Sustainable Bio-Inspired Anisotropic Proton Exchange Membranes by Self-Assembly of Bio-Based Solid Polymer Electrolytes

A new class of bio-inspired polymer membranes was elaborated using block copolymers BCP self-assembly. The BCPs are based on a proton conductive block, i.e. sulfonated poly pentafluorostyrene (sPPFS), paired with a highly hydrophobic monomers derived from biomass, i.e. terpen acrylate. With either cyclic ThymylAcrylate TA or linear TetraHydroGeraniolAcrylate THGA, both blocks with high or low glass transition temperatures Tg values were tailored and evaluated for film formation. PTA-b-PPFS or (PTA-s-PTHGA)-b-PFFS copolymers were first synthesized via nitroxide-mediated polymerization NMP, followed by a post-introduction of sulfonated groups through para fluoro/thiol reaction to introduce the ionic groups. The copolymer composition, i.e. various PFS contents, as well as the addition of an ionic crosslinker PBI influence the membrane morphologies and properties, i.e. mechanical strength, water uptake or conductivity. The immiscibility between the sPPFS and PolyTerpenAcrylates blocks was used as advantage to generate anisotropic segregated domains by creating bio-inspired nano-channels for proton conduction to further boost the through-plane membrane conductivity. Herein, using the bio-inspired strategy, more sustainable anisotropic membranes with up to 50 wt% of renewable bio-sourced carbon and only 15 wt% of Fluorine were tailored with similar features of benchmarked isotropic perfluorinated membranes.