Organic-inorganic Nanocomposite Membranes Research Articles

Effects of nanosized organic‐rectorite fillers on the morphologies and properties of PVDF UF membrane

AbstractIn this study, polyvinylidene fluoride/organic rectorite (PVDF/OREC) organic–inorganic nanocomposite membrane was prepared by phase conversion method. TEM and X‐ray diffraction (XRD) results demonstrate the successful fabrication of nanocomposite ultrafiltration membranes. When the OREC is less than 3 wt%, the nanosheets are mainly stripped and dispersed in the polymer matrix, with different numbers of intercalations. When the impurity content is 5%, the intercalation distribution dominates. When the impurity content increases to 7% and above, it becomes increasingly difficult for PVDF chain segments to enter the OREC interlayer and the OREC particles are dominated by simple blends on the order of micrometers in the polymer matrix. The inclusion of inorganic fillings significantly improved the mechanical properties of the membrane. The yield strength and tensile modulus of the membrane were increased by 53.7% and 574.9%, respectively, with an inorganic filler content of 5 wt%, while the elongation at the break was slightly decreased to 16.2%. This suggests a strong interaction between the OREC nanosheets and the polymer matrix. XRD and FTIR analyses indicate that OREC particles are effective heterogeneous nucleating agents that favor the formation of β‐phase crystals in the film. SEM surface and cross‐section results show that when joining can significantly reduce the average pore size of the membrane surface, large holes tend to reduce the number of holes in the skin layer distribution more uniformly. The AFM results show that the addition of OREC can significantly alter the surface roughness of ultrafiltered membranes, and that the changes in surface roughness and surface pore morphology of membranes with different clay contents are closely related to the distribution of nanoscale silicate sheets in the PVDF matrix.Highlights Prepared PVDF/OREC nanocomposite membranes via a phase‐inversion process. OREC acted as a potent nucleation agent, favoring β crystal formation. OREC resulted in smaller pore sizes and fewer large pores in the skin layer. The hydrophilicity of PVDF membranes was reformative by filling OREC. OREC led to increased water flux and BSA rejection due to pores and hydrophilicity.

Proton Exchange Membrane Fuel Cells: Focused on Organic-Inorganic Nanocomposite Membranes

The application of organic-inorganic nanocomposite membranes allows for a synergy between the desirable thermal and mechanical properties of inorganic materials with the reactivity, dielectric properties, durability, flexibility, and processability of the polymeric materials. Proton exchange membrane fuel cells (PEMFCs) suffer from some problems including water content management, carbon monoxide poisoning, hydrogen reformate, and fuel crossover through the membrane. Herein, specific solutions have been proposed to the above-mentioned problems using organ-inorganic nanocomposites. These solutions include doping proton conductive inorganic nano-particles in the proton exchange membrane, preparing nanocomposites via the sol-gel method, covalence bond of inorganic compounds with the polymer structure, and acid-based proton exchange nanocomposite membranes. Furthermore, hydrogen production with low carbon monoxide content using the ethanol steam reforming method, as well as the effect of CO in the hydrogen feed of PEMFC are explained and discussed. Finally, desirable conditions for achieving the maximum power density in exchange membrane cells (EMFCs) are discussed.

Incorporating functionalized graphene oxide in green material-based membrane for proton exchange membrane fuel cell application

A novel organic-inorganic nanocomposite membrane with green material based is prepared by incorporating sulfonated holey graphene oxide (SHGO) into nanocrystalline cellulose/polyvinyl alcohol (NCC/PVA) matrix as polymer electrolyte membrane (PEMs) via solution casting method. Introducing sulfonic acid group in graphene oxide (GO) yielded sulfonated graphene oxide (SGO) and the hole effect on the graphitic plane of GO for SHGO on NCC/PVA significantly improves the proton conductivity of membranes by creating more interconnected proton transfer channels and promoting proton transfer across the membrane. Highest proton conductivity values of 1.1 × 10-2 S cm-1 is obtained by NCC/PVA-SHGO-1.0 at 80o C under 100% relative humidity (RH). Additionally, mechanical and chemical stability tests indicate an enhancement in those properties. However, hydrogen permeation has slightly increase due to the hole effect. Increasing SHGO loading in NCC/PVA has improve its properties and performance. At 80o C, under 100% RH, NCC/PVA-SHGO-1.0 exhibit the highest power density and current density of 31.4 mW/cm2 and 60.2 mA/cm2, respectively which is three times higher compared to pristine NCC/PVA. This work summarise that incorporating SHGO into NCC/PVA membranes can significantly improves its properties, performance and membrane durability which entitle them as a potential candidate for PEMs.

