Joule-heating-induced Multi-stage Reconfiguration in Dynamic Polymer Nanocomposites with Low Percolation Threshold

Diels-Alder-based polymers (DAP) possess the distinctive ability to transition from a solid to a liquid phase when thermally stimulated. In addition, DAPs have the capability of solid-state plasticity. While DAPs provide a new approach to self-healing, actuation, and additive manufacturing, their respective nanocomposites are an area of research currently lacking attention. Herein, we report DAP/branched carbon nanotubes (b-CNTs) nanocomposites with an extremely low percolation threshold of electrical conductivity and Joule-heating-induced spatiotemporal controlled shape reconfigurability. The unique behavior of solid to low viscosity fluid transitioning allows the liquified DAP to effectively wet and infiltrate b-CNTs, leading to unprecedented fine dispersion. The dispersion of the fillers is further stabilized and maintained by chemical bonding between DAP and filler and by the rapid “click” behavior of the DAP upon cooling, which serves to “lock” the dispersion in place. These nanocomposites can self-heal and be 3D printed to strongly interbonded multi-material constructs with mismatched properties. By selectively activating different parts of the hybrid constructs, spatiotemporal control of shape reconfiguration was achieved via Joule-heating-induced network plasticity.