Synthesis and Physico-Chemical characterization of anion-exchange polymeric materials for electrochemical applications

In the last few years a number of new anion-exchange polymers have been developed, offering the possibility of assembling Membrane Electrode Assemblies (MEAs) to develop Anion-exchange Membrane Fuel Cells (AMFCs) and Anion-exchange Membrane-based Electrolyzers (AMEs). The current technologies of Anion Exchange Materials (AMs) for electrochemical application shows several limitations relate to the possibility of obtaining a reasonable low cost membrane having: high ionic conductivity, chemical stability in strong alkaline media, low permeability, low water swelling and good mechanical properties. The purpose of this study was to develop and characterize AMs based on Styrene–butadiene–styrene (SBS) copolymer, a thermoplastic material with a block structure widely employed in the rubber industry. In the present work is reported a controlled radical functionalization, initiated by benzoyl peroxide (BPO), of SBS with 4-vinylbenzyl chloride (VBC). The resulting thermoplastic polymer was converted into an anion exchange membrane via quaternization reaction with aliphatic amines, such as trimethylamine or 1,4-diazabicyclo[2.2.2]octane (DABCO). Electrochemical properties of these materials were measured and correlated with synthetic parameters. Correlations between transport properties and synthetic parameters were explained in terms of Cluster-Network morphological model. Performance of the synthesized SBS-based AMs were then evaluated in a working AMFC and compared with commercial materials. Diagnostics on AMFCs, by means of electrochemical impedance spectroscopy (EIS), were performed in order to evaluate measured performances.