Improved performance of organic–inorganic nanocomposite membrane for bioelectricity generation and wastewater treatment in microbial fuel cells

A growing demand for sustainable and green polymer membranes leads to the development of organic–inorganic based nanocomposites for various applications. In this study, the nanocomposite membranes were prepared by incorporation of nano-clay montmorillonite(MMT) into a chitosan(Cs) biopolymer matrix. Different weight ratios of Cs/MMT membranes were prepared by solution casting-solvent evaporation method and subsequently used as a proton exchange membrane in microbial fuel cells(MFC) applications. The effect of MMT addition in Cs matrix was investigated on the performance of dual-chambered MFC in terms of power generation and chemical oxygen demand(COD) removal. Among the tested membranes, Cs/MMT(1/1) showed the highest power density of 85.7 mW/m2 in comparison with neat chitosan and control Nafion of 77.2 mW/m2 and 0.7 mW/m2, respectively. The wastewater treatment efficiency for Cs/MMT(1/1) membrane was also enhanced by 1.4- and 2.5-times from neat Cs and Nafion membranes, respectively. Characterization studies such as FTIR and SEM showed the successful incorporation of MMT on Cs matrix. The decreased weight loss of Cs/MMT membranes upon the addition of MMT indicated the improved thermal stability. These tremendous improvements for performance showed that biopolymer Cs-based nanocomposite incorporated with MMT can be a candidate for alternative bio-PEM in MFC.

Synthesis and Characterization of Novel Green Hybrid Nanocomposites for Application as Proton Exchange Membranes in Direct Borohydride Fuel Cells

Organic–inorganic nanocomposite membranes for potential application in direct borohydride fuel cells (DBFCs) are formulated from sulfonated poly(vinyl alcohol) (SPVA) with the incorporation of (PO4-TiO2) and (SO4-TiO2) nanotubes as doping agents. The functionalization of PVA to SPVA was done by using a 4-sulfophthalic acid as an ionic crosslinker and sulfonating agent. Morphological and structural characterization by transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) confirmed the successful synthesis of the doping agents and their incorporation into the polymer. The influence of PO4-TiO2 and SO4-TiO2 doping and their content on the physicochemical properties of the nanocomposite membranes was evaluated. Swelling degree and water uptake gradually reduced to 7% and 13%, respectively, with increasing doping agent concentration. Ion exchange capacity and ionic conductivity of the membrane with 3 wt.% doping agents were raised 5 and 7 times, respectively, compared to the undoped one. The thermal and oxidative stability and tensile strength also increased with the doping content. Furthermore, lower borohydride permeability (0.32 × 10−6 cm2 s−1) was measured for the membranes with higher amount of inorganic doping agents when compared to the undoped membrane (0.71 × 10−5 cm2 s−1) and Nafion®117 (0.40 × 10−6 cm2 s−1). These results pave the way for a green, simple and low-cost approach for the development of composite membranes for practical DBFCs.

A CO2-gated anodic aluminum oxide based nanocomposite membrane for de-emulsification.

A carbon-dioxide-responsive organic-inorganic nanocomposite membrane based on a through-hole anodic aluminum oxide (AAO) template was constructed. The composite was prepared via a surface-initiated reversible addition-fragmentation chain-transfer (SI-RAFT) polymerization strategy to achieve the grafting of poly(methyl methacrylate-co-2-(diethylamino)ethyl methacrylate) brushes on the AAO membrane. The grafted polymer chain length could be controlled based on the feed ratio between the free chain transfer agent (CTA) and reactive monomer, e.g., methyl methacrylate and 2-(diethylamino)ethyl methacrylate, resulting in a membrane that features adjustable water permeability. Importantly, the membrane pore size and surface wettability could be switched from hydrophobic to hydrophilic upon the introduction of carbon dioxide and nitrogen gases. This allowed for the nanocomposite membrane to be utilized for controlled water flux and oil/water emulsion separation. The simple fabrication methodology as well as sustainable gaseous stimulus will be useful for the construction of future smart membranes.

