Recyclable and Self-Healing Polyurethane Vitrimers via Dynamic Bonding with In-Situ Polymerized PHPMA

The development of lightweight, durable, and recyclable polymer materials with self-healing properties remains a significant challenge in materials science, particularly for applications requiring extended service life and sustainability. This study addresses these challenges by introducing a novel thermoplastic polyurethane (PU)-based vitrimer system, synthesized via in situ polymerization using hydroxypropyl methacrylate (HPMA)-hydroxyl precursor and Tin(II) 2-ethylhexanoate (Sn(Oct)₂)-catalyst. Unlike conventional vitrimer systems, this approach leverages dynamic bond exchange reactions without the formation of new covalent bonds, ensuring efficient stress relaxation and recyclability. Notably, the PU-PHPMA-73-Sn(Oct)₂ composition exhibited superior mechanical properties and maintained its performance after three recycling cycles, highlighting its durability and circular potential. Stress relaxation studies further confirmed the temperature-dependent bond exchange kinetics, with activation energies of 122.8±8.1 kJ/mol and 21.6±2.4 kJ/mol for different compositions, correlating with the hydroxyl content. The vitrimer also demonstrated an 88.5 % self-healing efficiency, showcasing its ability to autonomously repair damage and extend material lifespan. This lightweight, self-healing, thermally stable, and recyclable vitrimer system presents significant advancements over traditional PU-based materials, with promising applications in medical devices, automotive components, adhesives, and advanced coatings, particularly where longevity and sustainability are critical.