Room-temperature self-healing polymers based on dynamic-covalent boronic esters

Cross-linked polymers constructed with dynamic-covalent
boronic esters were synthesized via photoinitiated
radical thiol−ene click chemistry. Because the
reversibility of the boronic ester cross-links was readily
accessible, the resulting materials were capable of undergoing
bond exchange to covalently mend after failure. The reversible
bonds of the boronic esters were shown to shift their exchange
equilibrium at room temperature when exposed to water.
Nevertheless, the materials were observed to be stable and
hydrophobic and absorbed only minor amounts of water over
extended periods of time when submerged in water or exposed
to humid environments. The facile reversibility of the networks allowed intrinsic self-healing under ambient conditions. Highly
efficient self-healing of these bulk materials was confirmed by mechanical testing, even after subjecting a single site to multiple
cut−repair cycles. Several variables were considered for their effect on materials properties and healing, including cross-link
density, humidity, and healing time.