Posters

SYNTHESIS AND CHARACTERISATION OF GAS PERMEATION THROUGH NOVEL BASED POLY IMIDE MEMBRANES

¹Dept. of Pure and Applied Chemistry, Thomas Graham Building, University of Strathclyde, Glasgow, G1 1XL, UK

² Department of Chemistry, The University of Liverpool, Crown Street, Liverpool, L69 7ZD, United Kingdom

Based on a new synthesis method novel poly(ether imide)s with high solubilities that retain excellent mechanical and thermal properties have been synthesised. The bis(ether anhydride)s that were not previously available were synthesised by nucleophilic displacement reactions between nitrophthalodinitrile and an aromatic diol in the presence of an alkali metal carbonate. The reaction produced the corresponding tetranitrile which was subsequently hydrolysed to bis(ether diacid) and finally the bis(ether anhydride) formed by cyclodehydration. Polyimides were prepared by chemical imidisation in N, N´-dimethylacetamide (DMAc) under nitrogen at room temperature. The membranes for gas separation were obtained by casting the polyimides dissolved in chloroform. Pure gas permeation experiments for CO₂, N₂, O₂ and Ar at 298 K and 4 atm were performed for all the polyimides. The diols utilised to obtain the new dianhydrides were Bisphenol-A and analogous derived diols which included fluorine atoms and methylene groups ortho to the oxygen bond. The obtained permeability data for the poly(ether imide)s showed the influence of these chemical structure changes. The fluorine atoms between phenyl rings caused a disruptive effect that reflected in less efficient packing of the polyimide and subsequently higher permeability to gases. This difference was measured by means of the fractional free volume calculated from the group contribution method defined by Bondi. The chemical structure alteration produced by the introduction of methyl groups ortho to the ether bond of the bis(ether anhydride) hindered rotation and constrained the number of possible structural conformations that the polymer was able to adopt, as a result the permeability increased. For the purpose of measuring the energy barriers for torsional rotation around the ether bond Spartan 5.0 molecular modelling software was used. The results obtained showed a clear difference. The energy barrier value for rotation around the ether bond increased dramatically from 0.4 kcal/mol for the dianhydride with no steric hindrance to 4 kcal/mol for the dianhydride sterically hindered by methyl groups in the ortho position. >From these values could be observed and corroborated that the methyl groups ortho to the ether bond represent a clear impediment for the polymer chain to rearrange itself, therefore more ”microvoids” available for gas diffusion might be present in the polymer matrix.

P02

PURIFICATION OF LEACHING SOLUTIONS FROM A POLYMETALLIC COMPLEX ORE BY MEANS OF ULTRAFILTRATION COMPLEXATION

Laboratory of hydrometallurgy and Inorganic Molecular Chemistry, Faculty of Sciences, Department of Chemistry and physics of inorganic materials, University of Sciences and Technology of Houari Boumediene (U.S.T.H.B), BP 32, El – Alia, 16111 Bab Ezzouar, ALGIERS, ALGERIA Fax : 213-2-24-73-11 Email : dakretche / hotmail.com

Ultrafiltration is a membrane process that is used to molecules separation according to their sizes. By this fact, it can be considered as a possible separation - concentration process inserted in a hydrometallurgical flow - sheet. On the other hand, water-soluble polymers can form more stable complexes with metallic ions. Their practical interest is increasing, since they often, involve the ultrafiltration complexation process applied to various media.

In this work, ultrafiltration and complexation with polyethyleneimine (noted PEI) are applied to the purification and concentration of leaching solutions from an Algerian polymetallic ore. Experiments were performed using a tangential ultrafiltration cell with a mineral membrane (Alumina) which has 50 nm of porosity and 250 cm2 of area. The pressure was fixed to 0.2 Bar and the temperature to 298 K (in a fixed room temperature). Solutions used were obtained by means of both sulphuric acid and ammonia leaching. Their average composition was 10-3M of Copper, 2.10-4M of Zinc and 10-5M of Lead. The PEI used was around 600.000.

Initially, conditional stability constants of copper, zinc and lead with PEI have been determined as a function of the pH. They have allowed doing a correlation with real solutions by fixing the pH. Rejections were studied versus the concentration of ligand added at a given pH. Results obtained have shown that copper was well retained and separated from zinc and lead. The separation factors were evaluated and they were higher in ammonia medium because the mixed complexes (amino-PEI) of copper were more stable. The enrichment factors were shifted and compared to others separation - concentration processes.

Finally, optimised parameters were used to perform ultrafiltration complexation using an IRIS 3028 organic membrane. Differences on the results have been discussed.

P03

SEPARATION OF COPPER AND SILVER BY DONNAN DIALYSIS USING BOTH CATION EXCHANGE AND MICROPOROUS MEMBRANE

Faculty of Sciences, Department of Chemistry and physics of inorganic materials, University of Sciences and Technology of Houari Boumediène (U.S.T.H.B), BP 32, El – Alia, 16111 Bab Ezzouar, ALGIERS, Algeria

Copper and Silver are often associated in ores. Their separation was studied by means of various methods and results were obtained depending upon their concentration ratios and their form in solution. In diluted solution, Donnan dialysis can be an efficient technique which can compete others processes as ion exchange resin because the reduction of the number of operations units.

In this work, Donnan dialysis of both copper and silver solutions were studied using both cation exchange (CMV and CMS) and microporous membranes (ultrafiltration membrane DDS 50 kD). In the first case, the receiver was composed by a nitric acid solution while the Polyethyleneimine (noted PEI) is added when the microporous membrane is used.

Donnan dialyses were performed using a laboratory cell in Teflon composed by two compartments of 100ml where both the feed and receiver solutions are mixed. The mole numbers of metallic ions are followed inside the two compartments by means of atomic spectrophotometer PERKIN ELMER 2380 at regular interval of time.

Fluxes of the two ions were measured and compared as a function of both the composition of the receiver compartment and the nature of the membrane. The effect of the pH in the feed compartment, where the metal concentration ratios were varied, was also studied and linked to the chemical potential of the two solutions and the ion electric charges. It was shown that the PEI enhances the ion transfer according to the conditional stability of the complexes formed during the transfer across the microporous membrane. Separation factors were shifted and effect of ammonia was also studied inside the feed compartment. It was shown that the separation between copper and silver is dependent of various parameters and the microporous membrane can be more efficient according to the initial composition of the feed solution.

P04

Heterogeneous membranes based on polymeric adsorbents for separation of small molecules

¹ Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Prague 6, Czech Republic

³ J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Prague 8, Czech Republic

Membrane separations are in permanent competition with alternative separation methods such as adsorption and column technologies. Membranes prevail in large-scale processes enabling automation of separation. So far to now the number of published results on membranes filled with a polymeric adsorbent has been rather low^, . Pervaporation membranes for removing volatile organic compounds from wastewaters were prepared by Sikdart, Ji, and Hwang. In the previous paper we described preparation of heterogeneous zeolite-based membranes with a polymer binder. Heterogeneous microporous membranes might be used as separation media for gases, membrane reactors, sensors, etc.

This study deals with the preparation and characterization of heterogeneous membranes based on polymeric adsorbents with a polymeric binder. The macroporous or hypercrosslinked copolymers with enhanced micropore contents and with specific surface area values from 400 to 1000 m²/g were used as fillers. Microparticles of hypercrosslinked copolymers were prepared via Friedel-Crafts reaction from dilute polystyrene solution. Polyisobutylene, poly(phenylene oxide), or an epoxide resinwere used as a binder.Thickness and the polymer/adsorbent ratios were changed in membrane preparation. Membranes were casted from solution or prepared by polymerization. A porous α-Al₂O₃ support improves mechanical properties of the heterogeneous membranes.

Separation selectivity and permeability to small organic molecules such as H₂/CH₄ and CH₄/CO₂ mixtures were determined using a Wicke-Kallenbach cell. Temperature and the gas ratios were changed during the measurements. The H₂ permeability obtained is about 0.1 to 1.3.10^-13 mol Pa^-1s^–1 m^-1. The CH₄permeability is about an order lower. The evaluated selectivity’s range from 1.3 to 19.1. The permeability and selectivity for H₂ increase with increasing amounts of H₂ in the gas mixture and with temperature. Increased selectivity was observed with the high adsorbent/binder ratio.

A molecular model of equilibrium sorption, dissolution or diffusion of species in microporous or compact subspaces of composite matrices may operate in heterogeneous membranes with a polymer binder. The differences in the diffusion flux of hydrogen and methane confirm that the separation on our heterogeneous membranes is governed by the size exclusion mechanism.

This works was supported by grant No203/99/0522 from Grant Agency of the Czech Republic, which the authors gratefully acknowledge.

P05

High-Performance Polymer Pervaporation Membranes for the Separation of Methanol/Methyl-tert-Butyl Ether Mixtures

Yurij P. Kuznetsov, Svetlana V. Kononova, Hans-Hartmut Schwarz^*, Regine Apostel^*

Institute of Macromolecular Compounds of Russian Academy of Sciences
Bolshoy pr., 31, 199004, St.-Petersburg, Russia; e-mail: kuznets / hq.macro.ru ;

^*Institute of Chemistry, GKSS Research Center, Kantstrasse 55, D-O-1530 Teltow, Germany

P06

Dehydration of N,N-Dimethylformamide by Hybrid Processes; 1. Membrane Development

H.C.W.M. Buijs^a, R.J. Van EE^a, A.H.A. Tinnemans^a, J.M.K. Timmer^b, P.F.M. Steegs^c, J.T.F. Keurentjes^c

P07

CHARACTERISATION OF NANOFILTRATION MEMBRANES FOR THE SEPARATION OF AQUEOUS DYE-SALT SOLUTIONS

University of Pardubice, Faculty of Chemical Technology, Department of Chemical Engineering, nám. Čs. legií 565, CZ-532 10 Pardubice, Czech Republic

The main objective of the present work was to study the process of nanofiltration of aqueous dye-salt solutions in order to describe the process of desalting of organic dyes by polymeric nanofiltration membranes. Nanofiltration experiments were carried out for different dye/salt ratios and different pressures. Experiments of basic nanofiltration membrane characterisation (permeation of single salt solution NaCl, MgSO₄) were carried out as well. All experimental data were analysed by extended Spiegler-Kedem model. Very good prediction was obtained for salt permeation. Prediction of performance of nanofiltration of aqueous solutions characterised by salt retention was possible even for high dye concentrations (Fig. 1), typical for desalting process. Also comparison of salt retention and permeation rate for dye-salt solutions for three commercial membranes (spiral wound modules) was carried out.

FIG. 1 The salt retention as a function of the salt concentration at different dye concentrations.

P08

SYNTHESIS AND GAS TRANSPORT PROPERTIES OF BLOCK COPOLYMERS COMPOSED OF POLY(STYRENE-co-ACRYLONITRILE) AND POLYSTYRENE

^aDepartment of Polymeric Membranes, Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovského nám. 2, CZ-162 06 Praha 6, Czech Republic

^bDepartment of Analytical Chemistry, Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovského nám. 2, CZ-162 06 Praha 6, Czech Republic

Radical copolymerization of styrene (S) and acrylonitrile (AN) aiming at the preparation of nitroxide-terminated macroinitiators for the block copolymers synthesis was carried out at 125 ^oC in the presence of a thermal initiator, dibenzoyl peroxide, and 2,2,6,6-tetramethylpiperidin-1-yloxyl (TEMPO) radicals. The starting mixtures had the azeotropic composition, i.e., they contained 63 mol % of S and 37 mol % of AN. The obtained TEMPO-terminated S-AN copolymers showed narrow molecular weight distributions. Both the linear semilogarithmic time - conversion and molecular weight - conversion dependences indicated a quasiliving copolymerization process. Polymerization of styrene initiated with the synthesized macroinitiators containing reversibly bound terminal TEMPO groups yielded film-forming poly(styrene-co-acrylonitrile)-block-polystyrene copolymers. Using the resulting diblock copolymer as a macroinitiator in copolymerization of S and AN, a triblock copolymer was obtained.

Membranes were prepared by casting chloroform solutions of the block copolymers; their permeabilities to nitrogen, oxygen, methane, carbon dioxide, and hydrogen were determined. The block copolymers under study are promising membrane materials, exhibiting in particular high selectivities to oxygen (the ratio between the permeability to oxygen and that to nitrogen being > 6).

The study was supported by the Grant Agency of the Czech Republic (No. 203/99/0572).