Proton Conductive Organic-Inorganic Nanocomposite Membranes Derived by Sol-Gel Method

На основі акрилових мономерів та кремнеземної неорганічної складової, сформованої у результаті золь-гель перетворення прекурсора - 3-метакрилоксипропілтриметоксисилану (МАПТМС), синтезовано протонопровідні органо-неорганічні нанокомпозитні мембрани. Методом лазерної інтерферометрії досліджено кінетику полімеризації in situ. Встановлено водопоглинання мембран і набрякання їх у метанолі, виміряно контактні кути змочування, що дало змогу розрахувати вільну поверхневу енергію мембран та її складові. Досліджено протонну провідність мембран за різних температур, оцінено енергію активації протонної провідності. Одержані гібридні мембрани демонструють високу протонну провідність, що дає можливість використовувати їх у паливних комірках.

Fabrication of silver nanoparticles decorated polysulfone composite membranes for sulfate rejection

The tactic of embedding functional nanomaterials into ultrafiltration (UF) membranes has been investigated in order to augment the integrated properties of the hybrid membranes. Mixing of hydrophilic inorganic nanoparticles or nanofillers into the polymeric membranes to form organic-inorganic nanocomposite membranes were found to be quite effective in improving membrane hydrophilicity. In the present study, polysulfone (PSf) membrane of three different compositions (9, 12, 18 wt%) in-situ immobilized with silver nanoparticles were fabricated using phase-inversion technique. The surface morphology of the membranes were studied by field emission scanning electron microscope (FESEM). The uniformity of the distributed nanoparticles and the elemental compositions were proved by energy dispersive x-ray Spectroscope (EDS). BET (Brunauer-Emmett-Teller), nitrogen adsorption measurement has revealed the increase in surface area from 10.15 to 18.85 m2/g for polysulfone membrane and 12.31 to 20.62 m2/g for silver-polysulfone (Ag-PSf) membrane. The surface charges of the fabricated membranes were studied using zeta potential measurements. Furthermore, water flux and sulfate rejection measurements were also carried out using a cross-flow membrane unit. Among the three different compositions, 12 wt% PSf-Ag membranes had significantly higher rejection rate than that of the other membranes.

A novel high-flux, thin-film composite desalination membrane via co-deposition of multifunctional polyhedral oligomeric silsesquioxane and polyoxometalate

This work describes the synthesis of a novel organic–inorganic nanocomposite membrane via an efficient one-pot approach of co-deposition of octa-aminopropyl polyhedral oligomeric silsesquioxane hydrochloride salt (OA–POSS) and polyoxometalate (POSS–Mo36) onto a support membrane. The structure and morphology of the thin film nanocomposite (TFN) membranes were characterized by FT-IR spectroscopy, atomic force microscopy (AFM), energy-dispersive X-ray analysis (EDX), and scanning electron microscopy (SEM). In addition, the effect of POSS–Mo36 on the performance of the thin film nanocomposite (TFN) membranes was investigated in a forward osmosis (FO) process. Experimental results demonstrate the enhanced desalination performance of the synthesized as compared to thin-film composite (TFC) polyamide membranes.

Self-crosslinked organic-inorganic nanocomposite membranes with good methanol barrier for direct methanol fuel cell applications

The organic-inorganic latex particles with sulfonic acid groups and core-shell structure are successfully obtained and then are heated to fabricate the self-crosslinked organic-inorganic nanocomposite membranes. Fourier transform infrared (FTIR) spectra confirm the chemical structure of membranes. The effects of inorganic component on the performances of nanocomposite membranes are investigated extensively. TGA analyses show that the membrane materials possess excellent thermal stability and 5% weight loss temperature increase with increasing SiO2 content. Solvent absorption measurement suggests the membranes are less permeable to methanol than water. The obtained membranes show conductivity values above 10−2Scm−1. More importantly, all the membrane materials exhibit more excellent methanol barrier and higher selectivity compared with Nafion® 117, demonstrating that those membranes could be a potential candidate as proton exchange membranes for future direct methanol fuel cells.

