Millisecond Response of Shape Memory Polymer Nanocomposite Aerogel Powered by Stretchable Graphene Framework.

Shape memory polymers (SMPs) change shapes as-designed through altering the chain segment movement by external stimuli, promising wide uses in actuator, sensor, drug delivery, deployable devices. However, the recovery speed of SMPs is still far slower than the benchmark shape memory alloys (SMAs), originating from their intrinsic poor heat transport and retarded viscoelasticity of polymer chains. In this work, monolithic nanocomposite aerogels composed of bi-continuous graphene and SMP networks are designed to promote the recovery time of SMP composites to a record value of 50 milliseconds, comparable to SMA case. The integration of stretchable graphene framework as fast energy transformation grid with ultrathin polycaprolactone (PCL) nanofilms (tunable in 2.5-60 nm) enables the rapid phase transition of SMP under electrical stimulation. The graphene-SMP nanocomposite aerogels, with density of ~10 mg cm-3, exhibit fast response (175±40 mm s-1), large deformation (~100%) and wide response bandwidth (0.1~20 Hz). The ultrafast response of SMP nanocomposite aerogels confers extensive uses in sensitive fuses, micro-oscillators, artificial muscles, actuators and soft robotics. The design of bi-continuous ultralight aerogel can be extended to fabricate multifunctional and multi-responsive hybrid materials and devices.