. W. Pola 2, 35-959 Rzeszów, Poland (mwalczak / prz.edu.pl)
Hyperbranched polyesters were prepared from 4,4-bis(4-hydroxyphenyl)pentanoic acid. The polymerization was carried out at room temperature using carbodiimide-coupling reagent in the presence of suitable catalyst.
The molecular weight distribution (MWD) of the polymer was controlled by: (i) using bisphenol A as a 'core' molecule, (ii) introducing monomer to the core in several portions of the same or different sizes, (iii) adjusting the conversion of functional groups at each addition of monomer.
For the purpose of numerical modelling of MWD in hyperbranched polymerization two models have been developed. The kinetic model was based on the Flory-Stockmayer principles and made use of the Smoluchowski coagulation equation. The Monte-Carlo model was in fact the polymerization process carried out in computer memory, following the basic paradigm of the chemical law of mass action. The two models provided exactly the same results, since the intramolecular cycle formation allowed for in computer experiments were negligible.
The real low-temperature polycondensation, however, does not proceed according to the simple mechanism of the second-order reaction between functional groups. As found by 1H NMR, acid anhydride groups are formed first. Then, the anhydride groups react with phenolic moieties to yield ester groups.
The applicability of the theoretical models and accuracy of their predictions in relation to the actual chemical system will be discussed.
P. Romiszowski, A. Sikorski
Department of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warszawa, Poland (prom / chem.uw.edu.pl)
We studied a simplified model of a polymer brush formed by linear chains, restricted to vertices of a simple cubic lattice. The macromolecules consisted of a sequence of hydrophilic and hydrophobic segments arranged in a specific sequence. The chains were grafted to an impenetrable surface, i.e. they were terminally attached to the surface with one end. The properties of this model system were determined by means of Monte Carlo simulations using a Metropolis-like sampling algorithm based on local changes of chain's conformations. The number of chains was varied from low to high grafting density. The model system was studied at different solvent quality from good to poor solvent. The structure and the dynamic properties of the brush were determined and discussed.
Piotr Murias, Josef Pleštil, Libor Matějka
Departament of Polymer Networks and Mechanical Properties, Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovského nám. 2, CZ-162 06 Praha 6, Czech Republic. murias / imc.cas.cz
In this contribution, we present polymer networks with inorganic nanobuilding blocks - polyhedral oligomeric silsesquioxane (POSS) units. The aminofunctional-POSS with isooctyl, isobutyl or phenyl substituents were incorporated as a pendant block in the epoxy-amine network, diglycidylether of Bisphenol A (DGEBA) - Jeffamine D2000. The hybrid structure and morphology were controled by (a) synthesis procedure (one-step or two-step) and by (b) varying type of POSS organic substituents. The two-step synthesis consisting in preparation of the adduct DGEBA-POSS in the first stage provides more homogeneous organic-inorganic network.
Formation, structure and mechanical properties of the DGEBA-based POSS containing epoxy network were determined by using chemorheology experiments, by SAXS and DMA.
Acknowledgments
The authors thank the Grant Agency of the Czech Republic(project Nr. 203/05/2252) and the Grant Agency of the Academy of Sciences of the Czech Republic (project IAA 400500701) for the financial support of this work.
P. M. would like to thank UNESCO-IUPAC fellowship.
A. Strachotaa, F. Ribotb, J. Kovářováa, L. Starovoytova, J. Brusa, J. Pleštil, M. Šloufa, M. Špírková, B. Strachotováa, L. Matějkaa
a Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovského nám. 2, CZ-162 06 Praha 6, Czech Republic
b Laboratoire de Chimie de la Matière Condensée, UMR CNRS 7574, Tour 54, 5e étage, Université Pierre et Marie Curie, 4 Place Jussieu, F‑75252 Paris Cedex 05, France
The synthesis and characterization of hybrid organic-inorganic epoxy networks containing nanometer-sized stannoxane cluster dications, [(nBuSn)12O14(OH)6]2+, is presented. The materials are based on the DGEBA - poly(oxypropylene)diamine (Jeffamine D2000) resin. The stannoxane was incorporated as inert nano-filler, as diseconadry diamine and as primary diamine.
The chemical stability of the stannoxane, and the influence of its incorporation on mechanical properties and on thermal stability of the prepared hybrid epoxy resins will be discussed. The effect of inert, bifunctional and tetrafunctional stannoxanes in these nanocomposites will be compared. The morphology, especially its dependence on the network curing conditions and on eventual subsequent treatment, was investigated.
Acknowledgement:
The authors thank the Grant Agency of the Czech Republic, Grant Nr. 203/05/2252, and the Grant Agency of the Academy of Sciences of the Czech Republic, Grant Nr. A400500701 and the European Commission, Grant EU-HPRN-CT-2002-0036 for financial support of this work.
The authors thank Huntsman Inc. for the donation of Jeffamine D2000.
B. Montero, C. Ramírez, M. Rico, L. Barral, J. Cano
Departamento de Física. Universidad de A Coruña. E. U. P. Avda. 19 de Febrero s/n, 15405, Ferrol. Spain. labpolim / udc.es
Polyhedral oligomeric silsesquioxanes (POSS) can be dispersed in thermosseting resins at nanometric scale to form inorganic/organic hybrid nanocomposites with enhanced properties1. POSS can acts as a flame retardant agent as well.
In this work, the mechanism of thermal degradation of an epoxy-amine system modified with an octaepoxy-POSS was studied by thermogravimetric analysis (TGA).
Three mixtures of amine-POSS with different ratios were compared resulting that the stoichiometric ratio presents the best thermal behaviour, and ternary samples were made with different wt % of POSS. It was tested that the char/ceramic yield obtained in oxygen and argon atmospheres, respectively, increase with the content of POSS. According to Van Krevelen correlation2, this increment demonstrates the flame retardant effect of POSS.
By the isoconversional Kissinger-Akahira-Sunose method, activation energies of degradation at each value of conversion (Ei), were calculated. As activation energy values do not vary greatly with the conversion between values of 0.3 and 0.8, it was possible to describe the whole reaction interval by a single kinetic model, although the real reaction is complex. Autocatalytical model explains the mechanism of the degradation of these systems.
Financial support: XUGA-PGIDIT05PXIC17201PN and MAT2004-01580.
1) JJ Schwab, JD Lichtenhan. Appl. Organometal. Chem.(1998),12,707.
2) DW Van Krevelen. Polymer (1975),16,615.
E. Grossman a, R. Verkera,b, I. Gouzmana, N. Eliazb
aSpace Environment Group, Soreq NRC, Yavne 81800, Israel (eitan / soreq.gov.il)
b School of Mechanical Engineering, Tel-Aviv University,� Tel-Aviv 69978, Israel
Polyimides are widely used in spacecraft, especially as the outer layer of thermal control insulation blankets that are exposed to the low Earth orbit (LEO) space environment. In order to withstand erosion by LEO atomic oxygen (AO), these surfaces are coated with a protective layer such as silicon oxide. However, ultrahigh velocity impacts of space debris lead to deterioration of the protective layer, mainly via holes formation, allowing penetration of AO and etching of the underneath polymer. A possible solution is the use of AO resistive self-healing polymers, such as organic/inorganic nanocomposites produced by incorporation of polyhedral oligomeric silsesquioxanes (POSS) into polyimide matrix.
The effect of hypervelocity space debris impacts and AO attack on the durability of polyimide films reinforced with different types of POSS was studied.� Three types of POSS structures were investigated: TriSilanolPhenyl-POSS, AminPropylPhenyl-POSS and AluminumPhenyl-POMS.� Hypervelocity debris impact was produced using a laser-driven flyer system that accelerates aluminum flyers to impact velocities of up to 3 km/s. AO irradiation was carried out by exposure to oxygen RF-plasma.� Erosion rate was evaluated by mass loss measurements. The fractured surface morphology was characterized using Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). Ultrahigh-velocity impact toughness and erosion resistance of the POSS-polyimide films were evaluated as a function of impact velocity, POSS/polyimide type and content, and AO fluence.
All POSS-polyimides samples revealed increased AO resistance with increasing POSS content, which is attributed to formation of silicon oxide passivation layer. In addition, POSS-polyimide films revealed higher toughness under ultrahigh velocity impact compared to POSS-free films. Upon AO exposure, the impacted POSS-free films showed a synergistic effect, associated with a large increase in the erosion rate and formation of new holes. The increased erosion rate of the impacted POSS-free film is related to impact-associated residual stresses that affect the oxidation mainly by increasing the diffusivity of oxygen. Such a synergistic effect was not observed for the impacted POSS-containing samples. A model explaining this behavior, in regard to the POSS-Polyimide superior mechanical properties is proposed.
G. Tishchenkoa, N. Kebrlováa, J. Brusa, J. Dybala, E. Rosovab, I. Dmitrievb, G. Elyashevichb, Z. Bastlc
a Department of Polymer Membranes, Institute of Macromolecular Chemistry, v.v.i. Academy of Sciences of the Czech Republic, Heyrovského Sq. 2, CZ-162 06 Prague 6, Czech Republic (tiscenko / imc.cas.cz)
b Institute of Macromolecular Compounds, Russian Academy of Sciences, Bolshoi pr. 31, St. Petersburg, Russia
c J.Heyrovského Institute of Physical Chemistry, v.v.i. Academy of Sciences of the Czech Republic, Dolejškova 3, CZ-182 23 Prague 8, Czech Republic
The excellent film-forming ability of natural biopolymer - chitosan (Chi) is widely used in preparation of the homogeneous dialysis membranes. The functionality and microheterogeneity of this type of membranes was enhanced in this study by introducing the nanofillers: octakis{[(2-carboxyethyl)sulfanyl] ethyl} polyhedral oligomeric silsesquioxanes (CESE-POSS) and metal ions (Ag+, Cu2+, Hg2+ or Fe3+) able to coordinate with CESE tethers and glucosamine moieties in chitosan phase.
For elucidating the contribution of both molecular fillers and metal ions to the structural differences of Men+-Chi/CESE-POSS membranes, their elastic properties and transport characteristics were compared. The transmembrane flux of electrolytes was determined under both the concentration gradient and the direct electric current.
It was shown that the elongation and breaking stress of the dry Men+-Chi/CESE-POSS membranes was higher than that of the Chi/CESE-POSS ones and vice versa if the membranes were hydrated. In contrast to the swollen membranes, the dry ones exhibited one order lower values of the elongation but approximately one order higher values of the breaking stress. The dependence of the elastic properties on the type of metal ion became more pronounced for hydrated membranes. The porosity played the leading role in transport of KCl species through hydrated Men+-Chi/CESE-POSS membranes at the direct electric current (2 mA); the higher the swelling of a composite membrane the lower its resistance and permselectivity.
In transport of NH3/CO2 vapors through the Men+-Chi/CESE-POSS membranes, the interactions of the diffusants with membrane phase were highly dependent on the type of immobilized metal ion. These findings can be useful in practical applications of composite chitosan membranes of dialysis type.
Acknowledgements. Our thanks are due to the GA ČR (grant 525/05/2584) and RFFI (grant 07-03-00177-а) for financial support of the study and Hybrid Plastics Co. (USA) for kind gift of CESE-POSS samples.
N. Hao, M. Böhning, S. Wohlrab, A. Schönhals
Federal Institute of Materials Science and Testing, Unter den Eichen 87, D-12205 Berlin, Germany
Nanocomposites were prepared using polycarbonate and polystyrene as polymeric matrices. As nanoparticles polyhedral oligomeric silsesquioxanes with phenethyl substituents (PhenethylPOSS) were used. The composites were prepared by solution blending.
The structure-property relationships of these nanocomposites were investigated by dielectric spectroscopy and gas transport measurements (permeation, sorption). Additionally, density and FTIR measurements were also employed. The results were discussed with regard to the phase structure of the prepared nanocomposites. Especial attention was paid to characterize the interfacial region between the polymeric matrix and the different nanoparticles.
On nanocomposites basing on PhenethylPOSS and Polycarbonate, as a main result it was found, that POSS can be mixed homogeneously into the polymer matrix up to a limited concentration of ca. 7 wt-%. For higher concentrations of POSS, a phase separated structure consisting of polymer and POSS rich phases was observed. This phase structure influences strongly the dielectric and gas transport properties of the nanocomposite.
For PhenethylPOSS/Polystyrene nanocomposites no phase separation was found up to 40 wt-% of POSS. The difference in the behavior of both systems is explained by differences in the interaction possibilities of the phenyl ring in the substituents of POSS with the molecular structure of the polymers.
A. Tajimaa, T. Higuchia,c, H. Yabub,c, M. Shimomurab,c,d
aGraduate School of Science, Hokkaido University, Japan
(a.tajima / mail.tagen.tohoku.ac.jp)
bIMRAM, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan
cFrontier Research System, RIKEN, Japan
dCREST, Japan Science and Technology Agency, Japan
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Polymer nano-particles have been used in the fields of photonics, electronics and biotechnologies. Shapes of nano-particles determine their physical properties. Thus, control of the particle shape is important. We found a simple preparation of various kinds of polymer nano-particles by mixing a poor solvent (i.e., water) into the polymer solution, and then evaporation of a good solvent (i.e., tetrahydrofuran (THF)). Here, we show the preparation of nano-particles consisting of two different homopolymers.
Four kinds of homopolymers (polystyrene (PS), polyisoprene (PI), poly(methyl methacrylate) (PMMA) and poly(octadecyl methacrylate) (PODMA)) were purchased from Polymer Source Inc. Equal amount mixture of PS and PI (sample 1) , PI and PMMA (Sample 2) or PI and PODMA (Sample 3) were dissolved in THF, and then water was added. After evaporation of THF, dispersions of nano-particles were obtained. From the dynamic light scattering (DLS) measurements, the sizes of three kinds of particles were ca.330 nm, 400 nm and 450 nm, respectively. After the PI segment stained by OsO4, the structures of particles were observed by scanning transmission electron microscopy (STEM).
In Fig. 1, the white part indicates the PI region, which is stained by OsO4. The black part indicates the PS region (Fig.1-a), the PMMA region (Fig. 1-b) or PODMA region (Fig. 1-c), respectively. In the case of sample 1, each component was clearly separated as hemispheres. On the other hand, in the case of sample 2, PMMA shell was formed on the PI core. Furthermore, in the case of sample 3, the particles spontaneously formed porous structure. These results show that the phase separation structures of nano-particles are changed by changing the type of mixing homopolymers.
L.V. Trandafilović1, V. Djoković1, N. Bibić1, M.K. Georges2, T. Radhakrishnan2,
1"Vinča" Institute of Nuclear Sciences P.O. Box 522, 11001 Belgrade, Serbia
2Department of Chemistry, University of Toronto at Mississauga, Mississauga, Ontario, L5L 1C6, Canada
CdSe/poly(2-(dimethylamino)ethyl methacrylate-co-acrylic acid) nanocomposites have been prepared and investigated. Poly(2-(dimethylamino)ethyl methacrylate-co-acrylic acid) has been synthesized by free radical polymerization in different co-monomer mol ratios (1:1, 1:2; DMAEMA:AA). Nanocomposites were characterized using structural and optical methods. The presence of nanostructured CdSe was confirmed by TEM analysis. The UV-VIS spectroscopy measurements of the nanocomposites showed a blue-shift of the onset of optical absorption, compared to bulk CdSe. XRD spectra revealed the cubic crystal phase of CdSe nanoparticles.
P. Vlasáka, J. Zelenkaa, M. Dušková-Smrčkováb, K. Dušekb
aSYNPO a.s.,Pardubice,Czech Republic (petr.vlasak / synpo.cz; www.synpo.cz)
bInstitute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic (www.imc.cas.cz)
We studied the effect of addition of nanoparticles in the ambient-cure polyurethane coating systems with the aim to improve diffusion of the solvent from drying coatings. Often, simultaneous chemical and physical drying lead to formation of glassy layer over the top of coating. Such glassy skin reduces significantly diffusion of solvent and thus deteriorates coating development, end-use properties, and durability.
