Silicone dielectric elastomer with improved actuated strain at low electric field and high self-healing efficiency by constructing supramolecular network

Abstract

Dielectric elastomers (DE) suffer from cracks and breaks during repeated cycles, thus a DE material with both high actuated strain (SA) and self-healing ability is highly desired. Herein, for the first time we report a self-healable silicone DE (SiR-SN) with large SA under low electric field by constructing supramolecular network assembled by hydrogen bonds and ionic bonds from two components involving carboxyl modified polymethylvinylsiloxane (PMS-g-COOH) and amino terminated polydimethylsiloxane (PDMS-NH2). The results show that as PMS-g-COOH content increases, the dielectric constant (ε′) of SiR-SN increases owing to an increase in dipole content whereas the elastic modulus (Y) decreases because of a decrease in crosslinking density, leading to the significantly increased SA at a given electric field. SiR-SN with 0.2/1 of the mass ratio of PMS-g-COOH to PDMS-NH2 shows much higher ε′ and SA than the commercial silicone DE. Interestingly, self-healing of SiR-SN at 80 °C leads to the re-formation of hydrogen bonds, and thus the recovery of network structure, whereas self-healing at 100 °C can lead to the conversion from hydrogen bonds into ionic ones, and thus the change of network structure. As a result, a self-healing efficiency of 115% in tensile strength and almost 100% in SA at a given electric field can be achieved after self-healing at 80 °C for 5 h, whereas an increase in Y and higher breakdown strength can be achieved after self-healing at 100 °C, which may sustain the repeated stress and prolong the service life. It is promising that this new self-healable silicone dielectric elastomer with large actuated strain under low electric field could be used especially in biological and medical fields.