1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
HIGHLY BRANCHED SULFONATED POLYETHERSULFONES AND POLYETHERKETONES: SYNTHESES AND POSSIBLE APPLICATION IN MEMBRANE PROCESSES
D. FRITSCHa, L. VAKHTANGISHVILIb, H.-R. Kricheldorf b
aInstitute of Chemistry, GKSS Research Centre, Max-Planck-Strasse, D-21502 Geesthacht, Germany
bInstitute of Technical and Macromolecular Chemistry, University of Hamburg, Bundesstrasse 45, D-20146 Hamburg, Germany
Dendrimeric macromolecules have attracted some interest and
applications over the last years. However, their synthesis is a
multi-step process and therefore complicated to perform.
Hyperbranched polymers are by chemical structure close to
dendrimers and also simple, one-pot syntheses are possible by
applying ABx-monomers as starting materials. ABx-monomers
may be synthesized prior to reaction separately or generated
during polymerization in a one-pot synthesis (see eq. 1).
We have followed this concept and reacted 2 tri-functional
monomers with difluorophenyl-sulfone as shown in Scheme 1. 
Depending on the
stoichiometry of the reactants soluble polyethersulfones resulted
(yield: 40-70 %). Using the simplest tri-functional compound
1,3,5-trishydroxybenzene, only cross-linked, insoluble polymers
resulted. To improve the reproducibility and the ability of
scaling-up, the well-known trimethyl-silyl-group (TMS) was
introduced by silylation of the trishydroxy compounds to improve
the reactivity of the leaving group. Following this strategy, the
reproducibility was enhanced and by this method even
trishydroxybenzene (Scheme 2) reacted to soluble, hyperbranched
polymers with high molecular weight. Introduction of some
functionality, e.g., by end group alkylation or sulfonation of
the main chains offers a new class of hyperbranched
polyethersulfones and polyether-ketones for appli-cations in
mem-brane processes.
PREPARATION AND APPLICATION OF MICROPOROUS TPX MEMBRANES
D.M. WANGa, C.Y. Changa, T.T. WUb, J.Y. LAIb
aDept. of Chemical Engineering, National Taiwan University, Taipei, Taiwan 10617
bDept. of Chemical Engineering, Chung Yuan University, Chung Li, Taiwan 32023
In the present work, poly(4-methyl-1-pentene) (TPX) was used to prepare hydrophobic microporous membranes, and the application of the prepared membranes to pervaporation and osmotic distillation was also investigated. In using the wet inversion method to prepare the microporous TPX membranes, a problem needs to be resolved is the appearance of skin layers, which would lower the permeability and thus limit the applicability of membranes. A solution is proposed in the present work: using soft nonsolvent to reduce solidification speed and induce TPX crystallization. The crystallization would result in polymeric particles and these particles could aggregate to form particulate membranes with inter-connected pores. The evolution of the formation of particulate membranes will be reported. It was found that, for TPX with low molecular weight, the crystallization proceeded very fast and the particulate membrane can be easily formed with suitable solvent and nonsolvent. However, for TPX with high molecular weight, appropriate additives in solvent or nonsolvent were required to form particulate membranes. It was also found that the aggregation of polymer particles was strongly affected by the nonsolvent used. Hence, microporous TPX membranes with different permeabilities can be fabricated by adjusting the composition of the coagulation bath. Because the strong hydrophobicity of TPX, the prepared membranes can form stable water-air and water-organic solvent interfaces, like polypropylene and polytetrafluoroethylene (PTFE). This property makes the prepared membranes applicable to the separation processes that need membrane contactors. Experiments were performed to evaluate the performance of the prepared membranes in organophilic pervaporation and osmotic distillation. When the membranes were used in pervaporation to separate aqueous solution containing 7 wt% of ethanol, the permeation flux was about 6 kg/m2h and the selectivity of ethanol to water was 5. When the membranes were used in osmotic distillation to concentrate protein, the permeation flux was about 3 kg/m2h. Same experiments were also performed by using the commercial PTFE membranes, the measured fluxes are similar to the above reported results, indicating that the performance of the microporous TPX membranes prepared in the present work is comparable to the commercial PTFE membranes.
Molecularly imprinted affinity membranes
M. Ulbricht 1*,2, W. Weigel 1, V. Kochkodan 1,3, T. A. Sergeyeva 4, S. A. Piletsky 5
1 Institute of Technical Chemistry, University Essen, D-45117 Essen, Germany;
e-mail: mathias.ulbricht / uni-essen.de
2 ELIPSA GmbH, Köpenicker Str. 325, D-12555 Berlin, Germany.
3 Institute of Colloidal & Water Chemistry, Ukrainian Academy of Sciences, Kyiv, Ukraine.
4 Institute of Molecular Biology, Ukrainian Academy of Sciences, Kyiv, Ukraine.
5 Institute of BioScience & Technology, Cranfield University, Bedfordshire, UK.
Molecular imprinting of polymers, a cross-linking polymerization of functional monomers in presence of a template, yields synthetic materials mimicking the function of biological receptors [1]. With this approach, time- and cost-efficient polymer chemistry and technology could yield stable, tailored materials for affinity technologies without a biological component. Molecularly imprinted membranes in particular have an especially large, but almost unexplored potential for substance-specific separation, analytics, screening or catalysis [2].
