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STRUCTURE AND DYNAMICS OF SYNTHETIC MACROMOLECULES AS PROBED BY EPR SPECTROSCOPY
G. JESCHKE
Max Planck Institute for Polymer Research, Postfach 3148, 55128 Mainz, Germany
Electron paramagnetic resonance (EPR) spectroscopy can characterize structure on length scales between a few Angstroem and 10 nanometers and dynamics on time scales between 10 picoseconds and 10 microseconds. As a magnetic resonance method, EPR probes the local environment of spins and thus does not depend on long-range order. Since most macromolecular systems are diamagnetic, EPR spectroscopy is usually applied as a probe technique. A broad range of spin probes is available, so that specific sites in complex systems can be addressed selectively.
Here we demonstrate how these advantages can be used to obtain information on synthetic macromolecular systems that is not easily available by other techniques. In particular, we discuss the conformation of [2]catenanes in different solvents based on measurements of the distance distribution (pair correlation function) of two spin labels, dynamic attachment of counterions to polyelectrolytes in solution, polyelectrolyte conformation on length scales of a few nanometers, and the role of surfactants in polymer-clay nanocomposites.
Fig. 1 Dynamic processes in the polyelectrolyte-counterion system that are observable by EPR spectroscopy.
MERGING SOLID-STATE AND SOLUTION-STATE NMR METHODS FOR INVESTIGATIONS OF SUPRAMOLECULAR SYSTEMS
I. SCHNELL
Max-Planck-Institut für Polymerforschung, Postfach 3148, 55021 Mainz, Germany
In the past, the fields of solid-state and solution-state NMR have developed almost independently of each other, but recent progress – particularly in magic-angle spinning (MAS) NMR techniques – provides a promising basis for combining NMR spectroscopic strategies more thoroughly. On the materials' side, the investigation of supramolecular order phenomena poses certain challenges on NMR methods, as the systems of interest are usually quite complex, sample amounts are little and isotopic labelling is usually not feasible due to demanding chemical syntheses.
In the solid state, the enhancement of spectral 1H resolution achievable under very fast MAS conditions opens up the possibility to investigate hydrogen bonds by 1H NMR spectroscopy [1]. Moreover, inverse 1H detection schemes from liquid-state NMR can be introduced into heteronuclear 1H-13C or 1H-15N solid-state correlation experiments [2]. In this way, signal sensitivity can be gained, and experiments become feasible for samples with low isotopic abundance, such as 13C or 15N [3]. Furthermore, individual internuclear distances as well as bond angles can be determined, for example in O-H× × × N [4] and N-H× × × N hydrogen bonds [2] and in arrays of multiple hydrogen bonds [5]. With respect to molecular dynamics, NMR experiments have been designed, whose sideband patterns are sensitive measures for internuclear distances as well as for local mobilities and (re)orientations of molecular segments. For example, different CHn groups can be used individually as "probes" for local molecular dynamics [2, 6].
NMR AS A PROBE INTO THE LOCAL AND SEMILOCAL ORDER IN COOPERATIVE INTERACTIONS OF POLYELECTROLYTES
J. KŘÍŽ
Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovského nám. 2, CZ-162 06 Praha 6, Czech Republic
Densely charged polyions with their counterions exhibit
partial local and semilocal order in the sense of a perturbed
statistics of chain conformations and counterion distribution
(entropy of the system with a given distribution r e.g. of the counterions can be expressed
as 
). Both phenomena
influence each other. Counterion condensation exerts screening of
repulsions along the charged chain inhibiting conformational
change and enforcing preferred conformations. Chain extension due
to repulsions bares the charges and forces counterions to
sediment near the chain and thus exert electrostatic screening.