P09

P10

Electrical properties of sulfonated poly(ether ether sulfone) dense membranes

(*) Departamento de Física Aplicada, Facultad de Ciencias. Universidad de Málaga. E-29071 Málaga. SPAIN

(**) Instituto de Ciencia y Tecnología de Polímeros, CSIC. E-28006 Madrid. SPAIN

Polysulfones are materials commonly used for ultrafiltration membranes, and also as the support layer in composite reverse osmosis membranes for water desalting. However, polysulfones are relatively hydrophobic polymers, so that attempts have been made to improve the hydrophilicity of polysulfones by a number of methods, for example, by introducing sulfonic groups. The ionic nature of these groups greatly enhances the transport of water through membranes, and the improvement of hydrophilicity helps for the membranes to become more fouling-resistant. Sulfonated polymers have got also special importance as materials for fuel cell membranes in last years, where a strong demand has arisen for polymer electrolytes.

In this work, two samples of sulfonated polysulfone with different sulfonation degrees (SG10 with 10% of sulfonation and SG20 with 20% of sulfonation) are studied. The polymer were characterised by their inherent viscosity, thermal transition and water adsorption. This last parameter clearly increases when the sulfonation degree increases (around 8% for SG10 and 15% for SG20 samples, while for the dense film or SG0 is only 1-2%).

Electrical characterisation of membranes was carried out by Impedance Spectroscopy (IS) measurements, when the membranes were in contact with NaCl solutions at different concentration (10-3≤ c (M)≤ 2x10-2), by means of a Frequency Response Analyser with frequency ranging between 10 Hz and 5 Mhz, and using equivalent circuits as models. Results showed how the sulfonation clearly affected the equivalent circuits of the different electrolyte/membrane systems as well as the electrical parameters for each membrane. In fact, conductivity for the SG10 membrane increased more than 1000 times with respect to the dense film, while the electrical resistance of the SG20 membrane was only 10 times higher than that corresponding to a solution layer of the same thickness and cross section. IS measurements for the SG10 membrane also allowed the determination of the interface parameters (charge transfer resistance and electrical double layer capacitance). Concentration dependence for the electrical parameters of the different membranes was also considered; a decrease of the electrical resistance of both membranes and interface when the salt concentration increases was observed, but equivalent capacitances and Warburg impedance associated to the different processes were practically independent of electrolyte concentration.

P11

*A.V.Topchiev Institute of Petrochemical Synthesis, Membrane Center, 29 Leninsky Pr., 119991, Moscow, Russia, ** A.N.Nesmeyanov Institute of Elementoorganic Compounds, 28 ul. Vavilova, 117813, Moscow, Russia

Relationships between chemical structure of polymers and their transport properties are well established and serve as a basis for prediction of the transport parameters and directed synthesis of novel advanced membrane materials. However, still unanswered is the question how features of the chemical structure of repeat units affect polymer transport parameters. For better elucidation of the mechanism of gas diffusion and sorption it is relevant to know how features of the chain dynamics and detailed structure of free volume affect gas permeation properties of polymers. In this work, we present a new approach to this problem, namely demonstrate a relation between conformation rigidity of macromolecules and the transport parameters. This correlation is considered for polyimides, an important class of membrane materials.

The calculations of conformational rigidity parameters of polyimides were carried out on the basis of approximations of free and hindered rotation for the polymers having various side groups as has been described earlier [1,2]. In the former case, the Monte-Carlo method [1] was employed, whereas the effects of hindered rotation were taken into account using the conformational energy function U(j ) found via the quantum mechanical method AM1 [2]. The values of conformational rigidity parameters calculated for different approximations and for various structures were compared with the transport parameters of the polyimides included in the Data Base [3] and experimental data measured by mass-spectrometric method in respect of different gas molecules.

A novel correlation for gas permeability is shown for several series of polyimides that are structurally related but distinguish by m- or p-substitution in phenylene rings of the main chains. It was demonstrated that a reduction of conformational rigidity due to the changes of the substitution type leads to a decrease in gas permeability. A magnitude of this effect depends on the nature of penetrants. These regularities are manifested more explicitly for the series of polyimides and polyetherimides having common dianhydride or diamine component. The parameters of these correlations in respect of gas molecules depend on molecular kinetic diameters of penetrants.

It can be assumed that conformational rigidity of polyimides influences the chain packing density, which results in smaller or larger free volume in a polymer. However, this factor can affect also the small scale mobility of the chains, which influences the gas diffusion coefficients. A discrimination between these two factors is an important problem of future studies, which are now in progress.

1. S.S.A. Pavlova, I.A. Ronova, G.I. Timofeeva, L.V. Dubrovina J.Polym.Sci. Polym.Phys.Ed., 1993, 31, 725.

2. M.J.S.Dewar, E.F.Zoebosch, E.Healy, J.J.Stewart J. Am. Chem. Soc. 1985. 107, 3903.

3. Gas separation parameters of glassy polymers, The Database, No 3585, Informregistr of RF, 1998.

P12

S.SOLOVIEV*, YU.YAMPOLSKII*, S.SEMENOVA**, V.DUBYAGA**, A.TARASOV**, N.USHAKOV*, E.FINKELSHTEIN*

*A.V.Topchiev Institute of Petrochemical Synthesis, Membrane Center, 29 Leninsky Pr., 119991, Moscow, Russia **ZAO-NTC VLADIPOR, VLADIMIR, 77 B.NIZHEGORODSKAYA.

Novel rubbery membrane materials are needed for separation of higher and lower hydrocarbons in natural and associated gases and removal of volatile organic compounds vapors from permanent gases. Such materials must reveal better stability than polydimethylsiloxane in contact with hydrogen sulfide and other sulfur containing compounds. Silamethylene polymers that contain Si-C bonds are very stable in respect to acid hydrolysis and can be considered as potential membrane materials for natural and associated gas treatment.

Poly(dimethylsilamethylene) (PDMSM) is amorphous rubber with the glass transition temperature T_g = –95^oC. Poly(dimethylsiltrimethylene) is semi-crystalline material (degree of crystallinity 10-50% depending of conditions of film formation, melting point T_m = 43^oC) with T_g = -75^oC. Permeability and solubility coefficients of normal alkanes C₁-C₄ were measured using mass-spectrometric and inverse gas chromatography methods, respectively. Permeability coefficients, P, Barrer, at 25^oC of PDMSM and PDMSTM are compared with those of polydimethylsiloxane (PDMS):

Gas	PDMSTM	PDMSM	PDMS
Gas	[-Si(CH₃)₂CH₂CH₂CH₂-]_x T_g, ^oC = -75	[-Si(CH₃)₂CH₂-]_x -95	[-Si(CH₃)₂O-]_x -123
CH₄	8.4	130	950
C₂H₆	26	360	2500
C₃H₈	37.6	563	4100
C₄H₁₀	224	2780	9000
a (C₄/C₁)	26	21	9.5

It is seen that an increase in T_g reduces significantly gas permeability. In the case of PDMSTM it can be additionally decreased because of cristallinity of this polymer. However, PDMSTM and PDMSM are more selective than PDMS.

Solubility coefficients S of three silicon-containing rubbers are compared below at 45^oC:

It can be concluded that the S values are approximately the same for all the polymers. Hence, a decrease in permeability is caused mainly by decreases in diffusivity of polymers with higher T_g and reduced segmental mobility.

Acknowledgement This work was supported by NATO Science for Peace grant 972638.

P13

APPLICATION OF HYDROPHOBIC (WATER-IMMISCIBLE) AND HYDROPHILIC (WATER-SOLUBLE) LIQUID MEMBRANES IN THE CARBOXYLIC ACIDS SEPARATION TECHNOLOGIES: COMPARATIVE ANALYSIS

Casali Institute of Applied Chemistry, The Hebrew University of Jerusalem, Campus Givat Ram, 91904 Jerusalem, Israel vkislik / vms.huji.ac.il

Application of Hybrid liquid membrane (HLM) and Aqueous hybrid liquid membrane (AHLM) methods in the separation of carboxylic acids is presented. Both systems are based on the three-step process, which involves ion-exchange dialysis through the two ion-exchange membranes (IEM) and reversed reaction-diffusion cycle with the liquid membrane (LM) carrier. The difference between these two methods is an application of water immiscible carrier solutions in the HLM and water-soluble carriers in the AHLM.

Separations of lactic, acetic and citric acid mixtures were tested. The basic parameters, such as mass-transfer rate, recovery, selectivity, membrane stability and regeneration ability were studied and compared, using both HLM and AHLM systems.

For the separation of carboxylic acid mixtures with the HLM system, Alamine 336 in kerosene, separated by anion-exchange membranes, was tested as LM. Results showed that the selective separation of acids may be achieved using a single set-up installation at continuous processing, but the key problems, such as leakage of the carrier and membrane instability, remain. Formation of reversed micelles and even microemulsion on the membrane surfaces led to the loss of transport rates and selectivity during prolonged operation.

At the AHLM treatment, branched polyethylenimine (BPEI) aqueous solutions, separated by anion-exchange membranes, or polyvinylsulfonic acid (PVSA) aqueous solutions, separated by cation-exchange membranes, were tested for the separation of acids. Sodium hydroxide or nitric acid were used as receiving (strip) solutions. High transport rates (4.5*10^-6 - 2.5*10^-5 mol/m²sec) and selectivities (8 - 400) were found. Stable fluxes were observed. Leakage of the polyelectrolites was not observed during the 600 hrs of processing. The membranes were completely regenerable and used repeatedly. Suggested interaction mechanisms and transport kinetics were discussed.

In comparison with the HLM and other liquid membrane systems, the AHLM can potentially provide many operational, economic and environmental advantages, some of them being higher transport rates and selectivies, low carrier losses and low contamination of the feed and strip solutions by water-soluble polymers, long membrane lifetime, ambient temperature, low energy requirements and chemical consumption, no special requirements for membrane resistance in organic solvents, fewer limitations on the variability of membrane pore size, etc. The AHLM is particularly attractive for application in the liquid waste treatment due to its high selectivity and uphill concentration. The AHLM separation technologies may be based on commercially available ion-exchange spiral or hollow-fiber membrane modules and equipment.

P14

Chemically and Thermally Stable Polydiacetylene Membranes Containing Boronic Acid Moiety

P15

P16

Extraction Recovery and Separation of Heavy Metals from Aqueous Solutions Using Microporous Hollow Fibers

Department of Chemical Engineering, Yuan Ze University, Chung-Li 320, Taiwan,*Fax: 886-3-4559373 E-mail: cejuang / ce.yzu.edu.tw

The extraction recovery and separation of Zn²⁺ and Cu²⁺ from sulfate solutions in a microporous hollow fiber module with a kerosene solution of di(2-ethylhexyl)phosphoric acid was investigated. The module used was the Liqi-Cel G261 Extra-Flow Membrane Contactor (Hoechst Celanese, X30 PP fibers). The aqueous solution was fed in the tube side of the module, and the organic solution flowed across the shell side in parallel to the aqueous solution. A mass transfer model was presented considering the aqueous stagnant layer diffusion, membrane diffusion, and organic stagnant layer diffusion on the basis of a good knowledge of the transport properties of the relevant geometry. It was shown that the calculated time profiles of aqueous-phase concentrations of metals reasonably agreed with the measured results (standard deviation, 12%). Under comparable conditions the non-equilibrium separation factor of Zn²⁺ over Cu²⁺, defined as the ratio of extraction percentages of both metals, was smaller than that obtained from equilibrium results. For example, at pH 2.1 and an extractant concentration of 0.2 mol/dm³, the non-equilibrium separation factor (after 20-min operation) was 3.6 only at 298 K whereas the equilibrium separation factor could reach about 13.4.

P17

Transport Resistance in Hollow-Fiber Membrane Extraction and Stripping of Metallic Species

The extraction of metallic species from aqueous solutions across a hollow fiber membrane containing carriers dissolved in kerosene has been studied, in which the metals were then stripped to a stripping phase. The systems of Cu²⁺-LIX64N-HCl as well as Cu(EDTA)^2--Aliquat 336-HCl were exemplified. A mass transfer model was developed, and was shown that the calculated time profiles of aqueous-phase concentrations of metallic species well agreed with the measured results (average standard deviation, 10%). In Cu²⁺-LIX64N-HCl system, the fractional resistance of interfacial chemical reaction gradually decreased and that of aqueous-layer diffusion increased at lower carrier concentrations when the experiment was started. However, the rate-controlling mechanism remained unchanged in the stripping process under the ranges studied. In CuL^2--Aliquat 336-HCl system, fractional resistance of membrane diffusion and organic-layer diffusion gradually decreased and aqueous-layer diffusion increased at high metal concentration when the experiment was started. However, the dominant resistance was membrane diffusion in the stripping process, and remained unchanged during the experiment.