We develop a modular concept for the rational design of structure and function of molecularly imprinted polymer (MIP) membranes. Using a novel surface functionalization approach, MIP composite membranes are synthesized which combine porous membranes as robust, highly permeable supports with stable, template-specific MIPs [3]. Supramolecular complexes of template molecules, such as e.g. triazine herbicides, and suited functional acrylates can be fixed by a photo-initiated cross-linking graft copolymerization in very thin MIP-layers which, covalently anchored, cover the entire surface of commercial microfiltration membranes. A next generation of the novel MIP composite membranes combines the low non-specific binding properties of special pre-coated support membranes with an exceptionally high substance-specificity of MIPs [4].
The high efficiencies for desorption (after MIP synthesis) and specific rebinding of the template are due to the low thickness of the MIP-layers. The fixation of the MIP-layer on the membrane support contributes to the high stability.
Those novel MIP composite affinity membranes enable the substance-specific solid-phase extraction (membrane SPE) from very dilute solutions at very high filtration rates. One application is the specific substance enrichment for trace analytics in complex watery matrices. However, due to the easy scale-up of the surface functionalization and the high stability of the MIPs receptors, substance-specific decontamination of large volume streams, e.g. water, is also feasible.
[1] G. Wulff, Angew. Chem. Int. Ed. Engl. 34 (1995) 1812-1832.
[2] S. A. Piletsky, T. L. Panasyuk, E. V. Piletskaya, I. A. Nicholls, M. Ulbricht, J. Membr. Sci. 157 (1999) 263-278.
[3] S. A. Piletsky, H. Matuschewski, U. Schedler, A. Wilpert, E. V. Piletskaya, T. A. Thiele, M. Ulbricht, Macromolecules 33 (2000) 3092-3098.
[4] T. A. Sergeyeva, H. Matuschewski, S. A. Piletsky, J. Bendig, U. Schedler, M. Ulbricht, J. Chromatogr. A, 907 (2001) 89-99.
POLYMERISED BICONTINUOUS MICROEMULSION (PBM) MEMBRANES: PREPARATION, CHARACTERIZATION AND APPLICATION
A. FIGOLI, W.F.C. SAGER, M. WESSLING
Membrane Technology Group, Faculty of Chemical Technology, University of Twente
P.O. Box 217, NL 7500 AE Enschede, The Netherlands. Email: a.figoli / ct.utwente.nl
In recent years more involved preparation routes have been investigated for the manufacturing of porous (open cellular) membranes compared to the classical (thermal induced) phase inversion method. These include for example the employment of pore forming solvents during evaporation, foaming of gas saturated polymer films or the controlled aggregation of latex particles. A new method which allows for systematic adjustment and control of the membrane morphology (pore size and distribution) within the nanometer range is to template thermodynamically stable systems, such as microemulsions.
In bicontinuous microemulsion, which consist of an interconnected network of water and oil channels, stabilised by the interfacial surfactant film, the oil (monomer) channels can be polymerised to form the polymeric matrix of the liquid membranes, while the water phase remains unchanged. Since microemulsions are thermodynamically stable systems, the width of the water channels can be adjusted over a certain range by their composition. In using surfactants that posses the same polymerisable group as the monomer (oil), the morphology of the microemulsions can be mainly retained during the polymerisation reaction.
We prepared nanoporous transparent free standing membranes as well as coatings with pore size adjustable between 3-70 nm by in-situ polymerisation of the following microemulsion system: acryolyloxyundecyl)trimethylammonium bromide (AUTMAB) as polymerisable surfactant, methylmethacrylate (MMA) as oil, 2-hydroxyethyl methacrylate (HEMA) as cosurfactant, and water.
Polymerisation was initiated either by UV-light or using a redox initiator at 30 oC. We will present a detailed study on the characterization and polymerization of the microemulsions employed and on the morphology and separation characteristics of the nanoporous transparent PBM-membranes obtained in their dry and wet states. Due to the small pore sizes involved, membrane thickness below 1 mm can be realized if the films prepared are cast on a porous support. This allows the application of PBM-membranes as NF/UF and as nanostructured supported liquid membranes, of which first results will be shown. Since PBM membranes offer the advantage of altering the pore size by keeping a very high porosity, they might be able to chose the gap between polymer and ceramic membranes, yielding in a well-defined pore size distribution accompanied by a high trans-membrane flux.
