Synthesis and Characterization of Sulfonated Cardo Poly(Arylene Ether Sulfone)s for Fuel Cell Proton Exchange Membrane Application

Abstract

AbstractSulfonated cardo poly(arylene ether sulfone)s (SPPA‐PES) with various degrees of sulfonation (DS) were prepared by post‐sulfonation of synthesized phenolphthalein anilide (PPA; N‐phenyl‐3,3′‐bis(4‐hydroxyphenyl)‐1‐isobenzopyrolidone) poly(arylene ether sulfone)s (PPA‐PES) by using concentrated sulfuric acid. PPA‐PES copolymers were synthesized by direct polycondensation of PPA with bis‐(4‐fluorophenyl)‐sulfone and 4,4′‐sulfonyldiphenol. The DS was varied with different mole ratios of PPA (24, 30, 40, 50 mol.%) in the polymer. The structure of the resulting SPPA‐PES copolymers and the different contents of the sulfonated unit were studied by Fourier transform infrared (FT‐IR) spectroscopy, 1H NMR spectroscopy, and thermogravimetric analysis (TGA). Sorption experiments were conducted to observe the interaction of sulfonated polymer with water. The ion exchange capacity (IEC) and proton conductivity of SPPA‐PES were evaluated according to the increase of DS. The water uptake (WU) of the resulting SPPA‐PES membranes was in the range of 20–72%, compared with 28% for Nafion 211®. The SPPA‐PES membranes showed proton conductivities of 23–82 mS cm–1, compared with 194 mS cm–1 for Nafion 211®, under 100% relative humidity (RH) at 80 °C.