Polyethylenimine‐Based Shape Memory Polyurethane with Low Transition Temperature and Excellent Memory Performance

Abstract Flexible shape memory polyurethanes (SMPUs) are the favorable candidates as a coating or substrate for wearable smart textiles, electronics, and biomedical applications. However, conventional SMPUs (e.g., 1,4 butanediol (BDO)‐based) are not suitable in these applications due to high rigidity, poor mechanical properties, low shape recovery, and high transition temperature. Herein, a polyethylenimine (PEI)‐based SMPU with low transition temperature and tailored properties are reported. The synthesized SMPU are characterized, and their properties are compared with BDO‐SMPUs. The chemical structure of PEI is explored to improve thermal and mechanical properties and to assess their effect on shape memory behavior. The bulky nature of PEI plays a critical role in lowering transition temperature and introduces flexibility in the structure at room temperature. A drop in Young's modulus is found from 13.6 MPa in BDO‐SMPU to 6.2 MPa in PEI‐SMPU. Simultaneously, tensile strength is increased from 3.77 MPa in BDO‐SMPU to 11.85 MPa in PEI‐SMPU. Owing to the improved mechanical properties in PEI‐SMPU, 100% shape recovery is observed, which displays a reproducible trend in ten repetitive cycles due to the presence of reversible physical crosslinks. Therefore, it is envisioned that this can serve as a potential shape memory material in smart wearable technologies.