Thermal Stability Of Membranes Research Articles

Solvent-free nanocomposite proton-conducting membranes composed of cesium salt of phosphotungstic acid doped PVDF–CTFE/PEO blend

In this research, novel nanocomposite membranes were prepared using polymer blend of polyethylene oxide (PEO) and polyvinylidene fluoride–chloro tetrafluoro ethylene (PVDF–CTFE) copolymer with cesium salt of phosphotungstic acid (Cs2.5H0.5PWO40) as proton conductor. Nanocomposite membranes were prepared by solvent-free procedure. The DSC studies show a decrease in crystalinity of polymer matrix with increasing PEO to PVDF–CTFE proportional ratio and the filler. The TGA studies show that membranes are stable up to 180 °C. The TGA also indicates that addition of cesium salt of phosphotungstic acid increases the thermal stability of membranes. The SEMs exhibit that membranes are non-porous and the additive components are homogenously dispersed. Conductivity tests for membranes were carried out in the range of 25–100 °C in dry and hydrated states. Results show that by increasing the temperature, membranes conductivities are increased. In dry state, except at the temperature of 45 °C, membranes which have the highest crystalinity, have the highest conductivity. The alteration of the conductivity in the range of temperatures in dry condition may be attributed to segmental motion of polymer which resulted in proton hopping from one site to another or increasing free volume for proton motion. In fully hydrated state, dynamic equilibrium between different proton moieties determines the mode of proton conductivity which can be described by Grothuss mechanism. In the presence of water molecule, the free proton may be formed. The conductivity for the membrane in hydrated state with the blend ratio of PVDF:PEO = 95:5 w/w and 10% addition of cesium salt of phosphotungstic acid at the temperature of 90 °C is 1.05 × 10−4 S cm−1.

Synthesis and characterization of SBA-15/poly (vinylidene fluoride) (PVDF) hybrid membrane

Poly (vinylidene fluoride) (PVDF) membranes with low contents of SBA-15 particles (≤ 0.72 wt.%, by weight of PVDF) were prepared by a phase inversion process. The thin membranes were then characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), tensile stress tests, thermogravimetric analysis (TGA), contact angle technique, water flux and BSA rejection to investigate the influence on the final properties of the developed membrane. The resulting modified membrane exhibited no particular influence on the structures of the air surface, cross-section and inner pores. The experiment results confirmed that the addition of low contents of SBA-15 particles could effectively improve membrane hydrophilicity, antifouling performance, mechanical property and thermal stability, and increased membrane flux with the resistance of BSA solution above 87%.

Anhydrous proton-conducting organic–inorganic hybrid membranes synthesized from tetramethoxysilane/methyltrimethoxysilane/diisopropyl phosphite and ionic liquid

Inorganic–organic hybrid membranes were prepared by sol–gel process with tetramethoxysilane/methyltrimethoxysilane/diisopropyl phosphite and 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4) ionic liquid as precursors. The Fourier transform infrared spectroscopy (FT-IR) and 31P, 29Si, 1H, 13C, and 19F nuclear magnetic resonance measurements have shown good chemical stability and complexation of (POH[(CH3)2CHO]2) with [BMIMBF4] ionic liquid in the fabricated hybrid membranes. The influence of the textural properties of all the prepared composite membranes could be interpreted from nitrogen adsorption–desorption measurements. The average pore size was increased proportionally with the ionic liquid weight percent ratio in the host phosphosilicate matrix from 2.59 to 11.71 nm, respectively. Thermogravimetric analysis and differential thermal analysis measurements confirmed that the hybrid membranes were thermally stable up to 260 °C. Thermal stability of the hybrid membranes was significantly enhanced by the presence of inorganic SiO2 framework and high stability of [BF4] anion. For all the composite membranes, the conductivities were measured within the temperature range (−30 °C) to 150 °C, and a maximum conductivity of 7 × 10−3 S/cm at 150 °C was achieved for 40 wt.% ionic liquid-based composite membrane under nonhumidified conditions.

