Alkoxyamine with reduced homolysis temperature and its application in repeated autonomous self-healing of stiff polymers

Covalently bonded stiff polyurethane capable of autonomous intrinsic self-healing was synthesized by introducing a specially designed alkoxyamine unit and a soft segment with sub-ambient T_g and high crystallinity into the main chain. The impact and the subsequent healing tests indicated that the polymer can be repeatedly re-bonded at room temperature as characterized by the recovery of impact strengths. The healing process does not need external stimulus and is insensitive to air due to rapid fission and recombination equilibrium of C–ON bonds. Careful investigation about the healing mechanism suggests that inter-diffusion of broken chain fragments across the cracked faces and dynamic reaction of reversible C–ON bonds in the alkoxyamine unit are responsible for crack remending. Owing to the easy tunability of structures of both alkoxyamine and polyurethane, various stiff polymers with similar remendability would be produced according to the principle proposed here in this work.