A supramolecular silicone dielectric elastomer with a high dielectric constant and fast and highly efficient self-healing under mild conditions

Abstract

Dielectric elastomer (DE) materials suffer from high driving voltages and cracks or breaks during repetitive actuation cycles. New DE materials with a simultaneous high dielectric constant (ε′) and fast and efficient self-healing ability are in urgent need. Herein, we report a self-healable silicone DE by constructing a supramolecular network assembled by coordination bonds between carboxylated polymethylvinylsiloxane (PMVS-COOH) and FeCl₃ as well as hydrogen bonds between carboxyl groups through introducing FeCl₃ into PMVS-COOH. Both experimental results and density functional theory indicate that the Fe³⁺/COO⁻ complex is formed and can further aggregate into clusters, which can simultaneously realize the crosslinking of PMVS-COOH and introduce interfacial polarization. Interestingly, the interfacial polarization largely increases with increasing FeCl₃ content and FeCl₃ can promote dipole polarization by disrupting some of the hydrogen bonds and releasing carboxyl groups when the FeCl₃ content is higher than 5%, leading to a significant enhancement in ε′. The as-prepared PMVS-COOH/FeCl₃ (SiR-Fe) DE with 8% FeCl₃ shows comparatively high ε′ (12.3 at 10⁴ Hz), much higher than that of the commercial silicone DE (∼2.7) or PMVS-COOH (6.1). Meanwhile, a self-healing efficiency of 99% in tensile strength and 100% in tensile toughness are achieved for SiR-Fe with 8% FeCl₃ after being treated for 1 h at room temperature. This is ascribed to the high chain mobility of SiR-Fe and the robust supramolecular dynamic network resulting from the combination of coordination bonds and hydrogen bonds. It is demonstrated that SiR-Fe can be effectively used as a dielectric elastomer sensor. And it is promising that this highly efficient self-healable SiR-Fe DE with high ε′ finds applications especially in biological and medical fields.