NMR can probe into the conformational order and dynamics of the chain by several methods of 1H SQC and MQC NMR (13C being excluded on grounds of sensitivity): (i) intensity change due to extreme broadening; (ii) signal sensitivity to the frequency of MAS; (iii) transverse relaxation; (iv) DQC and TQC relaxation even for the lone methyl groups; (v) relaxation of Cohen-Addad’s pseudo-solid echo; (vi) cross-peak asymmetry in Noesy-like exchange spectra (Spiess et al.); (vii) PFG diffusivity measurements. Results obtained on poly(N-diallyldimethyl chloride) (PDADMAC) and sodium poly(methacrylic acid) (PMANa) show that signal broadening at extreme dilutions is due to spin dynamics rather than pseudo-static dipolar interactions.
The relative order (in the sense of perturbed distribution) of counterions with I=3/2 nuclei (7Li, 23Na, 35Cl, 79Br or 81Br) can be probed by (i) combining T01 and T11 relaxation to obtain D R2 (Halle, Wennerstrom and Picullel); (ii) using T23 relaxation to the same result; (iii) using PFG diffusivity measurements. Confrontation of the results obtained for PDADMAC and PMANa with those with dilute-charged copolymers containing neutral units of acryl amide will show that these methods are able to asses at least semiquantitatively the perturbation of counterion density in dilute solutions.
Acknowledgements: The author thanks the Grant Agency of the Academy of Sciences of the Czech Republic for financial support given under the grant A4050206 and the Academy of Sciences of the Czech Republic for additional support (Projects No.: AVOZ4050913 and KSK4050111).
INVESTIGATING MORPHOLOGY AND DEFORMATION BEHAVIOR OF PC/PET NANOLAYERS BY MEANS OF SPECTROSCOPIC AND MICROSCOPIC METHODS
R. ADHIKARI, T.A. HUY, W. LEBEK, R. GODEHARDT, G.H. MICHLER, *E. BAER
Martin Luther University Halle Wittenberg, Germany
* Case Western Reserve University, Cleveland, USA
Polymers consisting of nanolayers have attracted an enormous research interest due to their promising mechanical, optical and barrier properties. Coextrusion is one way of combination of polymers to improve mechanical properties. Recent studies have shown that a significant variation in mechanical behavior of polymers results in changing the dimension from macroscopic to microscopic scale. This work deals with micromechanical deformation behavior of PC/PET nanolayers, which reveal a forced organization of thousands of ‘uniform’ alternating polymer layers. Both polymers are polyesters and can react by transesterification in the molten state to form block or random copolymer. Thus, depending on the thermal treatment the mutual interaction between the PC and PET layers can be influenced, which will greatly alter the morphology and the mechanical behavior of this material.
The principal techniques used are Fourier-transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM). Especially, the ability of FTIR spectroscopy to monitor the structural changes in molecular level of the individual phases during an in situ uniaxial deformation has been used. The morphology and strain induced structural changes in microscopic scale were visualized by the TEM. The connection between the molecular orientation and microstructural changes in PC/PET nanolayers will be discussed with special reference to a variable layer thickness and layer interactions.
CHAIN CONFORMATIONAL TRANSFORMATIONS IN SYNDIOTACTIC POLYPROPYLENE INDUCED BY STRESS OR HEATING
V.G. GREGORIOU, K.G. GATOS, G. KANDILIOTI, C. GALIOTIS
Foundation for Research and Technology-Hellas, Institute of Chemical Engineering and High Temperature Chemical Processes (FORTH-ICEHT) P.O. Box 1414, 26500 Patras, Greece
The mechanical as well as the thermal induced chain conformational transformations in syndiotactic polypropylene (sPP) were monitored using both Raman and FT-IR spectroscopic techniques. The study of the syndiotactic polypropylene has gained great scientific interest in recent years, primarily due to the presence of metallocene catalysts that allow the synthesis of polyolefins with high tacticity. Samples of syndiotactic polypropylene initially having helical crystalline conformations were stretched up to different levels of strain, and spectra were recorded. Quantitative analysis of these spectra revealed that the proportion of the helical and trans-planar conformations dramatically alters when the 100% level of strain is reached. In addition, molecular orientation studies based on polarized infrared spectra correlated the non-crystalline domains with the notable elastic properties of sPP specimens. Although the highly stretched samples contain pure trans-planar conformations, the removal of the external tension results in mixed conformations state where a partial return to the helical conformation is observed. Finally, the thermal induced phase transformation from trans-planar configurations to helical in the temperature range between 60oC and 90oC was monitored by using the above-mentioned vibrational spectroscopic techniques. These findings are in agreement with thermal studies also reported here that are based on DSC (differential scanning calorimetry) measurements.
