Room-Temperature Self-Healing Polymers Based on Dynamic-Covalent\nBoronic Esters

Abstract

Cross-linked polymers constructed\nwith dynamic-covalent boronic\nesters were synthesized via photoinitiated radical thiol–ene\nclick chemistry. Because the reversibility of the boronic ester cross-links\nwas readily accessible, the resulting materials were capable of undergoing\nbond exchange to covalently mend after failure. The reversible bonds\nof the boronic esters were shown to shift their exchange equilibrium\nat room temperature when exposed to water. Nevertheless, the materials\nwere observed to be stable and hydrophobic and absorbed only minor\namounts of water over extended periods of time when submerged in water\nor exposed to humid environments. The facile reversibility of the\nnetworks allowed intrinsic self-healing under ambient conditions.\nHighly efficient self-healing of these bulk materials was confirmed\nby mechanical testing, even after subjecting a single site to multiple\ncut–repair cycles. Several variables were considered for their\neffect on materials properties and healing, including cross-link density,\nhumidity, and healing time.