Gas Transport Properties of Sulfonated Copolyimides: Influence of Structural Parameters and Relative Humidity
F. Piroux 1,2, E. Espuche 1, M. Escoubes 1, R. Mercier 2, M. Pineri 3
Email: espuche / matplast.univ-lyon1.fr
The use of polymeric membranes in catalysis
I.F.J. Vankelecom, P.A. Jacobs
Centre for Surface Chemistry and Catalysis, Department of Interphase Chemistry, K.U.Leuven, Kastellpark Arenberg 23, B-3001 Heverlee, Belgium
ivo.vankelecom / agr.kuleuven.ac.be; Tel +32-16/32.15.94; Fax +32-16/32.19.98
In most catalytic membrane reactors, porous inorganic membranes are applied at elevated temperatures. In the field of fine chemical synthesis or catalytic waste water treatment, reaction temperatures are lower and the use of polymeric membranes becomes possible. This facilitates the module construction and gives rise to a whole new range of conditions in which catalysis/membrane hybrid processes become favourable.
Polymer membranes were combined with catalysis for three different purposes. First of all, an existing heterogeneous catalyst was incorporated in a dense, organic polymer.1 The dense membrane makes the use of a solvent redundant as the immiscible phases contact via the membrane in which the catalyst is incorporated. Through the sorption-diffusion mechanism, the membrane regulates the concentration of both reagents near the catalyst and excludes species that would decrease the catalytic efficiency.
In a second approach, the incorporated catalyst was a transition metal complex2 or a photosensitizer.3 The inclusion of the catalyst in the membrane polymer then simultaneously constitutes a way of catalyst heterogenisation, which opens interesting possibilities towards catalyst recycling and continuous mode operation. For both concepts, several types of polymers were applied already and polymer properties were optimised by mixing additives or by making polymer blends.
Thirdly, homogeneous catalysis can be combined with a membrane separation process.4 For instance, transition metal complexes can be used under the best possible conditions of homogeneous catalysis. By coupling this reactor to a membrane separation and by controlling the residence time in the reactor, converted product can be removed continuously through the membrane while the catalyst is retained. This concept could be developed thanks to the recent availability of solvent resistant nanofiltration membranes.
In this lecture, all three concepts will be explained and illustrated with examples of our most recent research in the field of oxidation of water pollutants, photochemistry and synthesis of chiral compounds.
References
1An efficient mimic of cytochrome P-450 from a zeolite-encaged iron complex in a polymer membrane
Rudy F. Parton, Ivo F.J. Vankelecom, Mark Casselman, Cvetana P. Bezoukhanova, Jan B. Uytterhoeven and Peter A. Jacobs, Nature, 1994, 370, 541-544.
2 Chiral Catalytic Membranes
I.F.J. Vankelecom, D. Tas, R.F. Parton, V. Van de Vyver, P.A. Jacobs, Angewandte Chemie, 1996, 35, 12, 1346.
3 Photosensitization with membrane occluded dyes
Frederik van Laar, Ivo F.J. Vankelecom, Wim Dehaen, Pierre A. Jacobs, In preparation for Journal of Photochemistry and Photobiology A: Chemical.
4 Nanofiltration coupled catalysis: a way to perform homogeneous reactions in a continuous mode
Koen De Smet, Ivo F.J. Vankelecom, Pierre A. Jacobs, Accepted for publication in Chem. Comm.
MODELING OF ASYMMETRIC MEMBRANE FORMATION BY DRY-CASTING METHOD
SACİDE ALSOY, BÜLENT ÖZBAS
İzmir Institute of Technology, Gaziosmanpaşa Bulv. No:16 35230, Çankaya, İzmir, Turkey, Email:sacide / likya.iyte.edu.tr
Many polymeric membranes are produced by phase inversion technique invented by Loeb and Sourirajan in 1962. One of the most challenging problems in membrane industry is to produce membranes with desirable structural characteristics which cause best performance for a specific application. The solution of this problem is facilitated by the development of mathematical models.
The polymeric membrane formation process is a complicated process due to phase separation, simultaneous heat and mass transfer mechanisms controlled by complex thermodynamic and transport properties of polymer solutions. In this work, a fully predictive mathematical model developed by Alsoy(1998) is used to describe the mechanisms of membrane formation by dry casting method. Model equations consist of coupled unsteady state heat and mass transfer equations, film shrinkage as well as complex boundary conditions especially at polymer-gas interface. A key component of the model is incorporation of multicomponent diffusion coefficients that consist of thermodynamic factors and self-diffusivities. The predictions from the model provide composition paths, temperature and the thickness of the membrane. The beginning of phase transition is determined when composition paths are plotted into the phase diagram. The model is applied to cellulose acetate/acetone/water system which is commonly used for asymmetric membrane formation. The predictive ability of the model is evaluated by comparison with the data obtained from gravimetric measurements. As shown in Figure 1 below, the predictions of total weight of the cellulose acetate membrane is in good agreement with the experimental results.