Preparation and characterization of anhydrous polymer electrolyte membranes based on poly(vinyl alcohol-co-ethylene) copolymer

Anhydrous polymer electrolyte membranes with cross-linked structure have been prepared based on poly(vinyl alcohol-co-ethylene) (PVA-co-PE) copolymer. The PVA units of copolymer served to induce thermal cross-linking with 4,5-imidazole dicarboxylic acid (IDA) via esterification while PE units controlled the membrane swelling and the mechanical properties of films. Upon doping with phosphoric acid (PA, H3PO4) to form imidazole-PA complexes, the proton conductivity of membranes continuously increased with increasing PA content. As a result, proton conductivity reached 0.01 S/cm at 100 °C under anhydrous conditions. X-ray diffraction analysis revealed that both the d-spacing and crystalline peak of membranes were reduced upon introduction of IDA/PA due to the cross-linking effect. The PVA-co-PE/IDA/PA membranes exhibited good mechanical properties, e.g., 150 MPa of Young’s modulus, as determined by a universal testing machine. Thermal gravimetric analysis also represented that the thermal stability of membranes was increased up to 200 °C upon introduction of IDA/PA.

Inorganic–organic hybrid membranes with anhydrous proton conduction prepared from tetramethoxysilane/methyl-trimethoxysilane/trimethylphosphate and 1-ethyl-3-methylimidazolium-bis (trifluoromethanesulfonyl) imide for H 2/O 2 fuel cells

Anhydrous proton-conducting inorganic–organic hybrid membranes were prepared by sol–gel process with tetramethoxysilane/methyl-trimethoxysilane/trimethylphosphate and 1-ethyl-3-methylimidazolium-bis (trifluoromethanesulfonyl) imide [EMI][TFSI] ionic liquid as precursors. These hybrid membranes were studied with respect to their structural, thermal, proton conductivity, and hydrogen permeability properties. The Fourier transform infrared spectroscopy (FT-IR) and 31P, 1H, and 13C nuclear magnetic resonance (NMR) measurements have shown good chemical stability, and complexation of PO(OCH 3) 3 with [EMI][TFSI] ionic liquid in the studied hybrid membranes. Thermal analysis including TG and DTA confirmed that the membranes were thermally stable up to 330 °C. Thermal stability of the hybrid membranes was significantly enhanced by the presence of inorganic SiO 2 framework and high stability of [TFSI] anion. The effect of [EMI][TFSI] ionic liquid addition on the microstructure of the membranes was studied by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) micrographs and no phase separation at the surfaces of the prepared membranes was observed and also homogeneous distribution of all elements was confirmed. Proton conductivity of all the prepared membranes was measured from −20 °C to 150 °C, and high conductivity of 5.4 × 10 −3 S/cm was obtained for 40 wt% [EMI][TFSI] doped 40TMOS–50MTMOS–10PO(OCH 3) 3 (mol%) hybrid membrane, at 150 °C under anhydrous conditions. The hydrogen permeability was found to decrease from 1.61 × 10 −11 to 1.39 × 10 −12 mol/cm s Pa for 40 wt% [EMI][TFSI] doped hybrid membrane as the temperature increases from 20 °C to 150 °C. For 40 wt% [EMI][TFSI] doped hybrid membrane, membrane electrode assemblies were prepared and a maximum power density value of 0.22 mW/cm 2 at 0.47 mA/cm 2 as well as a current density of 0.76 mA/cm 2 were obtained at 150 °C under non-humidified conditions when utilized in a H 2/O 2 fuel cell.

