Shape memory characteristics of thermadapt polyurethane incorporated with two structurally distinctive aliphatic isocyanates

Shape memory polymers (SMPs) have the ability to fix a temporarily deformed shape and recover its original shape. Owing to the shape memory effect, SMPs have been widely investigated for applications in various industries. Shape memory polyurethane (SMPU) is a common SMP material which possesses good shape memory and mechanical properties, and it is mostly focused on the thermoplastic SMPU. In this study, we introduced two structurally different aliphatic isocyanates, hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI), to fabricate thermadapt SMPUs. The formation of the hard segment in the SMPU matrix was tunable by varying the IPDI mol% of the total isocyanate content. The shape memory characteristics were strongly related to the contents of the hard segments and the crystallinity of the thermadapt SMPU. Owing to the transcarbamoylation reaction between the carbamate moieties, the network of our thermadapt SMPU can be rearranged to redefine its permanent shape, and the redefined shape can also be recovered from the temporarily deformed state.