CHARGED -HELICAL POLYPEPTIDES ORIENTED IN MULTILAYERS
M. MÜLLER, T. REIHS, B. KESSLER, K. LUNKWITZ
aInstitute of Polymer Research, Dresden, Hohe Straße 6, 01069 Dresden, Germany mamuller ipfdd.de
Polyelectrolyte multilayers (PEMs) fabricated by consecutive deposition of oppositely charged polyelectrolytes (PELs) due to electrostatic attraction [] enable selective surface modification and defined vertical nanoarchitectures. Using flexible PELs the internal structure of PEMs shows high entanglement, no distinct layering and a low degree of order. For the induction of macromolecular order in PEMs several concepts can be applied. For example PEMs of layered silicates alternating with polycations [] (i) and those composed of hydrophobic ionenes [] (ii) have been reported. Here we report on another concept based on charged stiff -helical polypeptides alternating with oppositely charged strong polyanions or polycations, respectively [] (iii).
PEMs composed of -helical poly(l-lysine) (PLL) and poly(vinylsulfate) (PVS) and those of poly(L-glutamic acid) (PLG) and PDADMAC, respectively, were deposited on unidirectionally scratched silicon substrates [, , ]. Dichroic ATR-FTIR spectroscopy was applied to quantify the orientation of the -helical rods. Based on the experimental dichroic ratio R of the amide I and amide II band order parameters S > 0.5 were determined (S=1 for high, S=0 for low order) suggesting a significant alignment of the -helical polypeptides in such PEMs. The influence of the polypeptide molecular weight and the layer number on the order parameter was studied.
PEMs exposing oriented -helices in-plane could be shown to specifically interact with -helical proteins, which can be used to create biomimetic layers for various applications.
References
THE THEORY OF THE ORIENTATION AND TRANSLATIONAL MOBILITY OF POLYMER NETWORKS WITH INCLUDED RIGID ROD-LIKE PARTICLES MANIFESTED IN THE NMR
YU. GOTLIB, I. TORCHINSKII, V. SHEVELEV
Laboratory of Theory and Computer Simulation of Polymers, Institute of Macromolecular Compounds, Russian Academy of Sciences, Bolshoi Prospect 31, V.O., St.-Petersburg, 199004, Russia; E-mail: yygotlib imc.macro.ru
In the recent years, there appeared many experimental investigations devoted to the structure and dynamics of polymer gels and networks with included rod-like particles. These systems may be of great interest due to the influence of the hard rods on the mechanical properties of gels, their applications as superabsorbents, in technique and medicine, etc. The theory of the relaxation spectra of homogeneous networks was also intensively developed. In this paper we present the results of the simplified ”coarse-grained” network theory of the network with included rods when the rods are long enough comparable with the distance between neighbouring junctions of the network and are distributed regularly in the network. The hard rods are described by effective quasi-elastic model in which the Lagrange multipliers in the equations of motion of hard rods are replaced by its average values. The relaxation spectra of this system are calculated for long-range network motions compared with the dimensions of the rod and the distance between junctions. The ”intrachain” effects of the influence of the rods on the short range motions were also discussed on the base of the theory developed by the authors previously. The fine structure of collective relaxation spectra of the network with rods were investigated. The relaxation spectra include collective branches and local motions of the rods at fixed junctions of the network. These relaxation spectra are responsible for the (1) local rotational and translational diffusion of the rods depending on the ratio of the length of the chain and rods and (2) for the motion of the network chains connecting the neighbouring rods. The local motions are mainly responsible for the relaxation times appearing in the temperature and frequency dependences of T1 in NMR and other types of orientational mobility.
