LAUSR

Abstract The development of polymer exchange membranes (PEMs) with high proton conductivity under high temperature and low relative humidity (RH) conditions is important to the improvement of the comprehensive performance of the fuel cell. In this paper, we present a novel approach for the design of semi-crystalline fluorinated PEMs (FSPP-1) via Ni(0)-catalyzed coupling polymerization. The structural characteristics of FSPP-1 are composed of retaining a portion of the fluorinated matrix (coil units) and introducing aromatic π-π interactions in the hydrophilic block (rod units), as well as precisely controlling the same block length along the main chain axis, which is a similar, molecular-level approach as the prototypical Nafion™ 117. The morphology, water state, and proton conductivity of FSPP-1 were investigated in detail, and the results show higher proton conductivity at 40% RH at 80 °C. The study also revealed that a dense, narrow distribution of hydrophilic nanochannels were formed with good connectivity of the hydrophilic nanochannels in FSPP-1. More importantly, π-π interactions in the hydrophilic block and helical perfluoroalkyl chains in the hydrophobic block coexisted in FSPP-1 ionomers, forming more small and dense crystallite domains, which was found to be beneficial to improving the stability of the nanochannels at elevated temperature and low RH. This strategy to simultaneously increase the density of ion transport channels and high temperature stability provides a baseline for the molecular-level design of high temperature PEMs.