Design of poly(1-hexadecene-sulfone)/poly(1,4-phenylene sulfide) membrane containing nano-zeolite and carbon nanotube for gas separation

Impregnating polymeric membranes with inorganic zeolite particles and organic carbon nanotube particles led to organic–inorganic nanocomposite membranes. In this work, nano-zeolite (NZ) and carbon nanotube (CNT) were used as nanofiller materials, while poly(1-hexadecene-sulfone)/poly(1,4-phenylene sulfide) (PHS/PS) blend was used as matrix material. PHS/PS/NZ membranes have shown fine dispersion, although layered-particulate morphology was seen in PHS/PS/NZ–CNT 10 membrane. Tensile strength of PHS/PS/NZ 1–10 was 53–58 MPa, while PHS/PS/NZ–CNT 1–10 showed higher values 67–78 MPa. Young’s Modulus of PHS/PS/NZ 1–10 was 122.2–137.7 MPa, while PHS/PS/NZ–CNT 1–10 showed higher values 143.4–166.5 MPa. Moreover, the nano-zeolite/carbon nanotube (NZ–CNT) filler was found more effective than nano-zeolite in enhancing CO2 permeability and permselectivity. The permeability PCO2 of PHS/PS/NZ and PHS/PS/NZ–CNT membranes increased with increasing filler concentration and reached 177.3 Barrer at 10 wt% filler content. The permselectivity αCO2/N2 for PHS/PS/NZ–CNT 10 membrane (36.1 Barrer) was also higher than PHS/PS/NZ 10 (32.9 Barrer).

Sulfonated Polyimide-Clay Thin Films for Energy Application.

Sulfonated polyimides (SPIs) are considered as the promising alternatives to Nafion as membrane materials for the polymer electrolyte membrane (PEM). They generally exhibit high ionic conductivity, good mechanical properties, excellent thermal and chemical stabilities. The six-membered ring, naphthalenic anhydride-based SPIs, not only exhibit superior chemical and thermo-oxidative stabilities but are also more resistant to hydrolysis than their five-membered phthalic anhydride-based SPIs. The composites based on napthalenic polyimides are also significantly stable in high temperature environment and show better stability to hydrolysis. Incorporation of inorganic fillers into organic polymers has gained tremendous attention and these new materials are called organic-inorganic hybrids. Few patents related to the synthesis and performance PEM materials have been reviewed and cited. Keeping in view the importance of sulfonated polyimide based nanocomposites as potential membrane materials for PEM in fuel cell, we have synthesized SPIs clay based nanocomposite as potential membrane material. The objective of this work was to synthesize clay based SPIs thin films which could be used as membrane materials in PEM fuel cell for energy applications. Methods/Experimental: At the first step the nanometric sheets of vermiculite clay prepared via sonication was surface modified by grafting 3-APTES. Then the SPI was synthesized via one-step high temperature direct imidization method, which serve as a matrix material. The organo modified VMT was dispersed via sonication in the SPI matrix. Four different sets of organic-inorganic nanocomposite membranes thin films, having VMT contents in the range of 1 to 7 wt.% were prepared by casting, curing and acidification route. The synthesis of SPIs clay based thin films were carried out at three different steps and fully characterized. The synthesis of SPIs and SPIs clay based thin films were analyzed via different analytical techniques. The XRD analysis tells the successful dispersion of clay in SPI matrix. Different physiochemical tests were conducted for the analysis of these membranes such as water uptake, hydrolytic stability, ion exchange capacity (IEC), dimensional changes and oxidative stability, to check their suitability as membrane materials for PEM. The proton conductivity of these membranes were measured via impedance spectroscopy which discloses three different active regions responsible for proton conduction. The activation energies of the membranes were higher at lower temperature and reaches to 8.2 kJ/mol at higher temperature (90oC). The synthesis of sulfonated polyimide/clay (SPI/clay) based organic-inorganic nanocomposite membranes were achieved successfully. The membrane display good hydrolytic, thermal and oxidative stability at elevated temperature. The proton conductivity of the membrane display an increase together with the frequency but decreases with temperature. Therefore some more efforts are required to achieve high degree of functionalization of both organic and inorganic components, for the "future" PEMs to avoid deterioration and to get improved performance.