Figure 1 : Predicted and measured total solution mass for CA/Acetone/H20 system
Reference :S. Alsoy, ”Modelling of Polymer Drying and Devolatilization Processes”, PhD Thesis, The Pennsylvania State University, University Park, USA (1998)
ELECTROCHEMICAL CHARACTERIZATION OF IONICALLY CONDUCTIVE POLYMER MEMBRANES
K. RICHAUa, V. KUDELAb, J. SCHAUERb
aGKSS Research Centre GmbH, Institute of Chemistry, Kantstr. 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
Cation conductive membranes, especially highly proton conductive membranes, are of interest not only for chlor-alkali electrolysis but for other applications like polymer electrolyte fuel cells as well. The challenge for electrochemical characterization in this case is the low specific resistance of the polymer required for such applications, which in turn makes resistance measurements a non-trivial problem.
We discuss the different possibilities to measure the direct current (DC) resistance as well as the alternating current (AC) impedance to characterize such membranes. To overcome the existing limitations, we were following three routes:
1. using appropriate electrolytes for DC and AC investigations,
2. using reversible electrodes for AC investigations and
3. using variable electrode distances for DC investigations.
The usefulness of these approaches for the case of highly proton conductive membranes will be discussed. As examples, commercially available membranes used for fuel cell applications like Nafion 117 as well as membranes made from sulfonated poly (phenylene oxide) with different degrees of sulfonation are employed.
The support of this work in the framework of the Scientific – Technological Cooperation between The Czech Republic and Germany (Project No. CZE 00/028) is acknowledged.
Chemical characterisation of electromembrane synthesis ethylene tetrafluoroethylene matrices using Raman and infrared spectroscopy
O. VAN VOLDEN, H.D. HURWITZ
Laboratoire de Thermodynamique Electrochimique, Membranes et Electrodes. Faculté des Sciences.Université Libre de Bruxelles. CP 256. Boulevard du Triomphe, 1050 Bruxelles, Belgium. e-mail : ovanvold / ulb.ac.be, hhurwitz / ulb.ac.be
The extensive development of industrial separation processes using electromembranes, like acid dialysis, classical electrodialysis or dipolar membrane electrodialysis and the intensive research on fuel cells with membrane electrolytic separators has focused the attention on the fabrication processes of ion exchange polymer membranes. With respect to such properties as water swelling, electric resistance and ion permselectivity, it has become necessary to perform more fundamental investigation on the mechanisms at the molecular level governing the sorption, interaction and transport of ions and water in the polymer membrane. Furthermore the influence on the above mentioned mechanisms of the original nature of the polymer matrix and of its succesive chemical alterations and functionalisations must be understood in order to orient succesfully the fabrication of the membrane.
In the present work we undertook a study of the role of the polymer matrix chemical nature as well as of some selected polymer film chemical modifications which all together determine the final electrochemical characteristics of these polymer electromembranes.
We used and compared ion exchange membranes realised with alternate ethylene-co-tetrafluoroethylene (ETFE) films. For this purpose we chose different commercially available films. Accurate chemical characterisation of these basic polymer material was the initial step of research performed by spectroscopic methods like FTIR (classical and ATR) FTRaman, calorimetry (DSC, TGA) and optical analysis (microscopy).
In the fabrication process a ion exchange membrane (IEM), the ETFE films were first submitted to an electronbeam irradiation. Thereafter polystyrene (PS) and divinylbenzene (DVB) used as a cross-linking agent were grafted on the peroxyde sites formed on the polymer chains inside the film and the associated grafting kinetics was carefully investigated. These grafted films were subsequently modified by chlorosulfonation to realise a cationic exchange membrane
The physical molecular state of the membranes which results from each chemical step selected for IEM was investigated by means of FTIR, FTRaman spectroscopy TGA and DSC.
The present research shed light on the fact that Raman spectroscopy is a unique source of information of the polymer electromembranes properties at each step during their synthesis. Raman spectroscopic observations in correlation with results of all other methods of analysis used in this work have been linked to the final fabricated electromembranes electrochemical properties as obtained by ampero-voltametry and impedance spectroscopy.
The Role of Physico-chemical Properties of Polymeric Membranes and Cell Adhesion in Vitro
L. De Bartolo1, S. Morelli 1and E. Drioli.1,2
1Research Institute on Membranes and Modelling of Chemical Reactors, IRMERC-CNR, c/o Univ. of Calabria, via P. Bucci cubo 17/C, 87030 Rende (CS); 2 Department of Chemical and Materials Engineering, Univ. of Calabria, via P. Bucci, 87030 Rende (CS)
Polymeric semipermeable membranes are used in bioartificial organs as immunoselective barriers between patient’s blood and the xenocytes to prevent rejection. Membranes provide also a large exchange area to supply cells with amounts of nutrients and oxygen necessary for their metabolism. In some devices, membranes act also as the substrata for cell adhesion, the hepatocytes being anchorage-dependent cells. The capacity of membrane to perform its function and to provide an adequate mechanical and chemical support for cell culture depends on its separation and surface properties.
