The Phase Structure and Properties of Polyurethanes Based on Polycaprolactone Block Copolymers Dangling Side-Chain PEG

Polycaprolactone (PCL)-based polyurethanes are widely used in biomedical applications. A common strategy to enhance their performance is modification with hydrophilic polyethylene glycol (PEG). Moreover, side-chain PEG incorporation enhances molecular mobility, thereby promoting phase separation and enabling the tuning of polyurethane properties from a phase structure perspective. This study compared the effects of side-chain PEG located in the soft segment versus hard segment on the structure and properties of polyurethanes. We designed and synthesized a series of PCL copolymer soft segments containing side-chain PEG, using them to prepare the corresponding polyurethanes. In this structure, the distanced side-chain PEG from the urethane bond reduced interference with hard segment aggregation, promoting a more continuous hard phase and leading to enhanced overall performance. Further research revealed that these polyurethanes exhibit both one- and two-way shape memory properties driven by the human body temperature (37 °C). This work expands the applicability of PCL-based polyurethanes in the biomedical field.