PVDF–TiO2 composite hollow fiber ultrafiltration membranes prepared by TiO2 sol–gel method and blending method

AbstractOrganic–inorganic polyvinylidene fluoride (PVDF)–titanium dioxide (TiO2) composite hollow fiber ultrafiltration (UF) membranes were prepared by TiO2 sol–gel method and blending method, respectively. The membranes were characterized in terms of microstructure, hydrophilicity, permeation performance, thermal stability, and mechanical strength. The experimental results indicated that PVDF–TiO2 composite UF membranes exhibited significant differences in surface properties and intrinsic properties because of the addition of inorganic particles. The TiO2 particles improved the membrane strength and thermal stability of PVDF–TiO2 composite UF membranes. In particular, hydrophilicity and permeability increased dramatically with the increase of TiO2, whereas the retention property of UF membranes was nearly unchanged. However, high TiO2 concentration induced the aggregation of particles, resulting in the decline of hydrophilicity and permeability. Compared with PVDF–TiO2 composite hollow fiber UF membranes prepared by TiO2 blending method, PVDF–TiO2 composite hollow fiber UF membranes prepared by TiO2 sol–gel method formed a dispersed inorganic network, and the stronger interaction between inorganic network and polymeric chains led to TiO2 particles being uniformly dispersed in UF membranes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Synthesis and characterization of proton conducting inorganic–organic hybrid nanocomposite membranes based on tetraethoxysilane/trimethylphosphate/3-glycidoxypropyltrimethoxysilane/heteropoly acids

A series of novel proton conductive inorganic–organic nanocomposite hybrid membranes doped with phosphotungstic acid (PWA)/phosphomolybdic acid (PMA) and trimethylphosphate PO(OCH 3) 3 have been prepared by sol–gel process with 3-glycidoxypropyltrimethoxysilane (GPTMS), and tetraethoxysilane (TEOS) as precursors. The hybrid membranes were studied with respect to their structural and thermal properties, elastic moduli and proton conductivity. Thermal analysis including TG and DTA confirmed that the membranes were thermally stable up to 200 °C. Thermal stability of membranes was significantly enhanced by the presence of SiO 2 framework. Proton conductivity of 1.59 × 10 −2 S/cm with composition of 50TEOS-5PO(OCH 3) 3-35GPTMS-10PWA was obtained (1.15 × 10 −2 S/cm for 10 mol% PMA) at 90 °C under 90% relative humidity. The proton conductivity of the nanocomposite membranes is due to the proton-conducting path through the GPTMS-derived “pseudopolyethylene oxide (pseudo-PEO)” networks in which the trapped solid acid (PWA/PMA) as a proton donor is contained. The molecular water absorbed in the polymer matrix is also presumed to provide high proton mobility, resulting in an increase of proton conductivity with increasing relative humidity.

Thermal stability of ion-exchange Nafion N117CS membranes

The effect of exchanged ions on the thermal stability of Nafion N117CS membranes was investigated by X-ray photoelectron spectra (XPS), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), thermomechanical analysis (TMA), and ion exchange capacity determinations. The ion exchange of alkaline metal ions was effective in improving the thermal stability of the Nafion N117CS membrane. Findings reveal that when Nafion was exchanged for cations with a larger ionic radius, the membrane attained superior thermal stability. On the other hand, we confirmed that the Na-exchange Nafion N117CS membrane possessed a distinctive degree of thermal stability among the alkaline ion-exchange Nafions, although the order of ionic radii is K > Na > Li. Thermal stability improved the most when the Nafion membrane was exchanged for alkaline ions, followed by divalent ions, then trivalent ions. As for the Nafion membrane when it was exchanged for divalent ions or trivalent ions, Nafion following the ion exchange had a thermal stability proportional to an increase in the ionic radius of the cation. This stability may be explained by the reduction of water content and a greater interaction between the sulfonate groups and the cations with larger ionic radii. Since the Al cations acted as a Lewis acid center, the decomposition of the ether bonds of the perfluoroalkylether pendant-chains of the Nafion membrane was observed for the Nafion N117CS membrane that had been exchanged for Al ions. The activation of molecular mobility in Nafion was observed between the decomposition stages of the loss of water and the loss of sulfonic groups. The temperature of activation of cation-exchange Nafion became much higher than that of Nafion in an acid form.

