Preparation and characterization of PVDF microporous membrane with highly hydrophobic surface

Using the mixture of triethyl phosphate (TEP) and N,N‐dimethylacetamide (DMAc) as solvent, PVDF microporous membranes with highly hydrophobic surface were prepared by a modified NIPS method with a dual coagulation process. The effects of the exposure time on these membranes before being immersed into the coagulation bath and the composition in the coagulation bath on precipitation rate, membrane morphology, membrane hydrophobicity, membrane mechanical property, and membrane performance were studied. The morphologies and hydrophobicities of PVDF microporous membranes were investigated by scanning electron microscopy (SEM) and contact angle (CA) measurement. The precipitation processes were observed by light transmittance measurement. The pore size distribution was determined by liquid permeation technique. PVDF microporous membrane obtained by passing evaporation period of 60 min before being immersed into the water bath showed a high water CA of 122.1°. Using ethanol (EtOH) as coagulation bath, the water CAs of the top surface and bottom surface of the membrane increased to 125.9 and 132.6°, respectively. To further improve PVDF membrane hydrophobicity, a dual coagulation process was used and the mixed solvent (TEP–DMAc) was added into the first coagulation bath for 30 sec. Increase in the TEP–DMAc content led to the change in the morphology type of the membrane, that is, from an asymmetric structure with a dense top surface to a symmetric structure with a skinless top surface, and the pore size distribution widened greatly. By increasing the mass ratio of TEP to DMAc, the denseness of the membrane surface decreased significantly. Adding 60 wt% of TEP–DMAc to the first coagulation bath and the mass ratio of TEP to DMAc was 60:40, the CA reached to a maximum as high as 136.6°, and PVDF microporous membrane showed a high porosity of 80% and an excellent mechanical property of 3.14 MPa tensile strength and 61.79% elongation ratio. Copyright © 2009 John Wiley & Sons, Ltd.     

Preparation and characterization of microporous PVDF/PMMA composite membranes by phase inversion in water/DMSO solutions

PMMA/PVDF composite membranes were prepared by isothermal immersion-precipitation of dope solutions consisting of PMMA, PVDF, and DMSO into both harsh and soft nonsolvent baths. The effects of PMMA and DMSO contents on the membrane morphology, crystal structure, thermal behavior and tensile strength of the formed membrane were investigated. For a PMMA-free casting dope immersed in a harsh bath, such as pure water, the formed membrane exhibited a typical asymmetric morphology characterized by skin, finger-like macrovoids, and cellular pores. In contrast, when a soft 70% DMSO bath was adopted, PVDF crystallized to form a membrane packed by spherulitic globules. Incorporation of PMMA gave rise to interesting morphological features; e.g., PVDF globules were observed to adhere to the interlocked polymer branches coexisting with the continuous porous channels, as revealed by high resolution FESEM imaging. XPS analysis of the surfaces of the composite membranes suggested the occurrence of a surface segregation phenomenon, wherein PVDF preferentially migrated to the top surface region of the membrane such as to minimize the interfacial energy. XRD analyses indicated that PVDF crystallized into ‘α’ structure in both PVDF and PMMA/PVDF composite membranes. The crystallinity of the membranes was found to decrease with increasing PMMA content, which was confirmed by DSC thermal analyses. The latter results also indicated a significant decrease in membrane’s melting temperature as the PMMA content was increased. Tensile strengths of the membranes were improved by inclusion of PMMA in either harsh or soft baths. However, elongation at break showed a reversed trend.     

Effect of the preparation conditions on the formation of asymmetric poly(vinylidene fluoride) hollow fibre membranes with a dense skin