Heteropolyacids - Chitosan Membranes for H2/O2 Low Temperature Fuel Cells

Proton exchange membrane fuel cells (PEMFCs) have received much attention in recent years because of their high power density, efficiency and zero-environmental pollution. As one of the key components in fuel cells, the proton exchange membrane is expected to have high proton conductivity and good electrochemical stability. In the attempt to promote PEMCFs commercialization, high cost of fuel cell systems and short lifecycle are the two main issues that need to be addressed, thus large research effort has been devoted in developing new polymer electrolytes that can replace the usually employed proton conductors, e.g. Nafion®, with other membranes of comparable performances but lower cost.As a low-cost and eco-friendly biopolymer, Chitosan (CS)-based membrane electrolyte is currently studied as alternative candidate for PEMFC application to possibly produce economically viable fuel cells. Several works have shown that Heteropolyacids (HPAs) can be used to prepare Chitosan polyelectrolytes (PECs) to be employed as proton exchange membrane in low temperature fuel cell. HPAs, such as phosphotungstic acid (PTA) or phosphomolybdic acid (PMA), are strong Bronsted acid as well as solid electrolytes, thus being very effective in the fabrication of high proton conductive organic–inorganic nanocomposite membranes for fuel cell. A survey of the already published works on the use of CS/HPA composite membranes show that they have been tested as proton conductors in direct methanol, in borohydride and hydrogen fed fuel cells [1-3 and refs therein]. In previous works [1-3] we have shown that CS/PTA membranes, prepared using an alumina porous medium for the slow release of H3PW12O40, show good performances when employed as electrolyte in H2 fed fuel cell with proton conductivity of ~ 14 mS cm-1. Notably, in ref. [4] CS/PMA membranes are reported to exhibit proton conductivity higher than that measured with CS/PTA, which is mainly because the proton conductivity of PMA is higher than that of PTA. However, a careful inspection of published papers revealed that CS/PMA membranes haven’t been yet tested in low temperature fuel cell. Starting from these findings, this paper in focused on the characterization of CS/PMA and mixed CS/PMA-PTA membranes prepared according to the above described procedure with the aim to evaluate their performance as proton conductors in hydrogen fed fuel cell. X-ray diffraction and Fourier Transform Infrared Spectroscopy analyses are performed to study the structure and composition of the membranes, while Scanning Electron Microscopy is used to get information on the membranes morphology and thickness as a function of the preparation conditions. The membranes are tested in a H2/O2 fuel cell working at low temperature (25°C) and fixed Pt loading (1 mg cm-2). Impedance Spectroscopy is used to get information of the conductivity of the membrane as well as to model the overall electrical behaviour of the cell. The role of humidification in influencing the proton conductivity of the membranes as a function of the employed HPA is also studied. References 1 -M. Santamaria, C.M. Pecoraro, F. Di Quarto, P. Bocchetta, J. Power Sources 276 (2015) 189-194. 2 - C.M. Pecoraro, M. Santamaria, P. Bocchetta, F. Di Quarto, Int. J. Hydrogen Energy, 40 (2015) 14616-14626. 3 - M. Santamaria, C.M. Pecoraro, F. Di Franco , F. Di Quarto, I. Gatto, A. Saccà, Int. J. Hydrogen Energy (2016), http://dx.doi.org/10.1016/j.ijhydene.2016.01.133. 4 - Z. Cui, W. Xing, C. Liu, J. Liao, H. Zhang, J. Power Sources 188 (2009) 24-29.

