Development of self-healing systems using encapsulated hydrophobic copolymers

Self-healing polymeric materials offer a promising solution as they reduce waste and extend the lifetime and functionality of end-products, contributing to sustainability and circular economy. Recent studies have been focused on combining intrinsic and extrinsic mechanisms to enhance healing performance under practical applications and develop more robust self-healing systems. Along this line, we developed a series of novel water-triggered self-healing polyurethane coatings through the encapsulation of hydrophobic n-butyl acrylate (BA)/glycidyl methacrylate (GMA) copolymers within polyurea microcapsules (MCs-Cp). Aqueous dispersions of these microcapsules were incorporated into two different types of waterborne polyurethane suspensions (PUs), namely polycarbonate (PU Cb ) and polyether (PU Et ), and the healing capability of the respective coatings was evaluated upon mechanical damage. The encapsulation of the organosoluble copolymers allowed their release upon rupture to the damaged area avoiding miscibility and compatibility challenges thereby ensuring their applicability even for water-based matrices such as the PUs. BA-rich copolymers (MCs-Cp30) demonstrated remarkable healing behavior in both matrices while GMA-rich copolymers (MCs-Cp70) showed limited efficiency unless used at high loadings. The comparison of self-healing performance with non-encapsulated copolymers revealed that the incorporation method (blended or encapsulated) strongly influences the dominant mechanism involved in the self-healing process. Overall, this work underlines the importance of fine-tuning multiple parameters such as copolymer composition, incorporation strategy and the nature of polyurethane matrices to achieve water-triggered self-healing systems.