Designing polymers with controlled nanoscale morphologies and scalable synthesis is of great interest in the development of fluorine-free alternative materials for proton exchange membranes in fuel cells. This study focuses on a precise, ring-opening polymerized polymer that self-assembles into hydrophilic and hydrophobic domains. The hydrophilic domains serve as pathways for rapid proton conductivity in the hydrated state. These polymers consist of a polyethylene backbone with a sulfonated phenyl group pendant on every 5<sup>th</sup> carbon, p5PhSA, with a high ion-exchange capacity of 4.2mmol/g. The morphology and proton transport of p5PhSA are evaluated under hydrated conditions using in situ X-ray scattering and electrochemical impedance spectroscopy techniques. Atomistic molecular dynamics (MD) simulations are also used to elucidate the structure and characterize the water dynamics. At 40°C and 95% relative humidity, the proton conductivity of p5PhSA is 0.28 S/cm, exceeding that of Nafion (the industry standard) at the same conditions. The MD simulations show that there is strong nanophase separation between the percolated hydrophilic and hydrophobic domains over a wide range of water contents. These hydrophilic channels are what facilitates the rapid proton transport in p5PhSA and demonstrate the potential of precise polymers as effective proton exchange membranes.

Proton transport and morphology in a hydrated precise sulfophenylated polyethylene

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.