Integrally skinned asymmetric poly(vinylidene fluoride) hollow fibre membranes were prepared and characterized. The effects of phase inversion methods (dry-wet or wet) and spinning conditions, such as the type of solvent (NMP, DMAc), the concentration of polymer in dope solution, temperature of the external coagulation bath and the composition of the inner coagulant on the morphology and on the formation of a dense skin layer were investigated. The structure of the membranes was analyzed by scanning electron microscopy and the gas permeation properties with six different gases (He, H₂, N₂, O₂, CH₄ and CO₂) were measured at 25 °C to confirm the integrity of the selective skin layer. Under the proper conditions highly selective and permeable PVDF hollow fibre membranes were thus obtained by dry-wet spinning of a 30 wt.% PVDF solution in DMAc, using hot water (50 °C) as the external coagulant and a bore fluid of pure water as the internal coagulant. The best membrane had a selective outer skin with an effective thickness of approximately 0.2 μm. The ideal selectivity of the hollow fibres approached or even exceeded the intrinsic ideal selectivity of a dense PVDF film, for instance the selectivity for He over N₂ was 86.2 for the hollow fibre, whereas it was 83.5 for a dense PVDF reference film. DSC and FT-IR/ATR analysis indicated a higher fraction of the β-crystal phase in the selective skin and a high overall crystallinity than in the melt-processed film. The latter explains the relatively high selectivity and low permeability of the membranes. Intrinsic polymer properties make the membranes also suitable for vapour transport than for gas separation.     

Fabrication of Hydrophilic and Sponge-like PVDF/Brush-like Copolymer Blend Membranes Using Triethylphosphate as Solvent简

Porous PVDF blend membranes with good hydrophilicity and a symmetric structure were prepared by the phase inversion method using amphiphilic brush-like copolymers, P（MMA-r-PEGMA）, as hydrophilic additive and triethylphosphate （TEP） as solvent. P（MMA-r-PEGMA） was synthesized by radical polymerization in TEP. Then the obtained amphiphilic copolymer solution was mixed with PVDF and TEP to prepare the dope solution. The effects of P（MMA-r-PEGMA） content and coagulation composition on membrane morphologies were investigated using scanning electron microscopy （SEM）. The results demonstrated that, even blended with amphiphilic copolymers, a symmetric structure can be formed. Hollow fiber membranes with a mainly symmetric structure were also fabricated. The dry hollow fiber membranes showed good hydrophilicity, high flux and good rejection performance because of their hydrophilic surface and pores wall.     

Fabrication of high performance Matrimid/polysulfone dual-layer hollow fiber membranes for O2/N2 separation

Matrimid/polysulfone (PSf) dual-layer hollow fiber membranes were fabricated by using co-extrusion and dry-jet wet-spinning phase-inversion techniques. The effects of the spinning dope composition, spinneret dimension, spinneret temperature and the air gap distance on the hollow fiber membranes separation performance were studied. Aging phenomenon was also studied. After coated by 3 wt% silicon solution, the hollow fiber membranes have an O₂/N₂ selectivity of 7.55 at 25 °C, 506.625 kPa which exceeds the intrinsic value of Matrimid. The membranes have an O₂ permeance of 9.36 GPU with an apparent dense-layer thickness of 1421 Å calculated from the O₂ permeability. SEM images show the high porosity underneath the dense skin. It indicates that non-solvent addition is not necessary in the inner spinning dope to induce the macroviod formation. The binodals of the Matrimid/solvent/H₂O and PSf/solvent/H₂O indicate that the composition of the spinning dope plays an important role in the structure and the gas separation performance of the dual-layer hollow fiber membranes. The delayed demixing of the inner spinning dope may fabricate low resistance support layers in the dual-layer hollow fiber membranes.     

Preparation and properties of Nafion/hollow silica spheres composite membranes

In present work, hollow silica spheres (HSS)/Nafion^® composite membranes were prepared by solution casting. The thermal properties, water retention, swelling behavior and proton conductivity of the composite membranes were explored. It was found that HSS dispersed well at micrometer scale in the obtained composite membranes by SEM and TEM observation. Thermal properties of composite membranes were improved than that of recast Nafion^® membrane. Compared with the recast Nafion^® membrane, the composite membranes showed higher water uptake and lower swelling degree at the temperature range from 40 to 100 °C. At the same HSS loading, the smaller the diameter of HSS in composite membranes, the more the water uptake, however, the swelling degree of composite membranes was increased. The proton conductivity of the composite membrane with 3–5 wt.% HSS (120 and 250 nm) increased distinctively at above 60 °C, reached the optimal value at 100 °C, and decreased slowly when the temperature exceeded 100 °C.     