The effects of shape and amount of nanoparticles on solvent diffusion and mechanical properties of coatings were studied. PUR coatings were prepared of a hydroxyl-functionalized acrylic copolymer and a commercial diisocyanate in stoichiometric ratio. Hydrophobicized nanoparticles of lamellar montmorinollite and spherical silica were used.
The addition of spherical as well as lamellar nanoparticles improved tensile properties, particularly the work to break. Lamellar nanoparticles reduced surface drying times, but somewhat more solvent remained in the film. Thus the coating hardness development was negatively influenced while the curing rate was not altered. Spherical silica nanoparticles prolonged surface drying times and decreased the curing rate. Lower reaction rate led to slower increase of Tg and delayed glassy skin formation. Solvent diffusion from the film was easier which resulted in lower solvent entrapment and higher hardness of coatings.
V. Djoković1, R. Krsmanović1, D. K. Božanić1, P. Sreekumari Nair2 T. Radhakrishnan3
1Institute of Nuclear Sciences "Vinća", P.O. Box 522, 11001 Belgrade, Serbia
2Department of Chemistry Lash-Miller Chemical Laboratories, University of Toronto, Ontario, M5S 3H6, Canada
3Department of Chemistry, University of Toronto at Mississauga, Mississauga, Ontario, L5L 1C6, Canada
E-mail: djokovic / vin.bg.ac.yu
Silver and silver/silver sulfide core-shell nanoparticles were prepared using sago starch as a host matrix. The presence of the both type of nanoparticles were shown by TEM and HTEM. The UV VIS spectra of the water solution of silver nanocomposites showed typical surface plasmon resonance (SPR) peak of nanostructured silver. Its position strongly depended on the concentration of the nanocomposite solution as well as on the thickness of silver sulfide shell. The observed effect was interpreted in terms of extended Mie theory for core-shell nanoparticles. The obtained theoretical curves showed good agreement with experimental data. XPS spectroscopy was carried out to investigate the presence of particular elements in the samples. The C 1s, O 1s, S 2p, and Ag 3d core levels were observed.
References
[1] Z. H. Mbhele, M. G. Salemane, C.G.C.E. van Sittert, J. M. Nedeljković, V. Djoković, A. S. Luyt. Chem. Mater., 15, (2003) 5019-5024.
[2] D. K. Božanić, V. Djoković, J Blanuša, P. Sreekumari Nair, M. K. Georges, T. Radhakrishnan, Europ. Phys. J. E in press
V. Tokareva, O. Shevchuka, G. Il'chuka, V. Ukrainetsa, V. Kusnezha, N. Bukartyka, R. Musiyb, S. Tokareva
a Lviv Polytechnic National University, 12 S. Bandera Str., UA-79013, Lviv, Ukraine (oshevch / polynet.lviv.ua)
b Department of Physico-Chemistry of Institute of Physico-Organic Chemistry and Coal Fuel Chemistry of the National Academy of Sciences of Ukraine, 3a Naukova Str. UA‑79053 Lviv, Ukraine
Nowadays quantum-sized effects in particular connection to the properties of nanocrystals consisting of limited number of atoms as well as the methods of synthesis of nanosized particles are the objects of intensive investigations. Among diverse techniques for obtaining such nanocrystals the synthetic methods, which apply controllable chemical reactions are intensively developed because of their high effectivity. The presented work is devoted to the elaboration of a new approach to fabrication of cadmium sulphide nanoclusters embedded into thin polymer layer grafted to solid surface via combination of adsorption-polymerization and sol-gel technique.
The process involves several successive stages, namely synthesis of membrane grafted to solids and synthesis of nanoparticles inside of such membrane. More precisely the process is performed as follows: (i) spin-coating of a peroxide oligomer on solid surface; (ii) melting and curing of the peroxide oligomer layer obtained; (iii) formation of polymer membrane at the modified surface via graft polymerisation of acrylic acid (AA) or successive graft polymerisation firstly of styrene (St) followed by AA; (iv) saturation of the grafted polymer membrane with Cd+2 ions followed by (v) treatment of such membrane with bonded Cd+2 ions by H2S to form nanoparticles of cadmium sulphide.
Obtained thin membranes with embedded MS nanoparticles have been investigated using electronic spectroscopy, scanning electron microscopy (SEM), electron emission energy analysis (EEEA) and atomic force microscopy (AFM). Applying the SEM combined with EEEA technique reveals that the ratio of Cd ions to carboxylic group in saturated membrane is of about 1 : 6. This value is in a good agreement with the co-ordination number of Cd. Notable changes in the surface layer morphology occurred at every stages are clearly seen at the AFM micrograms. Phase contrast AFM images confirm the predicted structures of thin polymer membranes filled by CdS nanoparticles.
Y. Lee, J. Jung, D. Li, G.S. Sur
School of Chemical Engineering and Technology Graduate School Yeungnam University
Nanocomposites of metal nanoparticles embedded within a polymer matrix have attracted much interest, particularly over the past decade, for their broadrange of potential applications in catalysis, magnetics, and photonics. Similar to the colloidal solutions, the hydrogels containing metal nanoparticles, can also play an important role in catalysis of many important chemical reactions in aqueous medium. But not much work has been reported so far on the radiolytic formation of metal clusters in the hydrogel matrix. The higher stability of a catalyst in gel matrix; uniform distribution without aggregation of small clusters; easy separation of a gel-immobilized catalyst from reaction mixture; easy accessibility of its large surface area and its repetitive usability, are some of the main advantages offered by such hydrogel systems. Therefore, Ag+ ions, in poly (vinyl alcohol) (PVA) and Isopropylachol have been reduced by electron beam irradiation to produce Ag clusters as nanoparticles in fully reduced and highly pure state. XRD (X-ray diffraction) technique confirmed the zero valent state of silver. UV-visible absorption spectral characteristics of Ag clusters obtained under different irradiation dose, Silver nitrate, isopropylacohol(IPA), poly (vinyl alcohol) (PVA) concentration. TEM(Transmission electron microscopy) of the nanocomposite films revealed the presence of Ag particles with diameter and shape in PVA matrix.
C. Prisacariu
Institute of Macromolecular Chemistry "Petru Poni", Aleea Grigore Ghica Voda, nr. 41 A, 700487, Iasi, Romania ( crispris / icmpp.ro)
A new approach to block copolymer structure and morphology of polyurethane (PUs) films was made by changes in the hard block chemical structure. 4,4'-dibenzyl diiscyanate (DBDI) of a conformational mobility was included in the hard block chemical structure, where the introduction of the -CH2CH2- spacer group between the two aromatic rings results in a different, much more dense packing structure of the PUs hard domains. DBDI was employed with chain extenders (CE) diethylene glycol (DEG) or ethylene glycol (EG) respectively. The macrodiol was hydroxyl-terminated poly(ethylene adipate) (PEA) MW = 2000 ± 50 (PEA 2000). Due to the specific conformational mobility of DBDI, in the corresponding PUs it observes an unusual large range of mechanical, physical and chemical properties which are associated with a specific pronounced separation into a domain - matrix morphology, and with a pronounced tendency of crystallization. There were tendencies to phase separation, with a characteristic length of ca 20nm, and when DBDI was employed with EG, to crystallization of the hard phase. The materials were characterized by means of differential scanning calorimetry (DSC) and X-ray measurements (WAXS). In the PU chain extended with EG, the hard segment (HS), crystallization performs in a high proportion (90%), this process being not affected by the presence of the soft segments (SS). This is in contrast to the almost general situation characteristic to conventional PUs with lower values of the melting peaks, when the interaction between the hard and soft segments is preponderant. Molecular orientation of the DBDI-DEG backbone structure was monitored by means of the infrared IR dichroic experiments. The effect of the strain history on the orientation of macromolecular chains was studied under unaxial extension, and in cyclical deformation experiments where the determination of the strain energy input and recovered energies have been made. While at a 50% polyurethane elongation it observed a strong tendency of the HS to orient in perpendicular to the stretching direction, at higher levels of elongation, up to 600%, it observed a pronounced tendency of the hard and soft domains to orient in parallel to the stretching direction. The higher the level of PUs elongation the more pronounced the organization of the HS and SS in parallel towards the stretching direction. High modulus domains derived from DBDI, containing the aromatic urethane blocks act to reinforce the rubbery prepolymer phase, and since the two (soft and hard) phases are interpenetrating, both are deformed by the applied stress. When the load is removed, the soft domains relax to a nearly isotropic state, while the rigid phase remains plastically deformed.
Y. Hiraia, H. Yabub,c,d, Y. Matsuoe, K. Ijiroe, M. Shimomurab,c,d.
aGraduate school of science, Hokkaido university,N10W8, Kita-ku, Sapporo, 080-0810, Japan (yujihirai / poly.es.hokudai.ac.jp)
bIMRAM, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan
cFrontier Research System, RIKEN Institute
dJST, CREST
eResearch Institute for Electronic Science, Hokkaido University
We have reported
that microporous polymer films can be prepared by casting a
solution of hydrophobic polymer (e.g. polystyrene, PSt) and
amphiphilic polymer on a solid substrate by using condensed water
droplet arrays as templates. The pincushion film was formed by
simple peeling of the top-layer of the microporous film with an
adhesive tape[1]. In this study, we show preparation of Ag
deposited pincushion films by vapor deposition and application of
these Ag pincushion films for surface-enhanced Raman scattering
(SERS) substrates. Microporous and pincushion films were
prepered, and Ag was deposited onto the pincusion films. Figure 1
show the Raman spectra of pyridine measured on the Ag deposited
films. Raman scatterings on the Ag deposited pincushion film (b)
were strongly enhanced than the Ag flat film (a). Furthermore,
Ag-PSt hybrid pincushion films whose pincushion was coated with
Ag only on the side of spikes show higher intensity of Raman
scatterings than that of the Ag deposited pincushion films (c).
These results show Ag deposited pincushion films prepared by
self-organization and vapor deposition can be applicable to
highly sensitive SERS substrates.
[1]H. Yabu, M. Takeyabashy, M.Tanaka,
and M. Shimomura, Langmuir, 21, 2005, 3235.
D. Ishiia, H. Yabua,b, M. Shimomuraa,b
a Frontier Research System, RIKEN Institute, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan (dishii / riken.jp)
bIMRAM, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
Superhydrophobic
surfaces are much paid attention since its good water repellent
property is used to ice and snow suppression and antifouling
technologies. Therefore, many researchers have been reported to
obtain such substrates of high contact angle to water.[1]
Recently, M. Jin et al. have been published high water
adhesive superhydrophobic polymer substrates by capillary forces
derived from tubular structures.[2] It is anticipated that
possession of both water-adhesive and repellent properties gives
new applications for bio and chemical technologies such as
microreactors, microdroplet manipulations, and micro devices.
So, we will try to control the water adhesive property by
changing surface characteristic.
Firstly we attempted to fabricate water adhesive superhydrophobic surfaces which are composed of polystyrene pillar structures and uniformly-distributed hydrophilic metal domains. The Metal-polymer composite substrate was obtained by selective all-wet electroless plating of self-organized honeycomb-patterned polymer films prepared according to our previous reports.[3] The water adhesive superhydrophobic surface was successfully obtained by peeling off an outer surface of the metal-polymer composite substrate. Next we will try to control of the water adhesive properties by changing the characteristic of hydrophilic metal domain by external stimuli such as electric field, magnetic field, light, thermal energy, and so on.
[1] For example; E. Hosono et al. J.
Am. Chem. Soc., 127, 13458 (2005). [2] M. Jin
et al. Adv. Mater., 17, 1977 (2005). [3] For
example; H. Yabu et al. Langmuir, 21, 1709 (2005).
I. Myskova, O. Kudina, O. Budishevska, S. Voronov
Lviv Polytechnic National University, 12 Bandera str, Lviv 79013 Ukraine budish / polynet.lviv.ua
One of the efficient ways to create new composite materials is the modification of interface in colloidal systems, which is performed via its activation and futher radical or polymeranalogical reactions. Perspective way of polymer surface activation is grafting of heterofunctional ditertial polyperoxides to it. To increase reactivity of modified surfaces polyperoxides containing primary - tertial peroxide fragments were used. Thermal stability of primary - tertial peroxide fragments is known to be essentially lower than that of ditertial.
We have synthesised polyperoxides with the primary - tertial peroxide groups via acylation of tert-butylperoxymethanol by polyanhydride according to the scheme:
O-MA-PM (St-MA-PM) used for the surface modification, forms polymer nanolayers with peroxide groups uniformly spread all over the surface. "Grafting to" the surface is performed via reactions of chain transfer and macroradical recombination. If necessary, on the second stage of modification the grafting of functional polymer layer is performed during the initiation "from the surface" as a result of thermal decomposition of O-MA-PM (St-MA-PM) peroxide fragments.
O-MA-PM grafting to the polystyrene latex particles and futher grafting polymerization of acrylonitrile allowed to obtain "core-shell" latexes, to modify the surface of polymethylmetacrylate latexes in order to increase their stability, to change the energetic characteristics of PET surface and to activate it. Modification of zirconium (IV) oxide filler by copolymer O-MA-PM allowed to improve physical and mechanical properties of composites based on polymethylmetacrylate matrix, for biomedical applications.
L. Hu*, Q. Guo, W. Zhao
Department of Applied Chemistry, Harbin Institute of Technolygy, Box 713, Harbin 150001, China (hulijiang / vip.sina.com)
Three silsesquioxane (SSO) building blocks based on (3-methacryloxypropyl) trimethoxysilane (MPMS), (3-glycidoxypropyl)trimethoxysilane (GPMS), Vinyltrimethoxysilane (VMS) and modified with 15 wt-% tetraethoxysilicate (TEOS) were prepared using hydrolytic condensation. The hardness (H), elastic modulus (E) and harmonic contact stiffness (HCS) for three films [f-MTSSO (film-MPMS-TEOS-SSO), f-GTSSO and f-GTSSO] and bulks (b-MTSSO, b-GTSSO and b-GTSSO) derived from the three SSO building blocks were tested by instrument-indentation testing (IIT). Different profiles of nanomechanical properties (H, E and HCS) of the films can be attributed to a different functionality and the functionated structure (cage and ladderlike) of the different SSO building blocks. The f-MTSSO shows better mechanical properties which are higher than the other films (f-GTSSO and f-VTSSO containing more OH or OCH3 groups). For the f-GTSSO with a bulky organic substituent, the unsatisfactory properties resulting from ring opening during hydrolytic condensation and an incomplete crosslinking network are discussed. However, the nanomechanical properties of the three bulks are very different from the corresponding nanomechanical properties of their films: b-VTSSO possesses the best nanomechanical properties (note: not b-MTSSO) among three bulks due to the differences in reaction conditions and chain less flexibility which are also discussed.
P. Chena, L. Hub*, Q. Guob, W. Zhaob
aChemical Centre, Harbin University of Commerce, Harbin 150076, China
bDepartment of Applied Chemistry, Harbin Institute of Technolygy, Box 713, Harbin 150001, China (hulijiang / vip.sina.com)
Based on silsesquioxanes (SSO) derived from the hydrolytic condensation of (3-glacildoxypropyl)trimethoxysilane (GPMS), 20 wt-% tetraethoxysilane (TEOS) and titanium tetrabutoxide (TTB), two-layer SSO films were prepared for nanoindentation and nanoscratch tests. The tests were carried out to study the influence of different amounts of TTB in the two-layer hybrid films on hardness (H), elastic modulus (E) and scratch testing profiles. The hardness profiles of the modified films showed two kinds of hardness corresponding to the two-layer structure. In the scratch-testing profiles, all final-scan profiles did not absolutely coincide or overlap with the first-scan profiles. All scratch profiles revealed a fluctuating characteristic and all scratch profiles can be divided into two regions in the horizontal displacement, because of the two-layer structure. The film containing an adequate amount of TTB (20 wt-%) was found to possess the largest H1 (0.60 GPa) and E1 (9.23 GPa), as well as the best scratch resistance.
