Self-functional healing coating for glass using capsules/chambers to robustly stop crack propagation

Abstract

A self-functional healing coating (SFC) for preventing crack propagation in glass is reported. The SFC consists of chambers and capsules containing a large amount of healing agent while maintaining the high transmittance of the coating material. A hydrogel precursor healing agent is phase separated within chambers in a polydimethylsiloxane (PDMS) matrix, whereas the Irgacure 2959 photoinitiator is encapsulated. Glass with the SFC (gSFC) is transparent and exhibits excellent self-healing properties because of embedded capsules and the matching refractive indices of the hydrogel precursor phase and the PDMS. Here, the healing agent and photoinitiator smoothly seep into the random and large-area cracks of gSFC by capillary action. The water-based mixture of poly(ethylene)glycol diacrylate (PEGDA) and 3-(trimethoxysilyl) propyl methacrylate (TMSPMA) used as a healing agent has a low viscosity and high wettability on glass. Polymerization of the healing agent is triggered by UV-activated photoinitiator. The catalyst-free, environmentally benign photopolymerizable hydrogel used in the gSFC has a spatiotemporal polymerization property suitable for random and large-area cracks. In addition, adhesion between the crack surfaces increase due to the TMSPMA adhesion-reinforcing agent in the hydrogel precursor to prevent crack propagation by healing the cracks, enduring approximately a four times higher force than the non-healed glass.