Separation of casein micelles from whey proteins by high shear microfiltration of skim milk using rotating ceramic membranes and organic membranes in a rotating disk module

This paper investigates the microfiltration of skim milk in order to separate caseins micelles from two whey proteins, α-lactalbumin (α-La) and β-lactoglobulin (β-Lg), using a modified dynamic filtration pilot (MSD) consisting in 6 ceramic 9-cm diameter membrane disks of 0.2 μm pores, rotating around a shaft inside cylindrical housing. A comparison was made with another dynamic filtration module consisting in a disk rotating near a fixed PVDF 15.5 cm diameter membrane with 0.15 μm pores. Maximum permeate fluxes were 120 L h⁻¹ m⁻² with the MSD module at 1930 rpm and at 40 °C, and 210 L h⁻¹ m⁻² at 2500 rpm and 45 °C, with the rotating disk module. Casein rejection was around 99% at high speed for both membranes. α-La transmission decreased with increasing transmembrane pressure (TMP) from 75% to 60% for ceramic membranes and from 25% to 10% for the PVDF one. β-Lg transmissions were lower, ranging from 23% to 15% for ceramic membranes and from 20% to 5% for the PVDF one. In a concentration test with the PVDF membrane at 2000 rpm, the flux decayed from 200 L h⁻¹ m⁻² at initial concentration to 80 L h⁻¹ m⁻² at VRR = 3.2 and 22.1% of the initial α-La mass was recovered in the permeate, against 8.1% for β-Lg. Permeate fluxes in the mass transfer limited regime (J_lim) of the MSD and rotating disk module operated at various speeds were well correlated by the equation J_lim = 17.13 V_av where V_av denoted the disk azimuthal velocity averaged over the membrane area. Measurements of J_lim, taken from Ref. [G. Samuelsson, P. Dejlmek, G. Tragardh, M. Paulsson, Minimizing whey protein retention in crossflow microfiltration of skim milk. Int. Dairy J. 7 (1997) 237–242] during MF of skim milk using tubular ceramic membranes at velocities from 1.5 to 8 m s⁻¹ with permeate co-current recirculation were found to obey the same correlation.     

PVDF membrane formation by diffusion‐induced phase separation‐morphology prediction based on phase behavior and mass transfer modeling

The equilibrium phase behavior of water (nonsolvent)‐DMF (solvent)‐PVDF system at 25°C was investigated via both theoretical and experimental approaches. Using binary interaction parameters, χ_ij, obtained previously, the theoretical phase boundaries were computed and were found to match closely the measured binodal and crystallization‐induced gelation data. Membranes were prepared using the isothermal immersion‐precipitation processes in various dope and bath conditions. The formed membranes demonstrated a broad spectrum of morphologies: At one extreme, asymmetric structure was obtained featuring a continuous tight skin and a sublayer composed of parallel macrovoids and cellular pores; at the other limit, skinless microporous membrane was produced with spherical particles packed into a bi‐continuous structure. The crystalline characters of PVDF gels and membranes were examined by small angle light scattering, scanning electron microscopy, and differential scanning calorimetry techniques. In addition, diffusion trajectories and concentration profiles in the membrane solution before precipitation were calculated for the immersion process. These results predicted reasonably the various morphologies observed in the membranes. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2079–2092, 1999     

Single-step synthesis of proton conducting poly(vinylidene fluoride) (PVDF) graft copolymer electrolytes

The single-step synthesis of proton conducting poly(vinylidene fluoride) (PVDF) graft copolymer electrolytes is demonstrated. The graft copolymers of PVDF backbone with poly(sulfopropyl methacrylate) (PVDF-g-PSPMA) and poly(styrene sulfonic acid) (PVDF-g-PSSA) were synthesized using PVDF as a macroinitiator for atom transfer radical polymerization (ATRP). ¹H NMR and FT-IR spectroscopy show that the “grafting from” method using ATRP was successful and the maximum grafting degrees were 35 and 25 wt% for PVDF-g-PSPMA and PVDF-g-PSSA, respectively. The IEC values were 0.63 and 0.45 meq/g, the water uptakes were 46.8 and 33.4 wt% and the proton conductivities were 0.015 and 0.007 S/cm at room temperature, for PVDF-g-PSPMA and PVDF-g-PSSA, respectively. Both membranes exhibited excellent thermal stability up to around 350 °C, verified by thermal gravimetric analysis (TGA).     

