Tailoring crosslinking networks to fabricate photocurable polyurethane acrylate (PUA) dielectric elastomer with balanced electromechanical performance

The trade-off between high dielectric permittivity and low Young's modulus is always a challenge for fabricating high-performance polyurethane acylate (PUA) based dielectric elastomers (DEs). In this work, networks with scattered crosslinking points (type-I) and domains of concentrated crosslinking points (type-II) that being prepared by different functional telechelic ends, were mainly introduced into the photocured PUA elastomers. As the increasing of chain length between crosslinking points (Ne), the Young's modulus (Y) of the PUA was restrained below 1.2 MPa while the elongation at break (EB) markedly increased. Compared to type-I network, a longer Ne in type-II network can lower the overall crosslinking density, which endows the materials with a relatively low Y (ca. 0.83 MPa) and a large EB (389%). In addition, the concentrated crosslinking points in type-II network enhanced the polarization effect between entangled long chains and crosslinking domains, which further upraised the dielectric permittivity of the elastomer up to 74.17 @ 103 Hz. The actuation strain of the PUA elastomer with type II network can reach utmost 13.88% @ 45.41 V∙μm−1 without any pre-strain. This work offers a new strategy to fabricate photocurable dielectric elastomer actuators (DEAs) with balanced electromechanical performance.