Conclusion
M. Rivera, I. Lopez, V. Dolidze, F. Aliev
Department of Physics, University of Puerto Rico, PO BOX 23343, San Juan, PR 00931-3343, USA (fmaliev / uprrp.edu)
We report the results of the investigations of the influence of filling of polymer with Aerosil nanosize particles on the glass transition and dynamics of the alpha- and the beta-relaxation processes in poly(butylmethacrylate) by dielectric spectroscopy and differential scanning calorimetry (DSC). The polymer was filled with hydrophilic and hydrophobic Aerosil particles of 12 nm diameter.
Both the alpha- and the beta- relaxation processes were observed in filled polymer. However in filled polymers the characteristic frequency of the alpha-process was shifted to higher frequencies in comparison with pure bulk polymer at the same temperature. This suggests that the filling of the polymer with nanoparticles has resulted in the shift of its glass transition temperature Tg.
This change in Tg was mainly due to the existence of a developed solid particle-polymer interface and the difference in the dynamic behavior of the polymer in the surface layers at this interface compared to the bulk behavior. This result was in agreement with DSC experiments.
The filling of the polymer with both hydrophilic and hydrophobic particles does not affect the beta-relaxation process. Variations of size of filling particles and their concentration are helpful in understanding of relaxation properties at polymer - solid interface as well as of a role of surface interactions in glass transition.
M. Špírkováa, L. Brožováa, O. Bláhováb
a Institute of
Macromolecular Chemistry AS CR, v. v. i., Heyrovsky Sq. 2,
162 06 Prague 6, Czech Republic; (spirkova / imc.cas.cz, brozova
/ imc.cas.cz,https://www.imc.cas.cz)
b Faculty of Mechanical Engineering, University of West Bohemia, Univerzitní 22, 306 14 Plzeň, Czech Republic;( blahova / ums.zcu.cz, http://www.fst.zcu.cz)
Hybrid organic inorganic (O-I) nanocomposite coatings were prepared on the basis of two consecutive and independent processes: sol-gel process (build-up of inorganic structures with epoxide-functions in situ) and polyaddition reaction (epoxy network formation with amines). These transparent and colorless coatings or free-standing films, featured by high degree of self-assembly of O-I matrix, contained also unmodified or chemically modified montmorillonite (MMT) platelets in concentration up to 5 wt. %.
Utility properties for potential practical use, namely gas transport properties (permeability measurements to hydrogen and oxygen), surface hardness (expressed as scratch resistance acquired from AFM experiments or Vicker dynamic hardness given from nanoindentation experiments), and wear properties (friction and wear coefficients obtained from tribology experiments) were tested for both nanoparticle-free matrix and for system containing MMT sheets. The results are compared with O-I matrix containing colloidal silica particles.
It was found that end properties of these systems markedly depend (beside concentration dependence) also on the kind of MMT modification. For potential practical use, coatings having temperature of glass transition temperature close to 20 0C and concentration 1 wt. % of unmodified MMT seems to be the most prospective.
The authors wish to thank the Grant Agency of the Academy of Sciences of the Czech Republic (grant A400500505) for financial support. Nanoindentation analysis was supported by the project of the Ministry of Education, Youth and Sports of the Czech Republic MSM 4977751303.
A.N. Shumakov, V. E. Yudin, V. M. Svetlichnyi, A.L. Didenko, E.N. Popova
Laboratory of Mechanical Properties of Polymers, Institute of Macromolecular Compounds, Russian Academy of Sciences, V.O. Bolshoy pr. 31, St. Petersburg, 199004, Russia (ashn / nm.ru, http://www.macro.ru)
Polymer composites containing dispersed nanoparticles present a class of materials with combination of properties generally not obtainable in conventional polymer composites. Among nanoparticles, carbon nanoparticles (CNP) are more attractive due to their extraordinary mechanical, electrical properties and large surface area which creates large interfacial area. The incorporation only small amounts of CNP to polymer can improve material properties sufficiently on conditions that CNP are properly dispersed in polymer volume.
We have been investigating the influence of carbon nanoparticles with different morphology such as Vapor-Grown Carbon Fibers (VGCF, Showa Denko Co.), Carbon Nanocones (CNC, n-TEC Co.) and Astralens (ASTRIN Inc.) on mechanical, rheological, electrical and tribological properties of semicrystalline (Tg=205°C, Tm=320°C) polyimide R-BAPB:
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This thermoplastic polyimide (PI) offer several advantages over conventional thermoset PI as matrices for advanced composite materials. In addition to the common high thermal stability and ability to be melt-processed by conventional techniques, they have high mechanical properties, stability to solvents and adhesion to filler.
It has been determined that CNP improve some properties of this PI. These are increase of Young modulus, electro-conductivity and extent of crystallinity of samples containing CNP as compared with unfilled samples. It was shown that the effect of CNP on PI type R-BAPB properties is not similar for particles with different morphologies. Thus, the aspect ratio, size and surface structure of nanoparticles have considerable influence on properties of final nanocomposites.
A. Stathopoulosa, P. Klonosa, P. Pissisa, M.M. Pradasb, J.L. Gomez Ribellesb
aNational Technical University of Athens, Physics Department, Zografou Campus, 157 73 Athens, Greece (astathop / central.ntua.gr)
bDepartment of Applied Thermodynamics, Universidad Politecnica de Valencia, P.O. Box 2201 2, E-46071 Valencia, Spain
Polyhydroxyethyl acrylates and methacrylates are representatives of some of the most important organic materials with many medical applications in majority. These hydrogels are biocompatible due to hydroxyl end groups and have an important ability to sorb remarkable amounts of water (hydrophilicity). However, the high amounts of water, present in human body, induce a not desirable instability in these materials. In order to improve their mechanical properties PHEA networks were modified with a hydrophobic component of PEA and the addition of silica inorganic phase (SiO2) via sol-gel method.
Thermally Stimulated Depolarization Currents (TSDC) technique was applied in order to study dielectrically the effect of water on copolymers of P(HEA-co-EA) with different contents of silica and PHEA or PEA compositions. The glass transition temperature of these systems has a strong dependence not only from the composition of the PHEA and PEA, but with the content of silica as well, presenting an increasing for higher amounts of silica. Increase in water content results in a significant decrease of Tg, which dielectrically is interpreted as plasticization of the α-relaxation. Another important observation is the existence of the βswrelaxation, which is affiliated to the rotational motion of the hydroxyl groups, which are strongly connected with water molecules via hydrogen bonding. This relaxation has a tendency to increase with water content and to shift to lower temperatures.
C. Ramírez, M. Rico, J. López, B. Montero, M. Ladra.
Departamento de Física, E.U.P. Ferrol, Universidad de A Coruña. Avda. 19 de Febrero s/n, Ferrol 15405, Spain.(labpolim / udc.es)
The morphologies generated by polymerization induced phase separation (PIPS) in different epoxy-amine systems modified with a thermoplastic, polystyrene (PS), were studied by SEM. The amino groups of the epoxy-amine systems were provided by a monoamine (MA) and a diamine (DA) in different proportions, so that the resulting polymer would vary from a linear polymer (epoxy-MA) to a highly crosslinked polymer (epoxy-DA).
The effects of reaction temperature, initial modifier concentration and degree of crosslinking of epoxy-amine system on the morphology: size, distribution and concentration of dispersed particles were discussed.
Different types
of morphologies1 were obtained depending on the
initial PS content: a) modifier particles dispersed in an epoxy
matrix (sea-island morphology), b) nodular epoxy particles
dispersed in modifier matrix (epoxy nodular morphology), c)
morphology of dual phase having both, sea-island and nodular
structure, which is typical of compositions near the critical
point.
This morphology was obtained for blends containing 9 and 12%wt. of PS
1) J.W. Park, S.C. Kim in IPNs
Around the World; S.C. Kim, L.H. Sperling Eds.; John Wiley
& Sons; Chichester, 1997, 27-48.
H. Shimizu, Y. Li
Nanotechnology Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki, 305-8565 Japan (shimizu-hiro / aist.go.jp)
The fabrication
of nanostructured polymer blends or alloys raises much hope, but
poses significant scientific and industrial challenges over the
past several decades. We have recently developed a high-shear
extruder, HSE3000mini. The extruder can reach a maximum screw
rotation speed of 3000 rpm, which rorresponds to the average
shear rate of 4410 sec-1 at the region of top part
of the screw. The specially designed feedback-type screw was used
to make the sample to circulate in the extruder during melt
blending. The high shear extruder has been successfully used to
prepare a novel nano-dispersed poly(vinylidene fluoride)
(PVDF)/polyamide 11 (PA11) polymer blend (H. Shimizu. et al. Macromolecules
2005, 38:7880). In this work, we try to apply this
technique to another polymer blend system, PVDF/poly(lactide
acid) (PLLA). Both PVDF and PLLA have been reported to show
strong ferro- and piezo- electricity. It is great interest to
blend the two polymers aiming at preparing the new ferroelectric
polymer material. Here high-shear processing was applied to this
blend system to improve the miscibility between PVDF and PLLA.
Figure 1 shows a
typical phase morphology of PVDF/PLLA=80/20 blend prepared with
the screw rotation speed of 1200 rpm (shear rate :1764 sec-1).
A co-continous morphology was clear observed with the phase size
of about 2 mm. The detail observation of the image indicates that
many PLLA domains with the size of less than 200nm are dispersed
in the PVDF phase. The improved miscibility between the two
compoents by high shear processing has been confirmed by dynamic
mechanical analysis (Fig. 2). The high-shear processed sample has
the reduced glass transition temperatrue compared to the
low-shear processed sample. In addition, the mechnical and
electrical properties were also systematically investigated and
will be reported during the conference.
M.A. Morris1,2, J.D. Holmes1,2 , M. Shaw1,2,3
Addresses and Email addresses: All mail should be addressed to: m.morris / ucc.ie. 1Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin, Ireland; 2Department of Chemistry, University College Cork, Ireland; 3Intel, Leixlip, Ireland.
As feature sizes in microelectronic circuitry reach ever smaller sizes the use of conventional lithography becomes ever more challenging. Advanced uv-lithographic ('top-down') methods may define feature sizes of 20 nm in the near future but beyond this scale fabrication facilities become prohibitively expensive and materials issues (such as masks and resists) may provide technological barriers to implementation. Self-assembly ('bottom-up') is often proposed as an alternative means of generating nano-structural architectures that might generate nano-scale electronic devices (such as CMOS) in smaller dimensions. However, self-assembled systems have low long range order and relatively high defect densities. To use these systems for development of practical CMOS circuitry these nano-architectures must be defined with absolute precision and periodicity over a 300 mm or 450 mm substrate. It is suggested here that microphase separation in block co-polymer systems affords the opportunity for the greatest structural control.
The random, 'finger-print', patterns created by phase separation in co-polymer thin films limits their applicability in electronics processing but by combining self-assembly with topographically engineered substrates highly regular 'defect-free' and aligned nanostructures can be produced. In this paper we outline substrate design and polymer processing to generate sub-15 nm feature size nanopatterns on silicon substrates. These patterns are based on the production of hexagonal arrays of cylinders of one of the polymer blocks in the background matrix. Various co-polymer systems (e.g. polystyrene-polyisoprene, polymethylmethacrylate-polystyrene) are described together with a comparison of their effectiveness in generating small feature size patterns. An experimental phase diagram was determined. We also show that the thickness of the polymer thin film can be controlled to within 1 - 2 nm using simple spin-coating from solvent. This precision allows us to control the orientation (to the substrate) of the phase separated polymer cylinders. We show that complex shapes and patterns can be formed using substrate engineering and that the techniques can be used to generate polymer alignment across 10 cm substrates. The patterns generated are described in terms of potential CMOS circuitry that might be developed
We also show how dry and wet etch techniques can be used to selectively remove one polymer block to generate 'templates' for placement of nanowires and nanotubes. These templates are rigid and chemically stable and we describe the development of gold nanowires and carbon nanotubes using both surface and polymer functionalisation. The potential future application of block co-polymers in nanoelectronic circuitry processing is described.
M.H. Hwanga, H.W. Leea, E.M. Leea, B.C. Jia, J.H. Yeuma, S.M. Parkb
aDepartment of Advanced Organic Materials Science and Engineering, Kyungpook National University, Daegu 702-701, Republic of Korea (jhyeum / knu.ac.kr)
bR & D Division/Test & Analysis Team, Korea Dyeing Technology Center, Daegu 703-834, Republic of Korea
Electrospinning is a relatively old technique used in polymer technology to spin small diameter fibers, which has recently found applications in tissue engineering as a scaffold fabrication tool. It consists of spinning fibers from a material solution, typically a polymer, by exploiting a high electric field generated between the solution depot and a collector unit.
In this study, poly(vinyl alcohol) (PVA)/chitosan nanofibers containing silver nanoparticles were prepared by electrospinning PVA/chitosan/silver aqueous solutions. Properties of the PVA/chitosan/silver solutions including viscosity, conductivity, and surface tension were measured, and effects of the polymer concentration, silver concentration, PVA/chitosan mass ratio and processing parameters on the electrospinnability of PVA/chitosan/silver were investigated.
With increasing PVA content, the morphology of blend nanofibers was changed from beaded fiber to uniform fiber. The PVA/chitosan blend nanofibers with silver nanoparticles showed very strong antimicrobial activity as well as high water uptake.
B. Gorzolnik, J. Babinot, N. Lacoudre, J. Penelle, D. Grande
Equipe « Systèmes Polymères Complexes », Institut de Chimie et des Matériaux Paris-Est, UMR 7182 CNRS - Université Paris XII, 2 rue Henri Dunant, 94320 Thiais, France (gorzolnik / glvt-cnrs.fr, grande / glvt-cnrs.fr)
It is a great challenge to produce mesoporous polymeric membranes with a simultaneous control of porosity and functionality (surface chemistry), while maintaining good mechanical properties and chemical stability. There is a need to obtain such functional mesoporous membranes by simple and highly reproducible approaches, being cost-effective and compatible with the production of materials at an industrial scale.
In this study, two alternative approaches leading to functional porous frameworks are envisioned and compared. The first approach relies on the synthesis of well-defined polystyrene-block-poly(D,L-lactide) (PS-b-PLA) diblock copolymers with a functional group (e.g. carboxylic acid group) at the junction between the two blocks. By proper selection of copolymer composition, polymer systems with preferentially cylindrical morphology (PLA cylinders in PS matrix) can be obtained. The PLA block is subsequently removed by hydrolysis, leaving behind a porous PS membrane with functional groups located along the walls of the channels. The second synthetic strategy entails the preparation of acid-functionalized polystyrene PS/PLA-based Interpenetrating Polymer Networks (IPNs), where the styrenic sub-network serves as the future membrane material, whereas the polyester partner can be selectively hydrolyzed under mild conditions in a subsequent step.
The possibilities afforded by both approaches are discussed; the precursors as well as the resultant porous materials are characterized by various physico-chemical techniques. Obtained functional nanoporous materials are of potential interest in supported catalysis, advanced filtration, and selective transport applications.
Acknowledgments. The financial support of the National Agency for Research (programme ANR/PNANO 2005, project POLYNANOCAT "ANR-05-NANO-025") is gratefully acknowledged.
E.S. Trofimchuk a, N.I. Nikonorovaa, E.A. Nesterova a, A.M.Muzafarov b, N.Ph. Bakeev a
aDivision of Polymer, Department of Chemistry, M.V. Lomonossov Moscow State University, Lenin Hills 1-3, Mocow, 119992, Russia (elena_trofimchuk / mail.ru)
bInstitute of Synthetic Polymer Materials, Russian Academy of Science, Profsoyuznaya ul. 70, Moscow, 117393, Russia
Solvent crazing is a fundamental property of solid amorphous and semi-crystalline polymers. In the crazing a polymer passes into high dispersed and oriented state, and the nanoporous system is formed. This method allows a polymer be filled uniformly with the second component and to disperse filler effectively to nanometrical level.
