Solvent Composition Effect on PDMS Composite Dielectric Elastomer Actuator

Abstract

Polydimethylsiloxane (PDMS) is inactive to electric fields, but when combined with ferroelectric cyanoethyl sucrose (CR-U), it becomes an electrically active actuator material. The PDMS/CR-U composites were prepared by casting method using tetrahydrofuran (THF) and acetone (ACT) as solvents. The effect of a mixed solvent composition was investigated. The viscosity of the PDMS/CR-U/solvent solution decreased as the THF composition increased. The composite film obtained by evaporation of the solvent and cross-linkage of PDMS showed a phase-separated structure. Spherical CR-U dispersed in the PDMS matrix with a skin layer on one surface side. Electrical resistance, dielectric constant, space-charge distribution, and electrically induced bending deformation behavior were investigated for these composite films. The composite films prepared from a THF-rich solvent exhibited lower surface resistivity than those prepared from a THF-poor solvent. Applying an electric field to the composite film resulted in an asymmetric space-charge distribution with charge accumulation in the skin layer. THF content decreased the viscosity of the solution, meaning the decrease of the apparent size of PDMS chain aggregates. It allows the dispersion of CR-U in the PDMS matrix and also results in the decline of resistivity, the increase of permittivity, and the increase of charge injection. The results explained the structure formation of the composite film and the electric field response as an actuator. A casting solvent of THF content of 87.5 wt% or more is essential for the function of the PDMS/CR-U composite.