Properties and mechanism of two-way shape memory polyurethane composite under stress-free condition

Two-way shape memory polymer can exhibit reversible shape transformation, which shows great application potential as a smart material. It is necessary to develop new reversible shape memory composite systems to achieve accurate and wide-range control of two-way shape memory behavior, especially under the condition of no external force. A chemically cross-linked two-component crystalline block copolymer was prepared, and the mechanism of two-way shape memory behavior under stress-free condition of the material was revealed. The results show that both the crystallization and thermal property of PLA/PCL-PU can be significantly changed by adjusting the proportion between PLA and PCL, and the dosage of crosslinking agent, and thus the shape memory property of PLA/PCL-PU can be regulated accordingly. The two-way shape recovery rate of the material can reach to 41.11%. This work provides a facile strategy to fabricate a biodegradable thermally induced two-way shape memory material under the stress-free condition with tunable shape memory properties.