Highly Proton Conducting Electrolyte Membranes Based on Poly(arylene sulfone)s with Tetrasulfonated Segments

Abstract

A series of fully aromatic polymers having only sulfone bridges linking the aromatic rings have been synthesized via polycondensations and studied as protonexchange membranes. Mixtures of tetrasulfonated 4,4′-bis[(4chlorophenyl)sulfonyl]-1,1′-biphenyl (BCPSBP), non-sulfonated BCPSBP, and 4,4′-thiobisbenzenethiol were copolymerized by nucleophilic aromatic substitution reactions to obtain sulfonated poly(arylene thioether sulfone)s (SPATSs) with ion exchange capacities (IECs) between 2.0 and 4.0 mequiv g −1 . The thioether bridges of the SPATSs were quantitatively oxidized to sulfone bridges to obtain the corresponding sulfonated poly(arylene sulfone)s (SPASs). Small-angle Xray scattering of dry SPATS and SPAS membranes showed that the tetrasulfonated segments promoted a distinct phase separation of the ionic groups already at quite low ionic contents. The SPAS polymers degraded between 300 and 340 °C in air, which was significantly above the degradation temperature of the corresponding SPATSs polymers. Moreover, SPAS membranes showed a significantly lower water uptake than the corresponding SPATS membranes. SPATS and SPAS membranes with IEC values of 2.4 and 2.2 mequiv g −1 , respectively, maintained high proton conductivity at low relative humidity (RH). At 30% RH and 80 °C, these membranes reached 8 and 10 mS cm −1 , respectively. The latter value coincided with that recorded for the stateof-the-art perfluorinated NRE212 membrane under the same conditions. Thus, the SPAS materials combine a straightforward synthetic pathway with a very robust polymer structure giving high proton conductivity at reduced RH.

Ion Transport by Nanochannels in Ion-Containing Aromatic Copolymers

“…At reduced RH, the tetrasulfonated copolymer membranes had significantly higher conductivity than the disulfonated ones. As discussed before, to improve the hydrolytic and oxidative stability of the polymer backbone, highly sulfonated poly(phenylene sulfone)s 86 were prepared from tetrasulfonated monomers. Because of the distinct phaseseparated morphology induced by the densely sulfonated structures, the SPATS (IEC 2.4 mequiv/g) and SPAS (IEC 2.2 mequiv/g) membranes maintained high proton conductivity at low RH.…”

Poly(arlyene ether sulfone) based semi-interpenetrating polymer network membranes containing cross-linked poly(vinyl phosphonic acid) chains for fuel cell applications at high temperature and low humidity conditions

“…For each measurement, at least seven samples were used and their average value was calculated. Ion-exchange capacity (IEC) of the membranes was measured by back-titration method [28]. The membranes were soaked in 1 M NaCl aqueous solution for 24 h, and then the solution was titrated with 0.01 M NaOH aqueous solution.…”

“…We also found the MEA from B15 membrane has better cell durability than that from the recast-Nafion ® membrane at the operating condition. The Hydrogen cross-over, one of the most important parameter for the fuel cell membranes, was estimated by measuring the hydrogen cross-over current density [28,77,78]. Fig.…”

Poly(ether ether sulfone)s and sulfonated poly(ether ether sulfone)s derived from functionalized 1,1‐diphenylethylene derivatives

“…High performance engineering thermoplastics such as sulfonated poly(ether ether sulfone)s possess excellent chemical, physical, mechanical and biological properties and are currently considered as the polymeric material of choice for the development of polymer electrolyte membranes for applications in fuel cell technology processes . Furthermore, sulfonated aromatic poly(ether ether sulfone)s with aromatic nuclei and flexible ether linkages along the polymer backbone exhibit good thermal stability and facilitate polymer processing while maintaining excellent oxidative stability . The synthesis of a plethora of different sulfonated poly(ether ether sulfone) derivatives with different polymer backbones, chemical composition, pendant groups, end groups and topology have been reported in the literature .…”