Two-Way Shape Memory Polymer from a Crosslinked Periodic Dynamic Network

We recently reported a high-performance one-way shape memory polymer that includes periodic dynamic bonds and exhibits supramolecular nanostructures under stain. The strategy of incorporating periodic dynamic bonds into the polymer greatly enhances shape memory material properties such as energy density and stretchability. The strain-induced supramolecular nanostructures are stable at room temperature and trap the chains in an elongated state. Upon heating, the supramolecular nanostructures become unstable, causing stretched chains to quickly contract. While this material outperforms other one-way shape memory polymers, its practical applications are hindered by the need for the mechanical re-programming after each triggering. Two-way shape memory polymer material is very desirable in many applications especially in the field of biomedical, soft robotics, and actuators. Thus, we incorporate thermal and light initiated crosslinkers into the materials to try and achieve reversible actuation upon change in temperature. Polymer chains will be aligned under strain; at the same time, dynamic bonds will hold the aligned chains in place and crosslinkers will permanently record chain conformation at the stretched state. There were already various realizations of two-way shape memory materials by employing semi-crystalline polymers and liquid crystal networks. We aim to make two-way shape memory polymer from a new approach by using this periodic dynamic network.