Poly(arylene ether ketone) with an Ultrahigh-Selectivity Hydrophilic Phase Proton Transport Channel by Grafting Sulfonated Benzotriazole Groups onto Pendant Chains

The practice of site control for functional groups to achieve better interactions has become popular in recent years. Capitalizing on such developments, sulfonated 5-carboxybenzotriazole (SCBTA), serving as a new monomer that combines multiple functional groups, is grafted onto pendant chains of poly(arylene ether ketone) (PAEK) via an amidation reaction to fabricate a series of novel proton-exchange membranes (NmAn-SCBTA). The structure of the resulting membranes is confirmed by 1H NMR and Fourier transform infrared (FT-IR). Transmission electron microscopy (TEM) and small-angle X-ray spectroscopy (SAXS) analyses reveal well-defined microphase-separated structures. Among these samples, a membrane having an amino bisphenol monomer content of 70% (N7A3-SCBTA) exhibits high conductivity (0.089 S·cm–1, at 90 °C), oxidative stability (95.7%), and tensile strength (65.74 MPa), while its selectivity is as high as 91.9 × 104 S·s·cm–3 at 25 °C; this value is even more than 27 times that of recast Nafion (3.3 × 104 S·s·cm–3). These results indicate that there is great potential for these membranes to be used in direct methanol fuel cells (DMFCs).