This study was undertaken to investigate the physicochemical aspects of the interaction between the membrane and mammalian cells in order to provide guidelines to the selection of cytocompatible membranes. To this purpose we investigated as potential substrata for cell culture various polymeric membranes: polysulfone (PSf), cellulose acetate (CA), polycarbonate (PC), polyacrilonitrile (PAN), polypropylene (PP) and perfluoropolymer (PF) membranes. This latter was made in our laboratory. The physico-chemical properties of the membranes were characterised by contact angle measurements. The different parameters acid (g +), base (g -) and Lifshitz-van der Waals (g LW) of the surface free energy were calculated according to Good-van Oss’s model. The adsorption of protein modified markedly both contact angle and components of membrane surface tension. In particular base parameter of surface tension decreased drastically with increased water contact angle.
Cells formed three-dimensional aggregates and re-established intercellular junctions. The morphology of cells cultured on different membranes was different on different membranes. On CA membranes cells feature protrusions of cytoplasmatic membranes similar to that observed also on collagen and PC membranes while on PSf membranes cells exhibited a round shape and shown tight junctions. Surface free energy of membranes affected liver cell adhesion. For each investigated membrane we observed that cell adhesion increased with increasing base parameter of membrane surface tension. The absolute value of cell adhesion is higher in the presence of serum proteins adsorbed on the membrane surface, which change the wettability by increasing base parameter of surface tension.
Functionalised ethylene vinyl alcohol copolymer (EVAL) membranes for protein affinity separation
Maria-Elena Avramescu, Wiebke Sager, Matthias Wessling
Faculty of Chemical Technology, University of Twente, Membrane Technology Group
P.O. Box 217, NL 7500 AE Enschede, The Netherlands
Especially for biological fluids, affinity membranes have recently been proven to be most suitable since high throughputs are warranted and pre-filtration and specific adsorption can often be combined in one step. Affinity membranes are based on the principle of specific reversible adsorption of the compounds targeted (ligate), whereby the binding sites (ligand) are immobilised directly or via spacer molecules on the membrane. Of special interest is the separation of immunoglobulins from blood for medical applications, which can be realised by, e.g., coupling protein A to the membrane pore-surface. For this purpose the basic membranes should have a microporous structure and allow for high fluxes. Beside specific coupling, non-specific adsorption of other blood compounds and proteins via their hydrophobic segments should be avoided. The polymer used for membrane formation should posses functional groups, such as –OH, –COOH, - NH2, to couple the protein. In this study we investigated the use of EVAL, a random copolymer of ethylene (hydrophobic) and vinylalcohol (hydrophilic) groups, to prepare suitable microporous membranes that can be modified to couple the proteins. Principally, activation of the primary alcohol groups is possible by wet chemistry in aqueous and organic medium, but the choice is restricted by the reactivity of the activation reaction. Bifunctional reagents can react twice with the –OH groups and cause often-unwanted crosslinking of the pores. To optimise surface modification and protein coupling, we investigated a variety of different reactions, including the glutaraldehyde and oxiran method in aqueous media and trichloro-s-triazine and sulfonyl chloride (tosyl and tresyl chloride) reactions in organic media. Phase inversion of the cast EVAL films results generally in the formation of membranes with a microporous structure on the glass side, that collapses into a dense structure upon direct drying in air, and a very open and loose structure on the side facing the coagulation bath, which might peel off. EVAL asymmetrical ultrafiltration membranes (pure water flux in the range of 20-200 l/h/m2/bar) consisting of a thin dense skin and cellular pores with finger-like macrovoids in the sublayer were prepared by adding substantial amounts of solvent (DMSO) into the coagulation bath (water). Since EVAL is a hydrophilic polymer, the dried membrane possesses a closed structure caused probably by a collapse of the initially formed pores so that they have been used as basic material for protein coupling only in aqueous media. Values of 0.1-0.2 m g BSA/cm2 of internal area were obtained by using glutaraldehyde and oxiran method for membrane activation. Unaltered completely dry membranes could be prepared if additives were used in the casting solution. Microfiltration membranes with the pure water flux in the range of 150-1500 l/h/m2/bar were prepared by using 10% 1-octanol as additive. The membrane preparation route enlarged the set of surface activation reactions by those based on organic solvents. 0.3-0.45 m g BSA/cm2 of internal area was coupled on the porous surface by trichloro-s-triazine and sulfonyl chloride (tosyl and tresyl chloride) reactions. The additivated membranes have been also modified by introduction of various functional groups by gas discharge techniques (plasma treatment) operated at low pressures. Using the plasma treatment modification we immobilised 0.5-0.6 m g BSA/cm2 of internal area. Values of 0.6-0.84 m g BSA/cm2 were reported for a complete BSA monolayer adsorbed on a porous surface.
POLYMERIC SUPPORTS WITH METAL ION COMPLEXES FOR SEPARATION OF BIOLOGICAL MIXTURES
M. Bleha, G. Tishchenko, K. Mészárosová
Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic,
Heyrovský Sq. 2, 162 06, Prague 6, Czech Republic
We present here the results of immobilized metal ion affinity chromatography (IMAC) on new chelating polymer supports – nonporous and porous copolymers of diethyleneglycol methacrylate (DEGMA) or glycidyl methacrylate (GMA) with ethylene dimethacrylate (EDMA) containing chelating groupings of ethylenetriaminetriacetic acid (EDTriA), quinoline-8-ol (HQ), iminodiacetic (IDA) and aspartic (ASP) acids. Ni+2, Cu+2 and Fe+3 complexes of the chelating polymers in the form of foils and beads were used for isolation of horseradish-peroxidase-specific (HRP) immunoglobulins (IgG1) from raw mouse ascitic fluids and of chitinase from a filtered culture media of Cl. aminovalericum.
