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 ( 1 H 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.