In this work hyperbranched polyethoxysiloxane (HPEOS) is suggested as an adsorption-active medium in the crazing of commercial polymer films (isotactic PP, HDPE and PET) and as a precursor of silica. HPEOS (Mw=30000) is a low-viscosity liquid (18 CP) and has ethoxy groups. Yield point of a polymer was found to reduce on 15 % in HPEOS at extension rate of 10-100 %/min that point to the formation of crazes inside the polymer. Two crazing mechanism (classical and delocalized) depending on a polymer type were realized.
After introduction of HPEOS into polymer matrices it can be transform to silica via hydrolytic polycondensation in a volume of pores. The content of filler in the composite can be achieved 45 wt.%. Solid silica phase was discovered to prevent collapse of the fine fibrillar porous system of a polymer. On the basis of TEM and SEM investigations we suggest that the structure of obtained composites is a system of two interpenetrating nets: polymer (organic net) and silica (inorganic net).
This structure permits us to increase tensile modulus of material in 1.5-2 times. The surface of composite films is hydrophilic and they possess unusual sorption properties in relation to vapors of different liquids (e.g. water, alcohol, ester, and others).
This work has been financially supported by the Russian Foundation for Basic Research (project 05-03-32482) and by the Grant of President of Russian Federation (project MK-3532.2007.3).
H. Yabua,b,c, Y. Hiraid, M. Shimomuraa,b,c
aIMRAM, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
bFrontier Research System, RIKEN, Japan
cCREST, Japan Science and Technology Agency, Japan
dGraduate School of Science, Hokkaido University, Japan
(yabu / tagen.tohoku.ac.jp)
Microporous polymer films are attractive materials due to their potential applications for some practical applications. We have reported simple casting process under humid condition to fabricate microporous polymer films by using condensed water droplet arrays on the solution as templates [1]. Here, we show preparation of metal-polymer hybrid porous films by using this self-organization process and electroless plating.
Microporous polymer films were prepared by casting a
chloroform solution of hydrophobic polymers (eg. poly-e-caprolacton
(PCL), scheme 1) and amphipilic copolymer (1) on a solid
substrate under humid condition. After preparation of microporous
film, thin palladium and platinum (Pd/Pt) layers were suputtered
onto the surface of the film. The Pd/Pt covered microporous film
was soaked in electroless plating solution containing silver ion
and reducer. After rising with water, the film was obsereved and
characterized by using a scanning electron microscope (SEM), an
atomic force microscope (AFM), an X-ray photoelectron
spectrometer (XPS), and an UV-Vis spectrometer. These
measurements reveal the metal-polymer hybrid porous film was
formed, and it has unique viewing angle limitation properties
(Figure 1).
[1] H. Yabu, M. Tanaka, K. Ijiro, M. Shimomura, Langmuir., 19(15), (2003)
[2] H. Yabu, Y. Hirai, M. Shimomura, Langmuir, 21(23), (2006)
I.Yu. Dmitriev, J. Baldrian*, E.Yu. Rosova, G.K. Elyashevich
Institute of Macromolecular Compounds, Russian Academy of Sciences, Bolshoi pr. 31, Saint-Petersburg 199004, Russia, (dmitriev / hq.macro.ru); *Institute of Macromolecular Chemistry, Czech Academy of Sciences, Heyrovski sq. 2, 16206 Prague 6,Czech Republic
Composite systems were prepared by oxidative polymerization of polypyrrole (PPy) in monomer solution on the surface of porous poly(vinylidene fluoride) (PVDF) films.
Porous structure of linear PVDF (Мw=190000) was formed by uniaxial extension of extruded and subsequently annealed films. According to X-ray diffraction investigations the crystalline phase of porous films consists of 100% piezoactive crystallites of polar β-form with sizes 12 nm, and supermolecular structure of this porous films is described by the hierarchy of structure elements in a wide range of nanosizes. Maximal overall porosity of PVDF films is 20%. Porous films contain a closed and opened to the surface pores. It was measured by mercury porosimetry that maximum of pore size distribution is located on interval 20 -100 nm. Content of PPy in the composites reached 9%. Specific surface of the samples after PPy deposition decreases from 16.0 to 10.5 m2/g in result of blocking of pores by conducting polymer. A very high adhesion of PPy layers to porous support was observed.
The effect of polymerization conditions on electroconductivity of composites has been investigated. It was established that maximal conductivity of the composites was reached at using of water-methanol solution (1:1).
The work is supported by Russian Foundation of Basic Research (Grant №07-03-00177-a) and by the Programme of Basic Research, Russian Academy of Sciences Division of Chemistry and Material Sciences, "Electroconducting and electroactive Polymers" (2006-2008).
M. Kojimaa, H. Yabub,c,d, M. Shimomurab,c,d
aGraduate School of Engineering, Tohoku University, 6-6-04, Aramaki Aza Aoba, Aoba-ku, Sendai, Japan (kojima / mail.tagen.tohoku.ac.jp)
bIMRAM, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai, Japan
cFrontier Research System, RIKEN, Japan
dCREST, Japan Science and Technology Agency, Japan
Microporous polymer films are attractive materials
due to their applications including filtration membranes,
photonic devices, and biomaterials. We have reported that
honeycomb-patterned porous films can be prepared by casting a
polymer solution of amphiphilic copolymer and hydrophobic polymer
under humid condition by using condensed water droplets formed on
a solution surface as templates [1]. In order for applications,
porous films need high stability. We have also reported
preparation of the honeycomb-patterned film with high solvent
stability by using photo-crosslinkable resin [2]. However, the
amphiphilic copolymer without cross-linkable groups was used, the
condensation of amphiphilic copolymer seems to induce the lack of
the film. In this report, we observed the distribution of the
amphiphilic copolymer in the honeycomb-patterned film by using a
confocal laser scanning microscope (CLSM).
A chloroform solution of amphiphilic copolymer 1 containing fluorescence moieties and polystyrene (PSt) (1:PSt=1:10) was cast on a solid substrate under humid condition. After solvent evaporation, the honeycomb-patterned polymer film was obtained (Fig. 1).
The CLSM image shows that the amphiphilic copolymer in the honeycomb-patterned film condensed around pores of the film to stabilize the template water droplets (Fig. 2).
[1] H. Yabu, Y. Hirai, M. Shimomura, Langmuir 22, 2006, 9760
[2] H. Yabu, M. Kojima, M. Tsubouchi, S. Onoue, M. Sugitani, M. Shimomura, Colloids and Surfaces A. 284-285, 2006, 254
D. GROMADZKIa,b, R. MAKUŠKAb, M. NETOPILÍKa, J. LOKAJa, M. JANATAa, O. DIATc, P. ŠTĚPÁNEKa
a Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky Sq. 2, 162 06 Prague 6, Czech Republic
b Department of Polymer Chemistry, Vilnius University, Naugarduko 24, LT-03225 Vilnius, Lithuania
c Structure et Propriétés d´Architectures Moléculaires, UMR 5819 (CEA-CNRS-UJF), DRFMC/SPrAM, CEA-Grenoble, 38054 Grenoble cedex 9, France
Comb copolymers consisting of polystyrene backbone and poly(tert-butyl methacrylate) (PtBuMA) side chains were synthesized by a combination of nitroxide-mediated (NMP) and iniferter controlled radical polymerization techniques. First, poly(chloromethylstyrene) with (DP)n = 196 and two random poly(styrene-co-chloromethylstyrene) copolymers with similar degree of polymerization (DP)n ~ 75 but different content of CMS units (8 and 14 mol %) were synthesized by NMP process. In the second step CMS units both in the homopolymer and the copolymers were converted to N,N-diethyldithiocarbamyl groups (DC) yielding photosensitive macro-iniferters. Finally, the photo-induced "graft from" polymerization was performed in THF solution. Grafting initiated by the macro-iniferters containing lower number of DC groups proceeded by a pseudo-living polymerization mechanism, i.e. the number-average molecular weight increased with conversion and the produced brushes showed low polydispersity index. Synthesis of molecular brushes using iniferter technique was ill-controlled as revealed by GPC. Aggregation behaviour of the synthesized polymers in various solvents was studied by dynamic light scattering and viscometry.
Support by the European Commission through a Marie Curie Research Training Network Self-organization under Confinement MCRTN-SOCON is gratefully acknowledged.
The Academy of Sciences of the Czech Republic (projects No. AVOZ 40500505, A100500501, A4050403, A400500703 and A4050409.) and the Czech Science Foundation (project Nos 203/07/0659 and 203/07/0987) are gratefully acknowledged for financing.
Y. Bolbukh1, P. Kuzema1, V. Tertykh1, B. Gawdzik2
aInstitute of Surface Chemistry, National Academy of Sciences of the Ukraine, General Naumov Str. 17, 03164 Kyiv, Ukraine (bolbukh / yahoo.com, tertykh / public.ua.net)
bFaculty of Chemistry, Maria Curie-Sklodowska University, V/C/Sklodowska Sq. 3,20031 Lublin,poland (barbara / hermes.umcs.lublin.pl )
Polymeric microspheres based on copolymer styrene cross-linked with divinylbenzene are attractive materials for a wide number of applications. The main disadvantage of the polystyrene phases is their sensitivity to solvent changes (shrinkage or swelling) associated with the presence of pores. Embedding of inorganic nanoparticles into these polymers presumably will allow improving their operational characteristics. The most commonly used filler for such systems is high-disperse silica.
The aim of this work was to investigate the change in the internal morphologies of styrene-divinylbenzene copolymers related to the presence of silica fillers with different amount of chemically active surface groups. The filled porous polymers were obtained by combined suspension-emulsion polymerization in the presence of silica fillers with different surface chemistry. As fillers a fumed silica with attached trimethylsilyl or both trimethylsilyl and silicon hydride groups were used. The copolymer internal structure resistance to solvent action was studied by treatment with benzene and following analysis of aniline or n-chloroaniline adsorption. The swelling degree was determined as difference of adsorption capacity before and after the solvent treatment. Adsorption of aniline or n-chloroaniline was performed at 20°C from aqueous solution in a concentration interval 0.055-0.0027 or 0.3×10-3-0.006×10-3 mol/l, respectively. Concentration of adsorbate in solution was determined by photometric analysis.
It was found that the morphological changes of polymer spheres are reflected in the isotherm type and adsorption capacity change. The silica with near 30 % of grafted trimethylsilyl groups was the most effective. The filling with modified silicas with surface trimethylsilyl or trimethylsilyl and silicon hydride groups results in the substantial increase of copolymer resistance against the swelling in benzene. The presence of silicon hydride groups on silica surface leads to loosened structure formation; however, the swelling resistance is increased.
A. Szilágyia,b, K. Sumarua, T. Shinboa, M. Zrínyib, T. Kanamoria
aResearch Center of Advanced Bionics, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8565, Japan (aszilagyi / mail.bme.hu)
bHAS-BME Materials Structure and Modeling Research Group, Department of Physical Chemistry and Materials Science, Budapest University of Technology and Economics, Budapest 1521, Hungary
Shape memory materials can be deformed and fixed into a temporary shape, and recover their original, permanent shape only on exposure to an external stimulus. Advanced properties of polymer gels combined with shape memory effect received an increasing interest because of their scientific and technological significance. In spite of remarkable properties of polymer gels, their applicability is restricted due to their poor mechanical stability.
Haraguchi et al. have developed a new type of nanocomposite (NC) hydrogel composed of poly(N-isopropylacrylamide) (pNIPAAm) and inorganic clay which shows improved mechanical and swelling/shrinking properties compare to chemically cross-linked pNIPAAm hydrogels. In this hydrogel, exfoliated and uniformly dispersed clay particles act as multifunctional cross-links.
In this study, we report the preparation of pNIPAAm-clay NC gels in aqueous media and swelling properties in different organic aqueous solutions. Organic-inorganic nanocomposite gels frequently exhibit unexpected hybrid properties synergistically derived from the two components. We show a unique shape memory behavior of pNIPAAm-clay NC gels, which can be induced by the change in solvent composition.
We also report the photo-induced volume change of pNIPAAm-clay nanocomposite gels functionalized with photochromic spirobenzopyran, which isomerizes to hydrophobic structure dissociating proton in response to blue light irradiation.
B. Strachotováa*, A. Strachotaa, M. Uchmanb, M. Šloufa, J. Spěváčeka, J. Pleštila, L. Matějkaa
aInstitute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, 162 06 Prague, Czech Republic (beata / imc.cas.cz)
bCharles University, Department of Physical and Macromolecular Chemistry, Albertov 2030, Prague, 12840 2 Czech Republic
Organic-inorganic hydrogels with a highly porous structure showing a very fast temperature response were studied. The gels were obtained from N‑isopropylacrylamide (NIPA), N,N'‑methylenebisacrylamide (BAA) and tetramethoxysilane (TMOS) by simultaneous radical polymerization and hydrolytic polycondensation of TMOS.
The pores were generated by the crystallization of a part of the solvent (freezing). The inorganic silica phase was shown previously by the authors to stabilize the porous structure and thus to enable very fast swelling and deswelling (ca. 6 s for each process).
In this contribution, the effects of synthesis parameters on the final hydrogel properties are studied: The effect of the incorporated silica amount and the effect of the content on chemical crosslinker BAA were investigated. Some aspects of the NIPA polymerization kinetics under the synthesis conditions will be presented as well.
Acknowledgment
The authors thank the Grant Agency of the Czech Republic, Grant Nr. 203/05/2252 for the financial support of this work.
G. Huerta, A. Strachota, B. Strachotová, L. Matějka
Department of Polymer Networks and Mechanical Properties, Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovského nám. 2, CZ-162 06 Praha 6, Czech Republic.
In this contribution, we will present new P(NIPAAm-co-SA) hydrogels containing titanium dioxide nanoparticles, which were synthesized by free radical polymerization in water with Bis-acrylamide (BAA) as the crosslinker and the system ammonium peroxodisulfate(APS) /N, N, N', N'‑tetramethylethylenediamine (TEMED) as base catalyst. The hydrogels showed dual pH and temperature sensitivity. The influence of relative content of comonomer on the swelling ratio of the crosslinked hydrogel was examined. The presence of the inorganic phase improves the mechanical properties of the gels. The syntheses were carried out at temperatures below the lower critical solution temperature (LCST) of poly(N-isopropylacrylamide) in two steps: During the first stage the temperature was held at T = +15 °C and during the second the temperature was fixed at T = -18 °C. The ice crystals, which grew during the second stage, served as the pore-forming agent.
Acknowledgments
The authors thank the UNESCO and the IUPAC, Project "Postgraduate Course in Polymer Science 2006/2007" and the Grant Agency of the Czech Republic, Grant Nr. 203/05/2252 for the financial support of this work.
H. Macková, D. Králová, D. Horák
Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky Sq. 2, CZ-162 06 Prague 6, Czech Republic (mackova / imc.cas.cz,)
Intelligent environment-sensitive and magnetic microspheres have been the subject of extensive research and development because their volume changes (swelling or shrinking transition) could be triggered by various external stimuli, such as temperature, solvent composition, hydrostatic pressure, electric field, antigen and radiation. The prominent role is played here by temperature-sensitive gels, important representative of which is nonionic poly(N-isopropylacrylamide) (PNIPAAm). PNIPAAm shrinks and/or swells in water in response to changes in temperature. The changes occur at ~ 32 °C (volume-phase transition temperature).
Magnetic PNIPAAm-based microspheres were prepared by inverse emulsion polymerization in paraffin oil in the presence of in situ precipitated maghemite (γ-Fe2O3) nanoparticles. The effect of several reaction parameters, such as the type and concentration of crosslinker (N,N'-methylenebisacrylamide, MBAAm), concentration of γ-Fe2O3, initiator (2,2′-azobis(2-methyloctanenitrile), emulsifier (Span 80) and polymerization temperature on the properties were examined. The magnetic microspheres were characterized in terms of their chemical structure, size and polydispersity and morphological and temperature-induced swelling properties. The particle size decreased with the increasing degree of crosslinking, concentration of γ-Fe2O3 nanoparticles, emulsifier and initiator. The particles exhibited thermosensitivity at the degree of crosslinking 10 wt.% and less, with the volume phase transition at ca. 35 °C as confirmed by swelling measurements. The microspheres contained ca. 8 wt.% of iron. The presence of magnetic nanoparticles and their concentration did not significantly affect the temperature sensitivity of the composites.