Emphasis was put on analysis of correlation between a nature of polymer structures, kind of coordinated metal ions, type and concentration of the chelating groups and the separation efficiency.
It was found that the stability of transition metal ion complexes with the chelating groups was sufficiently high (98-99.9%) in the pH range 4-8.5 for both the chelating beads and foils.
Separation experiments were carried out in a column and in a sandwich cartridge composed of two microporous membranes and a 2-mm layer of chelating polymer particles between them. A fifty-time smaller bed height in the cartridge than that in the column resulted in a remarkable decrease in the bed flux resistance. The influence of the membrane morphology and flow rates on resolution of the protein peaks was analyzed.
The best separation efficiency of IMAC columns was obtained using the Ni+2–IDA complex of porous GMA–EDMA chelating beads (7-13 m m). HRP–specific IgG1 with 92% recovery and 73% purity was isolated from a crude ascitic fluid by one-step procedure with decreasing pH in the elution buffer. In contrast to Ni+2–IDA complexes, Cu+2–IDA retained HRP-specific IgG1 as well as chitinase more firmly and more severe elution conditions were required (imidazole concentration gradient) for their isolation.
The opportunity of protein and enzyme purification with transition metal complexes incorporated in porous chelating membranes is discussed.
This work was supported by the Grant Agency of the Academy of Sciences of the Czech Republic (grant A 4050910).
Synthesis of novel polyelectrolyte complexes as pervaporation membranes for the separation of aqueous mixtures.
P. VAN DE VELDE, F.DU PREZ, E.GOETHALS
Ghent University, Polymer Chemistry Division, Krijgslaan 281 S4, 9000 Gent, Belgium; E-mail : Peggy.Vandevelde / rug.ac.be
The coreaction of highly and oppositely charged polymers in the form of polyelectrolyte complexes leads to the formation of ionically crosslinked polymer structures. One application of polyelectrolyte complexes as polymer material is the preparation of membranes (1). Because of their ionic nature and hydrophilicity, such polymer materials are of interest for their use as pervaporation membranes for dehydration processes.
Polyvinylethers belong to an interesting class of polymers that can be polymerized by living cationic polymerization of vinyl ether monomers with a wide range of functionalities and physical properties. Due to the versatility of the monomers and the convenient manipulation of its living polymerization and polymer architecture, polyvinylethers with desired functionalities among the main chain, controllable molecular weight and narrow polydispersities can be prepared (2). As the polycation of the complexes, the basic form of poly(aminoethyl vinylether) has been used. This polymer has been obtained with different molecular weights in three steps: the living cationic polymerization of chloroethyl vinylether, the substitution of the chloro into a phtalimide group and finally the transformation of the phtalimide into an amino group by hydrozinolysis. The charged form of this polymer has been used as starting material in the synthesis of polyelectrolyte complexes by mixing a solution of this polycation with different acid and sulphonic containing polyanion solutions, based on commercially available poly(acrylic acid) and poly(sodium styrenesulfonate). The polyelectrolyte solutions have been casted on various supporting materials.
The pervaporation qualities of these polyelectrolyte complex membranes have been investigated for the separation of azeotropic aqueous mixtures such as water/ethanol.
(1) S. Y. Nam, Y. M. Lee, J. Memb. Sci.135, 161 (1997).
(2) E. J. Goethals, W. Reyntjens, S. Lievens, Macromol. Symp. 132, 57 (1998).
Use of Polyelectrolyte Multilayer Systems for Membrane Modification
J. Meier-Haack, M. Müller
Institute of Polymer Research Dresden, P.O.Box 120 411, D-01005 Dresden, Germany; e.mail: mhaack / ipfdd.de
In membrane science special attention is focussed on the fouling phenomenon. Membrane fouling is often caused by biological matter in the feed (e.g. proteines), which is adsorbed by hydrophobic and/or electrostatic interactions to the membrane surface and is a main reason for pore blocking. Hydrophilic and/or charged membrane surfaces are prepared with the aim to reduce membrane fouling and to control the membrane performance.
A smart method to obtain hydrophilic and charged membrane surfaces is given by the layer-by-layer adsorption of polyelectrolytes and the build-up of polyelectrolyte multilayer complexes on polymeric substrates. Depending on the application the membrane surfaces can be easily equipped with positiv or negativ charges. Grafting of the first polyelectrolyte layer onto the membrane surface ensured excellent stability during filtration process. A twofold higher permeate flux was observed for polyelectrolyte complex membranes compared to that of the just grafted one (fig. 1) without changing the protein retention. Additional in-situ ATR/FTIR investigations confirmed low protein adsorption for repulsiv electrostatic interactions between the substrate and the protein under applied conditions.
