(371a) Synthesis of New Semicrystalline Block Co-Polymer Membranes for Artificial Photosynthesis

The dual requirements of product gas separation and high ion conductivity in a solar fuel generator present unique design opportunities for polymer membranes. For this application, the role of the membrane is centered on controlling transport of products and reactants of the reactions responsible for solar fuel generation. New synthetic efforts have focused on improving mechanical properties and decreasing product crossover while retaining the processability of the parent polymeric material. In order to incorporate all of the necessary properties for a solar fuel membrane, our efforts have focused on synthesizing block co-polymer membranes that satisfy various requirements with chemically distinct blocks. We used a combination of ring opening metathesis polymerization (ROMP) and anionic ring opening polymerization (AROP) to synthesize triblock copolymers consisting of a semi-crystalline poly(ethylene) (PE) midblock for low gas crossover and good mechanical properties.  We have also explored amine and imidazolium based ion-conducting polyether end-blocks due to their versatile chemical functionality and flexibility. The use of AROP allowed us to precisely control the length of our conductive end blocks. The conductivity and gas permeability of these membranes will be discussed as a function of the mole fraction of the functional end blocks.