Cross-linked poly(vinyl alcohol)/sulfonated nanoporous silica hybrid membranes for proton exchange membrane fuel cell

Organic–inorganic nanocomposite membranes of poly(vinyl alcohol) (PVA) and nanoporous silica containing sulfonic acid groups are synthesized in order to increase the proton conductivity, water retention and thermal stability of membrane. The cross-linked PVA/SBA-15-propyl-SO3H nanocomposite membrane was prepared by solution casting method. Infrared spectroscopy and scanning electron microscopy are used to characterize and confirm the structure of PVA and the cross-linked membranes. The impedance spectroscopy, water uptake and thermal stability of membranes are investigated to confirm their applicability in fuel cells. It was found that the cross-linked PVA/SBA-15-propyl-SO3H nanocomposite membrane appears to be a good candidate for using in PEM fuel cell.

Nano Composite Membranes of Sulfonated Amine-Poly(ether sulfone)s and SiO<sub>2</sub> for Fuel Cell Application

Organic-inorganic Nano composite membranes were prepared by Sulfonated amine-poly(ether sulfone)s (S-APES)s and SiO2. S-APESs were prepared by nitration, reduction and sulfonation of poly(ether sulfone) (ultrason®-S6010). Poly(ether sulfone) was reacted with ammonium nitrate and trifluoroacetic anhydride to produce the nitrated poly(ether sulfone), and was followed by reduction using tin(Ⅱ)chloride and sodium iodide as reducing agents to give the amino-poly(ether sulfone). The S-APES was obtained by reaction of 1,3-propanesultone and the amino-poly(ether sulfone) (NH2-PES) with sodium methoxide. The different degrees of nitration and reduction of poly(ether sulfone) were successfully synthesized by an optimized process. Organic-inorganic nano composite membranes were obtained by mixing S-APES (45 %) with hydrophilic SiO2 (20 nm, 4-10 %) obtained by sol-gel process. Different contents of SiO2 of the S-APES were studied by FT-IR, 1H-NMR spectroscopy, differential scanning calorimetry (DSC), and thermo gravimetric analysis (TGA). Sorption experiments were conducted to observe the interaction of sulfonated polymers with water and methanol. The ion exchange capacity (IEC), a measure of proton conductivity, was evaluated. The nano composite membranes exhibit conductivities (25 °C) from 3.51 x 10-3 to 4.10 x 10-3 S/cm, water swell from 57.25 to 60.50 %, IEC from 0.68 to 0.73 meq/g, and methanol diffusion coefficients from 2.81 x 10-7 to 3.33 x 10-7 cm2/S at 25 °C.

Dehydration of isopropanol by PVA–APTEOS/TEOS nanocomposite membranes

In the present work, dehydration of isopropanol was investigated by novel organic–inorganic nanocomposite membranes which were prepared through sol–gel reaction of polyvinyl alcohol (PVA) with γ-aminopropyl-triethoxysilane (APTEOS) and tetraethoxysilane (TEOS). The PVA chains were crosslinked by mixing silane coupling agents. This reaction between polymer chains and silanols agents could control degree of swelling of the nanocomposite membranes in aqueous isopropanol (IPA) solutions. The membranes were characterized by SEM and ATIR. Effects of APTEOS content in the membranes, feed concentration and temperature on pervaporation (PV) performance were investigated. It was found out that separation factor and permeation flux increase with increasing APTEOS content in the membranes. Arrhenius-type relationship was used for describing the temperature dependence of permeation flux. It was also found out that separation factor decreases with increasing temperature.

Nanocomposite proton conducting membranes based on amphiphilic PVDF graft copolymer

A novel comb-like amphiphilic graft copolymer of poly(vinylidene fluoride-co-chlorotrifluoroethylene)-graft-poly(4-styrene sulfonic acid-co-trimethoxysilyl propyl methacrylate), i.e. P(VDF-co-CTFE)-g-P(SSA-co-TMSPMA) was synthesized using an atom transfer radical polymerization (ATRP) technique. Successful synthesis and a microphase-separated structure of the copolymer were confirmed by proton nuclear magnetic resonance (1H NMR), FTIR spectroscopy and transmission electron microscopy (TEM). This graft copolymer was combined with tetraethoxysilane (TEOS) under acidic conditions to produce organic-inorganic nanocomposite membranes through an in-situ sol-gel reaction between TEOS and PTMSPMA, as characterized by X-ray diffraction (XRD) and TEM. Upon the introduction of silica, the proton conductivity and water uptake of the membranes decreased slightly but the thermal and mechanical properties of the membranes were enhanced significantly. Various morphologies of the nanocomposite membranes were obtained after controlling the TEOS concentration, which were correlated with the thermal, mechanical and transport properties.