Furthermore, pervaporation membranes with ultra-thin separating layers (nm-scale) have been prepared with the layer-by-layer adsorption of polyelectrolytes. Especially polyelectrolytes with high charge-densities gave very effective membranes for the separation of water-alcohol mixtures (fig. 2)
FIG. 1 FIG. 2
Facilitated Transport of Carbohydrates through a Supported Liquid Membrane Containing a Neutral Lipophilic Resorcinarene Carrier
J.-F.Verchère
OPTIMISATION OF TRANSPORT PROPERTIES OF THE POLYURETHANE-BASED PERVAPORATION MEMBRANES BY A POLYMER MOLECULAR STRUCTURE DESIGN
Aleksandra Wolińska-Grabczyk
Institute of Coal Chemistry, Polish Academy of Sciences, Sowińskiego 5, 44-121 Gliwice, Poland, e-mail: grabczyk / karboch.gliwice.pl.
The effectiveness of the overall membrane separation process for which the transport mechanism can be described by a solution-diffusion model is directly related to the intrinsic properties of the membrane material. The strength and nature of polymer-penetrant interactions and the physical structure of the membrane resulting from a polymer structure and polymer-polymer interactions all account for the rate at which any compound permeates through the membrane and for the membrane ability to accomplish the desire separation.
In this paper an approach to transport properties tailoring of the membrane material applied in the separation of organic/organic and organic/water mixtures will be presented based on a polymer molecular structure design concept. Segmented polyurethanes chosen for these studies enabled a wide range of structural modification to be performed within one group of polymers which resulted in a collection of membrane materials of diverse transport properties. The systematic structural variations of the investigated polyurethanes concerned the chemical constitution and the length of the both segments. They were introduced at the synthesis stage by using various polyether, polyester or polydiene diols with various molecular weights ranging from 650 to 2000, aromatic or aliphatic diisocyanate, and different low molecular weight diols or diamines as chain extenders in various molar ratios.
The influence of the chemical constitution or the length of a particular segment on the membrane performance will be demonstrated with respect to the kind and composition of the liquid mixtures being separated or to the single component of this mixture. The solvent systems studied were composed of an organic solvent mixed either with another organic compound or water, e.g. benzene/cyclohexane (or water), methanol/MTBE (or water).
The presented correlations will be discussed in terms of the polymer-penetrant and polymer-polymer interactions and structure of the membranes under investigations.
PREPARATION OF POROUS BILAYER HOLLOW FIBER MEMBRANES
W. ALBRECHT, TH. WEIGEL, TH. GROTH, B. SEIFERT, R. HILKE, D. PAUL
GKSS Research Center, Institute of Chemistry, Kantstraße 55, d-14513 Teltow, Germany, E-mail: Wolfgang.Albrecht / gkss.de
Hollow fiber membranes have been well established in a wide range of applications, in particular in the biomedical field for blood purification processes like dialysis, plasmapheresis etc. New applications are under development, which will use membranes as a support for adhesion-dependent cells in biohybrid organs to replace liver and kidney functions. Membranes in biohybrid organs will contact blood or plasma on one side and tissue cells on the opposing side. Hence, new types of membranes are required with a blood and a tissue compatible side. One of the way to realize such types is preparing a bilayer membrane to become an optimal support for both environments, such as the blood and the tissue side.
At bilayer hollow fiber membranes the membrane wall is composed of two chemically different polymer layers. One of the most important parameter characterizing bilayer membranes is a high integrity at the interface between both layers. Such membrane types should be prepared as hollow fibers using double tube in orifice (triple) spinnerets which allow the separate transport of the different spinning solutions and the bore fluid. In the past this technique was successfully applied for preparation of relatively dense, integrally asymmetric hollow fiber membranes and composite membranes in one preparation step if the second ”polymer solution” is a nonsolvent or integrates evaporable solvents besides polymer.
In the presentation first results of the preparation of porous bilayer hollow fiber membranes using a nonsolvent induced wet phase inversion (NIPS) process are presented. The results document that a formed body like a fiber in fiber composite is prepared if conventional triple spinnerets are used in combination with the NIPS process. Between both polymer layers a space without polymer material is generated destroying the structural integrity of the membrane wall. A modified spinneret triple was developed at which both polymer solutions are layered side by side in the spinneret before they will be extruded out of the spinneret. Using such a spinneret porous bilayer hollow fiber membranes with a high structural integrity of the membrane wall can be prepared if compatible polymer solution systems are applied. Using incompatible polymer solutions, structural integrity can be only generated if the outside polymer has a higher irreversible shrinkage during the drying process of the nascent fiber in fiber composite as the inside polymer. On basis of these model fibers first types of support membranes for biohybrid organs were prepared.
