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The cross-linkable copolymers (SHQx-TFVys) with varying degrees of sulfonation (DS) from 70 to 95% were prepared from potassium-2,5-dihydroxybenzenesulfonate (SHQ), decafluorobiphenyl (DFBP), and 4-(trifluorovinyloxy)-biphenyl-2,5-diol (TFVOH) as a cross-linkable moiety. To develop a highly stable polymer electrolyte membrane (PEM) for application in polymer electrolyte fuel cells (PEFC)s, cross-linked membranes were prepared by chemical cross-linking. The cross-linked membranes were synthesized by varying the amount of TFVOH (5–30 mol %) in order to achieve desirable PEM properties. The structures of the cross-linkable monomer and polymers were investigated by 1H and 19F NMR and FT-IR spectra. The cross-linked membranes exhibited good glass transition temperature and thermal stability up to 239–271 °C and 290–312 °C, respectively. The crosslinked membranes (DS range 80–95%) exhibited higher proton conductivity(0.098–0.151 S/cm) than Nafion 212 (0.092 S/cm). Moreover, all membranes possessed lower methano...

Crosslinked (C-ESFx-BP) and non-crosslinked (N-ESFx-BP) sulfonated poly(arylene ether) (SPAE) membranes containing high fluorine contents were prepared as a function of the degree of sulfonation (DS) and evaluated for use as a highly potential chlorine-resistant reverse osmosis (RO) membrane. C-ESFx-BP membranes were obtained by covalent crosslinking among ethynyl end groups of the polymer chains via thermal curing. Both C-ESFx-BP and N-ESFx-BP membranes show the increase in NaCl rejection with decreasing DS, while water permeability declines due to the decrease of hydrophilicity. In particular, C-ESF70-BP membrane showed excellent salt (NaCl) rejection up to 98.4% compared with that of N-ESF70-BP membrane of 90.3% but showed slightly lower water permeability of 0.6 L μm/m2 h bar than that of 0.8 L μm/m2 h bar for N-ESF70-BP. Moreover, these C-ESFx-BP and N-ESFx-BP membranes displayed the long-term stability longer than 30 days during the operation condition under high acidic chlorine concentration of NaOCl 4000 ppm unlike commercial PA membranes which are unstable under the chlorine treatment. The stability comparison between them were observed by ATR-IR, retention ratio of molecular weight (RRMW), contact angle and X-ray photoelectron spectroscopy (XPS).

New series of ethynyl-terminated sulfonated-fluorinated poly(arylene ether)s (ESF-6Fs) were synthesized via nucleophilic aromatic substitution reaction (SNAr) from potassium 2,5-dihydroxybenzenesulfonate (SHQ), 4,4′-(hexafluoroisopropylidene)diphenol (6FBPA), and decafluorobiphenyl (DFBP), followed by the reaction with 3-ethynylphenol. The cross-linked ESF-6F membranes exhibited high glass-transition temperatures in the range of 258−276 °C and good thermal degradation temperatures in the range of 308−328 °C. To optimize the proton conductivity and water uptake of the cross-linked ESF-6F membranes, various volume-related parameters (length-scaled parameters) were introduced. Using those parameters, the proton conductivity and water uptake of the cross-linked ESF-6F membranes were compared with sulfonated poly(arylene ether sulfone) random copolymer (BPSH), Nafion membrane, and another cross-linked membrane. In addition, the proton conductivity of optimized ESF-6F membrane was observed as a function of rela...

Side chain crosslinked (C-SFPEx-CMy) sulfonated poly(arylene ether) (SPAE) membranes containing fluorine moiety with varying degree of sulfonation (DS) were prepared and evaluated for use as a thin-film composite membrane for seawater desalination. C-SFPEx-CMy membranes were obtained by covalent crosslinking among ethynyl groups at the polymer side chain through thermal curing. The crosslinked network structure suppressed the water uptake and swelling ratio. A novel type of composite membranes (TC-SFPEx-CMy) were prepared side chain crosslinked SPAE layer containing fluorine moiety on top of PET non-woven with epoxy resin as bonding agent. TC-SFPEx-CMy show the increase in NaCl rejection as DS decreases from 30% to 70%. NaCl rejection of the membranes increased with increasing corsslinking moiety (CM) while water permeability decreases due to the crosslinked net work structure. Particularly, crosslinked membrane of 30 mol % of CM could enhance the salt (NaCl) rejection property up to 85.3 % as compared to...