P18

5-aminosalicyclic acid permeability enhancement by a pH-Sensitive EVAL Membrane

Institute of Biomedical Engineering, College of Medicine and College of Engineering, National Taiwan University, Taipei, Taiwan

A pH-sensitive membrane was synthesized by the covalent bonding of glycine on poly (ethylene-co-vinyl alcohol) (EVAL) membrane via isocyanation of surface hydroxyl groups of EVAL membrane and subsequent conversion to activated ester. The processes of surface modification would not change the membrane structure under the observable detection sensitivity of the scanning electron microscopy. Both of the EVAL membrane and the glycine-immobilized EVAL membrane appeared fairly dense structure almost without any holes existing in the top surface. The water swelling characteristics of EVAL membranes did not change greatly at pH = 2.0 and 7.4. The equilibrium swelling ratio were 10.4“b0.3 and 12.9“b2.6, respectively. However, the equilibrium swelling ratio of the modified EVAL membranes was greatly increased from 8.9“b0.6 to 27.1“b2.6 when the pH value was changed from 2.0 to 7.4, which could be very interesting from the point view of application for colon-specific drug delivery. Permeation by diffusion of 5-amoinosalicylic acid (5-ASA) through the prepared membranes was also studied at pH 2.0 and pH 7.4 at 37“aC. Regardless of the EVAL membrane and the glycine-immobilized EVAL membrane, the 5-ASA permeability at pH 2.00 is very conspicuously small, which agrees with that drug is protected in the acidic environment. However, the relative values of the 5-ASA permeability for the EVAL membrane and the glycine-immobilized EVAL membrane at 7.4 to 2.0 were 5.9 and 56, respectively. Especially, the significant increase (about fifty-six folds) in the 5-ASA permeability of the glycine-immobilized EVAL membrane is suitable for local treatment of ulcerative colitis.

P19

COMPARATIVE ANALYSES OF PHENOMENA OCCURRING IN WET PHASE INVERSION PROCESSES OF CA/ACE/WATER AND CA/DMF/WATER TERNARY SYSTEMS

NUŠA VOGRIN^a),b), SANJA CVAR^a), VOJKO MUSIL^b), MILAN BRUMEN^{c), d)}, ČRTOMIR STROPNIK^a).

University of Maribor:^a)Faculty of Chemistry and Chemical Engineering, Smetanova 17, SI-2000 Maribor, Slovenia, n.vogrin / uni-mb.si , crtomir.stropnik / uni-mb.si ; ^b)Faculty of Business and Economics, Razlagova 14, SI-2000 Maribor, Slovenia, vojko.musil / uni-mb.si ; ^c)Faculty of Education, Koroška c. 160, SI-2000 Maribor, Slovenia, milan.brumen / uni-mb.si; ^d)J. Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia

We present experiments on the formation of asymmetrical porous membranes prepared by wet phase inversion from two ternary systems, cellulose acetate (CA)/acetone (ACE)/water and CA/N,N-dimethylformamide (DMF)/water. Solutions of different concentrations were cast in different nominal thicknesses and immersed in a coagulation bath that contained only pure water. Nominal thicknesses of the two-component cast solutions were determined by the casting knives slits. During the membrane formation by wet phase inversion, ternary membrane forming systems shrink to (proto)membranes depending on the concentration of the casing solution and thickness. Besides longitudinal shrinkage there also is transversal or lateral shrinkage; the former will be presented quantitatively form, and the later will be given qualitatively. Distinctive turbidity phenomena occurring during membrane formation were instantaneous on-set or delayed, and they had different rates of the turbidity growth and turbiditie’s end value. Those phenomena are strongly dependent on cast solution concentration and thickness; their dependence will be presented. PWF reflects the properties of the membrane's skin as well as the form of the porosity of the membranes skin-carrying layer. Membranes prepared from CA/acetone are essentially not permeable for pure water under ultrafiltration conditions. For membranes prepared from the CA/DMF cast solutions, PWF varies from 0-750 l/hm². Also cross-section morphology obtained by scanning electron microscopy (SEM) usually shows the porous structure of the various membranes and thus the mechanism(s) of the membranes formation.

Data on turbidity and shrinkage, which took place during the polymeric asymmetrical porous membranes formation, pure water flux (PWF) and cross-section morphology of the membranes will be correlated and the mechanism(s) of membranes formation by means of wet-phase inversion will be proposed.

P20

Vapor Permeation of Aqueous Ethanol Solution through Novel Asymmetric Polyamide Membrane

Shu-Chin Fan ¹, Kueir-Rarn Lee ^2*, Hung-Ping Huang ³, Der-Jang Liaw ³, Juin-Yin Lai ¹

P21

Pervaporation and Vapor Permeation of Water - Alcohol Mixtures through Surface Resisting Expanded Poly(tetrafluorethylene) Membranes

P22

Comparison of Membrane Filtration Mechanisms Between Rigid and Soft Particles

P23

Investigation on the Formation of Macrovoids in Polymeric Membranes by FTIR/ATR Microscopy

P24

^aGKSS Forschungszentrum Geesthacht, GmbH., Institut für Chemie, Kantstrasse 55, D-14513 Teltow, Germany

^bInstitute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovského nám. 2, CZ-162 06 Praha 6, Czech Republic

The polyelectrolyte complex (PELC) membrane prepared previously by interfacial reaction of sodium cellulose sulfate and poly[dimethyl(diallyl)ammonium chloride] (pDMDAAC) was found to be strongly hydrophilic and suitable for pervaporation (PV) processes, enabling dehydration of alcohol/water mixtures with high selectivity. In the present study we have prepared new PELC membranes based on reaction of polyanionic sulfoethyl cellulose (SEC) with polycationic pDMDAAC or cationic surfactant benzyl(dodecyl)dimethylammonium chloride (BDDDMAC).

The aim of this work was to ascertain if and how the membrane hydrophilicity influences the dehydration of alcohols or organic mixtures in PV process. The expected results should also show the influence of particular cationic components on the surface wettability and membrane separation properties. For this purpose, contact angle measurements on membrane surfaces in various media (water and alcohols) were performed and the results confronted with PV characteristics of these membranes.

The results of contact angle measurements in water unambiguously show that the membrane based on SEC/pDMDAAC is significantly more hydrophilic compared with the SEC/BDDDMAC membrane. It is therefore evident that the polyanionic pDMDAAC is a much more hydrophilic component in the PELC system with SEC than the anionic BDDDMAC.

Whereas the PV performance in separation of water/propan-2-ol mixtures in the range from 0 to 20 wt% water in the feed is nearly the same for both membrane types, the hydrophobic SEC/BDDDMAC membrane is evidently more effective in separation of feed mixtures with higher water contents. This means that the membrane hydrophilicity does not significantly influence the flux and selectivity in the PV dehydration process. On the other hand, the above membrane possesses the highest differences in advancing contact angles measured in neat water and neat propan-2-ol, which could act as a driving force in separation process. This is possibly the reason of more convenient PV characteristics of this membrane type.

This work was performed in the frame of the Czech-German Bilateral Cooperation in Science and Technology, Projekt No. CZE-00-031.

P25

POLY(SULFONE)/N,N-DIMETHYLACETAMIDE/WATER MEMBRANE-FORMING SYSTEM: SYNERESIS PRESSURE – COALESCENCE MECHANISM OF MACROVOIDS FORMATION.

ČRTOMIR STROPNIK^a), VLADIMIR KAISER^a), VOJKO MUSIL^b) and MILAN BRUMEN^{c), d)}

University of Maribor:^a)Faculty of Chemistry and Chemical Engineering, Smetanova 17, 2000 Maribor, Slovenia, n.vogrin / uni-mb.si, crtomir.stropnik / uni-mb.si; ^b)Faculty of Business and Economics, Razlagova 14, 2000 Maribor, Slovenia, vojko.musil / uni-mb.si; ^c)Faculty of Education, Koroška c. 160, Maribor, Slovenia, milan.brumen / uni-mb.si; ^d)J. Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia

Poly(sulfone)(PSF)/N,N-dimethylacetamide(DMA)/water ternary system has already been applicated in the polymeric asymmetric porous membrane preparation by wet phase separation for a long time. Although macrovoids are beside the cellular structure the distinguishing feature of the polysulfone membranes cross section morphology their formation mechanism is not yet clearly understand. In the paper some experimental data dealing with the PSf membranes formation are consistently used for proposing a novel "syneresis pressure – coalescence mechanism" of macrovoids formation.

After immersion of the PSf/DMA binary solution into the coagulation bath consisting of pure water solvent and nonsolvent exchange takes place. Now the ternary PSf/DMA/water membrane forming system practically immediately starts phase inversion by nucleation and growth of the polymer lean phase: turbidity sets-on instantaneously. Coincidentally the system shrinks to less then 50% of the original thickness of the binary solution cast. Syneresis depends on cast composition and thickness. We postulated that during this longitudinal shrinkage syneresis pressure is induced which can be responsible for macrovoids formation. Channels, macrovoids with long tails and "drop-shaped" macrovoids are formed by coalescence of the nuclei of the polymer lean phase and by subsequent solidification of the polymer rich phase; syneresis pressure provides force for coalescence. In membranes cross-sectional morphology, observed by scanning electron microscopy, channels and different sorts of macrovoids are placed into the cellular structure.

Evidences for syneresis pressure will be presented. Continuation of the macrovoid from the PSf upper layer to the poly(methylmetacrylate) (PMMA) bottom layer of the PSf//PMMA double layered membrane as well as large openings on the bottom layer of the PSf membranes prepared from PSf/DMA solutions with 15 wt% or less polymer will be presented. Occasional presence of PSf latex in the coagulation bath will be explained and we will show that the intrusion of the nonsolvent is not necessary for macrovoids formation.

P26

Oxygen/Nitrogen Separation of TPX Membranes Modified by Acetylene/Nitrogen Plasmas

P27

Transport Mechanism of Hydrophobic Microporous Membranes for Ethanol Enrichment

P28

Effect of Surfactant Addition on the Vapor Permeation of Aqueous Ethanol Mixtures through Polysulfone Hollow Fiber Membranes

P29

POLYSILOXANE MEMBRANES CONTAINING LIQUID POLYBUTADIENE AND/OR SILICA FOR PERVAPORATION OF ETHANOL/TOLUENE MIXTURES

^aDepartment of Polymers, Institute of Chemical Technology, Technická 5, 166 28 Prague 6, Czech Republic, ^bInstitute of Macromolecular Chemistry, AS CR, Heyrovský Sq. 2, 162 06 Prague 6, Czech Republic

The composition and structure of the membranes prepared were correlated with their physical properties and behaviour in pervaporation of ethanol/toluene mixtures.

As expected, their tensile strength, elongation and hardness increased and equilibrium degree of swelling in toluene decreased with increasing concentration of silica in the polymer mixture. However, tensile strength, elongation and equilibrium degree of swelling in toluene decreased and hardness increased with increasing concentration of liquid polybutadiene in the mixture.

In pervaporation of toluene/ethanol mixtures, all the membranes preferably transported toluene. The presence and the type of a filler in the polysiloxane matrix had, however, a pronounced influence on the separation factor of pervaporation. The presence of silica increases the separation factor; with hydrophobized silica, this increase is even more pronounced. On the other hand, an addition of liquid polybutadiene to the polysiloxane mixture brought about a decrease in the separation factor if the concentration of toluene in the feed was low (up to about 5 wt. %). At higher concentrations of toluene in the feed, the separation factor of these membranes was high, which is plausibly brought about by the presence of swollen polybutadiene domains in the polysiloxane matrix.

This work was supported by the Ministry of Education, Youth and Sports of the Czech Republic (grant CEZ:MSM 223100002) and by the Grant Agency of the Czech Republic (project No. 203/96/1378).

P30

Department of Physical Chemistry, Institute of Chemical Technology in Prague, Technická 5, CZ-166 28 Prague 6, Czech Republic, email: Karel.Friess / vscht.cz

P31

Department of Physical Chemistry, Institute of Chemical Technology in Prague, Technická 5, CZ-166 28 Prague 6, Czech Republic, email: Karel.Friess / vscht.cz

In this work the sorption of organic vapors (benzene, toluene, cyclohexane, hexane and n-heptane) in polymer membranes PE (polyethylene) and PEBA (polyether block amide) at 25 ° C were studied. The sorption apparatus with Mc Bain spiral quartz balances enables to follow the sorption kinetics. From experimental data the diffusion coefficients were calculated and these values were compared with appropriate diffusion coefficients obtained by differential permeation method.

P32

Separation of Aliphatic Alcohol-Toluene Mixtures by Pervaporation through a Polyethylene Membrane

Department of Physical Chemistry, Institute of Chemical Technology in Prague, Technická 5, CZ-166 28 Prague 6, Czech Republic, email: N7800522 / hotmail.com

P33

Sorption and Diffusivity of Aliphatic Alcohols and Toluene in a Polyethylene Membrane

Department of Physical Chemistry, Institute of Chemical Technology in Prague, Technická 5, CZ-166 28 Prague 6, Czech Republic, email: N7800522 / hotmail.com

P34

¹Institute of Organic and Polymer Technology, ²-Institute of Inorganic Technology, Wroclaw University of Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland

The main drawback of the most polymeric ultrafiltration membranes is strong protein adsorption that is the origin of membrane fouling. In our previous papers we examined the influence of CO₂[1], acrylic acid [2] and nitrogen [3] plasma on the transport properties of ultrafiltration polysulfone membranes. Results clearly showed that modified membranes are less prone to fouling and their cleaning is more efficient. In the present work, ammonia was applied as a plasma medium.

