Thermoplastic Polyurethane Dielectric Elastomers with High Actuated Strain and Good Mechanical Strength by Introducing Ester Group Grafted Polymethylvinylsiloxane

In this study, ester group grafted polymethylvinylsiloxane (PMVS-COCH3) with low elastic modulus (Y) and strong polarizability was synthesized and introduced into thermoplastic polyurethane (TPU) with good mechanical properties, high dielectric constant (epsilon(r)), and easy recyclability to prepare high performance dielectric elastomer (DE). PMVS-COCH3 with high grafting degree and low molecular weight was synthesized via the thiol-ene addition reaction and then was solution blended with TPU at low PMVS-COCH3/TPU blending ratios. The as-prepared blends still exhibit good mechanical properties and relatively high electrical breakdown strength because the low content of insulated PMVS-COCH3 phase is dispersed in continuous TPU phase. Both simulation and experimental results indicate that the ester groups on PMVS-COCH3 can form hydrogen bonds with TPU, leading to the disruption of C = O/N-H hydrogen bonding between TPU chains and thus enhancing dipole polarizability. Meanwhile, the PMVS-COCH3 dispersed phase acts as a soft polar filler in the TPU matrix, resulting in interfacial polarization and lower Y. Both the introduction of interfacial polarizability and the improvement of dipole polarizability largely increase the er of the blend. The actuated strain under the same electric field of the blends over that of pristine TPU is largely improved. At the blending ratio of 3/7, the actuated strain reaches 6.9% without any prestrains, which is the highest actuated strain among various previously reported TPU-based DEs.