Proton‐conducting polyhedral oligosilsesquioxane nanoadditives for sulfonated polyphenylsulfone hydrogen fuel cell proton exchange membranes

Abstract

Abstract Three novel polyhedral oligosilsesquioxane (POSS) nanofillers functionalized with proton‐conducting sulfonic acid groups, mixed sulfonic acid and alkyl groups, and phosphonic acid groups were synthesized, characterized by IR, 1 H and 13 C NMR, and MALDI‐TOF MS, and formulated into sulfonated polyphenylsulfone (S‐PPSU) carrier polymers. High quality films were cast from 1‐methyl‐2‐pyrrolidinone (NMP), and through‐plane and in‐plane proton conductivity, mechanical properties, water uptake, dimensional stability, and leaching behavior were measured to assess their suitability for use as hydrogen fuel cell proton exchange membranes. Various nanofiller loadings and S‐PPSU sulfonation levels were studied. The morphologies of the composite membranes were determined by TEM and SEM X‐ray mapping. When compared with Nafion®, the POSS‐S‐PPSU composite membranes exhibited comparable proton conductivity in combination with superior dimensional stability, heat resistance, and mechanical strength. When compared with control S‐PPSU membranes, the composite POSS‐S‐PPSU membranes exhibited superior conductivity, comparable dimensional stability, and slightly decreased mechanical strength. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008