Preparation of PVDF/PEO-PPO-PEO blend microporous membranes for lithium ion batteries via thermally induced phase separation process

Microporous poly(vinylidene fluoride)/polyethylene oxide-co-polypropylene oxide-co-polyethylene oxide (PVDF/PEO-PPO-PEO, or PVDF/F127) blend membranes were prepared via thermally induced phase separation (TIPS) process using sulfolane as the diluent. Then they were soaked in a liquid electrolyte to form polymer electrolytes. The effects of F127 weight fraction on the morphology, crystallinity and porosity of the blend membranes were studied. It was found that both electrolyte uptake of blend membranes and ionic conductivity of corresponding polymer electrolytes increased with the increase of F127 weight fraction. The maximum ionic conductivity was found to reach 2.94 ± 0.02 × 10⁻³ S/cm at 20 °C. Electrochemical stability window was stable up to 4.7 V (vs. Li⁺/Li). The testing results indicated that the PVDF/F127 blend membranes prepared via TIPS process can be used as the polymer microporous matrices of polymer electrolytes for lithium ion batteries.     

Moisture barrier,wetting and mechanical properties of shellac/agar or shellac/cassava starch bilayer bio-membrane for food applications

Edible bilayer membrane composed of agar (AG) or cassava starch (CAS) as a cohesive structural layer and ethanol-cast shellac layer as a moisture barrier are investigated for their potential use in food preservation as bio-packaging film, membrane or coating. Bilayer membranes containing non-plasticized shellac exhibit low water vapor permeability (WVP), from 0.89 to 1.03 × 10⁻¹¹ g m⁻¹ s⁻¹ Pa⁻¹. A high value of contact angle (≈92°) and a low liquid water adsorption rate (26 × 10⁻³ μL s⁻¹) indicate that these barrier layers have a quite hydrophobic surface. However, the rigid and brittle characteristics of shellac induce a lack of integrity for this layer. It tends to be cracked and scaled off. The incorporation of PEG 200 (plasticizer) into shellac improves the flexibility that prevents the defects in structure and reinforces the adhesion between the shellac and the cohesive-structural layer. The use of plasticizer weakly affects the WVP of bilayer membranes; however, the surface hydrophobicity as well as the liquid water adsorption rate is comparable to that of non-plasticized shellac layer. Furthermore, PEG increases the stretchability of bilayer membranes. Either being plasticized or not, shellac layer could improve significantly the functional properties of bilayer barriers and give a promising use as biopackaging.     

Fabrication and characterization of a novel TiO2 nanoparticle self-assembly membrane with improved fouling resistance

A novel TiO₂ nanoparticle self-assembly membrane was prepared based on ultrahigh molecular weight poly(styrene-alt-maleic anhydride)/poly(vinylidene fluoride) (SMA/PVDF) blend membrane. TiO₂ nanoparticle solution was beforehand prepared via the controlled hydrolysis of titanium tetraisopropoxide. The diameter (10 nm or less) and anatase crystal structure were analyzed using transmission electron microscopy (TEM) and X-ray diffraction (XRD). The SMA/PVDF blend membranes prepared by the phase inversion method were immersed into the TiO₂ nanoparticle solution for a week to produce TiO₂ self-assembly membranes. The chemical compositions in membrane surface were analyzed by X-ray photoelectron spectroscopy (XPS). The membrane morphologies were measured by scanning electron microscopy (SEM). Finally, the membrane hydrophilicity, protein anti-fouling property and the molecular weight cutoff (MWCO) were characterized by water contact angle measurement, static protein absorption and filtration experiments, respectively. It is demonstrated that, in comparison to PVDF/SMA blend membrane, the permeability and anti-fouling ability of TiO₂ self-assembly membranes were significantly improved.     

The microwave spectrum of trimethyl silyl isocyanate (CH3)3SiNCO

The microwave spectrum of trimethyl silyl isocyanate has been investigated in the region 26.5–40 GHz. The spectrum belonging to the ground vibrational state is characteristic of a symmetric top indicating that the equilibrium configuration of the SiNCO chain is either linear or very nearly so. The ground state B₀ value is 1203.83 MHz which is consistent with the structure observed for SiH₃NCO. The ground state transitions are accompanied by many vibrational satellites belonging to the lowest bending mode whose frequency was estimated to be 64 ± 15 cm⁻¹. These results are consistent with electron diffraction results from which the SiNC angle is deduced to be ≈ 150°.     

