Rewritable Shape-Memory Polylactic Acid Fabricated by Thermo-Reversible Cross-Linking Based on the Diels-Alder Reaction

Abstract

We describe an intelligent biomass-plastic with a rewritable shape memory. First, we synthesized the network structure by cross-linking a polylactic acid (PLA) derivative with a diisocyanate linker. This structure performed much better as a shape memory than the inherent crystal domain. Then, we introduced the furan and maleimide functional groups, which form a thermo-reversible bonding based on Diels-Alder reaction, into the molecular structure of the PLA derivative. This bond works like a thermo-switch, providing two normally incompatible characteristics, namely shape memory and recyclability (rewritability). Currently, shape-memory plastics with cross-linked structures are not rewritable. When the thermo-switch is on at low temperatures, the bio-plastic ‘memorizes’ its original shape and can completely recover from a deformed shape. When the switch is turned off at high temperatures, the memory is erased and the plastic becomes rewritable.