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.
Highlights
Smart polymer actuators are lightweight and flexible materials with high moldability and are expected to be alternatives to conventional driving devices made up of many elements
The viscosity of the cast solution decreased from 11.00 Pa∙S (PDMS/CR-U (A100/T0)) to 0.27 (PDMS/CR-U (A0/T100)) with the THF content
PDMS/CR-U (A0/T100) composites showed an asymmetric cross-sectional structure in which CR-U large spheres dispersed in the PDMS matrix with a skin layer on one surface side
Summary
Smart polymer actuators are lightweight and flexible materials with high moldability and are expected to be alternatives to conventional driving devices made up of many elements. Wiranata et al investigated a simple and reliable fabrication method for polydimethylsiloxane (PDMS) dielectric elastomer actuators using carbon nanotube powder electrode [6]. The composite films prepared with THF as solvent showed bending deformation behavior in response to an electric field, but those with ACT as solvent did none. From the space-charge distribution analysis, a charge accumulation was observed in the skin layer of the film made with THF, and the repulsion of this accumulated charge was suggested to have caused bending deformation It has to be clarified why the composite structure from ACT is electrically inactive, and the non-uniform dispersion structure from THF is electrically active as an actuator. The mechanism of the morphology formation and its effect on the actuator function were discussed
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