Financial support of the Grant Agency of the Czech Republic (203/05/2256) is acknowledged.
N. Solomko, O. Budishevska, S. Voronov
Lviv Polytechnic National University, 12 Bandera Str., Lviv, 79013, Ukraine
For the creation of the polymeric biomaterials, which can be applied as a means for the drug delivery, the implants, the antiburning covering, for designing fabrics, the hydrogels on the basis of the natural polymers, in particular, the chitosan are perspective. The creation of the hydrogels, which are changing theyself volume at the change of the external conditions - pH, the temperature, the chemical composition, the radiation treatment, so-called the "smart" hydrogels, is the especially important problem in the chemistry of the medicobiological polymers.
The pH-dependent hydrogels were obtained by the radical cross-linking of the peroxided derivative of the chitosan (Chi-PM) or the radical grafting copolymerization of Chi-PM and the vinylpyrrolidone (VP) with the formation of the network structure copolymers.
The Chi-PM represents the chitosan salt with the regulated amount of the primary-tertiary peroxide fragments which is formed by the β-D-2-desoxy-2-aminoglucopyranosidic links with the ether tert- butylperoxymethylmaleate (PM):
The radicals, which are formed in result of the thermal decomposition of the primary-tertiary peroxide groups (PM) in the structure of the Chi-PM, carry out initiation of the radical reactions, including the vinylpyrrolidone homopolymerization, the cross-linking reactions of macromolecules and the forming of the hydrogels network. The initiating radicals do not allow the chitosan chain destruction, that is feature of the presented grafting copolymerization of the chitosan. It is determined, that the grafting efficiency of the polyvinylpyrrolidone makes up 60-95 %.
It is shown, that the rate and the value of the equilibrium swelling (Еe) of the obtained hydrogels depend on the ratio of Chi, PM, VP and рН of the medium. The Еe of the obtained hydrogels is changing in the range 30±15000%. The studies of the equilibrium swelling dependence of the obtained hydrogels from pH has shown, that there is the certain value of the medium рН for each of the samples. At these values as the result is an abrupt change of the volume, or "collapse", which can be changed in the range from рН 5 up to рН 7.
F. Nastase, C. Nastase, A. Morozan, A. Dumitru, S. Vulpe, I. Stamatin
3Nano-SAE Research Centre, University of Bucharest, Atomiştilor 405, P.O. Box MG-38, Bucharest-Magurele 077125, Romania (adina / 3nanosae.unibuc.ro, http://www.3nanosae.unibuc.ro)
The unique architecture and remarkable mechanical and electrical properties of carbon nanotubes (CNTs) envisage a great potential that remains, however, unexploited due to its poor dispersal in liquids and other processing problems. A co-spraying technique of a binary mixture thiophene-CNT in a plasma stream is proposed as alternative to chemical and electrochemical methods for nanotube functionalizing. FT-IR and Raman spectra were taken in order to analyze the structural properties of the resulting nanocomposites. Spectroscopic measurements indicate a chemical bonding between polymer matrix and nanotube surface. Surface micrograph obtained by Atomic Force Microscope (AFM) shows a smooth surface of the nanocomposites films. I-V characteristics present a combined effect of the conduction mechanisms imposed by SLCS and metallic/semi-metallic character of the nanotubes.
A. Morozan, A. Dumitru, C. Nastase, I. Stamatin, F. Nastase
3Nano-SAE Research Centre, University of Bucharest, Atomiştilor 405, P.O. Box MG-38, Bucharest-Magurele 077125, Romania (adina / 3nanosae.unibuc.ro, http://www.3nanosae.unibuc.ro)
Confidence in the potential of hydrogen as an energy vector and fuel bring the opportunities for enhancing electrolyser performance. The aim of this paper is to develop a new polymer electrolyte membrane structure for PEM-electrolyser. A series of nanocomposite membranes, including Nafion/ TiO2, Nafion/CNT, Nafion/TiO2CNT have been developed and characterized by RAMAN and FT-IR spectroscopy and AFM. The protonic conductivity of composites membrane was studied using a BekkTech® conductivity test cell. The application of nanocomposite membranes in electrochemical cells for water electrolysis was investigated. Experimental results obtained with respect to performance and longtime stability are reported and discussed related to Nafion membrane; further lines of development are indicated.
O. A. Smyrnov
Department of Theoretical Physics, Odessa I. I. Mechnikov National University, 2 Dvoryanskaya St., Odessa 65026, Ukraine (E-mail: smyrnov / onu.edu.ua)
The charge screening in isolated metallic and semiconducting single-walled carbon nanotubes (SWCNTs) is described in the random phase approximation (RPA). The spectrum of large radius excitons in semiconducting nanotubes is studied in the framework of elementary potential model, in which exciton is modeled as bound state of two oppositely charged quasi-particles confined on the tube surface and interacting through the obtained screened Coulomb potential. Due to the parity of the screened potential exciton states split into the odd and even series. It is shown that the binding energy of even excitons, calculated on the base of the null-range potential model for the initial band electrons spectra and the Bloch wave functions, in the ground state well exceeds the energy gap.
V. Peoglosa, Ch. Pandisa, E. Logakisa, A. Kyritsisa, P. Pissisa, P. Pötschkeb, J. Pionteckb, M. Omastovác, M. Mičušíkc
aNational Technical University of Athens, Zografou Campus 15780, Athens, Greece (vaselpi / central.ntua.gr)
bLeibniz Institute of Polymer Research Dresden, 01069, Dresden, Germany
cPolymer Institute, Slovak Academy of Sciences, 842 36,Bratislava, Slovakia
Nanocomposites of carbon nanotubes (CNTs) in various polymeric matrices have attracted considerable attention, especially the latest years, due to their exceptional mechanical and electrical properties. These unique characteristics stem from the distinct properties of the CNTs themselves. The nano size scale, very high aspect ratio (~ 1000), low density and exceptional mechanical and electrical properties of CNTs combined with the advantages of polymers, provide materials with potential applications as electromagnetic shielding coatings, electrostatically dissipative materials, aerospace structural materials and active elements in sensors.
In the present study, the nanocomposites were prepared by mixing a starting masterbatch of various polymers (such as polypropylene (PP) and polymamide 6) and 20 wt% multi-walled carbon nanotubes (MWCNTs) (Hyperion Catalysis) with the pure polymers in a Plasti-corder kneading machine PLE 331, followed by compression moulding using a laboratory hydraulic press SRA 100 in order to take different concentrations in CNTs. The final concentration of the samples in CNTs was varied from 0.1 to 20 wt%.
Structure-property relationships are investigated using various techniques: differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), measurements of volume and surface conductivity and dielectic relaxation spectroscopy (DRS). Attention is paid to the investigation of percolation, the transition from insulating to conducting phase through a conducting pathway formed by CNTs, by conductivity measurements for the samples above the percolation threshold (φc) and by dielectric function measurements for the samples below φc.
E. Bolhová, Z. Strecká, A. Ujhelyiová, J. Legéň
Department of Fibres and Textile Chemistry, Institute of Polymer Materials, Faculty of Chemical and Food Technology, Slovak University of Technology in Bratislava, Radlinského 9, 812 37 Bratislava 1, Slovak Republic, email: eva.bolhova / stuba.sk
The aim of this work was the study of the colouristic properties of modified polypropylene fibres by polyvinyl alcohol (PVA) and system polyvinyl alcohol and nanoclay (PVA/NA). The fibres were prepared with the content of 3 wt. % PVA and 3/0.5 wt. % PVA/NA using a pilot-scale equipment with a single-screw extruder with the diameter f = 16 mm. The particle size distribution of nanoclay was made in glycerine (plasticizer for PVA) at the various time of mixing with or without ultrasonication. The modified PP fibres were dyed by disperse dye from dyebath at the temperature of 120°C.
Nanoclay (Cloisite 15A) modified with quaternary ammonium salt was used to make modified PP/PVA/NA fibres. For the dyeing with disperse dye, it is supposed that the interaction between the disperse dye and nanoclay is mainly due to the van der Waals forces and hydrogen bonding.
The content of the PVA improves the dyeability of the modified PP/PVA fibres in comparison with the unmodified PP fibre at 120°C.
The addition of the PVA and NA increases dyeability and colouristic properties of the modified PP/PVA and PP/PVA/NA fibres. Longer homogenizing time of nanoclay in glycerine generally produced comparatively equal dyeing of prepared PP fibres. The dyeabilty of modified PP fibres depends on supermolecular and morphological structure of these fibres and namely on the condition of their preparation.
The influence of homogenizing time with or without ultrasonication on the properties of fibres was evaluated.
G.C. Lees, C.M. Liauw
Faculty of Science and Engineering, Manchester Metropolitan University, Chester Street, Manchester, UK. (g.c.lees / mmu.ac.uk and c.m.liauw / mmu.ac.uk)
The Montmorillonites used in this study were organically modified in the solid state in a Brabender Plasticorder W50e chamber using long chain alkyl(hydrogenated tallow(HT) or stearyl) dimethyl/aryl ammonium chloride intercalant (Quat).
The structures of the intercalated clays were studied using WAXS, FTIR (DRIFTS) and solvent swelling / dispersion viscosity studies.
It was found that the mono-stearyl type Quats were the most suitable intercalants for the subsequent in-situ styrene suspension polymerizations. This was because, in general, the distearyl type Quats led to reduced interfacial effects in the composites and reduced toluene dispersion viscosity due to the close proximity of long alkyl tails which facilitate their self-assembly into ordered arrays within the clay galleries. This makes penetration of the toluene into the galleries more difficult (toluene is used as a probe to gauge gallery compatibility with styrene for the suspension polymerizations) and hence restricts d space expansion and potential for subsequent clay exfoliation. Substitution of a methyl group by a benzyl group on the Quat lead to increased compatibility with toluene though the detrimental effect of two long alkyl chains was not overcome. The Quat level corresponding to maximum dispersion viscosity was selected for the styrene suspension polymerizations.
The effect of Quat level on the WAXS patterns of the intercalated clays confirmed the changing alignment of the alkyl chains on the Quat within the clay galleries and explained how these various alignments would change both the d spacing and the ordering of the alkyl chains within the clay galleries. Recent studies using a flow microcalorimeter have shown that clay "treatment" has a controlling influence on the intercalation mechanism.
In relation to the in-situ suspension polymerization of the clay /styrene systems the effect of different clay levels has been studied. For example, using the stearyl benzyl dimethyl ammonium chloride Quat, as the modified clay level is increased the molar mass distribution progressively broadens. This is a consequence of a slight reduction in the number average molar mass and a significant increase in the weight average molar mass.
H. Kubišováa, D. Měřínskáa, E. Vítková
aDepartment of Polymer Engineering, Faculty of Technology, Tomas Bata University, Nám. T.G. Masaryka 275, CZ-762 72 Zlín, Czech Republic (kubisova / ft.utb.cz)
The work deals with a PP/clay nanocomposites preparation and an evaluation of final level of an intercalation/exfoliation state. The polymer matrix was polypropylene brand named Mosten GB 003 and maleinated polypropylene Exxelor 1015 was added as a compatibilizator. Commercial product Dellite (Dellite 72T and Dellite 67G) was used as nanofiller. This type of nanofiller is according to producer done for polyolefinic matrixes. Samples contained different concentration of nanofiller and were prepared on a compoundation device Brabender. Time of compoundation and rotation speed were variable quantities. Level of sample an intercalation/exfoliation was evaluated by XRD technique which was supported by scanning electronic microscopy (SEM) and transmission electronic microscopy (TEM). Then changes of mechanical properties were measured. There was founded out that the level of an intercalation/exfoliation was not perfect as it can be seen from result of XRD patterns and SEM/TEM pictures. It affirmed that the time of compoundation was not determining for the good level of the exfoliation. Mechanical properties of samples filled by two type of nanofiller showed higher mechanical properties that a pure polypropylene. Better values were reached in case of adding Dellite 67G. To sum up, obtained results did not allowed to create any curves for mathematical description of the relation of used conditions versus clay content or type.
L. Kovářováa*, P.
Zádrapaa, J. Maláča
aDepartment of Polymer Engineering,
Faculty of Technology, Tomas
Bata University in Zlín, Nám. TGM 275, CZ-762 72 Zlín,
The study of polymer/clay nanocomposites is one of the most expanding regions in polymer science. These nanocomposites have many unique properties, such as thermal stability, gas/vapour permeability. Moreover, the increasing of mechanical and other properties can be observed. Following work deals with PVC/clay nanocomposites. Firstly, intercalated clay nanofillers were prepared. Two types of natural clays were selected for modification, namely sodium type of montmorillonite (commercial product Cloisite® Na+) and bentonite (trade named Bentonite P140). These clays were modified by both ion-exchange and ion-dipole intercalation methods. While for the first method the coupling agent, cetyltrimethylammonium chloride, was dissolved in water solution, in the second method two reaction components, essential modifying agent polyethylene glycol and co-intercalation agent isodecyldiphenyl phosphate, were mixed with the clay and then melted. Further, the effectiveness of intercalation was verified by X-ray diffraction and FTIR spectroscopy. Consequently, the modified nanofillers as well as the natural fillers were compounded with suspension type of PVC and other additives using double roll mill to produce sheet. The following properties were measured: mechanical properties, thermal stability and flammability. Finally, the comparison of properties of PVC/clay nanocomposites filled by differently modified clays utilizing two intercalation methods - ion-exchange and ion-dipole was performed.
P. Zádrapaa*, L. Kovářováa,
J. Maláča
aDepartment of Polymer Engineering,
Faculty of Technology, Tomas Bata
University in Zlín, Nám. TGM 275, CZ-762 72 Zlín,
This study deals with the preparation of polymer nanocomposites. The first aim of this work was the preparation of modified fillers from two types of natural clays. The first was sodium type of montmorillonite (MMT), and the second was bentonite, which contains more constituents than MMT (for example quartz, calcite, illite and others). Further, two methods of intercalations were studied. Ion-dipole method using the intercalation agent hexadexylamine (HDA), and ion-exchange method utilizing the modifying agent cetyltrimethylammonium bromide (CTAB). For the ion-dipole method various concentrations of clay/HDA were tested, while different additives, time of reaction and concentrations of CTAB were variables for the ion-exchange method. Consequently, prepared samples were characterized by X-ray diffraction and FTIR spectroscopy. Moreover, the commercially modified nanofiller, Cloisite
® 25A, and the natural clays were tested as well to compare final properties with other modified nanofillers. Then, four intercalated samples with the highest d-spacing were selected for the following research. In the second part of this study chosen modified nanofillers, as well as Cloisite® 25A and natural fillers, were compounded with a polymer matrix, called Surlyn® 9721. It is a copolymer of polyethylene and methacrylic acid. Consequently, following properties was measured: permeability for nitrogen and water vapour, stress-strain properties and thermal properties.M. Hricová, A. Marcinčin, J. Legéň
Department of Fibres and Textile Chemistry, Institute of Polymer Materials, FCHPT, STU in Bratislava, Radlinského 9, SK-812 37 Bratislava, Slovak Republic (marcela.hricova / stuba.sk)
Development of the polypropylene (PP) based composites, containing inorganic nanofillers is focused mainly on improvement of the mechanical properties, UV barrier properties and lowering of combustibility of polymers. In this paper, the effects of rheological properties of PP/boehmite composites, selected compatibilisers and spinning conditions on selected mechanical properties of PP composite fibres are presented.
The PP Moplen 500R (PP500R) and PP Moplen 561N (PP561N), commercial boehmite Disperal 40 (D40) as well as two types of compatibilisers: TEG (alkyl-polysiloxane) and S44P (ester of stearic acid and polypropylene glycol) were used in experimental work. The model PP/D40 composite fibres were prepared using two-step process: preparation of PP500R/D40 (5.0 wt%) concentrate dispersions and spinning of mixture of the PP561N and PP500R/D40 concentrate dispersions to obtain the final concentration of boehmite (0.5; 1.0 and 3.0 wt%) in the fibres.
