Sulfonated polysulfone containing phenyl side chain as proton exchange membrane

Abstract

Based on the preparation of chloromethylated polysulfone(CMPS), two types of sulfonated polysulfone, naphthalenesulfonic acid type sulfonated polysulfone(PS-NS) and pyrenesulfonic acid type sulfonated polysulfone(PS-TS) were successfully obtained via nucleophilic substitution with 2-naphthol-6,8-disulfonic acid dipotassium(NS) and 8-hydroxy-1,3,6-pyrene trisulfonic acid sodium(TS) as reagents, respectively. The PS-NS and PS-TS Proton exchange membranes (PEMs) were obtained by solution casting method after characterizing their structure by FT-IR and ¹H-NMR. The impact of phenyl side chain on performance including water uptake(WU), swelling ratio(SR) and proton conductivity(PC) of PEMs were explored. Atomic force microscopy(AFM) shows that the phase separation structures of PS-NS and PS-TS PEMs are distinct due to the positioning of the hydrophilic sulfonic acid groups far away from the hydrophobic main chain. So the PS-NS and PS-TS PEMs keep excellent size stability, oxidative stability and methanol permeability at high WU. At the same bonding amount(BA) of sulfonic acid, due to less hydrophilic chain segment and a larger number of sulfonic acid groups in the hydrophilic chain segment, which is conducive to the aggregation of ion cluster. The PS-TS present better size stability and anti-oxidative at high WU. The SR of PS-TS-3 PEM was only 20.3 and 48.1%. Meanwhile, the methanol permeability was only 7.54 × 10⁻⁷cm²·s⁻¹ at room temperature, much lower than commercialization Nafion115 PEM (16.8 × 10⁻⁷cm²/s at room temperature). The research results are of great significance for the design and preparation of high-performance membrane materials.