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 (∈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 PMVSCOCH3/ 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 ∈r 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.