The rheological measurements have confirmed any negative effect of solid particles of boehmite on flow properties of PP500R/D40 composites. Boehmite (5.0 wt%) increased the melt viscosity of PP about 15-30% but practically did not change its non-Newtonian behaviour. Both compatibilisers decreased composite melt viscosity approximately on the level of PP 500R one. The tenacity and Young's modulus of PP composite fibres containing up to 1.0 wt% of D40 were significantly increased in comparison with unmodified PP fibres. Concentrations of Disperal 40 in PP above 1.0 wt% gradually decrease basic mechanical properties of PP composite fibres.
M.S. Kim, J.H. Kim, Y.R. Lee, J.Y. Jang, H.M. Jeong
Department of Chemistry, University of Ulsan,Ulsan 680-749, Korea
In this study, we intercalated macroazoinitiator (MAI) into the gallery of sodium montmorillonite (Na-MMT), and the Na-MMT intercalated with MAI was used in the polymerization of ethyl methacrylate to obtain nanocomposites. We examined the shape memory effect of the nanocomposites along with their mechanical and rheological properties because we anticipated that the Na-MMT intercalated with PEG building block linked to poly(ethyl methacrylate) can perform its role as a fixed phase in shape memory behavior as well as a moiety to enhance mechanical properties.
In the nanocomposites prepared by in situ polymerization of ethyl methacrylate with macroazoinitiator intercalated at the gallery of Na-MMT, we observed that the PEG segment originating from macroazoinitiator was intercalated at the gallery of Na-MMT because of the affirmative interaction between Na-MMT and the PEG segment. The mechanical and rheological properties showed that the heterogeneously dispersed Na-MMT, which is intercalated with a PEG segment, effectively acts as filler and physical crosslinker. The shape memory behavior showed that only 1.2 wt% of Na-MMT can perform efficiently as a fixed phase to inhibit the slippage of matrix molecules and excess amounts of fixed phase, more than 7 wt% of Na-MMT, were not conducive for shape recovery.
M. Erceg, T. Kovačić, I. Klarić
Department of Organic Technology, Faculty of Chemistry and Technology, Teslina 10/V, 21 000 Split, Croatia (merceg / ktf-split.hr)
Poly(3-hydroxybutyrate) (PHB) is a fully biodegradable thermoplastic which has recently drawn much attention as an environmentally harmless alternative to petrochemical derived plastics. However, there is no large commercial production of PHB products because of its very low thermal stability at processing temperatures, pronounced brittleness and high cost. Recently developed nanocomposites consisting of a polymer and only a few percent of layered silicates as environmentally friendly nanofillers, often exhibit improved thermal, mechanical and other properties when compared to pure polymers and conventional composites.
This investigation is focused on the preparation of polymer nanocomposites of PHB with organically modified montmorillonite Cloisite 30B (30B), the effects of Cloisite 30B loading on the thermal stability of PHB and the determination of kinetic parameters and mechanism of their non-isothermal degradation.
PHB/30B nanocomposites with compositions 100/0, 100/1, 100/3, 100/5, 100/7 and 100/10 by weight were prepared by solution intercalation method.
The non-isothermal thermogravimetric analysis of PHB/30B nanocomposites was carried out over the temperature range 50-500°C at four heating rates (2,5; 5; 10 and 20°Cmin-1) in the nitrogen atmosphere.
The onset decomposition temperatures (T°) and the temperatures at the maximal degradation rate (Tmax) of PHB/30B 100/1, 100/3 and 100/5 are higher compared to pure PHB and therefore their thermal stability is improved. Sample PHB/30B 100/7 shows similar and sample PHB/30B 100/10 lower values of T° and Tmax compared to pure PHB.
The invariant kinetic parameters method1 (IKP) was used in combination with isoconversional methods (Flynn-Wall-Ozawa2 and Kissinger-Akahira-Sunose3) to determine the kinetic triplet for the PHB/30B non-isothermal degradation, i.e. the activation energy (E), the pre-exponential factor (A) and the conversion function f(a). By means of isoconversional methods, E and its dependence on conversion (a) are obtained. The values of Einv and Ainv obtained by IKP method were used for numeric evaluation of f(a). The dependence of f(a) vs. a can not be fitted precisely by any ideal kinetic model but its shape suggests the true f(a) characteristic. Finally, the true kinetic triplets for the non-isothermal degradation of each PHB/30B nanocomposite were obtained.
References
1) A.I. Lesnikovich, S.V. Levchik J Therm Anal, 1983, 27, 89.
2) T. Ozawa, Thermochim. Acta, 1992, 203, 159.
3) T. Akahira, T. Sunose Res Report Chiba Inst Technol., 1971, 16, 22.
P. Maroulasa, S. Kripotoua, P. Pissisa, G. Anthoulisa, E. Kontoua, A. Fainleibb, I. Beib
aDepartment of Physics, National Technical University, Zografou Campus, 157 80 Athens, Greece, e-mail : pmaroul / mail.ntua.gr
bInstitute of Macromolecular Chemistry of National Academy of Sciences, 48, Kharkivs'ke shose, 02160 Kyiv, Ukraine
Polycyanurate networks (PCNs) based on bisphenol A cyanate ester (BADCy) were synthesized under presence of organically modified montmorillonite (MMT), hopefully improving mechanical properties of PCN. The resulting nanocomposites differ in MMT content used, mixing conditions and the type of MMT modifier. Organically modified MMT used is commercially found with product names Cloisite 30B and Cloisite 15A. Mixing of the prepolymers with MMT was either mechanical or using ultrasound.
Dielectric techniques, including broadband dielectric relaxation spectroscopy (DRS) and thermally stimulated depolarization currents (TSDC) along with dynamic mechanical analysis (DMA), and to a lesser extent differential scanning calorimetry (DSC), were employed to investigate molecular mobility and glass transition dynamics in relation to morphology in polycyanurate/Cloisite nanocomposites. The local, secondary γ and β relaxations of PCN, the primary α relaxation, associated to the glass transition of the nanocomposite, and the Maxwell-Wagner-Sillars relaxation, related to microphase-separated morphology, were studied in detail. While the relaxations' position intensity and shape seems almost unaffected by the presence of MMT, dynamic glass transition temperature was found to decrease with the increase of MMT content along with an increase of conductivity. Further heating of specimens has a post curing effect accompanied with a shift of β relaxation to higher frequencies. Future in-situ dielectric measurements will hopefully provide significant information of the polycyclotrimerization of BADCy in presence of MMT.
C. Prisacariu
Institute of Macromolecular Chemistry "Petru Poni", Aleea Grigore Ghica Voda, nr. 41 A, 700487, Iasi, Romania ( crispris / icmpp.ro)
The present paper is part of a wider study on a series of systems of polyurethanes (PUs) where a novel diisocyanate (DI) of conformational mobility, 4,4'-dibenzyl diiscyanate (DBDI) was included in the hard block chemical structure. The aim was to improve understanding of the influence of the DI - chain extender (CE) couple on the molecular/supramolecular structure at the nm-scale in PU systems. Novel PU systems were achieved by approaching the 'one shot' synthesis route either in solution or in melt, in two distinct cases: when using 4,4'-diphenyl methane diisocyanate (MDI) as a conventional DI with a rigid geometry, and when using DBDI which displays a variable geometry due to the presence of a rotation axis -CH2-CH2 between the two aromatic rings bearing the two NCO groups. In both cases the DI was employed with CE ethylene glycol (EG), and with the macrodiol poly(ethylene) adipate (PEA). DBDI displays the same reactivity as MDI against n - butanol. On employing the one shot synthesis route, when using either MDI or DBDI, in the first stage there appear oligomers with preponderant -[DI-EG]n- structures. The oligomers corresponding to the -[MDI-EG]- type remain in solution of DMF due to the high interaction between oligomer - DMF. The situation changes dramatically when using DBDI in the PU synthesis: due to the intramolecular rotation of the DBDI scheleton, the incipient growing oligomer -[DBDI - EG]- adopts a plan parallel structure which allows a more compact intermolecular packing of the growing oligomers leading to phase separation, with a characteristic length of ca 20nm and to hard phase crystallization. Thus, the interaction between oligomer-oligomer becomes preponderant towards the interaction between oligomer - DMF and in solution there appear life species in suspension which continue to grow by interphasic reactions. As a result of the PU polyaddition with DBDI by the 'one shot 'synthesis route either in melt or in solution, it obtained opaque PU blends of two copolymers, one of which is soluble in DMF, the other is insoluble in DMF. In contrast, when using the conventional MDI, by selective dissolution in DMF, it obtained homogeneous soluble polymers inseparable in fractions. The materials were characterized by means of X-ray measurements (WAXS), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). These results provide new insight into the role played by nm-scale DI-CE oligomer structures in determining new PU blends of a bicomponent macromolecular structure.
T. Kovalchuk*a, M. Kusminskaa, A. Koriakina, I.Zarova, V. Zaitseva, J-B d'Espinoseb
aNational T.Shevchenko University, Vladimirskaya 64, Kiev Ukraine bEcole Supérieure de Physique et de Chimie Industrielles, 10 Rue Vauqelin Paris, France kovalchu / yahoo.com
Natural clays are excellent and cheap adsorbents, which can be tailored to a particular application by acid and thermal treatment, and functionalisation with silanes. By using composites of palygorskite (Pal) and complexing silanes, hybrid organominerals with improved adsorptive properties toward toxic cations are obtained. Such materials are considered to be a promising alternative to synthetic ion-exchangers. Functionalisation of Ukrainian Pal (S=146 m2∙g-1) is achieved via grafting with toluene solution of silanes (OMe)3SiPrNH2 [Am], (OEt)3SiPrNHC2H4NH2 [En], (OEt)3SiPr-SH [SH], and Et3N catalyst, followed with the thermal treatment to afford polycondensation. Amount of the functional groups, according to pH-titration, is as follows:
According to DRIFT, TG-MS and 29Si MAS NMR study, the silane layer in the composites is polymerised (observed as T3-species) and grafted to the surface via covalent bonding ≡Si-O-Si to edge silanol groups (Q2-species, consumed). While the starting Pal can be used for removal of Cu2+ from aqueous solutions with 0.1-0.2 mmol∙g-1 capacity, the hybrid materials are much more efficient. They offer increased affinity, already at low pH, and capacity (i.e. 0.4-0.7 mmol∙g-1 at pH 5.5). The strong improvement of sorption affinity and capacity is correlated to and is due to the coordination with the organic functions. Hydrolytic stability of these materials in aqueous solutions is a key-issue for their practical application. A thourough study, {involving repeated treatments of the composites with aqueous solutions of high m (0.1N KCl), extreme pH (3-9) and T°C}, show that a portion of the polysiloxane is removed from the composite. Only a part of groups, 0.15-0.25 mmol∙g-1, presumably those, covalently attached to the surface hydroxyls, can be retained during prolonged use and, therefore, are useful in adsorbent preparation. Moreover, this amount can be increased if additional Si-OH groups are generated in a starting palygorskite via activation treatment before preparation of organominerals.
V. Rabováa, P. Hronb
aDepartment of Polymers, The Institute of Chemical Technology, Technická 5, CZ-166 28 Praha 6, Czech Republic (rabovav / vscht.cz )
bDepartment of Polymers, The Institute of Chemical Technology, Technická 5, CZ-166 28 Praha 6, Czech Republic (hronp / vscht.cz)S
Chemistry in nanoscale as a part of material and chemical sciences deals with development of methods for preparation of nanoscale materials in leakers and layers of microleaker materials. A typical example of nanotechnology is a problem of polymer nanocomposites which has attracted attention of scientists dealing with improving polymer properties.
Recently, polymer-clay nanocomposites have attracted strong research and commercial interest due to profound improvements in material properties using a clay, which consist of silicate planar layers 1 nm thick and attracted with van der Waals forces. In general, the application of clays in polymers leads to an improvement in material properties (increased tensile strength, modulus, heat resistance, and reduced gas permeability).
The studied materials were prepared via "In situ" polymerisation of cyclic oligomers in the presence of fillers (or nanofillers) and via homogenisation of fillers and silicone rubber using mixing on a three-roll mill.
The apparent viscosity depended on shear rate was measured after the synthesis. Using the surface modified montmorillonites, compounds with different values of the apparent viscosity were prepared. Some mixtures were submitted to heating and it was measured the influence of the higher temperature on the apparent viscosity. The thermogravimetric analysis was used for determination of the stability of the mixtures and their particular components. The samples were vulcanised and the vulcanisates were used for measuring of mechanical properties and for determination of the structure of composites using X-ray diffraction.
Z. Dominkovics, K. Renner, B. Pukánszky Jr., B. Pukánszky
Laboratory of Plastics and Rubber Technology, Department of Physical Chemistry and Materials Science, Budapest University of Technology and Economics, H-1521 Budapest, P.O.Box 91, Hungary
Institute of Materials and Environmental Chemistry, Chemical Research Center, Hungarian Academy of Sciences, H-1525 Budapest, P.O. Box 17, Hungary
Layered silicate polymer composites attracted much interest recently because of their potential advantages. They are claimed to have improved thermal and dimensional stability, better barrier properties, and flame resistance than the unfilled polymer matrix. One of the main advantages of fillers dispersed on the nanoscale in polymers is claimed to be the large reinforcement reached at very low filler content, which should lead to light composites with considerable stiffness and strength. However, to really utilize all the potential advantages of polymer/layered silicate nanocomposites, the silicate must be exfoliated to a large extent into individual layers. For optimum performance the platelets should be distributed uniformly with an orientation parallel to the external load and adhere strongly to the polymer for efficient stress transfer. Unfortunately, usually none of these conditions are satisfactorily fulfilled and the theoretical reinforcing effect of the silicate is not reached as a consequence. Exfoliation is practically never complete. The majority of the papers published on these materials indicate the formation of an intercalated/partially exfoliated structure.
The structure and rheological properties of a large number of layered silicate polypropylene nanocomposites were studied with widely varying compositions. Unlike general practice, morphology was characterization at different length scales covering several decades by SEM, TEM, and XRD. Rheological measurements supplied additional information about structure. The results showed that these materials possess a very complex structural architecture. The introduction of a functionalized polymer decreases the size of the original clay. However, relatively large silicate particles were found also in composite samples yielding XRD traces without silicate reflection. XRD supplies information of limited value if silicate content is small, the gallery distance of the stacks is large or their regularity is low. On the other hand, XRD characterizes intercalation well. Although exfoliated individual layers can be detected by TEM, the method cannot be used to draw general conclusions about the overall the structure of layered silicate nanocomposites because of statistical sampling and bias. A large number of individual layers, i.e. large extent of exfoliation, lead to the formation of a silicate network structure, which can be detected very sensitively by Cole-Cole plots of dynamic viscosity. We found that not only two (individual layers, intercalated stacks), but four morphological entities, i.e. also particles and a silicate network, may be present simultaneously in the composites. Their presence and relative amount must definitely influence composite properties. However, currently used experimental protocols do not supply sufficient information even to estimate the relative influence as well as interplay among different structural features. An attempt was made to characterize morphology quantitatively, wherever possible. SEM and TEM micrographs were evaluated by image analysis, XRD traces by curve fitting, while a model was developed to determine relaxation time from rheological measurements.
J.H. Kim, M.S. Kim, J.Y. Jang, Y.R. Lee, H.M. Jeong
Department of Chemistry, University of Ulsan, Ulsan 680-749, Korea (hmjeong / mail.ulsan.ac.kr)
The unique properties of the nanocomposites arise from the maximized interfacial contact between the polymer and sodium montmorillonite (Na-MMT), which has a high surface-to-volume ratio, because it is composed of stacks of 1nm thick parallel lamellae with a high aspect ratio. In the nanocomposites, the segmental motions of the polymer chains are restricted due to the confinement of the polymer chains between the silicate layers as well as the silicate surface-polymer interaction in the nanostructured composites.
