Large increase in actuated strain of HNBR dielectric elastomer by controlling molecular interaction and dielectric filler network

Titanium dioxide (TiO₂) as the high-dielectric-constant filler and a nontoxic, renewable, and biodegradable epoxidized soybean oil (ESO) as the plasticizer were introduced into a hydrogenated nitrile-butadiene rubber (HNBR) matrix to form a dielectric elastomer (DE) with high actuated strain at a low electric field. The results showed that the actuated strain increased from 5.8% for pure HNBR to 13.6% for the 30 wt% ESO/(10 wt% TiO₂/HNBR) composite. The increase in actuated strain was due to the increased dielectric constant by the addition of TiO₂ and the weakened HNBR molecular interaction with the presence of ESO. In addition, the actuated strain of the 30 wt% ESO/(40 wt% TiO₂/HNBR) composite increased by almost 170% over that of the 40 wt% TiO₂/HNBR composite at 30 kV mm^-1, mainly because of the breaking up of the TiO₂ filler network by the addition of ESO, but the greatly weakened HNBR molecular interaction also played a role. The corresponding mechanism was proposed based on the interaction between HNBR and ESO. Furthermore, a relatively high tensile strength (about 6 MPa) was successfully achieved for the 30 wt% ESO/(40 wt% TiO₂/HNBR) composite, a big advantage for the practical application of a DE. Our work demonstrated that a filler/polymer DE with a relatively high actuated strain and tensile strength could be successfully achieved by controlling the molecular interaction and dielectric filler network, which provides a new idea for the preparation of high performance DEs.