This work was carried out with the financial support of
Russian Foundation of Basic Research (grants 02-03-33132,
02-03-06376), INTAS (projects 99-1114,
00-445, 00-712) and ESF Program "SUPERNET".
[1] Yu.Ya.Gotlib. 4th International Symposium ”Molecular Order and Mobility in Polymer Systems”, St.Petersburg, June 3-7, 2002, Book of abstracts, L-006.
INFRARED SPECTROSCOPY AND X-RAY DIFFRACTION STUDIES ON THERMAL BEHAVIOR OF BIODEGRADABLE POLYHYDROXYALKANOATE
H. SATO1, A. PADERMSHOKE1,2, M. NAKAMURA3, H. YAMAGUCHI1, H. TERAUCHI3, S. EKGASIT2, I. NODA4, Y. OZAKI1
1Department of Chemistry, School of Science and Technology, Kwansei-Gakuin University, Sanda, Hyogo 669-1337, JAPAN
2Department of Chemistry, Faculty of Science, Chulalongkorn University, Patumwan, Bangkok 10330, THAILAND
3Department of Physics, School of Science and Technology, Kwansei-Gakuin University, Sanda, Hyogo 669-1337, JAPAN
4The Procter and Gamble Company, 8611 Beckett Road, West Chester, Ohio 45069, U.S.A.
The thermal behavior of a new type of bacterial copolyester, poly(3- hydroxybutyrate-co-3-hydroxyhexanoate); P(HB-co-HHx) (HHx = 12 mol%) was investigated by using wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). The WAXD measurements were carried out over a temperature range of 25 to 110 oC in the range of 2θ = 5 - 13o. The WAXD pattern at room temperature shows that the P(HB-co-HHx) copolymer has an orthorhombic system (α=β=γ=90°) with a=5.76Å, b=13.20Å, c=5.96Å (fiber repeat), which is identical to the crystal system of Poly(3-hydroxybutyrate) (PHB). Temperature- dependent variations in the lattice parameters, a and b, of P(HB-co-HHx) are quite different from each other as in the case of PHB. Only the a lattice parameter increases with temperature, while the b lattice parameter changes very little in the P(HB-co-HHx) crystalline. It seems that the intermolecular and intramolecular interactions between the C=O group and the alkyl group decrease along the a axis of P(HB-co-HHx) crystalline with temperature. The DSC measurements of the chloroform solution cast P(HB-co-HHx) shows a re-crystallization peak clearly around at 51oC. The variations of the FT-IR spectra around at 60oC may be caused by the re-crystallization process of the sample. The (110) peak area of WAXD patterns of the chloroform solution cast P(HB-co-HHx) shows a maximum value at around 45oC. The maximum of the (110) peak area demonstrate the re-crystallization process of P(HB-co-HHx). It is in good agreements with the results of DSC and FT-IR.
CRYSTALLINITY OF POLY(ETHYLENE TEREPHTHALATE) BY FAR INFRARED SPECTROSCOPY
M. DOSIERE
Université de Mons-Hainaut, Laboratoire de Physicochimie des Polymères
Place du Parc, 20, B –7000 –Mons (Belgique)
The vibrational spectra of synthetic polymers between 4000 and 400 cm-1have been intensively studied since it was suggested that the infrared spectra could be used to determine their crystallinity. Further investigations showed unfortunately that this success was largely illusory. What is observed in a vibrational spectrum is not necessarily the presence of crystalline material in a sample but the presence of particular conformers of a macromolecule which can exist in the crystal. For example, only the fully extended trans conformation of the polyethylene chain will pack into the crystalline regions and in the case of poly(ethylene terephthalate) the glycol residue must be in the trans conformation. However, in both these polymers the trans conformer can be present in the amorphous regions. Therefore, the hypothesis that measuring the trans/gauche ratio is equivalent to measure the crystalline/amorphous ratio is false. It must however not be concluded that spectra in the medium Infrared (MIR) region have nothing to say about the crystallinity of polymers. So a close examination of the MIR spectrum of a semi-crystalline polymer will usually reveal that with increasing crystallinity, bands arising from molecular units in the correct conformation to enter the crystalline regions become considerably sharper and narrowed while bands due to non-crystalline conformers have decreased in intensity.
