Copper-Coated Liquid-Crystalline Elastomer via Bioinspired Polydopamine Adhesion and Electroless Deposition

Abstract

This study explores the functionalization of main-chain nematic elastomers with a conductive metallic surface layer using a polydopamine binder. Using a two-stage thiol-acrylate reaction, a programmed monodomain is achieved for thermoreversible actuation. A copper layer (≈155 nm) is deposited onto polymer samples using electroless deposition while the samples are in their elongated nematic state. Samples undergo 42% contraction when heated above the isotropic transition temperature. During the thermal cycle, buckling of the copper layer is seen in the direction perpendicular to contraction; however, transverse cracking occurs due to the large Poisson effect experienced during actuation. As a result, the electrical conductivity of the layer reduced quickly as a function of thermal cycling. However, samples do not show signs of delamination after 25 thermal cycles. These results demonstrate the ability to explore multifunctional liquid-crystalline composites using relatively facile synthesis, adhesion, and deposition techniques.

Keywords: actuation; electroless deposition; liquid crystalline elastomers; polydopamine adhesion.