Improvement of Extrinsic Self-Healing Performance by Dual pH-Responsive, Two-Compartment Microcapsules

Most intrinsic self-healable polymers require external forces to provide the initial adhesion, which greatly limits their application to self-healing technology in coatings. The high self-healing performance of extrinsic self-healable coatings remains a challenge. Here, we propose the use of dual pH stimulation responsive, two-compartment microcapsules to enhance the extrinsic self-healing performance of coatings. Curing agent polyetheramine (PEA) was encapsulated in the responsive poly(N,N-dimethylacrylamide- co -dodifluorophetane acrylate) with N,N-methylenebis(acrylamide) cross-linker that was taken as the Pickering emulsifier and used to stabilize O/W emulsions, in which the oil phase comprised healing agent E51 and stimulus response monomer (diethyl methacrylate) and 6-hexadiol diacrylate cross-linker. After the Pickering emulsion polymerization, double-compartment microcapsules (DCMCs), which simultaneously encapsulated the healing agent E51 and PEA as core materials, stimulus response polymers with acid-responsive amines groups, and alkali-responsive amides or esters groups as the shell, were successfully fabricated. Compared to the coatings of double microcapsules, the self-healing efficiency of the DCMC coatings was greatly improved by the dual chamber structure and shell smart design of pH-responsive polymers.