The infrared bands arising from the vibration of neighbouring chains in a molecule appear below 400 cm-1, i.e. in the far infrared region, a favoured region for the direct observation of intermolecular modes in polymers. The FIR spectra of isotactic polypropylene1 and poly(aryl ether ether ketone)2 have been successfully used to determine the degree of crystallinity of these polymers.
This communication concerns the determination of the degree of crystallinity of poly(ethylene terephthalate) or PET from DSC, density, wide-angle X-ray measurements and FIR spectra. A Brüker IFS 66V working under vacuum with a Mylar beam splitter and a globar as source was used to record the FIR spectra of isotropic films of PËT. Samples with various degrees of crystallinity have been obtained by annealing amorphous films in the temperature range of 80 to 230 °C. The analysis of the FIR spectra of amorphous and semi-crystalline PET films clearly shows that :
a) bands at 138, 238, 381-384 and 438 cm-1 are ”crystalline bands”; b) bands at 290, 344, 425 and 500 cm-1 are ”amorphous bands” ; c) the absorbance of the band at 632 cm-1 is related to the thickness of the sample. The different ways to estimate the degree of crystallinity of PET is discussed.
References
1. Goldstein,M.; Seeley,M.E.; Willis,H. A.; Zichy V. J. I. Polymer,14, 530 (1973).
2. Damman, P.; Fougnies, Ch.; Moulin, J.-F.; Dosière M., Macromolecules, 27, 1582-1587 (1994).
3. Kong, Y. ; Hay, J. N., Polymer,43, 3873 (2002)
SHEAR-INDUCED ORDER IN NEMATIC POLYMERS
P. BECKERa, H. SIEBERTa, L. NOIREZb, C. SCHMIDTc
aAlbert-Ludwigs-Universität Freiburg, Institut für Makromolekulare Chemie, Stefan-Meier-Str. 31, D-79104 Freiburg, Germany
bLaboratoire Léon Brillouin, CE-Saclay, F-91191 Gif-sur-Yvette, France
cUniversität Paderborn, Department Chemie, Warburger Str. 100, D-33098 Paderborn, Germany, schmidtc chemie.upb.de
Nematic liquid crystals exhibit peculiar phenomena in shear flow, which are caused by the coupling between director orientation and flow. Most interesting is the fact that there are two different types of nematics: flow-aligning materials, which adopt a stable director orientation in shear flow, and tumbling materials, which are characterized by the absence of a stable director orientation when sheared. The former systems form a monodomain in shear flow, whereas quasi-periodic defect structures are observed for the latter.
We have used in situ deuteron NMR on different types of sheared nematic polymers to investigate their flow behavior [1,2]. In a systematic study on side-chain liquid crystal polysiloxanes with varying side-chains we employed 2H NMR, small angle neutron scattering, and x-ray scattering to determine the type of flow behavior, the shape of the polymer molecules, and the phase structure, respectively. As a result the flow behavior of these side-chain polymers could be clearly related to their phase structure. Only polymers with smectic clusters in the nematic phase show the tumbling phenomenon. In this respect, the side-chain polymers are similar to small molecule nematics.
On the other hand, lyotropic nematic solutions of poly(benzyl-L-glutamate) are also of the tumbling type. The flow behavior exhibited in our NMR studies is very similar to that of an aqueous surfactant solution consisting of nematic worm-like micelles. This indicates once more that the phase structure, in this case long semi-rigid chains with nematic order, determines the flow properties.
1. D. A. Grabowski and C. Schmidt, Macromolecules, 27, 2632 (1994).
2. H. Siebert, P. Becker, I. Quijada-Garrido, D. A. Grabowski, and C. Schmidt, Solid State Nuclear Magnetic Resonance, 22, 311 (2002).
