Three-dimensional graphene coated shape memory polyurethane foam with fast responsive performance

Abstract

Shape memory polymers (SMPs) that change shapes as designed by external stimuli have become one of the most promising materials as actuators, sensors, and deployable devices. However, their practical applications have been greatly limited due to the long recovery time, which mainly originates from their low recovery stress, inherent viscoelastic hysteresis effect and low heat transmission efficiency. In this work, a novel method is proposed to prepare fast responsive reduced graphene oxide/shape memory polyurethane/polyurethane foam (rGO/SMPU/PU foam) shape memory composites. The elastic PU foam is used as framework to be coated with SMPU and rGO by solution polymerization and self-assembly methods, which result in rGO/SMPU/PU foam with three-dimensional networks. The rGO/SMPU/PU foam exhibits a fast response (of less than 1 s) under a large compressing deformation (80%) due to the synergistic effect of the high elasticity of PU foam, the short energy transmission distance of the SMPU layer and the high thermal conductivity of the rGO layer. Moreover, owing to the outstanding shape fixity ratio (R_f) and shape recovery ratio (R_r) of SMPU and the mechanical properties of PU foam, the rGO/SMPU/PU foam shows an excellent shape memory effect (more than 98% R_f and R_r at 80% strain) and cyclic stability simultaneously. Such rGO/SMPU/PU foam material demonstrates the potential applications in high-sensitivity temperature sensors and temperature codes.