New DEA materials by organic modification of silicone and polyurethane networks
Dielectric elastomer actuators (DEAs) can be optimized by modifying the dielectric or mechanical properties of the electroactive polymer. In this work both properties were improved simultaneously by a simple process, the one-step film formation for polyurethane and silicone films. The silicone network contains polydimethylsiloxane (PDMS) chains, as well as cross-linker and grafted molecular dipoles in varying amounts. The process leads to films, which are homogenous down to the molecular level and show higher permittivities as well as reduced stiffnesses. The dipole modification of a new silicone leads to 40 times higher sensitivities, compared to the unmodified films. This new material reaches the sensitivity of the widely used acrylate elatomer VHB4905. A similar silicone modification was obtained by using smart fillers consisting of organic dipoles and additional groups realizing a high compatibility to the silicon network. Polyurethanes are alternative elastomers fo r DEAs which are compared with the silicones in important properties. Polyurethanes have an intrinsically high dielectric constant (above 7), which is based on the polar nature of the polyurethane fragments. Polyurethanes can be made in roll-to-roll process giving constant mechanical and electrical properties on a high level.