Design of epoxidized natural rubber/poly(lipoic acid) elastomer with fast and efficient self-healing under a mild temperature

Most of the dynamic covalent bonds (DCBs) for self-healing rubber must be activated at relatively high temperatures due to the requirement of high energy during the exchange of dynamic bonds, which may lead to unexpected degradation or excessive crosslinking of rubber. Herein, we designed and fabricated a highly stretchable, self-healable and reprocessable rubber by introducing dynamic disulfide bonds into the crosslink network of epoxidized natural rubber (ENR). Lipoic acid (LA) was firstly uniformly dispersed into ENR via a latex film formation technique, and then underwent a dynamic covalent ring-opening self-polymerization during hot pressing process, during which the carboxyl group of poly(LA) attacked the epoxy group of ENR to form β-hydroxyl ester bond crosslinks. As a result, a revisable covalently crosslinked network without rigid steric hindrance groups was constructed, which exhibited a super self-healing efficiency of 99 % after self-healing at 80 °C for only 3 h. The elongation at break of the elastomer could reach 1115 % and the recovery rate of reprocessing was as high as 91 %.