A novel comb-shaped polybenzimidazoles crosslinked sulfonic acid functionalized polyphosphazenes high temperature proton exchange membrane

Abstract

Designing high temperature proton exchange membranes (HTPEMs) with high H+ conductivity and long durability has been challenging. Here, a comb-shaped polybenzimidazoles (CbPBI) and crosslinkable polyoxy (benzenesulfonic acid) phazenes (PBSP) proton conductors are prepared, then they are used to fabricate a series of PBSP-CbPBI membranes with good comprehensive performances. CbPBI provides high flexibility and large free volume, which facilitates the construction of proton transport channels. And PBSP is the bifunctional proton conductor and crosslinker that introduces abundant sulfonic acid groups while retaining the crosslinkable property. By strongly chemical binding with CbPBI, the basicity of the imidazole ring is enhanced, avoiding the leaching of PBSP, thus enabling the overall crosslinked membrane to exhibit a durable intrinsic proton conductivity. Benefiting from the construction of the dual crosslinked network (covalent and ionic crosslinking), the oxidative stability, dimensional stability, and fuel-blocking properties of the PBSP-CbPBI membranes perform well. The proton conductivity of PBSP(50)-CbPBI membrane reaches 0.163, 0.084, 0.057, and 0.043 S/cm, respectively, at 180 °C and different relative humidity (100 % RH, 50 % RH, 30 % RH, and 0 RH). Enduring hot-washing for 96 h, the less decay of membrane in conductivity and weight demonstrates good durability. The design strategy such as the construction of monolithic crosslinked macromolecular structures in PBSP-CbPBI membranes shows wide application prospects in HTPEMs.