THEORY OF INTRACHAIN RELAXATION SPECTRA FOR POLYMER NETWORKS POSSESSING A SHORT- OR LONG-SCALE ORIENTATIONAL ORDER.
V. TOSHCHEVIKOV, YU. GOTLIB, I. TORCHINSKII, V. SHEVELEV
Laboratory of Theory and Computer Simulation of Polymers, Institute of Macromolecular Compounds, Russian Academy of Sciences, Bolshoi Prospect 31, V.O., St.-Petersburg, 199004, Russia; E-mail: vova imc.macro.ru
Relaxation spectrum of any complex polymer system is an important characteristic because it can be manifested in NMR, polarised luminescence, mechanical and dielectric relaxation, etc. Many works were devoted to study the dynamic properties of isotropic Gaussian polymer networks (see, e.g., [1]).
We consider ”intrachain” relaxation spectra for polymer networks possessing a some types of chain segments ordering. ”Intrachain” relaxation spectra [1] are displayed at the times smaller than the maximal relaxation time of a network strand and correspond to motions at which the network junctions remain immobile. We discuss the influence of chain rigidity, which can lead to local ordering of chain units on the relaxation of autocorrelation function of second Legendre polynomial P2(t). The quantity P2(t) characterises the diffusion rotation of chain segments with respect to a given direction and is manifested in NMR and polarised luminescence. Both bending and torsional rigidity of network strands are taken into account. The origin of power- and stretched exponential time dependences in P2(t) is discussed.
The second part deals with relaxation properties of polymer networks with long-scale nematic order caused by nematic-like interactions between both chain segments [2] and included rod-like particles. Relaxation spectrum of ordered network consists of two branches corresponding to relaxation of chain segments projections along and perpendicular to the director. Dependences of relaxation times on the order parameter and a parameter characterising the chain stretching between network junctions and degree of cross-linking are considered.
This work was carried out with the financial support of
Russian Foundation of Basic Research (grants 02-03-33132,
02-03-06376), INTAS (projects 99-1114,
00-445, 00-712) and ESF Program "SUPERNET".
CRYSTALLIZATION OF POLYMERS INDUCED BY SUPERCRITICAL CARBON DIOXIDE
S.G. KAZARIAN, K.L.A. CHAN, O. FLEMING
Department of Chemical Engineering and Chemical Technology, Imperial College London, South Kensington Campus, SW7 2AZ, United Kingdom
Supercritical CO2 can swell and plasticize glassy polymers, it can also affect semi-crystalline polymers by plasticizing their amorphous phase. CO2-induced plasticization of amorphous polymers increases the mobility of polymer chains, which allows the chains to rearrange into more ordered configurations, resulting in induced crystallization and concomitant change in morphology. FTIR and Raman spectroscopy have been applied to elucidate the morphology and microstructure of polymers processed with supercritical CO2. Poly(ethylene terephthalate) (PET) and syndiotactic polystyrene (sPS) subjected to high-pressure or supercritical CO2 have been investigated. The changes in degree of crystallisation of PET were followed via bands in Raman spectrum. ATR-IR spectroscopy has also been applied to PET processed with supercritical CO2. We have also examined the changes in the ATR-IR spectrum of a films of amorphous PET and sPS that have been subjected to supercritical CO2. Dramatic changes in the IR spectra have been observed indicative of appearance of the crystalline form of polymer. Further support for our assignment comes from our recent measurements of the confocal Raman spectra of the same PET and sPS samples treated with scCO2 and comparison of these results to Raman spectroscopic studies of polymer films treated with organic solvents. This preliminary study has supported the proposal that crystallinity has been induced in amorphous PET and sPS after treatment of the sample with scCO2. A novel spectroscopic cell has also been developed to allow us to measure in situ both confocal Raman and ATR-IR spectra of polymers subjected to supercritical fluids.
