Enhancing Electromechanical Performance of Silicone Dielectric Elastomers Through Grafting of Hydroxyl Side Groups via Thiol‐Ene Reaction

ABSTRACT Dielectric elastomers (DEs) have shown great application potential in actuators, sensors, and soft robots. One key challenge for DEs is the ultra‐high voltages required to reach considerable strains due to the intrinsic low dielectric permittivity ( ε r ) of common elastomers. Here, silicone elastomers with tunable ε r are reported. In this case, poly(methylvinyl‐co‐dimethyl) siloxanes (PMVS) with various vinyl contents were first synthesized and grafted with polar hydroxyl groups and then crosslinked through a photochemical thiol‐ene reaction. Mechanical and dielectric properties as a function of the grafting ratio of dipole hydroxyl groups were systematically investigated. The grafted elastomers PMVS‐ME all show reduced Young's modulus ( Y ) (as low as 0.15 MPa) while increased ε r (as high as 5.87) compared to elastomers derived from pristine PMVS. Meanwhile, ε r of the grafted elastomers increases concurrently with the grafting ratio while Y shows no drastic variation. Among them, a single layer thin film actuator prepared from PMVS‐7‐ME demonstrates a remarkable electromechanical performance with a large area actuation strain of 21.8% under an electric field of 15.7 kV/mm without prestrain, which is 18.5 times that of its un‐grafted counterpart.