Synthesis of midblock-sulfonated triblock copolymers

A well-defined midblock-sulfonated PHMA-bPS-b-PHMA and PFMA-b-PS-b-PFMA has been synthesized using ATRP methodology to prepare the triblock copolymers in two steps using a difunctional initiator with subsequent sulfonation. Polymers with ionic groups serve the critical functions of water and ion transport in applications such as fuel cells and water treatment membranes and can be engineered to tune the permselectivity of chemical protection barriers. PHMA-b-PS-b-PHMA and PFMA-b-PS-b-PFMA were sulfonated using acetyl sulfate in 1,2-dichloroethane. The modular ATRP scheme used in this work enables a new series of sulfonated polymers to be explored by systematically varying both the sulfonation level of the center block as well as the reinforcing properties of the outer hydrophobic blocks. The addition of fluorine to the outer blocks did not enhance the phase development or proton conductivity of these materials due to the poor self-assembly of the fluorinated end blocks compared to more flexible alkyl-containing methane late blocks.