The effect of surface modifications on protein microfiltration properties of Anopore™ membranes

The synthesis, characterization, and protein microfiltration behavior of a series of organic–inorganic nanocomposite membranes are reported. It is shown that by modifying the surface of an Anopore™ alumina membrane with a variety of chemistries that membrane fouling can be significantly reduced. The work presented here shows that electrostatic repulsion between the surface and protein can be used to reduce fouling, as can making the surface more hydrophilic. Two methods were used to make hydrophilic nanocomposite membranes: adsorption of Pluronic F108 onto Anopore™ membranes with an octadecylsilane overlayer, and the grafting of poly(ethylene glycol) (PEG) to either amine-functionalized surfaces or dendrons with amines on their outer periphery. Both approaches led to a significant reduction in membrane fouling with the PEG grafted materials displaying superior performance to the F108 functionalized samples. IR, XPS, and TGA were used to characterize the composite membranes, and the results of these methods correlate with the microfiltration data presented. Mathematical modeling of the microfiltration data indicates that the pore constriction model best describes the change in protein flux over time. The current work presents an alternative approach to membrane design for microfiltration, which has historically been dominated by polymeric membranes.

Nano Composite Membranes of Sulfonated Poly(2,6-Dimethyl-1,4-Phenylene Oxide)/Poly(2,6-Diphenyl-1,4-Phenylene Oxide) Copolymer and SiO<sub>2</sub> for Fuel Cell Application

The Sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) / poly(2,6-diphenyl-1,4-phenylene oxide) (S-PPO) was prepared by oxidative coupling polymerization with 2,6-dimethyl phenol, 2,6-diphenyl phenol, CuCl(І) and pyridine, and followed sulfonation with chlorosulfonic acid. Copolymer was consisted of 2,6-diphenyl phenol 30 mol% and 2,6-dimethyl phenol 70 mol%. Organic-inorganic nano composite membranes were prepared with copolymer and a series of SiO2 nanoparticles (20 nm, 4, 7 and 10 wt%). The composite membranes were cast from dimethylsulfoxide solution. The membranes were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Sorption experiments were conducted to observe the interaction of sulfonated polymers with water and methanol. S-PPO copolymer and nano composite membranes exhibited proton conductivities from 0.79×10-3 to 0.98×10-3 S/cm, water uptake from 21.70 to 24.77 %, IEC from 0.720 to 0.955 meq/g and methanol diffusion coefficients from 2.97×10-7 to 3.70×10-7 cm2/S.

Synthesis and Characterization of Branched Sulfonated Poly(ether Sulfone-Ketone) Copolymer and Organic-Inorganic Nano Composite Membranes

Branched sulfonated poly(ether sulfone-ketone) copolymer was prepared with bisphenol A, 4,4-difluorobenzophenone, sulfonated chlorophenyl sulfone (40mole% of bisphenol A) and THPE (1,1,1-tris-p-hydroxyphenylethane) as a branching agent. THPE was used 0.4 mol% of bisphenol A to synthesize branched copolymers. Organic-inorganic nano composite membranes were prepared with copolymer and a series of SiO2 nanoparticles (20 nm, 4, 7 and 10 wt%). The composite membranes were cast from dimethylsulfoxide solutions. The films were converted from the salt to acid forms with dilute hydrochloric acid. The membranes were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Sorption experiments were conducted to observe the interaction of sulfonated polymers with water and methanol. Branched copolymer and nano composite membranes exhibited proton conductivities from 1.12x10-3 to 6.04x10-3 S/cm2, water uptake from 52.9 to 62.4%, IEC from 0.81 to 1.21 meq/g and methanol diffusion coefficients from 1.2x10-7 to 1.5x10-7 cm2/S.