Enhancing the Tensile Behavior of HTCE Films Using β‐Hydroxyethylurea as Chain Extender via a One‐Step Solvent‐Free Strategy
Cong Zhu, Tianqi Li, Wenhao Liu, Teng Wang, Mengjing An, Yunjun LuoABSTRACT
Multi‐hydrogen bond chain extenders are widely used to improve the mechanical properties of polyurethane elastomers, but their incorporation often requires polar organic solvents, limiting solvent‐free processing and large‐scale production. Herein, a one‐step solvent‐free strategy was developed by dispersing β‐hydroxyethylurea (2‐Hu) in low‐molecular‐weight polyethylene glycol (PEG) to construct a mixed chain‐extending system for hydroxyl‐terminated polycaprolactone polyether (HTCE)‐based polyurethane. Fourier transform infrared spectroscopy (FTIR) confirmed successful polyurethane formation, while small‐angle x‐ray scattering (SAXS) and low‐field nuclear magnetic resonance (LFNMR) revealed that 2‐Hu enhanced hydrogen bonding, promoted hard‐domain aggregation, and strengthened microphase separation. Density functional theory (DFT) calculations demonstrated stronger intermolecular hydrogen‐bonding interactions for 2‐Hu than for 1,4‐butanediol (BDO). Consequently, the crosslink density increased from 3.06 × 10 − 4 to 3.41 × 10 − 4 mol·mL − 1 , and the tensile strength improved from 0.86 to 1.00 MPa. Moreover, the 2‐Hu‐containing polyurethane exhibited complete elastic recovery after 10 loading–unloading cycles, demonstrating excellent reversible deformation enabled by the dynamic hydrogen bonding network. This solvent‐free strategy provides a simple and scalable route for preparing polyurethane elastomers containing multi‐hydrogen bond interactions.