Blends based on sulfonated poly[bis(benzimidazobenzisoquinolinones)] and poly(vinylidene fluoride) for polymer electrolyte membrane fuel cell

A new blend system consisting of an amorphous sulfonated poly[bis(benzimidazobenzisoquinolinones)] (SPBIBI) and the semi-crystalline poly(vinylidene fluoride) (PVDF) was prepared for proton exchange membranes. The miscibility behavior of a series of blends of SPBIBI with PVDF at various weight ratios was studied by WXRD, DSC and FTIR. The properties of the blend membranes were investigated, and it was found that the introduction of PVDF in the SPBIBI matrix altered the morphological structure of the blend membranes, which led to the formation of improved connectivity channels. For instance, the conductivity of the blend membrane containing 10 wt% PVDF displayed the highest proton conductivity (i.e., 0.086 S cm−1) at room temperature, a value almost twofold that of the pristine SPBIBI membranes (i.e., 0.054 S cm−1) under identical conditions. The result was thus comparable to the proton conductivity of Nafion 117 (i.e., 0.09 S cm−1). Moreover, the dimensional stability, the elongation at break, the methanol permeability and the oxidative stability were enhanced in various extents by introducing PVDF into the blend membranes.