The significant increase of surface hydrophilicity during plasma treatment is observed; water contact angle decreases from 87.3 for PSU to 33.7^o for modified sample and polar component of surface tension raises from below 1 to above 39 mN/m. Hydrophilicity gained during plasma treatment decreases during aging in water and after few days total surface tension achives value close to that of polysulfone. It has to be pointed out however that polar component of these samples though lower than immediately after treatment, stays much higher (> 10 times) than for untreated polysulfone.

FTIR-ATR spectrum suggests a presence of thin modified layer on the top of the PSU.

Small and wide but distinct band between 3600 - 3100 cm^-1 is observed after plasma treatment. It may consist mainly stretching N-H bonds of amides and amines. XPS confirms the presence of nitrogen (12.5%) and lack of additional oxygen on the surface. SEM pictures reveals that ammonia plasma cleans surface and this effect is more pronounced for the longer treatment time. No signs of etching are observed.

Membrane performance was characterized by protein filtration indexes: fouling index, flux recovery after membrane cleaning, flux reduction in filtration and solute rejection. For the membrane treated with plasma all filtration indices are better than for unmodified one what suggests that membrane surface after plasma action has an amphoteric character.

P35

^aLaboratoire de Chimie des Polymères, CP 206/01, ^bService de Chimie Analytique et des Interfaces, CP 255, Université Libre de Bruxelles, Boulevard du Triomphe, 1050 Bruxelles, Belgium.

^con leave from the Chemistry Departement of the University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland.

Polysulfone is an attractive material for preparation of membranes due to its high mechanical and chemical stability. Polysulfone based anion-exchange membranes were prepared by halomethylation of polysulfone with subsequent amination with different amines.

Halomethylation was carried out in 1,2-dichloroethane with SnCl₄ as catalyst and a halomethylating agent [1]. The reaction conditions were optimized to obtain the best substitution. The polymers were characterized via ¹H NMR, FTIR-ATR and FT-Raman. Quantitative information about the level of substitution was obtained by ¹H NMR.

Two pathways of amination reactions were studied : amination with tertiary amines and amination with primary amines followed by quaternization with iodoalcanes. It is known that the selectivity of an ion-exchange membrane is related to the specific interactions existing between the ionic site and the exchanged ion. In particular, the separation of monovalent anions may be improved by taking into account differences in the ionic hydratation behaviours. Therefore, we varied the amine length chain in order to modulate the hydrophobic/hydrophilic properties of the membranes.

When the reactions were carried out in solution, the membrane was formed by the casting solution process. Otherwise reactions occurred directly on a film of halomethylated polysulfone where only one side was in contact with the reactive medium. In this way, we could follow the efficiency of the amination along the thickness of the film by characterising both sides. The progress of the reaction was followed by Raman spectroscopy or surface spectroscopic methods.

P36

P37

Composite Membranes for Fuel Cells FED with Hydrogen Containing Traces of CO

P. Staiti ^a, E. Passalacqua ^a, V. Antonucci ^a, U. Costantino^b, M. Casciola^b, L. Massinelli^b, R. Ornelas^c, D. Travagin ^c

P38

Simultaneous Crosslinking of Acrylic Copolymers during the Process of Membrane Formation

GKSS Research Centre Geesthacht GmbH, Institute of Chemistry, Kantstr. 55, D-14513 Teltow, Germany

Future separation applications will have high demands on membrane performance and functionality and require the development of novel membranes with tailored properties. To achieve this it is often necessary to apply custom-made polymer systems possessing, for example, special functional groups, reactive sites or the ability of crosslinking. On the other hand, Membrane formation processes are highly sensible to the properties of the polymer used. Slight changes of the polymer/solvent interactions or the viscosity have dramatic effects on the membranes obtained, especially, if a phase inversion process is used for the preparation.

Our research focusses on the combination of the membrane forming process with a simultaneously performed chemical modification of the polymer. In the example given here this modification is a crosslinking reaction of an acrylic copolymer containing vinyl benzyl chloride. During the cure these groups react with a crosslinking-agent, e.g. an amine, in order to form a polymer network. Membranes prepared from such a crosslinked polymer exhibit an increased resistance against high temperatures or aggressive media. The simultaneous process of membrane formation and polymer modification is a convenient and economical pathway to crosslinked membranes. The fundamental questions in this context are: In which way does a simultaneously reacting system influence the membrane formation and how can this process be controlled by adjusting the processing parameters in order to obtain membranes with the desired properties?

To get answers we investigated the kinetics of the crosslinking reaction by means of electric conductivity and viscosity measurements. From the obtained data we deduced a model mechanism, established suitable kinetic equations and determined rate constants and activation energies. With these tools we are able to describe the course of the reaction properly and design a procedure for the membrane preparation. The membranes obtained were characterised and properties like the pore size distribution, the swelling behaviour or the chemical and thermal stability were correlated to the degree of crosslinking that can be calculated from reaction kinetics.

P39

The transport of drugs within swollen polymeric membranes studied by molecular dynamic simulation

Drug diffusion in water swollen poly (vinyl alcohol) (PVA) membranes was investigated in the present work. By means of molecular dynamics simulations, we can have an understanding in a microscopic way of how the solute diffusion is affected by the swelling agents and what other factors might influence the diffusion behavior as well. Systems composed of swelling agent (water) and poly(vinyl alcohol) with concentrations ranging from pure water to pure poly(vinyl alcohol) were first simulated. Then, two kinds of drugs, theophylline and benzocaine, were separately inserted into these systems. The simulated results indicate that systems with higher degree of swelling ratio resulted in higher fractional free volume. In addition, with increasing swelling ratio, the mean-square-displacement of polymer chains also increased. As a result of the above effects, the diffusion rate of drugs could be accelerated as the amount of swelling agents enhanced. Further, it was found that the calculated solute diffusivity agreed well with the experimental data. By analyzing the relationship between the drug diffusivity and the fractional free volume, it can be observed that the dependence of diffusivity on free volume follows the correlation proposed by Cohen and Turnbull. The comparison of the dynamic properties of these two kinds of drugs within different swelling conditions was also made in the present study. Besides the swelling agent, the drug might significantly affect the movement of the polymer chain. We have also found that the drug hydrophilicity and steric hindrance could have a dramatic effect on the drug diffusivity in polymeric membranes. Therefore, although the drugs have the same van der Waals volume, the diffusion behavior might still be markedly different even in the same swollen condition.

P40

M. PONCE^A, J. MARCHESE^A, A. OCHOA^A, L. PALACIO^B, P. PRÁDANOS^B, A. HERNÁNDEZ^B

^bG. of Surfaces and Porous Materials, F. Ciencias, University of Valladolid, Spain

An experimental study of the flux decline in cross flow ultrafiltration of aqueous solutions of BSA at different pH (3, 4.9, 9) has been carried out on modified polymeric membranes. Three membranes were made from 17% polyethersulfone (PES), 0.5% tetrahydrofurane in N-N, dimethyl-formamide and polyvinyl-pyrrolidone (PVP) as additive. They will be called hereafter MPES (0%PVP); MPES-K30 (2% PVP of 30 KDa) and MPES-K360 (2% PVP of 360 KDa). The hydraulic permeabilities (L_h), cut-off and mean pore diameter (d_p) of the synthesized membranes are shown in the table.

Membrane	L_h .10¹⁰ (m/Pa.s)	Cut-off (KDa)	d_p (Å)
MPES	0.9	10.67	40.52
MPES-K30	1.014	8.29	40.03
MPES-K360	1.540	8.13	34.08

BSA filtration lead in all cases to a decrease in the permeate flux and total protein rejection versus time while the total membrane resistance increases with a decreasing slope.Based on this, membrane fouling was interpreted in terms of the cake filtration model. The rate of cake formation (K_CF) and its specific resistance (C_CF) are given in the following table.

Membrane	pH	K_CF. 10^-5 (s/m²)	C_CF.10^-12 (m/g)
MPES	3.0 4.9 9.0	0.198 7.486 0.192	1.744 33.942 0.872
MPES-K30	3.0 4.9 9.0	0.249 0.314 0.069	1.129 1.424 0.315
MPES-K360	3.0 4.9 9.0	0.201 1.015 0.201	0.911 4.602 0.910

The experimental results obtained show that for the analyzed membranes, K_CF and C_CF are greater at pH=4.9 with respect to those obtained at pH=3 and 9. At pH = 4.9, the hydrophobic character of the membrane and the lack of electrical charge of the BSA (isoelectric point) leads to the consolidation of the cake by means of hydrophobic forces between solute-membrane and solute-solute. At pH values far from the isoelectric point, both the membrane and the BSA are negative in alkaline conditions and positive in acid media. This decreases the rate of cake formation and cake resistance due to electrostatic repulsion.

The decreased fouling capacity of MPES-K30 and MPES-K360 membranes at pH=4.9 with respect to the MPES is attributed to the presence of the functional group (>N–C=O) of the PVP which gives a more hydrophilic nature to the surface of these membranes (decreases the solute-membrane hydrophobic interaction).

P41

CHARACTERIZATION OF HYDROPHOBIC MICROPOROUS MEMBRANES USED IN MEMBRANE DISTILLATION

^a Dpto. Física Aplicada, Facultad de Ciencias, Universidad de Málaga, 29071 Málaga, SPAIN.

^b Group of Surface and Porous Material, Dpto. Termodinámica y Física Aplicada, Facultad de Ciencias, Universidad de Valladolid, 47071 Valladolid, SPAIN

The main application for hydrophobic microporous membranes is membrane distillation. Where the water flux J depends on the transmembrane water vapour pressure difference D p, as

where C is a permeability constant which characterises the membrane and can be predicted in the framework of different transport models. The correct selection and application of the transport model requires the knowledge of membrane morphology, including porosity, tortuosity (roughly taken as 2) and pore size. A lack of information on both the actual pore size distribution and tortuosity results in unsatisfactory predictions. In this work the liquid expulsion permoporometry method has been used because its experimental conditions are very similar to those in membrane distillation. From the data of the air flow versus the imposed pressure difference trough a previously wetted membrane, the pore size distribution is determined. At the same time the ratio of porosity and tortuosity of transport pores is obtained. The Knudsen-Poiseuille transition model is considered.

Different membranes usually employed in membrane distillation have been characterised in several configurations:

P42

CHARACTERISATION OF UF MEMBRANES BY LIQUID-LIQUID DISPLACEMENT POROMETRY AND SCANNING FORCE MICROSCOPY

^aUniversitá degli Studi di Genova, Dipartimento di Chimica e Chimica Industriale, Corso Europa 30, Genoa, Italy

^bUniversidad de Valladolid - Group of Surfaces and Porous Materials, Real de Burgos, Spain

The liquid-liquid displacement porometry (LLDP) has been used to analyse several polysulfone membranes in the UF range. This technique is based on the simultaneous measurement of the applied pressure and the flux of a liquid, which displaces another wetting liquid previously filling the pores. The technique is able to cover the UF range and obtain the experimental permeability distribution with applied pressures always lower than 14 bar. Another experimental advantage of the technique is that it tests membranes always in the wet state and only the open to flux pores, giving results closer to the operating conditions. Moreover, if an adequate model for the pore geometry is used, then the pore size distribution is easily obtained.

This technique has been applied to three GR polysulfone membranes, namely GR51, GR61 and GR81, all of them from Dow Denmark, with several wetting-displacing liquid pairs. In all the cases the obtained results have been compared with those obtained from scanning force microscopy (SFM) pictures conveniently treated by using a computerised image analysis protocol. The small differences in the so obtained results can be explained by taking into account that LLDP can detect all pores opened to flow while SFM can only detect pore entrances on active layer.

P43

V. ŠINDELÁŘ^a, P. SYSEL^a, R. HOBZOVÁ^a, K. FRIESS^b, V. HYNEK^b, M. ŠÍPEK^b

Departments of Polymers^a and Physical Chemistry^b, Institute of Chemical Technology, Technická 5, 166 28 Prague 6, Czech Republic

The separation and recovery of volatile organic compounds (VOC) from waste air streams using membrane technology is expected to provide an attractive alternative to other conventional processes. Non-porous membranes prepared from elastomeric polymers were successfully tested for the preferential removal of organic vapours from air (1). Nevertheless, not only the membranes with high permeability and good selectivity but also with acceptable thermal and chemical stability are needed.

