Role of Backbone Segmental Dynamics and Water Concentration on Ion Transport in Hydrated Anion-Conducting Polyelectrolytes

Understanding the roles of chain dynamics and water absorption in ion transport is essential for designing effective hydrated polyelectrolytes for electrochemical systems. We synthesized and characterized a series of crosslinked poly (2-vinylpyridine) (P2VP)-based polyelectrolytes with varying degrees of crosslinking. By incorporating varying amounts of crosslinkable 4-vinylbenzocyclobutene (BCB) units, followed by thermal crosslinking and subsequent methylation, we controlled the degree of crosslinking in P2VP-based polyelectrolytes to modulate the segmental dynamics of the polymer chains. Our results indicate that increasing the degree of crosslinking reduces water absorption and swelling. Although higher crosslinking levels decrease ionic conductivity, the segmental dynamics of the polymer backbone show minimal influence on ion transport. Molecular Dynamics results show that the diffusivity of iodide ion is directly correlated with water concentration in crosslinked P2VP-based polyelectrolytes and a uniform iodide ion diffusivity across all degrees of crosslinking in P2VP was observed when maintaining constant water concentration. This study not only provides a novel platform for exploring the structure-property relationships of polyelectrolytes, but also offers insights to guide future advances in polyelectrolytes for use in fuel cells and water electrolyzers.