Polydopamine-modified sulfonated polyhedral oligomeric silsesquioxane: An appealing nanofiller to address the trade-off between conductivity and stabilities for proton exchange membrane

To address the trade-off between conductivity and stabilities for proton exchange membrane (PEM), polydopamine-modified sulfonated polyhedral oligomeric silsesquioxane (D-sPOSS) is facilely prepared and introduced into sulfonated poly(arylene ether sulfone) (SPAES) polymer matrix. The interaction between sulfonic acid groups of POSS (or of polymer chain) and basic groups of polydopamine not only can avoid the excessive swelling and maintain a high-level mechanical strength of the membrane, but also can enhance the proton hopping diffusion with uninterrupted trajectory. While the resulting D-sPOSS doped hybrid membranes exhibit prominent dimensional stability, oxidative stability and thermal stability in comparison with the sulfonated POSS (sPOSS) doped hybrid membranes and the plain SPAES membrane, the D-sPOSS doped hybrid membranes also possess superior proton conductivity, low methanol permeability and excellent single cell performance. Particularly, the proton conductivity of the hybrid membrane with 2 wt% content of D-sPOSS at 80 °C and 100% RH achieves 0.243 S cm−1, which is approximately 2 times higher than that of Nafion-117 membrane, 2.4 times higher than that of the pristine SPAES membrane and 1.5 times higher than that of the sPOSS doped hybrid membrane with 2 wt% loading under the same condition.