Aromatic polyimides (PI) exhibit very good mechanical, dielectric and chemical resistance also at elevated temperatures. Non-porous polyimide membranes show high separation factors for separation of mixtures of permanent gases but low permeability for both permanent gases and organic vapours.

The crosslinked modified PI were employed in this work (2). The starting materials were 1) polyamic acids (PAA) based on pyromellitic anhydride/4,4´-oxydianiline (ODA) and 4,4´-oxydiphthalic anhydride/ODA, and 2) toluene-2,4-diisocyanate terminated poly(ethylene adipate) (TDI-PEA) with molecular weight 1300 and 2700 g mol^-1.Transport properties of membranes made of polymeric materials varying in the PAA chemical structure, TDI-PEA molecular weight and PAA/TDI-PEA weight ratio were studied. The diffusion and sorption coefficients of saturated organic vapours (benzene, methanol) were measured by a sorption vacuum apparatus with the quartz spiral balance at 25 ⁰C. The permeability coefficients of nitrogen, oxygen, carbon dioxide, benzene and methanol were measured by a differential flow permeameter with thermal conductivity detection of the gas mixture composition (3).

This work was supported by the grant CEZ:MSM 223100002 and by the grant of the Institute of Chemical Technology, Prague 112010015.

P44

Department of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland

Monte Carlo simulations of simple models of polymer membranes were carried out. The model consisted of star-branched chains, which have had one arm end attached to an impenetrable surface. The grafted ends of chains were allowed to slide along the surface. The chains were confined to simple cubic lattice and consisted of f = 3 branches of equal length. The model chains were athermal, i.e. good solvent conditions were modeled. The polymer chain lengths as well as the density of the system were varied.

The simulations were performed using the set of local micromodifications of the chain conformations. The influence of the branching on the static and dynamic properties of the system studied was shown. The relation between the structure and short-time dynamics (relaxation times) as well as the long-time dynamics (diffusion) were discussed.

P45

Department of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland

Monte Carlo simulations of simple models of polymer membranes were carried out. The model of the membrane consisted of star-branched chains, which have had one arm end attached to an impenetrable surface. The chains were confined to simple cubic lattice and consisted of f = 3 branches of equal length. We have investigated the behavior of a single probe chain, which was not tethered to the surface while located in the membrane. All model chains were athermal. The polymer chain lengths as well as the density of the system were varied.

The simulations were performed using the set of local micromodifications of the chain conformations. The influence of the membrane environment on the static and dynamic properties of the single probe chain was shown.

P46

PERVAPORATION characteristics OF ETHANOL-WATER MIXTURE THROUGH PHOSPHATE ESTER CONTAINING SILICONE COMPOSITE MEMBRANE

Phosphate ester containing silicone was synthesized by adding proper amount of 2-hydroxyethyl methacrylate and

-polydimethylsiloxanediol in sequence to POCl₃ ether solution at 0 °C. A skinless microporous PVDF membrane was modified by plasma polymerization of tetramethyltetravinylcyclotetrasiloxane onto the surface in order to enhance the adhesion of silicone and PVDF substrate. The silicone resin was then cured on the modified PVDF membrane to form a composite membrane that was applied to the pervaporation of aqueous ethanol solution. For comparison, the PVDF and surface modified PVDF membranes were also tested. Pervaporation performances of three membranes are shown in Fig. 1. The composite membrane is ethanol-permselective with the separation factor of 4.1 and high permeation rate of 4 kg/m²h at feed concentration of 10 wt%. The permeation rate is nearly constant over entire range of feed concentration.

Fig. 1. Permeate composition (a) and permeation rate (b) versus feed composition. (◆) PVDF membrane; (■) modified PVDF membrane; (▲) composite membrane

P47

Nano-structure in a particulate PVDF Membrane as revealed by Electron Microscopy

Department of Chemical Engineering, Tamkang University, Taipei, Taiwan ROC 25137

Microporous PVDF membranes were prepared by isothermal phase inversion from the 1-octanol/DMF/PVDF system at 25 ^oC. For this system, crystallization was found to dominate the precipitation process and the formed membrane was composed of arrays of spherical particles whose surfaces were rough and particulate. The detailed nano-scale morphologies of the membranes were observed with a low voltage FESEM at very high magnifications (e.g., 150KX); wherein, 4 typical types of crystal morphologies were evident: (1) large spherical particles (ca. 2 m) constituting most of the membrane cross section; (2) leaf-like twisted sheets around spherical particles; (3) fibrillar crystal elements connecting spherical particles; (4) truncated spherical particles with a flattened plane facing the bottom surface of the membrane. Each of these crystals was composed of different shapes (granular, fibrilar, lamellar) of entities whose sizes fell over the range 10-20 nm, as manifested in Figure 1.

Fig. 1: Crystal morphologies in a PVDF membrane. (a) Leaf-like sheets; (c)Fibrils and spherical particles

P48

EFFECT OF FLOW ARRANGEMENT ON THE PERFORMANCE OF MEMBRANE MASS-TRANSFER DEVICE

Department of Chemical Engineering, Tamkang University, Tamsui, Taipei 25137, Taiwan ROC, Email: twcheng / mail.tku.edu.tw

Both effects of dialysis and ultrafiltration on the performance of a membrane mass exchanger have been investigated theoretically under various flow arrangements. The flow arrangements in a membrane mass exchanger include the parallel flow and the cross flow. In parallel-flow type, the directions of the streams beside the membrane are counter-current or co-current. In cross-flow type system, the flow directions of both streams beside the membrane are orthogonal. Figure 1 is the plots of the calculated results. It shows that the effectiveness  increases with increasing transfer unit a, i.e. increasing the solute mass transfer coefficient or decreasing the flow rate in retentate phase. The increase in ultrafiltration flux  will further enhance the effectiveness. The effectiveness is more sensitive to the flow rate of retenteate than the flow rate of dialysate. The mass transfer rate in the counter-current flow system is the highest while the co-current flow system is the lowest. However, the effect of ultrafiltration flux on the enhancement of effectiveness is the greatest for co-current flow system.

Figure 1 Effectiveness of membrane mass-transfer device: (a) counter-current flow; (b) co-current flow; (c) cross flow

P49

Porous Structure of Nylon 6 Membrane Prepared from Meta-Solution Containing Compatible Nucleation Seeds

Commercial Nylon-6 porous membranes suffer from the drawbacks of having to use an ”incipient dope” and a high formic acid content precipitation bath. The present research pursues novel method of synthesis for Nylon 6 porous membrane based on compatible reactive blend of PPO/PA6. Variation of compatibility between PPO and Nylon 6 in blends was obtained by changing the physical and chemical modification technology through in-situ reactive blending process. Each dope consists of 25wt.% of polymer. And PPO content represents only 1 or 2 wt.% of total polymer used. Dopes thus prepared are cloudy meta-solution containing compatibilized nucleation seeds of PPO insoluble in formic acid.

The meta-solution properties of dopes are adjustable by varying PPO content, compatibility of the dispersed phase, and nonsolvent content. During membrane formation the dispersed compatible PPO served as nucleation induction medium. Highly micro-porous, water-wettable skinless membranes could be easily obtained in aqueous bath of 15wt.% to 20wt.% formic acid concentration.

The morphology of micro-porous membranes is revealed to be influenced much more by the compatible seeds than both nonsolvent content in dope and solvent addition in precipitation bath. The most porous structure (see figures below) represents the best wettability and largest water flux of 67g/cm² min.

P50

Institute of Macromolecular Chemistry, Academy of Sciences of the Republic, Prague, Czech Republic

Instituto de Ciencia y Technologia de Polymeros Consejo Superior de Investigaciones Cientificas, , Madrid, Spain

Langmuir monomolecular layers were prepared by depositing a fluorinated polyimide (PIM) solution in chloroform at water/air surface. The polyimide was designed to be soluble in workable solvents, as THF and Cl₃H.

A sharp monotonous increase in surface pressure with decreasing the monolayer area indicated that there was no reconfiguration of polymer molecules well packed in the monolayer during the compression. No collapse of the monolayer was observed up to the highest used surface pressure of 75 mN/m. Similar surface pressure-area curves were obtained repeating the measurement with the same monolayer. Langmuir-Blodgett film consisting of 26 monomolecular layers was deposited by horizontal touching the surface of the porous poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) membrane. The supporting PPO membrane prepared by the phase-inversion process was asymmetric with the largest pores in the skin side of diameter about 18 nm.

Overcoating the porous supporting membrane with the PIM film resulted in a decrease in permeability and a significant increase in selectivity for gasses.

P51

Jagiellonian University, Faculty of Chemistry, 30-060 Krakow, Ingardena 3, Poland

Chitosan, (1® 4)-2-amino-2-deoxy-b -D-glucan, is a biopolymer, a deacetylated derivative of chitin, which is obtained at a low cost from shellfish wastes. Chemically, chitin and chitosan are polysaccharides which at carbon-2 of their cellulose-like backbone have acetamido and amino groups, respectively. Amino groups render chitosan soluble in acidic media, which allows for gel formation in a variety of configurations, e.g. beads, membranes, coatings, capsules, fibers and sponges. As a functional material chitosan offers a unique set of characteristics: hydrophilicity, biocompatibility, biodegrability, antibacterial properties and remarkable affinity to proteins. It is biologically inert, safe for humans and the natural environment. These characteristics make chitosan suitable for application as a supporting/conjugate material in systems constructed to be functional in biological environments, e.g. in biomedical and pharmaceutical processes, in the food industry, in agriculture and wastewater treatment. Examples of such applications include: preparation of drugs, contact lenses, haemedialysis membranes and surgical dressing materials, enzyme/cell encapsulation and immobilization and coating of fertilizers and pesticides for their controlled release to soil. The knowledge of transport properties and of physical strength of the membranes is of importance for the development of chitosan-based controlled release systems.

The insight into diffusional properties of gel chitosan membranes prepared by glutaraldehyde treatment and protein coating was the aim of this study.

Chitosan membranes were prepared by a solvent evaporation technique, followed by crosslinking with glutaraldehyde and coating with BSA. The effects of of the treatments on the pore structure of chitosan membranes were determined. The diffusion rates of 12 nonelectrolytes ranging in molecular radius between 2.5 and 14 A through the membranes were measured, and the results were interpreted in terms of the capillary pore model and free volume model of solute diffusional transport through hydrogel membranes. Glutaraldehyde crosslinking was found to reduce the membrane water content and consequently the membrane pore size and surface porosity, whereas further BSA coating brought about the opposite effect. The latter effect lessened with an increase in glutaraldehyde pretreatment of the membranes. The optimal chitosan membrane preparation, compromising between the solute flux and membrane stability and durability was obtained when the membranes were crosslinked with glutaraldehyde at concentration between 0.01 and 0.1 % (w/w).

P52

A Two-dimensional modeLling of the mass transfer in cross-flow ultrafiltration. INFLUENCE OF DIFFERENT DIMENSIONLESS NUMBERS.

LEAPS, Avenue Escadrille Normandie-Niemen, 13397 Marseille Cedex 20, France, johanne.paris / leaps.u-3mrs.fr

Up to now, ultrafiltration permeate fluxes are difficult to predict as well as the limitations encountered. The classical models such as the gel-polarization model, the osmotic pressure model or resistance-in-series model don't predict in a general way the permeate flux. Basically the common failure of these simple models is to average all parameters (permeate flux, solute concentration) over the whole membrane length. In order to take into account their variations along the membrane length, we have developed a new two-dimensional model and compared simulation results to experimental data. This work deals with the mass transfer phenomena in a tubular membrane (r, q , z) with radius R and length L (Figure 2) in the case of laminar crossflow. The convective-diffusion equations coupled with the resistance-in-series model for permeate transport have been solved numerically by means of finite volumes analysis, using a non uniform mesh, which was refined close to the boundary layer.

The permeate fluxes predicted are in agreement with the experimental results (Figure 1) and the influences of the velocity, the initial concentration, the transmembrane pressure and the membrane length are very well described. An important prospect is to test this new model using others solutions and different membranes such as hollow fibers.

P53

FACILITATED TRANSPORT OF XYLENE ISOMERS THROUGH SUPPORTED LIQUID MEMBRANES CONTAINING CYCLODEXTRINS

The permeation of p- and m-xylenes through supported liquid membranes containing various cyclodextrins (CDs) was investigated using a solution-diffusion model. The mass transfer mechanism is elucidated as partitioning of xylenes from the organic phase into an aqueous phase, formation of an inclusion complex with CD, diffusion of the complex, and extraction into the receiving phase. The formation constants in aqueous solutions for CDs and p-xylene are 1.6 to 2.4 higher than those for CDs and m-xylene. The diffusivity coefficients of free xylenes in pure water solutions are in the range of 1.5´ 10^-9 m²/s to 2.0´ 10^-9 m²/s. When xylenes form complexes with CDs, the diffusivity coefficients of the complexes increase to 1.0-1.6´ 10^-8 m²/s. Thus, the addition of the CD into the membrane phase for xylene permeation yields a two-fold benefit in the favor of p-xylene: an increase in selectivity and an enhancement of the mass transfer flux.

