Enabling large actuated strain at low electric field by grafting cyanoester dipoles onto a poly(styrene-b-butadiene-b-styrene) elastomer using thiol-ene click chemistry

A dielectric elastomer can undergo a large deformation when it is subjected to an applied electric field. As a result, it finds potential usage in artificial muscles, soft robotics, and medical devices. However, current dielectric elastomers suffer from low dielectric constants (e.g., <4.5). Grafting highly dipolar groups onto a dielectric elastomer has been proved to be an efficient method to improve the dielectric constant and thus the electroactuation property. However, grafting a side chain bearing two or more dipolar groups onto the polymer main chain has not been explored in the past. In this work, we grafted cyanoester groups onto a poly (styrene -b butadiene -b-styrene) (SBS) elastomer to improve its dielectric constant and actuation performance using the thiol-ene click reaction. A series of new dielectric elastomers with different grafting densities were obtained with excellent actuation properties: a dielectric constant up to 11.6 at 10(5) Hz and a large actuation strain of 9% at a low field of 13.9 MV/m. This work provides us a new and effective strategy to improve the performance of dielectric elastomers.