1,2,3-Triazole-Functionalized Polysulfone Synthesis and Application in Proton Exchange Membranes for Low and High Temperature PEMFC

Abstract

The 1,2,3-triazole functionality demonstrates high chemical stability towards severe hydrolytic, oxidizing, and reducing conditions, even at elevated temperatures. Furthermore together with aromatic character and ability to form hydrogen bonds, it is reported to possess anti-oxidant properties1. All these features make polymers functionalized with 1,2,3-triazole of interest in proton exchange membranes as reinforcement or matrix for application in low and high temperature fuel cells. We will describe a fast and high-yielding synthesis of 1,2,3-triazole functionalized polysulfone through microwave-assisted copper-catalyzed azide-alkyne cycloaddition (CuAAC) click chemistry. Polymers with various degrees of substitution of the side-chain functionality of 1,4-substituted 1,2,3-triazole with alkyl and aryl pendant structures were prepared and characterized to assess the completeness of the reaction. The thermal and thermo-chemical properties of the modified polymers were also characterized. In one approach, cast membranes of 1,2,3-triazole functionalized polysulfone were doped with phosphoric acid for application in HT-PEMFC and their properties compared with conventional polybenzimidazole based systems. These novel membranes presented promising performance with high proton conductivity in anhydrous conditions and satisfactorily high elastic modulus2. In another strategy with targeted low temperature PEMFC applications, nanocomposite membranes were prepared based on functionalized polysulfone and a perfluorosulfonic acid ionomer. As already evidenced for PBI-PFSA composites3, the specific interaction between the basic triazole functionalized polymer and the acidic ionomer lead to electrolytes with improved mechanical properties and without significant loss in proton conductivity. 1. J. Totobenazara and A. J. Burke, Tetrahedron Lett., 56, 2853–2859 (2015). 2. R. Sood, A. Donnadio, S. Giancola, A. Kreisz, D.J. Jones, S. Cavaliere, ACS Appl. Mater. Interf., in press.