Rapid, Photomediated Healing of Hexaarylbiimidazole-Based Covalently Cross-Linked Gels

Abstract

The intrinsic healing of covalently cross-linked polymer networks is commonly effected via the utilization of backbone-borne functional groups able to reversibly cleave or rearrange, thereby enabling mixing and coreaction of network strands that bridge contacted interfaces; however, such materials often exhibit slow healing rates and are susceptible to creep under load. To address these deficiencies, we incorporated hexaarylbiimidazole (HABI) functionalities, groups that are homolytically cleavable, to yield relatively low reactivity lophyl radicals under UV or visible light irradiation and which, in the absence of light, spontaneously recombine without significantly participating in deleterious side reactions, into the backbone of poly(ethylene glycol)-based polymeric gels. Whereas the network connectivity of these HABI-incorporating gels was stable in the dark, they exhibited significant creep upon irradiation. The influence of swelling solvent on the reaction kinetics of backbone-borne HABI photolysis ...