In this study, we prepared sodium montmorillonite (Na-MMT) intercalated with poly(ethylene glycol) methacrylate (PEGM) whose molecular weight of PEG segment is 440, and polymerized that with methyl methacrylate (MMA) and buthyl methacrylate (BMA). We utilized this polymerized material to modify the reactive hot melt polyurethane adhesive, because we anticipated that finely dispersed silicate layers can accelerate the solidification of an RHA during cooling to manifest early and enhanced development of initial bond strength.
The initial green strength and final bond strength between ABS sheet and PET fabric generally increased when 14.7 phr of polymerized acrylic copolymer was added in the adhesive. And this effect was more evident when the content of Na-MMT intercalated with PEGM (Na-MMT / PEGM) in the acrylic copolymer was increased.
L. Sacarescu[1], I. Mangalagiu[2]*, G. Sacarescu1, M. Simionescu1, R. Ardeleanu1
1 Institute of Macromolecular Chemistry "Petru Poni", Iasi, Romania
2Al.I. Cuza University of Iasi, Bd. Carol-11, 700506 IASI, Romania
Polysilanes are a specific class of conjugated polymers with intriguing optoelectronic properties originating from an unexpected s-conjugation. In the last few years these materials are subject of an intensive research work aiming to various optoelectronic applications.
In order to discover and investigate new materials with EL properties, highly reactive polysilane structures with monomodal molecular weights distribution were synthesized by a homogeneous coupling technique.
This research work started with polydiphenylsilane, a highly crystalline and insoluble material by taking advantage of its similarity with polydimethylsilane, a polymer already used in large scale production of flat panel displays. The chemical structure of polydiphenylsilane was modified to obtain both solubility in common solvents and to induce new properties by attaching of various organic segments.
Therefore it was observed that small quantities of Si-H groups lead to a highly soluble material on one side and to a further developement of new polysilanic structures on the other:
Chain fragmentation thermal control
Photo-control of conformation Hybrid redox-conjugative conduction:
This research work opens new insides in understanding the conduction mechanism within the organic semiconductors by taking into account the following advantages:
· low deposition temperature in HV-CVD technique;
· solubility in common solvents;
· formation of high quality thin films for multilayer devices;
· better opto-electronic properties due to a specific design of the new chemical structure;
· hybrid conduction mechanism with higher charge carriers mobility;
· both photo and electrochemical sensitivities;
· control of the thermo-mechanical properties and morphology of the polymer;
· control of the opto-electronic transition energy value.
· control of the electronic properties by light irradiation.
These advantages gives polysilanes the potential of exploitation in a wide area of applications with higher impact on the EL devices market: foldable-displays, cell-phones, biosensors, solar cells, computerized clothing and electronic luggage tags.
References:
1. Ishikawa M., Ohshita J., In Handbook of Organic Conductive Molecules and Polymers: Vol. 2. Conductive Polymers: Synthesis and Electrical Properties, Ed. By H.S. Nalwa, John Wiley & Sons Ltd., 1997, Chap. 15.
2. Corriu R.J.P., Devylder N., GuErin C., Henner B., Jean A., Organometallics, 13, 3194, 1994.
3. Kunai A., Toyoda E., Horata K., Ishikawa M., Organometallics, 14, 714, 1995.
4. Shaheen S. E., Brabec C. J., Padinger F., Fromherz T., Hummelen J. C., Sariciftci N. S., Appl. Phys. Lett., 78, 841, 2001.
5. Brabec C. J, Sariciftci, N. S., Hummelen, J. C., Adv. Funct. Mat., 11, 15, 2001.
6. Agosti E., Rivola M., Hernandez V., Del Zoppo M., Zerbi G., Synth. Met.,100, 101, 1999.
7. Sacarescu L., Ardeleanu R., Sacarescu G., Simionescu M., Eur. Polym. J., 40/1, 57-62, 2003.
8. Sacarescu G., Ardeleanu R., Sacarescu L., Simionescu M., J. Organomet. Chem., 685, 202, 2003.
9. L. S\c\rescu, R. Ardeleanu, G. S\c\rescu, M. Simionescu, N. Hurduc, RSC-Chemical Communications, 788, 2006.
10. a) G. Sacarescu, L. Sacarescu, R. Ardeleanu, M. Marcu, N. Voiculescu, Eur. Polym. J., 36, 2089, 2000; b) G. Sacarescu, L. Sacarescu, R. Ardeleanu, P. Kurcok, Z. Jedlinski, Macromol. Rapid Commun., 22, 6, 405, 2001.
11. V. Papaefthimiou, A. Siokou and S. Kennou, Surf. Sci., 569 (1-3): 207-218, 2004.
12. H. Ishii, K. Sugiyama, E. Ito, K. Seki, Adv. Mater., 11 (8), 605, 1999.
Aknowledgements: to Romanian Ministry of Research and Education-MATNANTECH program, grant no. 36/2005 and no. 107/2006 for financial support.
[1] Institute of Macromolecular Chemistry "Petru Poni", Iasi, Romania;
[2] "Al. I. Cuza" University of Iasi, Romania.
J. Sokołowskaa, M. Zaborskia, M. Lipińskaa
aTechnicalUniversity of Lodz, Institute of Polymer and Dye Technology, Stefanowskiego 12/16 Lodz 90-924, Poland (marian.zaborski / p.lodz.pl)
The properties of magnetite Fe3O4 and maghemite γ - Fe2O3 with micro- and nanometric particle size were investigated. Fe3O4 and γ - Fe2O3 were used as received from Aldrich. Surface area of Fe3O4 and γ - Fe2O3, particle size, crystal structure and tendency towards agglomeration were determined.
The composites of iron oxides and acrylonitrile rubbers were prepared. Hydrogenated (HNBR) and carboxylated (XNBR) rubber were used. Dicumyl peroxide and zinc or magnesium oxides were used as the crosslinking agents, respectively.
There was no significant influence of iron oxides on the crosslinking process. The crosslinking time increased only slightly when dicumyl peroxide was used. The same effect was observed for the crosslinking efficiency estimated from the ΔM and νe parameters. It is probably due to the donor character of iron oxides which decreased the ionic decomposing of the peroxide what consequently affected the crosslinking process.
Iron oxides accelerated the crosslinking process of carboxylated acrylonitrile rubber. The covalent and ionic crosslinks were created. Iron oxides were partially responsible for that. However, it seems that the effect depends on the particle size - the smaller particle size, the smaller influence was observed. This is the result of the worse dispersion of iron oxide with nanometer particle size in elastomer medium. It was found that for the reinforcing effect no less than 50 phr of iron oxides had to be used. As the result the stress at elongation 100 % or 300 % and tensile strength increased. It is interesting that the vulcanizates containing the iron oxides demonstrated high hysteresis losses. The value of W1 - W5 was high what indicated the ability of the filler to create its own structure in elastomer medium. It is known that the materials with such hysteresis behavior can be applied as good shock absorbers. The same effect was observed for both rubbers. No matter which crosslinking agent was used for XNBR iron oxides were found to be the active fillers. The mechanical properties of the vulcanizates were very good.
Iron oxides increased the conductivity of vulcanizates and acted as the dyes. Magnetite dyed in black, while the γ - Fe2O3 in reddish-brown colors. It was demonstrated that iron oxides have practical applications in elastomer technology. They could be used as fillers, dyes or substances increasing the electrical conductivity. The ferromagnetic present in elastomers generated the magnetic properties of the vulcanizates, as well.
J. Jung, Y. Lee, D. Li, G.S. Sur*
School Of Chemical Engineering and Technology Graduate School Yeungnam University, 214-1 Dae-Dong, GyeongSan, GyeongBuk, Republic Of Korea 712-749
In regard of today's safety requirements, in vehicle construction selected high strength materials. A kind of high strength material of up to 1650 MPa can be achieved by new process in comparison to a usual value of approximately 1100 MPa for cold formed material. During the new process the materials are heating up to high temperature. And the materials are subsequently carried over to the forming die and formed for cooling down of the materials to under room temperature. This process lead to a high-strength constructional element. A problem connected with this process is scaling of the materials surface due to a high temperature oxidation. A simple way to prevent any corrosion is the modification of the materials surface by appropriate organic or inorganic coating agents. In this study, organic-inorganic silica nanocomposites were prepared by sol-gel method for protecting a corrosion from coating agents. These coating agents protected the materials from scaling during high temperature process.
Acknowledgement : The funding of this research by the Minisrty of Commerce, Industry, and Energy through High Performance Nano Composite Program is gratefully acknowledged.
M. Zaborskia, J. Sokołowskaa, H. Bemb, W. Baryńa
aTechnicalUniversity of Lodz, Institute of Polymer and Dye Technology, Stefanowskiego 12/16 Lodz 90-924, Poland (marian.zaborski / p.lodz.pl)
bTechnicalUniversity of Lodz, Institute of Applied Radiation Chemistry, Żeromskiego 116 Lodz 90-924, Poland
Mechanical properties of natural rubber (NR), acrylonitrile-butadiene rubber (NBR) and styrene-butadiene rubber (SBR) vulcanizates containing bismuth oxide and bismuth vanadate were investigated. In addition, X-ray resistance of composites was estimated.
The activity of bismuth oxide and bismuth vanadate as the fillers of elastomers was studied on the base of rheometric measurements and equilibrium swelling using Wolff and Parks-Lorentz theory. It was found that pigments revealed reinforcing effect and influenced on the crosslink density of the rubbers. Moreover, bismuth oxide was more active filler than bismuth vanadate.
NR vulcanizates containing bismuth compounds exhibited the best mechanical properties. The density of composites increased with elevated concentration of the filler. However, when the amount of the filler was relatively high, this parameter was still about 2 g/cm3.
The lead equivalent was measured and X-rays screening effect of vulcanizates containing bismuth compounds was estimated. Composites with the bismuth oxide favoured X-ray absorption in higher extent in the comparison with the bismuth vanadate.
It was found that 2,7 mm thick rubber sheet containing bismuth oxide and 1 mm thick lead sheet having the same 1 m2 surface exhibited identical X-ray screening properties. However, the former sheet was about 2,5 times lighter (4.62 kg versus 11.34 kg).
M.A. Smirnov, V.Bukoshek*, G.K. Elyashevich
Institute of Macromolecular Compounds, Russian Academy of Sciences, Bolshoi pr. 31, 199004 Saint-Petersburg, Russia, (smirnov / hq.macro.ru);
*University of Ljubljana, Faculty for Natural Sciences and Engineering, 1001 Ljubljana, Slovenia
Porous anisotropic structure of linear PE was formed by uniaxial extension of extruded and subsequently annealed films. The extrusion of PE was performed using slit die at high velocity of the melt flow. According to electron microphotographs supramolecular structure of porous films surface consists of the large crystalline structural forms located perpendicular to orientation direction and connected by stressed ties with pores between them.
The films obtained at various spin draw ratios were used as supports for conducting polymer - polypyrrol (PPY) prepared by oxidative polymerization of pyrrole in situ with ferrum (III) chloride in water-methanol mixture. The composite systems prepared in this process had the anisotropic electrical properties because the structure of conducting polymer is influenced by orientation degree of PE films. The dependence of anisotropy of electrical conductivity on the orientation degree of support has been investigated. It was found that this dependence is nonlinear. It may be explained by the fact that the growth of orientation degree leads to the increase of overall porosity of PE films and, as consequence, to increase of PPY content in composite. The thicker PPY layer formed on the film surface with higher orientation degree masks the surface relief, and the effect of support on the structure of PPY layer decreases. As a result the anisotropy of PPY layer becomes lower.
Electroconductivity of PE/PPY composites reached more than 100 S/cm that is extremely high value for polymer composite systems.
The work is supported by Russian Foundation of Basic Research (Grant №07-03-00177-a) and by the Programme of Basic Research, Russian Academy of Sciences Division of Chemistry and Material Sciences, "Electroconducting and electroactive Polymers" (2006-2008).
I. Amici-Kroutilová, L. Matějka, J. Pleštil, M. Šlouf
Department of Polymer Networks and Mechanical Properties, Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky sq.2, 162 06 Prague 6, Czech Republic,
kroutili / imc.cas.cz
Hybrid Inorganic/Organic (I/O) polymeric materials are nowadays at the centre of a wide interest because of their combination of the excellent features of polymers (like low cost, low weight and easiness of synthesis-processing) and the ones of the ceramic materials (like high stiffness, flame resistant and barrier properties). A very large body of work has been studying practically all the combination polymers - inorganic (or I/O) materials. This body of work has been focused mostly on nanostructured hybrid polymeric materials, as they were proven to have higher properties than their standard (microstructured) counterparts.
There are mostly two synthesis path generally used to achieve such nanostructures: 1) in-situ generation of a multiphase material from a homogeneous system, 2) modification of the material structure (also by means of copolymerisation) by ex-situ generated species.
In this research it has been used this twofold synthesis path in-situ/ex-situ on thermosetting polymer based on diglycidyl ether of Bisphenol A (DGEBA) and poly(oxypropylene)diamine (Jeffamine D2000). The main issue of this research has been thus the modification of the macromolecular structure of the epoxy-amine networks by means of nanostructuring generated by in-situ or ex-situ hybrid compounds. The goal has been to establish and study preparation-structure-properties relationships.
Y. Li, H. Shimizu
Nanotechnology Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki, 305-8565 Japan (yongjin-li / aist.go.jp)
Conductive polymer composites based on insulating
polymer matrix and electrically conductive filler attracted many
attentions recently. The investigations of the conductive polymer
composites have mainly focused on decreasing the percolation
threshold for lowing cost, improving processability, and
enhancing mechanical properties of the composites. In this work,
poly(vinylidene fluoride) (PVDF)/polyamide 6 (PA6)/carbon naotube
(CNT) nanocomposites have been prepared using a high-shear
extruder processed under different screw rotation speeds. The
physical properties and the morphologies of the nanocomposites
have been investigated. The high-shear processed nanocomposites
show a significantly improved electrical conductivity and
mechanical properties as compared with those processed under low
shear rate. The morphological investigation indicates that the
high-shear processed PVDF/PA6/CNT nanocomposites have unique
nanostructured morphologies. The CNT has been homogenously
located in the PA6 phase in the co-continuous PVDF/PA6 blend and
no any CNT can be found in the PVDF phase. Moreover, many PA6
nanodomains with the size of several tens nanometer are found in
the PVDF phase, as shown in Fig.1. In this figure, the white part
shows the PVDF phase and the grey part and particles denote the
PA6 phase and nanodomains, respectively. It is considered that
high-shear processing takes the critical role for the formation
of the unique structure. On the one hand, the high shear
processing improves the dispersion of the CNT in the PA6 phase.
On the other hand, the high-shear processing enhanced the
miscibility between PA6 and PVDF; the many PA6 nanodomains are
formed in the PVDF phase. The unique structure of the
nanocomposites prepared using high-shear processing accounts for
the improved electrical and mechanical properties as compared
with the same composites prepared using the normal melt mixing
methods. The improved dispersion of CNT in PA6 phase can reduce
the percolation threshold for electrical conductivity. Moreover,
the formation of PA6 nanodomains in PVDF phase can further
enhance the concentration of CNT in the PA6 phase, thereby
decreasing the percolation threshold of CNT in PA6 phase. It is
expected that the high-shear processed PVDF/PA6/CNT
nanocomposites can be used for the bipolar plates of polymer
electrolyte membrane fuel cells.