Effect of preparation variables on morphology and pure water permeation flux through asymmetric cellulose acetate membranes

In this study, cellulose acetate (CA) ultrafiltration (UF) membranes were prepared using the phase inversion method. Effects of CA and polyethylene glycol (PEG) concentrations in the casting solution and coagulation bath temperature (CBT) on morphology of the synthesized membranes were investigated. Based on L₉ orthogonal array of Taguchi experimental design 18 membranes were synthesized (with two replications) and pure water permeation flux through them were measured. It was found out that increasing PEG concentration in the casting solution and CBT, accelerate diffusional exchange rate of solvent 1-methyl-2-pyrrolidone (NMP) and nonsolvent (water) and consequently facilitate formation of macrovoids in the membrane structure. Increasing CA concentration, however, slows down the demixing process. This prevents instantaneous growth of nucleuses in the membrane structure. Hence, a large number of small nucleuses are created and distributed throughout the polymer film and denser membranes are synthesized. Rate of water flux through the synthesized membranes is directly dependent on the size and number of macrovoids in the membrane structure. Thus, maximum value of flux is obtained at the highest levels of PEG concentration and CBT (10 wt.% and 23 °C, respectively) and the lowest level of CA concentration (13.5 wt.%). Analysis of variance (ANOVA) showed that all parameters have significant effects on the response. However, CBT is the less influential factor than CA and PEG concentrations on the response (flux).     

Regulation of the microstructure of polyvinylidene fluoride membrane via incorporation of nano-ZIF-7 for improving hydrophobicity and antiwetting performance

The design and fabrication of a membrane with super hydrophobicity and antiwetting property is of great importance for improving membrane performance in distillation, desalination, gas absorption, and separation. In this work, polyvinylidene fluoride (PVDF) membranes were modified by Zeolitic Imidazolate Framework-7 (ZIF-7) nanocrystals to improve the hydrophobic property and antiwetting performance. ZIF-7/PVDF hybrid membranes were prepared via the nonsolvent-induced phase separation (NIPS) method. Different concentrations of ZIF-7 nanocrystals (0, 0.5, 1, 2, 3, and 5 wt%) were introduced into the PVDF dope solution, and the physical structure of the resulting membranes were systematically characterized. Due to the hydrophobic nature of ZIF-7 nanocrystals, the solvent–nonsolvent exchange rate had been regulated effectively during phase inversion. The morphology of top and bottom surfaces, together with the inner structures of the hybrid membrane, has been changed obviously, showing a more twisted finger-like macrovoid layer and a thicker sponge-like layer compared to pristine PVDF membrane. Furthermore, the hydrophobicity and antiwetting properties of these hybrid membranes improved obviously when the incorporated concentration of ZIF-7 was higher than 1 wt%. The M(2) membrane, which possessed the highest surface roughness and water contact angles, showed the best antiwetting property and recovered gas permeance ratio (>95%) after being immersed in aqueous solution for 10 hr.     

Effect of clay on the corrosion protection efficiency of PMMA/Na-MMT clay nanocomposite coatings evaluated by electrochemical measurements

The preparation of PMMA-clay nanocomposites was investigated by using sodium dodecylbenzenesulfonate (SDS) and potassium peroxodisulfate (KPS) as a surfactant and chain initiator for an in situ emulsion polymerization reaction, respectively. The as-prepared nanocomposites were then characterized by Fourier transformation infrared (FTIR) spectroscopy, wide-angle X-ray diffraction (WAXRD) patterns and transmission electron microscopy (TEM).It should be noted that the nanocomposite coating containing 1 wt% of clay loading was found to exhibit an observable enhanced corrosion protection on cold-rolled steel (CRS) electrode at higher operational temperature of 50 °C, which was even better than that of uncoated and electrode-coated with PMMA alone at room temperature of 30 °C based on the electrochemical parameter evaluations (e.g., E_corr, R_p, I_corr, R_corr and impedance). In this work, all electrochemical measurements were performed at a double-wall jacketed cell, covered with a glass plate, through which water was circulated from a thermostat to maintain a constant operational temperature of 30, 40 and 50 ± 0.5 °C. Moreover, a series of electrochemical parameters shown in Tafel, Nyquist and Bode plots were all used to evaluate PCN coatings at three different operational temperatures in 5 wt% aqueous NaCl electrolyte. The molecular barrier properties at three different operational temperatures of PMMA and PCN membranes were investigated by gas permeability analyzer (GPA) and vapor permeability analyzer (VPA). Effect of material composition on the molecular weight and optical properties of neat PMMA and PCN materials, in the form of solution and membrane, were also studied by gel permeation chromatography (GPC) and UV-vis transmission spectra.     