Membrane Thermal Stability at Different Developmental Stages of Spring Wheat Genotypes and Their Diallel Cross Populations

Yüksek sıcaklığa toleransta hücre zarlarının kararlılığı önemli bir fizyolojik seleksiyon kriteri olabilir. Yüksek sıcaklık membran kararlılığı, yüksek sıcaklığa maruz bırakılan yaprak dokusunun içerisinde bulunduğu sulu ortamdaki elektriksel iletkenliğin ölçümüyle belirlenmektedir. Bu araştırma, tarla koşullarında yetiştirilen 4 yazlık buğday anacı ve bunların altı Fdiallel melez döllerinde, iki farklı yöntemle MTS, yüksek sıcaklık membran kararlılığı ve RI, zarar indeksi hesaplanan membran kararlılığının farklı gelişme dönemlerindeki değişimlerini belirlemek amacıyla gerçekleştirilmiştir. Ölçümler, yaprak büyümesi erken vejetatif dönem , sapa kalkma ve erken süt olum evrelerinde gerçekleştirilmiştir. MTS ve RI ölçümleri üç farklı büyüme evresinde benzer eğilim göstermiştir. Bununla birlikte, büyüme evreleri genotiplerin MTS ve RI değerlerini önemli düzeyde etkilemiştir. Genotiplerin membran kararlılığı parametreleri büyüme evresi ilerledikçe azalmıştır. Tüm ölçümlerde özel uyum yeteneğinin genel uyum yeteneğine üstünlük sağlaması, memran kararlılığı özelliklerinin yönetiminde eklemeli olmayan gen etkilerinin etkin olduğunu göstermektedir. Erken süt olum evresinde bayrak yaprak membran kararlılığı, tane verimiyle önemli düzeyde ilişkili bulunmuştur. Anaçlardan Genç 99 ve 84ÇZT04 düşük verim, Chil’s ve Seri 82 yüksek verim potansiyeli göstermişlerdir. F2 döllerinde tane verimi, başak verimi ve tane ağırlığı anaçlardan yüksek bulunmuştur. Bu sonuçlar, membran kararlılığı ölçümleri yönünden genotiplerdeki mevcut çeşitliliğin sıcak stresli çevrelerde buğday ıslahında kullanılabileceğini göstermektedir

Impact of High Nighttime Temperature on Respiration, Membrane Stability, Antioxidant Capacity, and Yield of Rice Plants

ABSTRACTNighttime temperature is one of the major environmental factors influencing plant metabolic processes. The respiration rates, membrane thermal stability (MTS), and total antioxidant capacities of leaves were investigated in rice (Oryza sativa L.) plants when exposed to high nighttime temperature (HNT) (32°C) or ambient nighttime temperature (ANT) (27°C), and with or without potential preventive exogenous effector (chemical) treatments. The exogenous effector treatments included α‐tocopherol (vitamin E), glycine betaine, and salicylic acid, which play important but different roles in inducing thermal tolerance in many plant species. Plants were subjected to an HNT through use of continuously controlled infrared heaters, starting from 2000 h until 0600 h. High nighttime temperature increased respiration rates, decreased MTS, and negatively affected the yield (by 95%). Application of salicylic acid somewhat lowered the reduction in yield due to HNT (76 vs. 95%) by decreasing the respiration rates and increasing MTS and total antioxidant capacity of rice plants.

Thermal stability of proton exchange fuel-cell membranes based on crosslinked-polytetrafluoroethylene for membrane-electrode assembly preparation

We investigated thermal properties of proton exchange membranes (PEMs) prepared by the radiation-induced grafting of styrene into crosslinked-polytetrafluoroethylene films and the subsequent sulfonation for fuel-cell applications. A conventional thermogravimetric analysis was found to be unreliable because the resulting curve varied greatly with the heating rate. Thus, in order to obtain accurate information, we performed an ex-situ heat-treatment analysis, which involved heating of the PEMs at fixed temperatures of 200–350 °C and measurement of their remaining weight, ion exchange capacity (IEC) and proton conductivity ( σ) after washing in pure water. The IEC and σ did not change at any temperature up to 200 °C, indicating high thermal stability. At 250 °C, however, the PEM properties deteriorated probably via radical cleavage of the C–S bond between a sulfonic acid group and an aromatic ring, and condensation of two sulfonic acid groups. Finally, the PEM was hot-pressed with two electrodes at 200 °C to produce a good membrane-electrode assembly for a fuel cell.

