Interpenetrating networks of elastomers exhibiting 300% electrically-induced area strain

Mechanical prestrain is generally required for most electroelastomers to obtain high electromechanical strain and high elastic energy density. However, prestrain can cause several serious problems, including a large performance gap between the active materials and packaged actuators, instability at interfaces between the elastomer and prestrain-supporting structure, and stress relaxation. Difunctional and trifunctional liquid additives were introduced into 400% biaxially prestrained acrylic films and subsequently cured to form the second elastomeric network. The goal of this research was to determine the effect of different functional additives and concentrations on the microstructure, the mechanical properties, and the actuation of composite films. In the as-obtained interpenetrating polymer networks (IPNs), the additive network can effectively support the prestrain of the acrylic films and as a result, eliminate the external prestrain-supporting structure. However, the large amount of additive used to completely preserve prestrain was found to make the films too stiff, causing damage to IPN composite films. Furthermore, the interpenetrating network formed from a trifunctional monomer is more effective than that formed from a difunctional monomer in supporting the high tension of the VHB network. This high efficiency trifunctional additive leads to the enhancement of the breakdown field, due to less damage on the microstructure. The IPN composite films without external prestrain exhibit electrically-induced strains up to 300% in area, comparable to those of VHB 4910 films under high prestrain conditions.