Polyethylene-block-polyacrylate based block copolymers for high ionic conductivity polymer electrolytes*

Block copolymer-based polymer electrolytes are a unique class of electrolytes due to their ability to harness the properties of different polymer blocks. Typically, block copolymer electrolytes combine the mechanical properties of a high glass transition temperature (Tg) block and the ion-conducting properties of a low Tg block. The ionic conductivity of such systems is usually low due to the restricted segmental mobility of the glassy block. Here, we develop and study the polyethylene-block-polyacrylate based block copolymers doped with ionic liquids, and observe a significantly high ionic conductivity of ~1 mS/cm at room temperature. The ionic conductivity remains high over a broad temperature range. This high ionic conductivity is enabled by the low Tg of both blocks. Furthermore, we study the mechanical properties of these polymers and find them to be elastic solids. We study the role of interfacial width and segmental relaxations to understand the high ionic conductivity of these polymer electrolytes. We expect these polymers to serve as high ionic conductivity solid-state electrolytes with high temperature and mechanical stability.