C. W. Wang, C. W. Lin*
Department of Chemical Engineering, National Yunlin University of
Science and Technology, 123, Sec. 3, University Road, Touliu,
Yunlin,
Taiwan (lincw / yuntech.edu.tw)
The nanocomposites based on PVDF/SiO2 with proton conducting capability were prepared. The dispersive phase was synthesized by using tetraethoxysilane (TEOS) as precursor, and sulfosuccinc acid (SSA) as a crosslinking agent, to form a tight network structure and SiO2-SiO3H particles with a high porosity. 3-(trihydroxysilyl)-1- propane - sulfonic acid ((THS)pro-SO3H) is added to conduct more SO3H groups. Inorganic phase of the hybrid membrane was contributed from the condensation reactions of both TEOS and (THS)pro-SO3H, and the SO3H of the hybrid membrane was obtained from both SSA and (THS)pro-SO3H. Through the infrared spectra, the characteristic adsorption peaks indicates a success of condensation reaction between TEOS and SSA. It was also confirmed through the 29Si solid-state NMR spectra that (THS)pro-SO3H was involved in the reaction, and the condensation extent of TEOS and (THS)pro-SO3H was studied. With the increase of the TEOS content, the thermal stability of the hybrid membrane can be promoted. The PVDF/SiO2-SO3H hybrid membrane exhibits proton conductivity of as high as 10-3 Scm-1. As water state of membranes is closely related to the proton conductivity and methanol permeability, differential scanning calorimetry (DSC) was employed to investigate the water state distribution of the hybrid membrane. The surface morphology of the membranes were investigated by using SEM, suggesting that (THS)pro-SO3H may be regarded as a pore- forming additive. Besides, a wide-angle X-ray diffraction (WAXD) was employed to investigate the crystalline behavior of the hybrid membrane.
D. K. Božanića, V. Djokovića, P. Sreekumari Nairb, M. K. Georgesc, T. Radhakrishnanc
a Vinča Institute of Nuclear Sciences, P.O. Box 522, 11001 Belgrade, Serbia
bDepartment of Chemistry Lash-Miller Chemical Laboratories, University of Toronto, Ontario, M5S 3H6. Canada
cDepartment of Chemistry, University of Toronto at Mississauga, Mississauga, Ontario, Canada, L5L 1C6
The nanocomposites of lead sulfide (PbS) and cadmium selenide (CdSe) in a sago starch biopolymer matrix have been synthesized and investigated. The X- ray diffraction analysis of the PbS-sago starch nanocomposite exhibited strong diffraction maxima that correspond to the PbS cubic crystal structure. TEM micrograph of the PbS nanocomposite showed the spherical particles with narrow size distribution and an average diameter of 4 - 5 nm. In the case of CdSe-sago starch nanocomposite, monoclinic crystal structure of CdSe was found. The onset of the UV-VIS absorption spectra of the both PbS- and CdSe sago starch nanocomposite aqueous solution is blue shifted with respect to the bulk semiconductors. However, CdSe-nanocomposite showed well defined exciton shoulder.
H.W. Leea, M.H. Hwanga, J.H. Yeuma, Y.H. Kimb, J.T. Leeb
aDepartment of Advanced Organic Materials Science and Engineering, Kyungpook National University, Daegu 702-701, Republic of Korea (jhyeum / knu.ac.kr)
bDepartment of Cosmeceutical Science, Daegu Haany University, Gyeongsangbukdo 712-715, Republic of Korea
Scaffolds based on collagen, one of the most representative extracellular matrix proteins, have been used in different tissue engineering applications and led to the development of bioengineered tissues such as blood vessels, heart valves and ligaments.
In this study, poly(vinyl alcohol) (PVA)/collagen nanofibers containing bovine serum albumin (BSA) were prepared by electrospinning PVA/collagen/BSA aqueous solutions. The protein- containing PVA/collagen nanofibers were characterized with regard to morphology, BSA loading efficiency, in vitro BSA release, and BSA stability. Furthermore, properties of the PVA/collagen/BSA solutions including viscosity, conductivity, and surface tension were measured.
With increasing PVA content, the morphology of blend nanofibers was changed from beaded fiber to uniform fiber. The protein stability study showed that BSA was protected during the electrospun nanofibers preparation and stabilized inside/outside the PVA/collagen nanofibers.
I. V. Semiletova, T. Yu. Karpenko, Yu. Shchipunov
Institute of Chemistry, Far East Department, Russian Academy of Sciences
690022 Vladivostok, Russia (semiletova / ich.dvo.ru)
A novel approach was developed for jellification of polysaccharide and protein aqueous solutions. As a silica precursor, tetrakis(2-hydroxyethyl) orthosilicate was used. It possesses a complete compatibility with biopolymers that was obvious from the absence of denaturating effect and precipitation or phase separation in the system after its mixing with biopolymer in a solution. This allowed jellifying most of practically important polysaccharides, whose do not form gels, and such protein as albumin. In addition, hybrid hydrogels were prepared with carrageenans and gelatin that can provide gel formation.
All the studied biopolymers played an important role in the sol-gel processes, catalyzing them. By this reason, the processing could be performed in a wide pH range extending from 2 to 10.
Hydrogels thus prepared were used further to fabricate xerogels and aerogels. The properties and structure of all the types of prepared nanocomposites materials were studied with the help of a dynamic rheology, differential scanning calorimetry, scanning electron microscopy and atomic force microscopy.
It was found that the biopolymers served as a template for silica generated in situ by the sol-gel processing. Biopolymer macromolecules were covered by an inorganic shell owing to silica nucleation and subsequent growth of precipitate. This was demonstrated by the atomic force microscopy. The suggested mechanism differs from that for the sol-gel processing performed with common silica precursors. The silica precipitation on biopolymer macromolecules determined the structure and properties of hybrid nanocomposites. They depended on the biopolymer type, charge and concentration as well as conformation of their macromolecules. Although the macromolecules were covered by silica shell, biopolymers did not loose their ability for conformational rearrangements. It was demonstrated in a case of hybrid nanocomposites materials with entrapped kappa- and iota-carrageenans and gelatin. These polysaccharides and protein experienced a reversible coil-to-helix transition with varying the temperature that provided a thermoreversible change in the mechanical properties of hybrid materials around the biopolymer phase transition temperature.
I. Portnayaa, R. Khalfinb, O. Ramona, U. Cogana, D. Daninoa
a Faculty of Biotechnology and Food Engineering, Technion - Israel Institute of Technology,TechnionCity,Haifa,32000, Technion City, Haifa, 32000, Israel. (portnaya / techunix.technion.ac.il).
bFaculty of Chemical Engineering, Technion - Israel Institute of Technology, Technion City, Haifa, 32000, Israel.
The association of caseins into micelles determines many of the important physical and technological properties of milk. The mechanism of this association has been only partially clarified. Beta-casein is the most abundant casein. At neutral pH it is highly amphiphilic, and has a net charge of -11.5, that is concentrated mainly along the first 50 amino acids of its N-terminus. Previous studies by us and others showed that at neutral pH beta-casein self-organizes into detergent-like micelles that have an oblate shape. The critical micellar concentration (CMC), micellization enthalpy and the self-assembly mechanism were found to be dependent on the temperature and ionic strength.
In present work we studied the structure and the behavior of beta-casein below and above it's isoelectric point (pI~5.1). Our analysis shows that the net charge at low pH is greater than at pH 7, and the charge distribution is different. Nevertheless, we found that the protein remains amphiphilic and self-organizes into micelles. The shape and size of the micelles were studied by cryogenic transmission electron microscopy (cryo-TEM). Using isothermal titration calorimetry (ITC) and sedimentation equilibrium we also studied the CMC and aggregation number of the micelles as a function of temperature, pH and ionic strength. Small-angle x-ray scattering (SAXS) was used to study the conformation and radius of gyration (Rg) of the beta-casein monomers and micelles.
The thermodynamic analysis of the beta-casein association and quantitative demonstration of the process cooperativity below and above the protein's pI were performed. The micellization parameters and the driving force for the self-assembly of beta -casein at the different pH conditions are discussed.
J. Faucheu1 C. Gauthier1, E. Bourgeat-Lami2, J.-Y. Cavaillé1
1MATEIS, UMR CNRS 5510, INSA-Lyon, Bât. Blaise Pascal, 7 Av. Jean Capelle, 69621 Villeurbanne Cedex, France
2LCPP, UMR CNRS 140, CPE, Bât. F308, 43 Bd. Du 11 Novembre 1918, BP 2177, 69616 Villeurbanne Cedex, France
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Nanoparticles with high aspect ratio has drawn increasing
interest as reinforcement agents in polymeric materials. Laponite[1]
is a disc-like nanometric synthetic layered silicate. Through
specific synthetic routes, different latex morphologies of
nanostructured latexes can be obtained. The evaporation of water
from latexes[2]
under adequate conditions of temperature and humidity lead to
free standing film which mechanical properties can be evaluated
through Dynamic Mechanical Analysis and tensile tests. This study
aim at presenting the morphology obtained through both
polymerization routes and the effect of this specific
nanostructure on mechanical properties.
Figure1A: TEM image: Morphology of a nanostructured P(MMA-co-BA)/Laponite film, clay platelets (dark dashes) are located around the latex particle creating a honeycomb-like network of laponite. Scale Bar: 100nm
Figure1B: Shear Modulus vs. Temperature, latex film synthesized through two different routes (1) and (2) with different amount of laponite.
DMA experiments show a strong increase of the rubbery plateau level when laponite is present in the nanocomposite film. However differences between the synthesis routes is underlined for both the matrix and the filled polymer behavior.
Comparison of mechanical behaviors[3] and morphologies of latexes synthesized by either route underlines the differences between polymerization mechanisms and Laponite/Polymer interactions.
[1] Q. Sun et al., Macromol. Mater. Eng. (2004) 289: 288
[2] P.A. Steward et al., Adv. Coll. Int. Sci. (2000) 86: 195
[3] N. Agarwal et al. Pol. Eng. Sci. (2000) 40: 376
L. Zhao*, Y. Li, H. Shimizu
Nanotechnology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Japan
Biodegradable poly(L-lactide) (PLLA)/poly(butylene succinate) (PBS) blends incorporated with an organoclay were prepared using a high-shear extruder, of which the shear condition can be controlled by the various screw rotation speeds. In this study, the morphologies of the PLLA/PBS (50/50) blends with different clay loading as well as four preparing shear conditions corresponding to the screw rotation speed of 100, 300, 600 and 1000rpm were compared. It was found that the high-shear processing is very effective for forming a wide range of the co-continuous structures, while the low-shear one is not effective for controlling the co-continuous structures. The processing method can control the co-continuous structures of the PLLA/PBS blends adding clay with vary wide dynamic range from several tens of μm to sub-μm levels. This kind of material is expected to the formation of size-matching separator or filters.
a Laboratory of Physical Chemistry, A.B. Bekturov Institute of Chemical Sciences, Valikhanov Str. 106, Almaty, 050010, Kazakhstan, (znazym / mail.ru, jumadilov / mail.ru)
In recent years much attention has been focused on artificial carriers based on porphyrins. Porphyrins are π-conjugated macrocycles, which play a vital role in living organisms. They are parts of many enzymes, vitamins, the crucial role of porphyrins in hemoglobin or chlorophyll is generally known. In all these systems, porphyrins are present as metal complexes. Metal complexes of porphyrin are used as photosensitizes for photodynamic therapy of tumors because of their interaction with DNA. The catalytic capabilities make them useful as catalyst in many reactions. The searches of natural catalysts analogues have led to formation of a new catalytic system based on the nature porphyrins fixed on the synthetic polymeric carriers. In this study the catalytic properties of the complexes based on poly(acrylic acid) (PAAc), polyvinyl alcohol (PVA) and metalloporphyrins (PhpMe) were shown on the modeling oxidation reaction of oxalic acid. It was established that the presence of the catalysts led to increase of the reaction rate. It is shown, that complexes have high catalytic activity which presume their further practical application. We presently report about formation of micro particles on the surface of obtained complexes that predicts creation of nanosized composites. The observed results of different metal binding by porphyrins on the polymer will be presented. Fig.1 demonstrates optical microscope micrographs of the polymer carriers surfaces after complexation. It is seen that on the surface of polymer carriers some particles with size of approximately 30-40 μm have been achieved.
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FIG.1. Optical microscope micrographs of particles (30-40 μm) on the surface of PAAc hydrogel (a) and PVA film (b) after complexation.
M. Reitera,b, T. Ikomaa, N. Hanagataa, A. Roguskaa
aBiomaterials Center, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan, (http://www.nims.go.jp/eng/)
bCharles University, Faculty of Mathematics and Physics, Ke Karlovu 5, CZ-128 00 Praha 2, Czech Republic (http://alma.karlov.mff.cuni.cz/biofyzika, michal.reiter / matfyz.cz)
Fish scale is promising and safe source of collagen for biomedical applications, but still a little is known about differences in fibril formation process compared to pig dermis collagen. The denaturation temperature (ca. 35 °C) of type I collagen extracted from scale of Pagrus major (Oreochromis niloticas) is lower than pig dermis collagen (42 °C) usually used for biomedical applications. The collagen fibril formation is of great importance for the design of scaffold in tissue engineering and improves the denaturation temperature at about 40°C. We observed adsorption morphologies and reassembly structures of the both kinds of collagen on hydroxyapatite (HAp), titanium, mica and platinum coated cover glass using atomic force microscopy (AFM). The nanostructures of supramolecular assembly after slowly drying in the air as well as in liquid were evaluated by tapping mode AFM. The AFM force spectroscopy allowed us to characterize collagen monomer and fibril adhesion to the substrates.
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T. Karpenkoa, Yu. Shchipunova, Yu. Burtsevab, N. Shevchenkob, T. Zvyagintsevab
aInstitute of Chemistry, Far East Department, Russian Academy of Sciences
690022 Vladivostok, Russia (karpenkotu / ich.dvo.ru)
bPacific Institute of Bioorganic Chemistry, Far East Department, Russian Academy of Sciences, 69002 Vladivostok, Russia
O-glycoside hydrolases (EC3.2.1), endo-1,3-β-D-glucanases (LO and LVI) and α-D-galactosidase were entrapped into polysaccharide-silica hydrogels generated in situ by the sol-gel technique. It could be successfully done when a novel silica precursor tetrakis(2-hydroxyethyl) orthosilicate was used. Advantages of this precursor over generally applied tetramethozy- and tetraethoxysilanes are compatibility with biopolymers, complete solubility in water and jellification of solutions in wide pH range extending from 2 to 10.
It was demonstrated that both the endo-1,3-b-D-glucanases and a-D-galactosidase retained or even had sometimes an increased activity after the immobilization1. The optimal conditions of their functioning (pH and temperature) were not notably changed. At the same time, the entrapment into silica matrix had a stabilizing effect on the enzymes that was manifested in a prominent increase of the thermal and long-term stability.2
An important point is that the entrapped enzymes, of which substrates are polysaccharides, were accessible to these high-molecular substances. The accessibility of enzymes is explained by an appropriate porosity of the silica gel matrix. As shown by scanning electron microscopy and atomic force microscopy, it consists of a three-dimensional network of cross-linked silica fibrils.
References
1. Y. A. Shchipunov, T .Yu. Karpenko, I. Yu. Bakunina, Yu. V.Burtseva, T. N. Zvyagintseva, J. Biochem. Biophys. Methods, 2004, 58, 25.
2. Y. A. Shchipunov, T .Yu. Karpenko, Yu. V.Burtseva, N. M. Shevchenko, T. N. Zvyagintseva, J. Mol. Catal. B.-Enzym, 2006, 40, 16.
Abou El Fettouh Abd El-Hakim*, Ahmed Badran**, Ahmed Youssef*, Hisham Essawy**.
National Research Center, Packaging and Packing materials Dept*. Polymers & Pigments Dept**. - Dokki 12311-Cairo-Egypt.
Email: aaabdelhakim / yahoo.com
Two types of organophilization of montmorillonite (MMT) were prepared using Cetyltrimethyl ammonium bromide (CTAB) and Cetylpyridinium chloride (CPS). The basal space were determined and found equal to 19.35 and 21.47, where it was 12.0 for the neat MMT. The polymethylmethacrylate/montmorillonite (PMMA/MMT) nanocomposites were prepared by simultaneous polymerization methods. The polymerization were carried out by swelling of the two types of organophilization MMT in methyl methacrylate monomer contains the monomer soluble, benzoyl peroxide as initiator for the suspension polymerization process. Then the monomer dispersed in aqueous medium contains different concentration of potassium per sulfate as initiator of monomer in aqueous medium to carry out the emulsion polymerization process, that for the soluble part of monomer. The X-ray investigations revealed presence of intercalation and exfoliation, that according the polymerization conditions. Also the TGA and DSC were carried to determine the thermal behavior properties of the prepared nanocomposites.