Heat driven self-healing isocyanate-based crosslinked three-arm Star-shaped polyglycolide based on dynamic transesterification

Dynamic combinatorial chemistry (DCC) involves reversible reactions which can be controlled by thermodynamics method. Transesterification is one of the most widely explored DCC reactions. In this paper, transesterification was used to synthesize self-healing network. First, a three-arm star-shaped hydroxyl-terminated polyglycolide (HTPG) was fabricated though the ring-opening polymerization (ROP) of glycolide by using triethanolamine (TEA) as initiator and tetrabutyl titanate (TBT) as catalyst. Then the self-healing network i.e. isocyanate-based crosslinked star-shaped polyglycolide (ICSPG) was prepared through the crosslink between hexamethylene diisocyanate trimer (HDIT) and HTPG. In order to explore the mechanism of the self-healing, a polyurethane based on a tri-functional polyether polyol (PPPU) was synthesized. The structures of HTPG, ICSPG and PPPU were characterized by fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (H-1 NMR). The mechanical properties and self-healing properties were characterized by dynamic mechanical thermal analysis (DMTA) and polarizing optical microscopy (POM). And the welding test was used to further characterize the self-healing properties of ICSPG. It was found that mechanical recovery is about 70%. The POM results showed that ICSPG exhibited self-healing properties at high temperature.