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

The solid proton conductor, phosphatoantimonic acid, HSbP₂O₈ · H₂O was prepared by ion exchange of the corresponding potassium salt. The composite membranes of SPEEK with up to 40 wt% of HSbP₂O₈ · H₂O 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 HSbP₂O₈ · H₂O and the conductivity was reduced with further increase of HSbP₂O₈ · H₂O 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.     

Synthesis, phase relationship and crystal structure of the new binary compound Ir13Al45

The new phase Ir₁₃Al₄₅ was synthesized in equilibrium with an aluminum-rich melt. Its crystal structure was established from single-crystal diffraction data. The compound crystallizes in the space group Pnma and represents a novel structure type (Pearson symbol oP232, a=16.760(2) Å, b=12.321(1) Å, c=17.425(2) Å). The structure can essentially be described as a simple hexagonal column packing of pseudopentagonal columns formed by irregular Al polyhedra centered by Ir atoms. Ir₁₃Al₄₅ forms peritectically at 895 °C and exists in equilibrium with the melt in a narrow temperature interval of 19 °C.     

Anti-trade-off in dehydration of ethanol by novel PVA/APTEOS hybrid membranes

Novel organic–inorganic hybrid membranes were prepared through sol–gel reaction of poly(vinyl alcohol) (PVA) with γ-aminopropyl-triethoxysilane (APTEOS) for pervaporation (PV) separation of ethanol/water mixtures. The membranes were characterized by FTIR, EDX, WXRD and PALS. The amorphous region of the hybrid membranes increased with increasing APTEOS content, and both the free volume and the hydrophilicity of the hybrid membranes increased when APTEOS content was less than 5 wt%. The swelling degree of the hybrid membranes has been restrained in an aqueous solution owing to the formation of hydrogen and covalent bonds in the membrane matrix. Permeation flux increased remarkably with APTEOS content increasing, and water permselectivity increased at the same time, the trade-off between the permeation flux and water permselectivity of the hybrid membranes was broken. The sorption selectivity increased with increasing temperature, and decreased with increasing water content. In addition, the diffusion selectivity and diffusion coefficient of the permeants through the hybrid membranes were investigated. The hybrid membrane containing 5 wt% APTEOS has highest separation factor of 536.7 at 50 °C and permeation flux of 0.0355 kg m⁻² h⁻¹ in PV separation of 5 wt% water in the feed.     

Poly(arylene ether) ionomers containing sulfofluorenyl groups: Effect of electron-withdrawing groups on the properties

For polymer electrolyte membrane fuel membrane cell (PEMFC) applications, the effect of electron-withdrawing groups on the properties of sulfonated poly(arylene ether) (SPE) ionomer membranes was investigated. A series of poly(arylene ether)s containing fluorenyl groups and electron-withdrawing groups (sulfone, nitrile, or fluorine) was synthesized, which were sulfonated with chlorosulfonic acid using a flow reactor to obtain the title ionomers. The ionomers had high molecular weight (M_n > 77 kDa, M_w > 238 kDa) and gave tough, ductile membranes by solution casting. The ion exchange capacity (IEC) of the membranes ranged from 1.6 to 3.5 mequiv/g as determined by titration. The electron-withdrawing groups did not appear to affect the thermal properties (decomposition temperature higher than 200 °C). The presence of nitrile groups, especially at positions meta to the ether linkages, improved the oxidative stability of the SPE membranes, while it led to a deterioration of the hydrolytic stability. The perfluorinated biphenylene groups were effective in providing high mechanical strength with reasonable dimensional change, probably due to a somewhat decreased water absorbability. The SPE membrane containing sulfone groups showed the highest proton conductivity (10⁻³-10⁻¹ S/cm) at 20-93% RH (relative humidity) and 80 °C. The nitrile-containing SPE membrane showed smaller apparent activation energies for oxygen and hydrogen permeability and is thus considered to be a possible candidate for applications in PEMFCs.