Hybrid acid–base polymer membranes prepared for application in fuel cells

For application in fuel cells, a series of hybrid acid–base polymer membranes were prepared by blending sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (SPPO) with (3-aminopropyl)triethoxysilane (A1100) through a sol–gel process. As indicated by scanning electron microscopy, energy-dispersive X-ray analysis, and thermogravimetric analysis, the acid–base interaction improves not only the membrane homogeneity and thermal stability but also the mechanical strength and flexibility. Apart from the low cost, the developed membranes exhibit high proton conductivity and low methanol permeability as compared to Nafion ® 117. Further, the optimal membrane shows better performance than Nafion ® 117 in a single cell test. All these properties make the hybrid membranes suitable for application in fuel cells.

Characterization and performance of proton exchange membranes for direct methanol fuel cell: Blending of sulfonated poly(ether ether ketone) with charged surface modifying macromolecule

Modification of sulfonated poly(ether ether ketone) (SPEEK) membrane was attempted by blending charged surface modifying macromolecule (cSMM). The modified membrane was tested for direct methanol fuel cell (DMFC) application; i.e. a SPEEK/cSMM blend membrane was compared to a SPEEK membrane and a Nafion 112 membrane for the thermal and mechanical stability, methanol permeability, and proton conductivity. Thermal and mechanical stability of the blended membrane were slightly reduced from the SPEEK membrane but still higher than the Nafion 112 membrane. The blend membrane was found to be promising for DMFC applications because of its lower methanol diffusivity (2.75 × 10 −7 cm 2 s −1) and higher proton conductivity (6.4 × 10 −3 S cm −1), than the SPEEK membrane. A plausible explanation was given for the favorable effect of cSMM blending.

Composite polymer electrolyte membranes comprising triblock copolymer and heteropolyacid for fuel cell applications

AbstractHybrid organic/inorganic composite polymer electrolyte membranes consisting of a triblock copolymer (tBC) and varying concentrations of heteropolyacid (HPA) were investigated for application in proton exchange membrane fuel cells (PEMFC). An ABC triblock copolymer, that is, polystyrene‐b‐poly(hydroxyethyl acrylate)‐b‐poly (styrene sulfonic acid), PS‐b‐PHEA‐b‐PSSA, at 28:21:51 wt % was synthesized via atom transfer radical polymerization (ATRP) and solution‐blended with a commercial HPA. Upon the incorporation of HPA into the tBC, the symmetric stretching bands of both the SO group (1187 cm−1) and the OH group (3440 cm−1) shifted to lower wavenumbers (1158 and 3370 cm−1). The shift in these FTIR absorptions suggest that the HPA particles strongly interact with both the sulfonic acid groups in the PSSA domains and the hydroxyl groups in the PHEA domains. When the weight fraction of HPA was increased to 0.2, the room‐temperature proton conductivity of the composite membrane increased from 0.048 to 0.065 S/cm, presumably because of the intrinsic conductivity of the HPA particles and the enhanced acidity of the sulfonic acid in the tBC. The water uptake of the composite membranes decreased from 130 to 48% with an increase of the HPA weight fraction to 0.4. The decrease in water uptake is likely a result of the decrease in the number of available water absorption sites because of the hydrogen bonding interaction between the HPA particles and the tBC matrix. Scanning electron microscopy and transmission electron microscopy images showed that the HPA nanoparticles with a diameter of 200–300 nm were uniformly distributed throughout the tBC matrix up to an HPA weight fraction of 0.4. Thermal stability of the composite membranes (decomposition temperature > 400 °C) was enhanced as compared with the pristine tBC membrane, presumably because of the strong specific interaction of the HPA particles with the sulfonic acid and hydroxyl groups. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 691–701, 2008

