Preparation and characterization of transparent polymeric electrolyte containing ionic liquid with long alkyl chains for electroactive polymers

Abstract

Transparent polymer electrolytes are important components in fabricating transparent ionic electroactive polymers (iEAPs). Ionic liquids (ILs) have been widely used as the ionic source for polymeric electrolytes due to their broad electrochemical window and non-volatility. ILs with long alkyl chains, such as 1-decyl-3-methylimidazolium chloride (C₁₀MIMCl), may reduce the crystallinity and allow higher transparency of polymer electrolytes. However, it has been reported that the strong ionic interaction in C₁₀MIMCl hinders the migration of ions and thus affects the electromechanical deformation of polymer/C₁₀MIMCl electrolytes. In our work, iEAPs made of PVA/C₁₀MIMCl electrolytes were fabricated with high optical transparency. The poor electromechanical deformation of the electrolyte containing the long alkyl chain IL has been overcome. The hydrogen bonding formed between the IL cations (C₁₀MIM⁺) and the polymer chains enabled the Cl⁻-controlled deformation. In addition, the hygroscopicity of IL allows for a higher degree of ion dissociation while the absorbed water widens the migration channels for Cl⁻, and the combined effect has significantly improved the actuation performance of the iEAPs. We also found that the deformation of PVA/C₁₀MIMCl iEAPs increases with higher water content in the electrolyte, achieving the highest average bending curvature of 40.53 ± 0.21 m⁻¹ under 2 V DC. Compared with the iEAPs using the same IL reported in the literature, the actuation response of the iEAP containing C₁₀MIMCl is improved.