P54

EFFECT OF MORPHOLOGY OF POLYMERIC MEMBRANE ON THE PERFORMANCE OF MICROFILTRATION

Microfiltration is an economic mode of solid-liquid separation. This unit operation has been widely used for separation of fine particles or colloids in various fine chemical processes, such as biotechnological, ceramic, material processing, etc. It has attracted a considerable amount of attention in recent years. In such an operation, the major problems are the cake formation or concentration polarization nearby the filter membrane and the internal membrane fouling. In order to select an optimum operating condition and a correct membrane for a given fine chemical process, the main effort of this study will be devoted to study the effects of membrane morphology and operating conditions on the efficiency of cross-flow microfiltration. Three kinds of membranes with the same mean pore size of 0.1 m, such as MF, Durapore and Isopore membrane, are selected for filtration experiments. The variations of filtration resistance and cake mass for three kinds of membranes during filtration are measured. Although more particles blocks in the membrane pore, Isopore membrane results in a highest filtration rate due to less cake formation. The filtration rate of Durapore membrane is lower than that of Isopore membrane. It is because more particles deposit on Durapore membrane to form cake. MF membrane results in a lowest filtration rate due to most cake formation and serious pore blocking. Filtration rate will increase with either increasing cross-flow velocity or increasing filtration pressure.

P55

PHOTOGENERATION OF SINGLET OXYGEN BY PORPHYRINS IMMOBILIZED ON POLYMERIC MEMBRANES

S.L.KOTOVA^a, T.N.RUMYANTSEVA^a, A.B.SOLOVIEVA^a, S.A.ZAVYALOV^b, N.N.GLAGOLEV^a, N.A.AKSENOVA^a

^aDepartment of Polymers and Composites, N.N.Semenov Institute of Chemical Physics of Russian Academy of Sciences, 4 Kosygin st., 117977 Moscow, Russia

^bLaboratory of Adsorption of Active Particles, L.Ya.Karpov Institute of Physical Chemistry, 10 Vorontsovo Pole st., 103064 Moscow, Russia

The factors controlling singlet oxygen generation by solid systems containing porphyrins photosensitizers (PPS) were investigated. As photosensitizers, some meso-substituted porphyrins were used – tetraphenylporphine (TPP), mono-amino-TPP (MATPP) and sodium salt of tetra-para-sulpho-phenylporphyrin (TSPPNa) in their molecular and protonated forms. The PPSs were immobilized on polymeric membranes - ”Nafion”, polydimethyldiallylammoniumchloride (PDMDA), polyvinylcaprolactam (PVCL) and also deposited in vacuum on quartz plates.

The process of photogeneration was investigated in the medium of molecular oxygen in an all-soldered glass unit, applying a semiconductor sensor as a detector for singlet oxygen. The generation efficiency was determined by ratioing the steady-state concentrations of singlet oxygen inside the working volume of the unit.

As a result of the study, the essential effect of polymeric matrix on the immobilized porphyrins activity as photosensitizers has been revealed. The porphyrin-quartz systems were significantly (by orders of magnitude) less efficient photo-sensitizers than the corresponding systems which included immobilized porphyrins.

The activity of porphyrins immobilized on membranes noticeably increased with temperature, while it weakly depended on temperature in the case of porphyrins deposited on quartz. The energies of activation were minimum two times higher for the porphyrins immobilized on polymeric membranes. The same influence of polymeric support was obtained in the experiments with porphyrins deposited in vacuum onto polymeric membranes.

It has been shown that the amount of a porphyrin put into a polymeric membrane and also the film thickness are important factors which determine the efficiency of the given systems as photosensitizers in singlet oxygen generation.

P56

ION-EXCHANGE MEMBRANES BASED ON SULFONATED POLY(2,6-DIMETHYL-1,4-PHENYLENE OXIDE) AND ITS BLENDS WITH BASIC POLYMERS

^aInstitute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky Sq. 2, CZ-162 06 Prague 6, Czech Republic

^bUniversité Pierre et Marie Curie, Laboratoire de chimie macromoléculaire, Tour 44, 1^er étage, Case 185, 4 Place Jussieu, 75252 Paris Cedex

Poly(2,6-dimethyl-1,4-phenylene oxide) was sulfonated with chlorosulfonic acid to different degrees. New ion-exchange membranes were prepared either from sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (SPPO) alone or by mixing solutions of SPPO in the ammonium form and of polybenzimidazole or poly(2-ethylaniline) in the same aprotic solvent, casting the solution as a thin film, evaporating the solvent and treating the membrane with aqueous hydrochloric acid. The polymer - blend membranes were crosslinked by interactions of sulfonic groups of SPPO and basic groups of the other polymer as they were insoluble in aprotic solvents in which all the used polymers alone were soluble. A very small amount of either polymer in the blend will bring about crosslinking of the membrane. Spectroscopic studies showed the protonation of basic nitrogen-containing groups in the blends.

From SPPO (alone) with a sulfonation degree of 25 – 50 %, it is possible to prepare membranes with ionic conductivities comparable with Nafion membranes. However, such membranes swell considerably in water, and their mechanical strength in the water-swollen state is low. The membranes prepared from blends of SPPO with a basic polymer have better mechanical properties in aqueous environment than the membranes from pure SPPO at the same ionic conductivities. The membranes are conductive if the concentration of SPPO in the blend is higher than the percolation threshold, the value of which depends on the components used.

The membranes were tested in H₂/O₂fuel cells. Their performance in the fuel cell increased with increasing concentration of SPPO sulfonic acid groups in the blend. The membranes formed with the highly sulfonated SPPO alone or predominating, which swelled excessively in water, did not give reproducible results and their performance was usually inferior to that of the membranes having an optimum ratio of both components.

P57

Mechanism of selective transport trough ultrafiltration membranes from the standpoint of generalized sieving model

State Institute of Highly Pure Biopreparations, Pudozhskaya ul. 7, St.Petersburg, 197110, Russia, e-mail: ACULINA / VC3709.spb.edu

I It is thought that the resolving power ultrafiltration (UF) membranes is principally determined, alongside with the distribution of pores by size (PSD), by sieving mechanism. In UF universally adopted is Ferry’s mechanism, which is based on diffusion entrance of molecules into pores and has, therefore, low enough selectivity. May be the low selectivity of this type of sieving mechanism is just the course of assignment of ultrafiltration to low selective separation methods. However, the analysis of experimental data carried out had showed that, contrary to popular opinion , the low quality of UF separation is determined principally by high width of PSD function but not by the sieving mechanism which appeared to be high resolving (close to ”yes-no” type).

Except the determining role of PSD function in UF selectivity the traditional sieving model did not take into consideration the influence of gel polarization (GP) filtration mechanism. To take into account the influence of GP on membrane filtration properties it was supposed that gel layers overlap membrane pores only partially, which leads to reducing of all ports sizes by a value ΔR. It was shown that ΔR depends linearly on pore radius R (ΔR = kR¹, where k is a constant depending GP level), which explains, in particular, the parallel shifting of UF membranes retention curves to low molecular weights in the course of GP.

Thus, it is shown that the selective behavior of UF membranes can be described in the framework of generalized sieving model according to which UF process can be represented as a process of molecules sieving by yes-no mechanism through UF membranes with pores reduced by the value ΔR = kR.

The results obtained point to the advisability of manufacturing of UF membranes with narrow PSD function, which is bound to lead to the considerable increase in UF resolving power.

¹streacly speaking, the expression for ΔR has the form: ΔR = kR + ΔR_0,where k is a constant depending on GP level and ΔR₀ is the layer of irreversible adsorption which depends on hydrophilicity of membrane material and solute.

P58

Determination of membrane structure with the use of retention curve analysis

State Institute of Highly Pure Biopreparations, Pudozhskaya ul. 7, St.Petersburg, 197110, Russia, e-mail: ACULINA / VC3709.spb.edu

The analysis of ultrafiltration membrane (UFM) retention curve (RC) gives the possibility to estimate membrane structure pore size, pore size distribution (PSD), the thickness of selective layer (l_S), and UFM defects i. e. to obtain practically the same information as with the help of traditional structure-sensitive methods.

The determination of average pore size is based on the existence of the so-called ”critical ratio” between mean hydraulic pore radius (R_h) and the minimal radius of the retained protein molecules (r_L)

where φ(M) is RC, f(R) is PSD function, φ[r(M)/R] == φ(λ) is the sieving function,

where φ*(M) and φ(M) are the retention curves of a defective membrane and it selective pores and J₁and J₂arefluxes through the selective pores and defects, respectively .

where f₀ is porosity, J₀ is water flux at 1 bar, M_L is molecular weight cut-off, and

Eq.4 is the basis of the modern system of UF membrane classification on the thickness of selective layer, which gives the possibility to compare the arbitrary membranes of any type by their structure properties

As an example of this type of structure analysis the investigation of track-etched ultrafilters (TEUF) obtained either by a traditional technology for homogeneous filters or by a new technology for membranes with asymmetric structure. is described. The problem of structure analysis of more than 60 types of membranes with unknown structure was easily solved with the use of RC analysis. This analysis gave the possibility to exclude from consideration all defective membranes, all microfilters and all membranes with large amount of nanopores. After this exclusion only about 40 types of membranes have been left for structure analysis. The use of classification diagram for the left membranes showed the difference in structure between two membrane series and gave the possibility not only to determine membrane structure but also to compare TEUF with membranes of traditional type by its permeable and selective properties.

P59

Laboratoire de Chimie Physique Macromoléculaire (UMR CNRS-INPL7568), Groupe ENSIC, 1, rue Grandville F54001 Nancy-France
(email: droizard / ensic.inpl-nancy.fr)

Several routes were investigated to design high performance materials and membranes for the separation by pervaporation of non polar mixtures such as toluene n-heptane ones. The interest for this type of separation is very strong from the industrial point of view due to the high potential of application in the petroleum refineries. On the other hand the separation of non polar molecules is also a real challenge from the academic point of view: indeed considering the results known from the open literature the performances of available membranes are still far from those required for a viable process based on a pervaporation separation step. Starting from recent results directed to the fractionation of alcohol-ether and alcohol-alcane mixtures, we developed the synthesis of segmented copolymers from small -functionalised oligomers able to promote physico-chemical interactions with aromatic molecules such as benzene or toluene; the repeating unit of the polymer soft block is the oxyethylene group whereas the hard block one is based on urethane groups synthesised from an aliphatic diisocyanate and a triol. These poly(ether urethane) allowed the easy preparation of crosslinked dense films, which were well stable in pure toluene and endowed with good mechanical properties for pervaporation operations. Various methods were used to determine and analyse as far as possible the transport properties of these materials in relation with the observed selective mass transfer. Sorption characteristics were determined from vapour and liquid swelling equilibrium isotherms; infinite diffusion coefficients were calculated by numerical fitting of initial permeation data recorded in the transient state with pure liquids. Thanks to the tailoring approach used in the synthetic steps, a strong relationship between the polymer-structure and the pervaporation performances, i.e. flux and selectivity, could be demonstrated. The results showed a high selectivity for all prepared copolymers that was intrinsically due to the stronger affinity of toluene for the polar soft blocks as evidenced by sorption measurements; on the other hand the pervaporation selectivity was always slightly lower than the sorption one registered with mixtures that revealed a diffusion step favouring the aliphatic component.

P60

ON THE ROLE OF b -CYCLODEXTRINS IN FILLED POLYMERIC MEMBRANES: FACILITATED OR HINDERED TRANSPORT ?

F.Mikusek ¹, E.Favre ², D.Sacco ¹, D.Roizard ¹

¹ UMR 7568 INPL-CNRS, LCPM, ENSIC, 1 rue Grandville, B. P. 451, F-54001 Nancy, FRANCE *e-mail : frederic.mikusek / ensic.inpl-nancy.fr

² UPR 6811 CNRS, LSGC, ENSIC, 1 rue Grandville, B. P. 451, F-54001 Nancy, FRANCE

The concept of facilitated transport through specific carriers has been extensively investigated in liquid membranes. Nevertheless problems of membrane stability lead to supported membranes and finally to overcome carrier loss through membrane leaching, to bound carriers. Meanwhile researchers working with dense membrane focused on membrane improvement through specific compounds addition into membrane composition in order to involve more specific interactions and thus improve membranes capabilities. Following this track, we made membranes with bound b -Cyclodextrins with a view to investigate whether specific complexation could occur and participate to the separation of a two terpene mixture, namely limonene and a -pinene (the latter, being more likely to be complexed); this peculiarity was already demonstrated in chromatographic processes .