Sorption, Diffusion and Permeation Properties of Oxygen and Water Vapor in Copolymer of Ethylene-and Polar Monomers
Y. HIRATA, S. MARAIS, Q.T. Nguyen, and M. METAYER
Laboratoire ” Polymères Biopolymères Membranes”, UMR 6522, Université de Rouen / CNRS, UFR des Sciences, 76821 Mont-Saint-Aignan Cedex
Poly(ethylene-co-vinyl acetate) (EVA) completely hydrolyzed, leading to poly(ethylene-co-vinyl alcohol), is one of the most impermeable polymers. For a better preservation of fresh fruits and vegetables, however, the higher barrier property for water and oxygen through the polymeric films prevents from extending their life time. Increasing in the water permeability and keeping the low permeability for oxygen are required to reduce the respiratory intensity and the anaeorobic fermentation rate.
Asymmetric membranes, based on EVA containing 70 wt.% of the unit of vinyl acetate, were prepared by a treatment of unilateral hydrolysis using solutions of sodium hydroxide dissolved in a mixture of water and methanol. The depth of hydrolyzed layers and the concentration of hydroxyl groups in the membranes were controlled by the treatment time and the concentration of sodium hydroxide in the solutions. The transport properties of water and oxygen through the asymmetric membranes were studied by permeation and sorption measurements. The effects of the treatment time using 0.8 M NaOH solution on the permeabilities of the asymmetric membranes to water and oxygen are shown in Fig. 1. The permeability coefficient for water has a maximame at 0.5 hour while the permeability coefficient for oxygen decreased with the treatment time. These results suggest that materials for packaging may be suited to increase permeability to water and improve permselectivity simultaneously.
Fig. 1 Plots of permeability coefficients for H2O ( ) and O2 ( ) at 25°C v.s. treatment time.
TRANSPORT AND SORPTION PROPERTIES OF MICROPOROUS POLYETHYLENE FILMS AND COMPOSITE MEMBRANES
G.K.Elyashevicha, E.Yu.Rosovaa, G.A.Tiscenkob, M.Blehab
a Institute of Macromolecular Compounds, Russian Academy of Sciences, Bolshoi pr. 31, St. Petersburg 199004,Russia; E-mail: elya / hq.macro.ru
b Institute of Macromolecular Chemistry, Academy of Sciences of Czech Republic, Heyrovsky Sq. 2, Prague 162 06, Czech Republic; E-mail: tiscenko / imc.cas.cz
New composite systems consisting of microporous polyethylene (PE) film and conducting polymer layer have been elaborated. PE films as microporous membranes were formed by the technique based on the melt extrusion. They are characterized by a large number of through flow channels 0.05–0.45 m m in size and specific properties of the surface which provide high adhesion of the film to coating. Microporous films are the most suitable materials for preparing composites because their pores enable formation of a continuous conducting network inside the sample. It was established that composite membranes exhibit ion-exchanging properties and can be used in electrochemical processes (electrolysis and electrodialysis).
Polypyrrole (PPy) and polyaniline have been used as conducting polymers. Conducting layers were formed by polymerization in gas phase (polypyrrole) or from monomer solution (polyaniline) and as a deposit of dispersion (polyaniline). Surface and volume electrical conductivity of composites have been measured.
Diffusion permeability and ion transport selectivity of composite systems PE-PPy with different thicknesses of PPy layers and various porosities of the PE support were studied. The dependences of diffusion and transport characteristics in electrolytes on porous, hydrophilic and ion-exchange properties of the composite membranes have been observed. The optimum combinations of PPy content and membrane porosity ensuring maximum fluxes of electrolytes through the membranes or maximum transport selectivity for ions were determined.
Sorption behavior of PE support and composite membranes in various vapors have been investigated. The effect of air humidity and thickness of PPy layers in PE-PPy membranes on the sorption of water vapor was analyzed.
The work was supported by Russian Foundation of Basic Research (Grant № 01-03-32290).
Novel polyamides as permselective gas membranes
Jorge E. Espeso, Enrique Ferrero, Angel E. Lozano,
José G. de la Campa, J. de Abajo
Instituto de Ciencia y Tecnología de Polímeros, CSIC. 28006 Madrid. SPAIN
Aromatic polyamides have been tested as polymer membranes for gas separation in many instances. Reasonable selectivities have been found for a number of gases, but low permeabilities have hindered a bigger development of these polymers for gas separation until now. Attempts have been made in past years to improve permeability to gases, mainly by means of modifications on the chemical structure, and significant advances in these approaches have led to novel polyamides with better permeability-selectivity properties. As aromatic polyamides are unmeltable, rather insoluble materials, modifications are very difficult to achieve by attacking the polymer structure with chemical reagents, so that new monomers are usually synthesized and utilized for the preparation of soluble, film-forming modified species.
In this contribution, aromatic polyamides are reported that have been prepared from new monomers containing aliphatic side substituents and bulky groups, as depicted in the figure:
The effect of bulky pendent groups and aliphatic side substituents on the permeation characteristics of the novel polyamides, is generally positive, and the films show higher permeability to technical gases tan classical wholly aromatic polyamides, while retaining comparable values of selectivity.