Thermal stability and proton conductivity of silane based nanostructured composite membranes

A series of silane based nanostructured composite membranes were synthesized from 3-glycidoxy propyl trimethoxy silane (GPTMS) and 2(3, 4 epoxy cyclohexyl) ethyl triethoxy silane (EHTES) with varying proportion of aqueous orthophosphoric acid, nanoclay (Cloisite® 30B) and multi-walled carbon nanotubes (MWNTs) by sol–gel method. Thermal stability of the composite membranes studied by thermogravimetric analysis (TGA) showed that the composite membranes were stable up to 200 °C. However, the thermal stability decreased with an increase in GPTMS proportion and phosphoric acid content but it increased with increasing proportion of nanoclay and nanotubes in the membranes. The improved thermal stability of the membranes was due to the formation of C–O–C bonds and Si–O–Si bonds between the two silanes as confirmed from FT-IR studies. The proton conductivity of the membranes, measured at four different temperatures (80 °C, 100 °C, 120 °C and 140 °C) and at 30% relative humidity, was found to increase with an increase in weight proportion of EHTES, orthophosphoric acid, Cloisite® 30B and MWNTs in the composites. The increase in proton conductivity with the increase in wt. proportion of nanoclays and nanotubes in the composites membranes was due to the presence of chemisorbed water in the composites as confirmed by differential scanning calorimetry (DSC). Phase morphology studied by scanning electron microscopy (SEM) showed that the membranes were of dense structure and the nanoparticles were distributed uniformly through out the polymer matrix.

Preparation and characterization of microporous poly(vinyl butyral) membranes by supercritical CO 2-induced phase separation

Microporous poly(vinyl butyral) (PVB) membranes were successfully prepared by supercritical CO 2-induced phase separation. The obtained membrane structures were characterized by scanning electron microscope. The results indicated that the process parameters, such as PVB concentration in casting solution, CO 2 pressure, temperature and depressurization time, had significant effects on the membrane structure. The increase of PVB concentration led to a decrease of the mean pore size. With the increase of temperature and CO 2 pressure, the top surface of the membrane became dense, the pore size of cross-section increased and the asymmetry became more pronounced. With the increase of the depressurization time, the top surface became porous and the pore size of cross-section increased. Macrovoids occurred at a certain distance from the skin layer of the membrane prepared under the pressure of 15 MPa or at the PVB concentration of 19% (w/w). The crystallinity and thermal stability of membranes were characterized by wide-angle X-ray diffraction, differential scanning calorimeter and thermogravimetric analysis. The relations between the membrane characteristics and the process parameters were extensively discussed.

Effect of growth temperature on ether lipid biochemistry in Archaeoglobus fulgidus

The archaea are distinguished by their unique isoprenoid ether lipids, which typically consist of the sn-2,3-diphytanylglycerol diether or sn-2,3-dibiphytanyldiglycerol tetraether core modified with a variety of polar headgroups. However, many hyperthermophilic archaea also synthesize tetraether lipids with up to four pentacyclic rings per 40-carbon chain, presumably to improve membrane thermal stability at temperatures up to approximately 110 degrees C. This study aimed to correlate the ratio of tetraether to diether core lipid, as well as the presence of pentacyclic groups in tetraether lipids, with growth temperature for the hyperthermophilic archaeon, Archaeoglobus fulgidus. Analysis of the membrane core lipids of A. fulgidus using APCI-MS analysis revealed that the tetraether-to-diether lipid ratio increases from 0.3 +/- 0.1 for cultures grown at 70 degrees C to 0.9 +/- 0.1 for cultures grown at 89 degrees C. Thin-layer chromatography (TLC) followed by APCI-MS analysis provided evidence for no more than one pentacycle in the hydrocarbon chains of tetraether lipid from cultures grown at 70 degrees C and up to 2 pentacycles in the tetraether lipid from cultures grown at higher temperatures. Analysis of the polar lipid extract using TLC and negative-ion ESI-MS suggested the presence of diether and tetraether phospholipids with inositol, glycosyl, and ethanolamine headgroup chemistry.

