High‐efficiency shape memory copolymers of polycaprolactone/thermoplastic polyurethane fabricated via in situ ring‐opening polymerization

Abstract

AbstractShape memory blends of polycaprolactone/thermoplastic polyurethane (PCL/TPU) were prepared by in situ ring‐opening polymerization (ROP) of ε‐caprolactone (CL) and thermoplastic polyurethane (TPU). Fourier infrared spectrometer and 1H‐NMR were used to characterize the chemical structure of PCL/TPU copolymers. The results show that TPU has been involved in the ROP of CL, leading to the formation of copolymers with homogeneous morphologies. Besides, pure PCL and all the blends exhibit an excellent shape fixation ratio of 100%, due to their high crystallinity. When a small amount of TPU is introduced, the crystallinity of PCL decreases, and as a result, the shape recovery ratio of the copolymer is enhanced compared with pure PCL. However, with the increased loading of TPU, the content of PCL as the reversible phase decreases and the storage modulus of the PCL/TPU blend declines, so the driving force for the blends to return from the temporary shape to the initial shape becomes smaller, leading to a decrease in the shape recovery ratio. Notably, when the amount of TPU is only 5%, the shape recovery ratio of the blend could reach 83.3%, which is 26% higher than that of pure PCL, and meanwhile, the tensile strength of the blend decreases slightly. This study provides a new strategy for the design of shape‐memory materials with high shape‐memory properties.