Dielectric elastomers with dual piezo-electrostatic response optimized through chemical design for electromechanical transducers

A new class of elastomers that simultaneously shows sensing, actuation and energy conversion functionalities is synthesized to meet the current requirements for electroactive materials. These new materials consist of a silicone network (polydimethylsiloxane-α,ω-diol crosslinked through chain ends) semi-interpenetrated with different percentages (2, 5, and 10 wt%) of polyimide derivatives stepwise modified by different strategies to improve the compatibility with the silicone core network. By addressing the right chemical pathway, the resulting semi-interpenetrated structures (S-IPNs) show noticeable dielectric permittivity, eps′ (up to 11), and breakdown strength, Ebd (up to 88 μm V−1), improvements as compared with the starting polymers (silicone with eps′ = 2.9 and Ebd = 38 μm V−1 and our best polyimide with eps′ = 6.2 and Ebd = 23 μm V−1). The S-IPNs with 10 wt% polyimide are able to gain energy up to 132 mJ cm−3 at 100% strain and up to 164 mJ cm−3 at maximum strain to develop large actuation strain (up to 8.7%) and show very good piezo-response (up to 44 pm V−1), making them highly suitable for cutting-edge electromechanical applications. For a better evaluation, S-IPNs are compared with one of the commercially available dielectric elastomers, most often used for this purpose