Photoresponsive Self-Healing Epoxy Composites with Azobenzene Grafted Mesoporous Silica for Controlled Release and Visualization

The substantial progress made in extrinsic self-healing has been limited to microcapsules containing heat-active polymerizable monomers. Fabrication of self-healing microvascular and nanoparticle systems that are responsive to light is, therefore, an important task. In this study, using azobenzene-grafted mesoporous SBA-15 (Azo-SBA) as the functional nanocontainer to adsorb a photoactive repair agent (glycidyl methacrylate, GMA)(GMA@Azo-SBA), a facile yet feasible strategy is demonstrated to prepare photoresponsive self-healing epoxy composites. The resulting composite integrates the controllable fixation and release of the repair agent driven by the isomerization of azobenzene and photo-induced self-healing properties under UV irradiation. The hydrogenated epoxy resin composite, incorporated with isophorone diamine (IPDA) as the curing agent and 2 wt.% GMA@Azo-SBA and 4 wt.% photoinitiator, exhibits desirable self-healing properties; the microcracks of the composite can be completely repaired after self-healing for 15 min. In addition, the pyrene-modified GMA monomer with fluorescence characteristics as a fluorescent probe is further employed to successfully visualize the fixation and release process of the repair agent under UV irradiation.