Crosslinkable sulfonated poly(arylene ether ketone) copolymers with various degrees of sulfonation (DS) were prepared and evaluated for use as proton exchange membranes (PEM). The copolymers were synthesized via step growth polymerization using 2,8-dihydroxynaphthalene-6-sulfonated salt (2,8-DHNS-6), 4,4′-(hexafluoroisopropylidene) diphenol (6F-BPA), 4,4′-biphenol (BP), and 4,4′-difluorobenzophenone (DFBP). 1 H NMR and FTIR-ATR spectra confirmed the structure of the copolymers and were also used to determine the obtained DS values of the copolymers. Crosslinked membranes were obtained by thermal curing of the crosslinkable copolymers. The membranes formed a crosslinking network structure via covalent bonding. The glass transition temperatures ( T g ) of the crosslinked membranes were determined by differential scanning calorimetry (DSC) and ranged from 208 to 258 °C. The decomposition temperatures ( T d ) of the membranes ranged from 309 to 325 °C for acid forms. The resulting membranes were characterized via an evaluation of their essential membrane properties, such as ion exchange capacity (IEC), water uptake, and proton conductivity. The performance of the membranes was found to be dependent on the DS and IEC.

End-group cross-linkable sulfonated poly(arylene ether) polymer (E-SFQK) was synthesized via direct polymerization of potassium 2,5-dihydroxybenzenesulfonate (SHQ) and decafluorobiphenyl (DFBP), followed by a reaction with ethynylphenol (EP). The cross-linking reaction of the ethynyl end group of E-SFQK was performed at 250 °C. After cross-linking, proton conductivity, water uptake, and swelling ratio of cross-linked membrane decreased from 0.16 (noncross-linked membrane) to 0.13 S/cm, from 86% to 42%, and from 31% to 13%, respectively. The effect of cross-linking time on proton conductivity, water uptake, and swelling ratio were also investigated. Methanol permeability of cross-linked membrane was compared with Nafion 117 due to solubility of noncross-linked membranes in methanol. The cross-linked membrane performed better, with a methanol permeability of 88 × 10−8 cm2/s, as compared with 154 × 10−8 cm2/s for Nafion 117. The cross-linked membrane also exhibited improved chemical resistance and oxidative ...

Novel sulfonated poly(arylene ether) copolymers containing cross-linking moiety and fluorine atoms were prepared for proton exchange membranes of fuel cells. The copolymers were synthesized using potassium 2,5-dihydroxybenzenesulfonate (SHQ), 4,4′-(hexafluoroisopropylidene)diphenol (6F-BPA), decafluorobiphenyl (DFBP), and 1-ethynyl-2,4-difluorobenzeneand (CM) as a cross-linking moiety through polycondensation. The chemical structures of the cross-linkable copolymers were analyzed by 1H NMR, 19F NMR, and FTIR-ATR spectra. Cross-linked membranes are obtained by thermal curing of the cross-linkable copolymers. The thermal properties of the cross-linked membranes were characterized by TGA and DSC. Intrinsic viscosity and gel fraction were also evaluated in order to measure the molecular weight and cross-linking density, respectively. The cross-linked network structure greatly suppressed the water uptake and swelling of the cross-linked membrane. The proton conductivity and methanol permeability of the membran...

As a novel class of proton exchange membrane (PEM) materials for application in fuel cells, sulfonated poly(arylene ether ketone)s (SPAEK-BPs) were prepared by polycondensation via a nucleophilic substitution reaction followed by post-sulfonation. In this way, SPAEK-BPs with different degrees of sulfonation (DS) were quantitatively synthesized via the use of chlorosulfonic acid as the sulfonating agent. It was discovered that only one sulfonic acid group can be selectively introduced without degradation per each repeating unit of polymer due to requirements for controlling reaction conditions such as reaction time and temperature. In this study, the experimentally observed DS were close to the theoretical values expected from the monomer ratios. The glass transition temperatures ( T g 's) and decomposition temperatures ( T d 's) of the polymers varied from 167 to 213 and 298 to 343 °C, respectively. In addition, the proton conductivities of the SPAEK-BP membranes exhibited up to a maximum of about 0.083 S/cm at 25 °C and 0.098 S/cm at 80 °C.