Preparation and properties of highly branched sulfonated poly(arylene ether)/polyacrylonitrile composite materials as proton exchange membranes

Highly branched sulfonated poly(arylene ether ketone)s (BSPAEKs) exhibit excellent potential as proton exchange membranes (PEMs). However, the mechanical properties of the branched membranes must be further improved. In this work, a series of BSPAEK-based composite membranes containing different amounts of polyacrylonitrile (PAN) were fabricated as PEMs. The expected ionic cross-linking and hydrogen bonding between BSPAEK and PAN was confirmed by Fourier transform infrared spectroscopy. The tensile strengths of the composite membranes with PAN contents from 5 to 20 % ranged from 16.4 to 23.0 MPa, which were notably higher than that of the BSPAEK membrane (13.1 MPa). Furthermore, the oxidative stability of the composite membranes was enhanced significantly from 295 to 430 min (2 ppm FeSO₄ in 3 % H₂O₂) with increased PAN doping. Although the proton conductivity of the composite membrane was lower than that of BSPAEK, the proton conductivity of the composite membranes was still above 10⁻² S cm⁻¹ and satisfied the requirement of the fuel cells. The results indicate that this material is a suitable candidate PEM for evaluation in fuel cell applications.