PDMS-based DEA materials incorporating covalently attached softening agents

The use of polydimethylsiloxane (PDMS) materials for the processing of dielectric elastomer actuators (DEAs) is a field of research that gained much in interest particularly in recent years. Up to now a significant limitation to the application of DEAs is their high operation voltage in the range of several thousand volts. There are various approaches to face the challenge of lowering the required voltage and, thus, making these materials even more attractive for versatile applications. Promising concepts to overcome this restriction are the reduction of the film thickness, the increase of the permittivity or the lowering of the mechanical stiffness. The object of this work is to improve the actuation properties of PDMS-based DEA materials by decreasing their Youngs modulus. Therefore a symmetric low-molecular PDMS chains are incorporated covalently into the PDMS network. They form loose chain ends during the network formation and act as a kind of softener within the PDMS network. PDMS materials featuring a broad range of Youngs moduli Y were manufactured by varying the amount of the low-molecular PDMS additive between 0 wt% and 50 wt%. Our concept allows for the precise adjustment of the elastomers stiffness from about Y = 1.7 MPa (0 wt% softener) down to circa Y = 190 kPa (50 wt% softener) starting from one and the same set of basic components. The chemical, mechanical, electrical, and electromechanical properties of these novel materials are presented in detail.