Finally, we applied FTIR Imaging approach to study polymeric materials subjected to high-pressure CO2. The enhanced chemical visualisation allows us to measure the effects of CO2 on the morphology of polymer blend, and simultaneously measure sorption of CO2 into different domains of heterogeneous polymer blend. This is the first time that FTIR Imaging was applied under high-pressure in a previously unknown way to study materials in contact with supercritical fluid. Spectroscopic FTIR imaging opens a window of opportunities that would facilitate the understanding of materials processes with supercritical fluids. The implications of this novel imaging technology to study high-pressure processes will be discussed.
VIBRATIONAL SPECTROSCOPY OF ION IRRADIATED
CARBON-CONTAINING MACROMOLECULES
G. STRAZZULLAa, G. BARATTAa, R. BRUNETTOa, F. CATALDOb
aINAF-Osservatorio Astrofisico di Catania, Via S. Sofia 78, I-95123 Catania, Italy
bSocietà Lupi arl, Chem Res Inst, Via Casilina 1626/A, 00133 Rome, Italy
A large variety of carbon rich macromolecules has been studied in our laboratory, before, during, and after ion irradiation (3-60 keV ions), by in situ IR and Raman spectroscopies. The studied materials include: (a) frozen hydrocarbons (benzene, methane, butane, acetylene, etc.) films that have been deposited at low temperature on a substrate, and irradiated with fast ions. Irradiation causes the formation of an organic refractory residue. (b)CCondensed PAHs (coronene, pentacene, etc.) whose IR and Raman spectra have been studied also during ion irradiation. (c)Thin samples of fullerene (C60 and C70) films obtained by depositing some drops of fullerene in a CS2 diluted solution on a substrate and allowed to evaporate to leave a uniform microcrystalline fullerene film.
Here we discuss some of the most relevant results and compare the spectra of the very different samples most of which, because of irradiation, evolve towards amorphous carbons that have some common spectral characteristic.
SEARCH OF STRUCTURAL AND ORIENTATIONAL CHARACTERISTICS OF THE SURFACE POLYMER LAYERS BY METHOD OF FTIR- SPECTROSCOPY
B.Z. VOLCHEK, E.N. VLASOVA, S.V. KONONOVA, I.I. TARASENKO, G.P. VLASOV
Insitute of Macromolecular Compounds of Russian Academy of Science, Bolshoi prospect 31, v.o., 199004, St.-Petersburg, Russia
At present time, the great interest to study of nanostructures is observed. Among them, in particular, the thin boundary monolayers consisting of long macromolecules, connected by one of its end to some impenetrable surface, are in special interest. Such structures have received the name of polymeric brushes. The polymeric brushes are the rather widespread polymeric system or at least the elements of such system. Theoretical investigation of macromolecule properties which are forming brushes, have shown, that the orientational and conformational characteristic, so as the nature of phase transitions depends on external conditions, such as a chemical structure of surface, density of an polymer chains inoculation, distance of an inoculation from a surface, quality of the solvents, and flexibility of macromolecules. In the report, the opportunity of application FTIR-spectroscopy for study of major parameters of polymeric brushes is analyzed. Two types of polymeric brushes were investigated. The first one is a planar polymeric brushes consisting of solid planner surface (Al, Au) with bounded to it polyaminoacids in helical conformation. A technique of grazing incidence reflection was applied and the original technique of definition of orientatonal macromolecular parameters of polymeric chains was suggested. Another type of systems were cylinder brushes, where polyaminoacids in helical conformation play role of cylinder surfaces with hydrocarbon chains of different length attached to its rigid skeleton. In this case, the conformational and orientational characteristics of hydrocarbon chains in block, LC and isotropic states by a method of FTIR-spectroscopy were determined.
Influence of the surface on structural and orientational characteristics in the thin polymeric layers may appear in two-ply polymeric systems such as combine membranes. These membranes consist of rigid base – polymer with tg>>tk and diffusion layer (tg < tk ). It was shown by a method of FTIR-spectroscopy in technique of ATR and transmission that unusual selective properties of such membranes (in divitation to Henis - Tripody principle) are refer in the more case to the changes in conformational composition of thin surface layer between two polymers (skin layer) then to orientation of macromolecules of diffusion layer.