A series of experiments has been carried out on pure compounds in order to point out the role of b -CD in the transport process. We investigated different types of membranes with or without cyclodextrins. Diffusion measurements lead to the conclusion that diffusion through the material was more difficult when b -CD content was increased. Furthermore, diffusion flux decrease could be described based on tortuosity mechanism such as the one that was developed by Cussler et al (Cussler 1988). In a second step, pervaporation measurements were made at three temperatures in order to investigate the effect of b CD content and temperature, on pure component fluxes. Again, rather than enhancing transport, b -CD hindered transport, the enhancement factor being below one in all cases investigated. Our conclusions are shown to be consistent with results already reported on benzene transport through hydroxypropylmethyl cellulose membranes with various a -CD content .

P61

P62

^aResearch Institute on Membrane and Modelling of Chemical Reactors, CNR-IRMERC, c/o Università della Calabria, via P. Bucci, cubo 17/C, I- 87030 Rende (CS) Italy

^bDipartimento di Chimica, Università della Calabria, via P. Bucci, I- 87030 Rende (CS) Italy

The diffusion of penetrant gas in a polymer material is an important process with implications in many technological processes. Atomistic simulation techniques have proven to be a useful tool for the understanding of structure-property relationship of materials and can be used for a detailed description of the complex morphology and transport processes of glassy membranes. Molecular dynamics determinations of the transport coefficient of O₂, N₂ and H₂ in amorphous poly (ether-ether-ketone) and perfluoro membranes are presented. The packing models have been constructed and simulated by means of the InsightII/Discover software of Molecular Simulation Inc.. First completely refined amorphous polymer boxes have been made. A modified Theodorou–Suter method provided by the Amorphous Cell module of InsightII/Discover using pcff and compass forcefields¹has been utilised for the chain packing. A multistage equilibration-compression procedure ^2,3 has been utilised to obtain the system in a relaxed state at the real density. The MD simulation have been performed for about 2 ns for the analysis of gas transport process. The diffusion process results from jumps of penetrant molecules within adjacent holes in the polymer matrix. The free volume and the occurring jump mechanism have been characterised and visualised with different methods. Solubility and diffusion coefficients have been also been calculated using the Gusev-Suter transition state Monte Carlo method⁴.

²D. Hofmann, L. Fritz, J. Ulbrich, C. Schepers, M. Boehning, Macromol. Theory Simul. 9 (2000) 293–327

P63

Permeability of oxygen and nitrogen to study morphology of segmented polyurethanes

Institute of Coal Chemistry, Polish Academy of Sciences, 44-121 Gliwice, Sowiñskiego 5, Poland, e-mail: grabczyk / karboch.gliwice.pl

Permeability measurements for oxygen and nitrogen were carried out on a series of structurally different polyurethanes with liquid crystalline properties. Polymers were synthesised from poly(oxytetramethylene) diol (PTMO), 2,4-tolylene diizocyanate (2,4-TDI) and 4,4’-bis(2-hydroxyethoxy)biphenyl (BHBP). The structural variations applied for this set of polymers concern the length of the both soft and hard segments due to the different molecular weights of the PTMO diols (2000, 1000 and 650) and different molar ratios of the reagents (1:4:3; 1:2:1). The polymers were synthesised in DMF solution by a standard two-step procedure involving the initial end-capping of the PTMO with the required ammount of 2,4-TDI followed by a chain extension with BHBP.

Gas permeability measurements were performed at 30°C and at different pressures using equipment designed and constructed in our laboratory. The time lag method was used to determine the diffusion coefficient (D). Solubility coefficient (S) was calculated using the relation S=P/D. The obtained transport parameters were correlated with the experimental data concerning the free volume values calculated from the positron annihilation lifetime spectra, T_g values determined from the DSC measurements, the density values, and the hydrogen bonding indexes measured by FTIR. The relationships found were discussed in terms of the structural variations among the investigated polyurethanes as well as their two-phase morphology with liquid crystalline hard segment domains.

P64

Sorption and diffusion of liquid hydrocarbons and their vapours in the polyurethane-based membranes

Institute of Coal Chemistry, Polish Academy of Sciences, 44-121 Gliwice, Sowiñskiego 5, Poland, e-mail: grabczyk / karboch.gliwice.pl.

Sorption and diffusion are the key processes which determine transport of small molecules through pervaporation membranes. Studies of the both elementary steps undertaken by us recently concern the segmented polyurethanes which have been synthesised and already extensively investigated by us as membrane materials in various pervaporation applications. The polyurethanes chosen for the purpose of this work differed in the hard segment structure to determine the influence of these segments on the sorption and diffusion processes. They were obtained from poly(oxytetramethylene)diol (PTMO-2000), 2,4-tolylene diisocyanate (TDI) and various aromatic chain extenders: 4,4’-bis(2-hydroxyethoxy)biphenyl (LC), hydroquinone bis(2-hydroxyethyl) ether (HQ), 4,4’-diaminodiphenylmethane (PP). The initial molar ratio of the reagents was 1:4:3. Due to a high degree of a microphase separation assured by the synthesis conditions, the hard segments formedduring the chain extension step should be almost exclusively located in the hard domains of the polyurethanes.

Sorption and desorption experiments were carried out for benzene and cyclohexane at 30°C using a modified McBain’s microbalance or an immersion/weight gain method. Diffusion coefficient and sorption equilibrium values were calculated from the sorption/desorption kinetic curves and discussed with respect to the structure of the investigated polyurethanes. The sorption capacity of the polyurethanes was found to be the same up to 0.8 solvent activity and to convert into a strong structure-solvent uptake relation for the solvents in a liquid state according to the following set of the decreasing sorption equilibrium values PP> HQ> LC. The diffusion coefficients of the investigated systems were found to follow the set of the decreasing D values HQ> LC> PP for the both solvents in the liquid as well as in the vapour state.

P65

P. SYSEL^a,*, M. FRYČOVÁ^a, V. KRYSTL^b, P. HRABÁNEK^b, B. BERNAUER^b, M. KOČIŘÍK^c

Departments of Polymers^a and Inorganic Technology^b, Institute of Chemical Technology, 166 28 Prague 6, Czech Republic

^cJ. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, 182 23 Prague 8, Czech Republic

The incorporation of zeolites into a rubbery polymer membrane may result in an improvement of its (transport) properties in both gas separation and pervaporation. Nevertheless, the high-performance glassy polymers with outstanding mechanical and chemical stability at elevated temperatures (200-300 ⁰C) are needed for some applications. Aromatic polyimides rank among the most stable polymers. The poor adhesion between the rigid glassy polymer matrix and the zeolite constitutes the main difficulty. The silylation of the zeolite with 3-aminopropyltriethoxysilane was studied as a tool to improve zeolite incorporation in polyimide membrane (1).

In the present work 3-aminopropyltriethoxysilane terminated polyimide precursors (polyamic acids) of controlled molecular weight and Silicalite-1 are used to prepare the zeolite-filled polyimide membranes. The accessibility of the pores of the zeolite built in polyimide matrix was studied using sorption of iodine (from the vapour phase) (2). The permeation characteristics of membranes (dependence of fluxes on the inlet composition of the hydrogen-methane mixture and/or temperature) were measured using in-house designed and built instrument with the flow permeation Wicke-Kallenbach cell.

P66

L. TOMAN, L. BROŽOVÁ, I. KELNAR, P. VLČEK, J. SPĚVÁČEK,
M. JANATA, B. MASAŘ

Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky Sq. 2, CZ-162 06 Praha 6, Czech Republic

Immiscible blends are generally preferred to miscible blends because the useful properties of each blend component can be combined (1). However, most immiscible blends have a heterogeneous morphology due to unfavorable interactions at the molecular level leading to poor mechanical properties. To overcome these problems, functionalized polymers are used as compatibilizers, which can minimize the interfacial tension and improve the adhesion between the two phases. The result is a phase finely dispersed in a matrix and as a consequence improvement of the blend properties (2). Immiscible blends such as polyamide (PA)/polyisobutylene (PIB) are the preferred systems because of low price and also because of high chemical resistance of PIB (e.g., to ozone and aggressive reagents). However, mechanical properties of the uncompatibilized blends are insufficient for practical applications.These undoubtedly attractive blends of PA/PIB could not be produced so far due to the fact that no compatibilizer for them is known at present. Recently (3), a unique multifunctionalized PIB was discovered as effective compatibilizer of PA/PIB blends. Synthesis of this compatibilizer (PIB-C) is based on the in situ cationic polymerization leading to multifunctional PIB (4) bearing pendant reactive groups along the chain.

Gas transport properties of membranes were determined using a laboratory high-vacuum apparatus with a static permeation cell (5) at 30 ^oC. The membranes were made of selected composites such as PA6/PIB-C (3 vol.%), PA6/PIB (82/18 vol.%), and PA6/PIB/PIB-C (82/13/5 vol.%). PA6 and PIB are commercial Ultramid B3 and Oppanol B50 (BASF). Gas transport properties were studied for highly pure N₂, O₂, CO₂, H₂,and CH₄. Composite membranes show low permeation rates in the range of 0.01 to 0.001 Barrer.

1. D. H. Kim, K. Y. Park, J.Y.Kim, K. D. Suh, J. Appl. Polym. Sci.78, 1017, (2000).

5. J. Schauer, P. Sysel, V. Maroušek, Z. Pientka, J. Pokorný, M. Bleha, J. Appl. Polym. Sci., 61,1333 (1996).

P67

A.B.Remizov¹, S.A.Petrova¹, D.I.Kamalova², A.Yu.AlentIev³, Yu.P.Yampolskii³

¹Kazan State Technological University, K.Marx st., 68, Kazan 420015, Russia,
e-mail: Remizov / kstu.ru

²Kazan State University, Kremlevskaya st., 18, Kazan 420008, Russia,
e-mail: Dina.Kamalova / ksu.ru

³A.V.Topchiev Institute of Petrochemical Synthesis, Leninskii pr., 29, Moscow 117912, Russia, e-mail:Alentiev / ips.ac.ru

The investigation of new polymer materials having the optimal combination of permeability and separation of gas mixtures is an important problem of membrane science. These properties are substantially due to the free volume distribution of the polymers and the local mobility of polymer chains and their fragments.

A large number of data of the local dynamics and the free volume distribution of the polymers was received by using molecular probes. Every probe allows one to receive the information on different aspects of the local dynamics, the relaxation transitions and the free volume of glassy polymers. These data add each other.

The results of IR spectroscopic studies for conformational probes in many polymer matrices which are different by the free volume and the polymer chain mobility are given. Measured temperatures of freezing of the conformational transitions in polymer matrices (T_f) were analyzed. The probes with various sizes of mobile fragments (from 13 A³ to 108 A³) were used.

We have compared the values T_f as for one probe in different matrices as for different probes in one polymer. For this purpose we used literature data on b -relaxation transitions and data on positron annigilation lifetime spectroscopy.

P68

ANISOTROPY OF MECHANICAL PROPERTIES IN ORIENTED POLYETHYLENE FILMS AND MEMBRANES: THE EFFECT OF CONDUCTING POLYMER LAYER

^*Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky Sq. 2, 162 06 Prague 6, Czech Republic

^**Technical University of Liberec, Textile Faculty, Department of Textile Materials, Hálkova 6, 461 17 Liberec, Czech Republic

^***Institute of Macromolecular Compounds, Russian Academy of Sciences, Bolshoi prospekt 31, St. Petersburg, 199004 Russia

Microporous films of high-density polyethylene have been prepared by melt extrusion followed by annealing and uniaxial extension¹. Correspondingly, three basic stages of flat materials were obtained². Some of the resulting membranes were subsequently covered with a layer of conducting polymer (polyaniline or polypyrrole) directly during the oxidative polymerisation of a corresponding monomer. Stripe specimens for tensile testing were cut from the prepared flat materials with the angle between their axes and the machine direction varying from 0^o to 90^o in 10^o increments. The angular dependences of modulus of elasticity, tensile strength and strain at break were plotted as polar diagrams. Average stress-strain traces for selected directions of the tested materials were also constructed. The results show a dramatic effect of the test direction both on the absolute values of mechanical characteristics and the whole courses of the stress-strain curves. The samples without the conducting layer showed a maximum of their strength and modulus in the machine direction, while strain at break showed a maximum at 40^o. The layer of a conducting polymer changed distinctly the shape of the polar diagrams of the microporous membranes. This behaviour was explained by the brittleness of a relatively thick layer of polypyrrole on one hand, and by a certain plastification of the polyethylene support by polyanilin, on the other. Morphology of the torn surfaces assessed by light microscopy also showed a distinct anisotropy of the fracture processes, particularly in the microporous membranes³.