Surface chemistry and physical properties of Nafion/polypyrrole/Pt composite membrane prepared by chemical in situ polymerization for DMFC

We modified Nafion by means of chemical in situ polymerization of pyrrole monomers with platinum (Pt) precursors for an application into an electrolyte of direct methanol fuel cells (DMFCs). SEM and EPMA exhibited the presences of polypyrrole and Pt at the surface region of Nafion, after diffusing and polymerizing pyrrole monomers with Pt precursors. XPS and FT-IR spectra were used to characterize the surface of Naf–Ppy–Pt composite membranes, demonstrating that pyrrolinum groups of polypyrrole were interacted with sulfonic groups or Pt precursors (PtCl 6 − or PtCl 4 −). After in situ polymerization of pyrrole monomers, the morphological reorganization of sulfonic groups in Naf–Ppy–Pt composite membranes occurred via electrostatic interaction. Thermal stability, proton conductivity, methanol permeability, and cell performance of composite membranes were analyzed by TGA, AC impedance, refractometer, and potentiostat. Naf–Ppy–Pt composite membranes had higher thermal stabilities of sulfonic groups and side chains than Nafion and Naf–Ppy as a result of the interaction between Nafion–SO 3 −⋯polypyrrole–NH 2 + and the presence of thermally stable Pt. The cell performance of Naf–Ppy–Pt 0 0 2 was enhanced significantly compared to that of Nafion under the specific condition, due to more reduction of methanol crossover than that of proton conductivity. Therefore, this synthetic method offers a facile way to improve physical properties of polymer electrolyte for the fabrication of advanced composite membranes.

Preparation and characterization of proton-conducting sulfonated poly(ether ether ketone)/phosphatoantimonic acid composite membranes

The solid proton conductor, phosphatoantimonic acid, HSbP 2O 8 · H 2O was prepared by ion exchange of the corresponding potassium salt. The composite membranes of SPEEK with up to 40 wt% of HSbP 2O 8 · H 2O were prepared by introducing the solid proton conductor from the aqueous suspension. The composite membranes were characterized using FT-IR, powder X-ray diffraction, SEM, DSC/TGA. Thermal stability of the composite membranes was slightly lower than that of SPEEK. The composite membranes had higher water uptake when compared with SPEEK and the membranes exhibited controlled swelling up to 50 °C. The proton conductivity of the membranes was measured under 100% relative humidity up to 70 °C. The composite membranes showed enhanced proton conductivity up to 20 wt% of HSbP 2O 8 · H 2O and the conductivity was reduced with further increase of HSbP 2O 8 · H 2O loading. A maximum of four-fold increase in proton conductivity at 70 °C was observed for the composite membrane with 20 wt% of solid proton conductor.

Thermal characterization of Flemion® membranes substituted by alkali metal cations

The thermal behavior of perfluorosulfonated membranes of three equivalent mass (EW=910, 1000 and 1100 g eq−1) has been studied for membranes in acid form and in the alkali metal countercations substituted samples. The water contents of the membranes decrease progressively with increasing EW and the countercations charge density. The monovalent cations substitutions increase the membranes thermal stability. DSC curves show a single endothermic peak around 120°C that give low peak temperature for low EW and high peak temperature for large cations size. The membrane mechanical properties changed for different EW and temperatures of membranes. Stress-strain analysis showed that K+ substituted membranes at both temperatures present a highest YM compared to the other alkali cation substitutions. The thermal properties of perfluorosulfonated membranes depend on the water contents, cation size, temperature and also on EW value.