Structure-Dependent Ionic Conductivity in Poly(Ionic Liquid)-b-Poly(methyl methacrylate)-Grafted Nanoparticles

Abstract

In this study, we present a hybrid electrolyte design based on single-ion conducting block copolymer-grafted nanoparticles with superior ionic conductivity. By grafting poly(methyl methacrylate) (PMMA) as a neutral core layer on nanoparticles and sequentially polymerizing poly(1-vinylimidazolium-bistriflimide) (PVIm-TFSI) as the charged corona, we achieve well-defined copolymer hybrids with controlled charge gradient and particle dispersion. Three copolymer systems with different PVIm-TFSI chain lengths are analyzed, revealing that longer chains (430 kDa) enhance both particle dispersion and molar conductivity by forming well-connected corona layers, while other shorter chains (170 and 97 kDa) result in sparse strings and aggregated structures, respectively, and they exhibit lower conductivity. Potentiostatic polarization experiments show that the PVIM-TFSI chains rearrange and polarize irreversibly under applied electric fieds and this effect enhances ion conductivity. The polarization response of the copolymer hybrid indicates that PMMA grafts limit the polarization, and the PVIm-TFSI rearrangement in the copolymer occurs at long times. These findings underscore the critical importance of polymer hybrid structures in optimizing ionic conductivity, providing practical insights for applications in electroactive actuators, biomedical devices, wearable sensors, and electrochemical devices, such as capacitors and batteries.