The authors wish to thank H. Hejzlarová and V. Kovačič, TU Liberec, for valuable discussions and professional help. Financial support from the Grant Agency of the Academy of Sciences of the Czech Republic (project A4050904) is also gratefully acknowledged.

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M. RAAB^*, M. VALKO^**, H. HEYZLAROVÁ^**, V. KOVAČIČ^**,
G.K. ELYASHEVICH^***

^*Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky Sq. 2, 162 06 Prague 6, Czech Republic

^**Technical University of Liberec, Textile Faculty, Department of Textile Materials, Hálkova 6, 461 17 Liberec, Czech Republic

^***Institute of Macromolecular Compounds, Russian Academy of Sciences, Bolshoi prospekt 31, St. Petersburg 199004, Russia

Microporous membranes from high-density polyethylene convert a relatively cheap commodity polymer in a valuable product with a broad application potential¹. At the same time, the description and explanation of the structure transformations from an extruded film through annealed (hard-elastic) film up to the final microporous membrane is a challenge for scientific research. In this study light microscopy with digital image analysis and scanning electron microscopy were used for the investigation of the torn surfaces of tensile specimens taken in different directions from the individual stages of membrane preparation. The combination of these two microscopic techniques enabled the assessment of the fracture morphology as a function of the test direction at different levels of structural hierarchy. In particular, a close relation between the orientation of microscopic structure elements and the macroscopic development of the fracture process has been established. Qualitative results of this morphological study are in agreement with the data of the sound propagation velocity² and anisotropy of macroscopic tensile mechanical properties³.

Financial support of the Grant Agency of the Academy of Sciences of the Czech Republic (project A4050904) is gratefully acknowledged.

P70

MOLECULARLY IMPRINTED POLYMER MEMBRANES FOR USE IN TRANSCUTANEOUS MONITORING DEVICES

Drug Delivery Research Group, Welsh School of Pharmacy, Cardiff University, CF10-3XF, UK.

Several studies have looked at the phenomenon of outward transdermal migration of analytes and have aimed to produce a continuous transcutaneous monitoring device. Work by Peck et al. (1981-1991) demonstrated that a number of drugs, including Theophylline and Caffeine can be detected transcutaneously by transdermal collection systems (TCS). However, these patches rely on analytes passing through the stratum cornuem (SC) by diffusion alone so that only limited success was achieved. The recently released `glucose watch’ relies on iontophoresis to enhance the rate of transcutaneous diffusion but an ideal transcutaneous monitoring device would bypass the stratum corneum barrier.

We aim to develop a novel `noninvasive’ transcutaneous monitoring device that contains two modules. A molecularly imprinted layer superimposed on an array of microneedles. The latter can penetrate the stratum corneum to a depth of 150 m m, whilst avoiding contact with the nerve endings and hence pain. The analyte can be detected after it has passed through the microneedles and reaches the imprinted layer. It may be possible to attach a thin layer of molecularly imprinted polymer by surface grafting onto the microneedles. Alternatively, a separate membrane may be attached to the needles. Currently we are looking at the second of these options and have produced a flexible, thin, durable imprinted polymeric membrane.

A thin polymeric membrane was formed from a solution of the following: methyl methacylate, tri (ethylene glycol dimethacylate) as the cross-linker, methacrylic acid as the functional monomer, 2-2’-azobis (isobutyronitrile) as the initiator and theophylline as the template in chloroform. The solution was distributed between two glass plates and irradiated with ultraviolet light (365 nm), which caused radical co-polymerisation. The membrane was washed to remove weakly bound absorbed copolymer and to extract the template.

Diffusive permeability and selectivity of the membrane were determined using Franz diffusion cell methodology, with the donor-receptor chambers separated by the imprinted membrane.

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Department of Physical Chemistry, Kuban State University, Stavropol’skaya str., 149, Krasnodar, 350040, Russia, e-mail: berezina / chem.kubsu.ru

The key role of polymer synthetic ion exchange membranes is emphasized both for realisation of effective electrodialysis and for theoretical description of kinetics and dynamics of this process. The interpretation method of experimental dependences of membrane electrotransport properties on the salt solutions concentration has been suggested, which takes into account the structural inhomogeneity of polymer charged membrane. This approach permitted to form a system of the structural-transport parameters for membranes and to estimate the ions kinetic properties during the transfer of the mass and charge. It is established, that the concentration dependences of electroconductivity and diffusion flux are basic to membrane characterization. The approach is useful both for the description of membrane electrodiffusion properties and for the stating and solving of dynamical problems of electrodialysis. We have now the data bank to characterization of ion exchange membranes of different manufacturing companies. This information is necessary to choose materials with optimal properties for the real processes. For more comprehensive description of membranes behaviour the above-mentioned system can be added by dynamical hydration numbers of counter-ions and co-ions, calculated from investigation of electroosmotical permeability for the same sample of membrane. The interrelation between structure-transport parameters and test characteristics of membrane materials presented in the catalogs and certificates of production companies was revealed.

The authors are grateful to the Russian Fund of Basic Researches and the Krasnodar Territory Administration (project N 00-03-96024).

P72

CONDITIONING METHODS OF PERFLUORINATED SULFOCATIONIC MEMBRANES MF-4SС AND NAFION

Department of Physical Chemistry, Kuban State University, Stavropol’skaya str., 149, Krasnodar, 350040, Russia, e-mail: berezina / chem.kubsu.ru

It is known, that the structure and properties of perfluorinated membranes are specially dependable on conditions of pretreatment [1-3]. However, in the literature on characterization of the membranes of this type, there is no common opinion about a standard procedure of their conditioning. Objects of research were commercial and experimental samples of a sulphocationic membranes MF-4SС (Russia) and also membranes of Nafion-115 and Nafion-117 types (USA). The different conditioning methods are studied: pretreatment with acids and saline solutions at a room temperature, boiling in water, acids and hydrogen dioxide during variable time (from 30 min to 3 hours). Exchange capacity, water content, hydrate capacity, specific electroconductivity were determined with the help of the standard techniques. It is revealed, that the hydrate capacity of a membrane extends at the transition from K ⁺- to H⁺-form and becomes more enlarged after boiling in an acid and water. This stands in agreement with the data of the authors [2]. The analysis of concentration dependences of electroconductivity and diffusion permeability in a wide range of salt solutions concentrations has shown that the transition from saline pretreatment at a room temperature to thermal conditioning methods results in the variation of the character of concentration dependences and in the increase of membrane electroconductivity as in proton, so in the salt forms. The diffusion permeability of membranes MF-4SС and Nafion-115 increases in 3-4 times. The comparison of the obtained structural-transport parameters of membranes points out the extension of interchain space and the growth of the "free" water volume fraction in cluster zones of perfluorinated polymers.

The work is carried out with the financial support from the Russian Fund of Basic Researches (project N 00-03-96026).

2. Zawodzinski Th. A. and coll. // J.Electrochem. Soc. 1993. Vol.140. N4. P.1041.

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Department of Physical Chemistry, Kuban State University, Stavropol’skaya str., 149, Krasnodar, 350040, Russia, e-mail: berezina / chem.kubsu.ru

The dependence of the conductivity of heterogeneous and homogeneous ion exchange materials on the volume fraction of a conducting hydrophilic phase was studied. The methods of the percolation theory were used to analyze the data obtained. The parameters of the percolation eguation were determined for the case of a decrease in the material conductivity during water desorption from heterogeneous membranes with constant concentration of fixed charges (the first-kind percolation transitions). It was shown that the methods of the percolation theory are applicable also for the description of the conducting properties of ion exchange membranes with the variation in the number of fixed charges on a polymer matrix in the course of the material preparation from conducting and nonconducting components (the second-kind percolation transitions). Estimation of f_cr and t percolation parameters showed that the obtained values of critical index t agree with the theory (t = 1.6± 0.4) for all the materials, and the value of the threshold parameter f_c varies over the 0.15-0.35 range depending on the structural type and preparation method of a material.The percolation model was used also for interpretation of transport phenomena in the polyaniline –Nafion system, obtained during template synthesis in free standing membrane.

P74

TEMPLATE SYNTHESIS OF POLYANILINE IN THE PERFLUORINATED SULPHOCATIONIC POLYMER MATRIX

*Department of Physical Chemistry, Kuban State University, Stavropol’skaya str., 149, Krasnodar, 350040, Russia, e-mail: berezina / chem.kubsu.ru

The preparation of composite polymer materials is the effective method of improving properties of individual polymers. Many conducting polymers – polyaniline, polypirrole, polythiophen and their analogues have been widely studied in the different fields of applied chemistry and electrochemistry. Of particular interest is the polyaniline-Nafion composite membrane, which is studying by cyclic volt-ammetry, optical, radioisotope methods. The aim of this work is to gain information concerning the process of template synthesis of aniline in the martix of perfluorinated membranes ( Nafion type )of russian production MF-4SC. The synthesis was carried out by chemical method, when the free-standing membrane was placed between two solutions: one side of the membrane is exposed to an oxydant solution (0,01 M FeCl₃+ 0,5 M H₂SO₄), and the other to a monomer solution (0,01 M aniline + 0,5 M H₂SO₄). The polymerisation of aniline with the formation of green color emeraldine-form of polyaniline occurs in the cluster zones of membranes during meeting diffusion process of spices. The transport properties of composite polyaniline-MF-4SC films were studied with help of electroconductivity, diffusion and electroosmotical permeability measurements in comparison of the same properties of the initial samples of MF-4SC in proton form. The structural image of microheterogeneous composite film created on the base of comlex study of electrotransport phenomena permits to reveal the mechanism of charge transport and doping level in this polymer compositions.

P75

GAS TRANSPORT PROPERTIES OF POLYPYRROLE-SULFONATED POLYPHENYLENE OXIDE MEMBRANES

Z. Pientka^*, L.Brožová^*, M.Bleha^*, G.A.Polotskaya^**, D.V.Andreeva^**, G.K.Elyashevich^**

^*Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, 162 06 Prague 6, Heyrovský Sq.2, Czech Republic

^**Institute of Macromolecular Compounds, Russian Academy of Sciences, 199004 St.Petersburg, Bolshoy pr.31, Russia. E-mail:galina / AP3634.spb.edu

Polypyrrole (PPy) has unique physical properties including electric conductivity and gas separation (α_O2/N2=18). However, these properties of PPy are difficult to implement because of its poor processability. A promising method for improving processability is the combination of PPy with other polymer, particularly, by pyrrole polymerization into the matrix of a host polymer.

In the present work sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (SPPO) was chosen as the polymer matrix due to its good mechanical and gas separation properties. Furthermore, SPPO is a convenient polymer matrix because randomly placed sulfonated groups after special treatment by ferric chloride contain Fe³⁺ ions, which can act as oxidative agent for pyrrole polymerization. The aim of this work was to estimate the contribution of PPy to gas separating properties of the PPy-SPPO system. To solve this task, gas separating membranes of different structure were prepared by oxidative polymerization of pyrrole from vapour phase into SPPO matrix or on its surface.

Homogeneous membranes (PPy-SPPO dense film of ~20 μm thickness) have gas permeability coefficients similar to SPPO matrix, and selectivity relatively higher. It was established that increasing PPy content from 2.5% to 20 %wt. decreases gas permeability of PPy-SPPO membranes. Defective structure of the dense film is formed if the PPy content is higher than 20%wt. For increasing performance, composite membranes containing PPy-SPPO as thin top layer (~3 μm) on microporous support were developed.

Two-layer membranes consisting of PPy thin layer (~7.10^-2 μm) on the surface of SPPO layer (~20 μm) have considerably improved gas separating properties in comparison with the polymer matrix without decreasing its high mechanical advantages. It was calculated that PPy exhibits its high selectivity in the two-layer membrane.

PPy-SPPO membranes were examined by AFM. Their electric conductivity and mechanical properties were also studied. This work was supported by Russian Foundation for Basic Research (N⁰ 01-03-32290).

membrane	Porous PPO	PPO/PIM (26 LB layers)
	Flux P/l x 10⁶ [cm³(STP)/cm² .s.cm Hg]
N₂	137 ± 2.6	17.7 ± 0.19
O₂	150 ± 10	48 ± 2.24
CH₄	209 ± 7.2	23.2 ± 0.61
CO₂	250 ± 12.5	115 ± 6.8
H₂	680 ± 44	260 ± 15
	selectivity
α(O₂/N₂)	1.11	2.74
α(CH₄/N₂)	1.52	1.31
α(CO₂/N₂)	1.80	6.51
α(H₂/N₂)	4.94	14.87

Posters

F.Mikusek 1, E.Favre 2, D.Sacco 1, D.Roizard 1

F.Mikusek ¹, E.Favre ², D.Sacco ¹, D.Roizard ¹