Preparation of Self-Healing Antifogging Hard Coatings Using Carboxy-Functionalized Polysilsesquioxanes and Oligo(ethylene glycol)s

Water-resistant antifogging hard coatings possessing self-healing properties were successfully prepared by applying <i>N</i>,<i>N</i>-dimethylformamide solutions containing the mixtures of carboxy-functionalized polysilsesquioxane (PSQ-2C) with oligo(ethylene glycol)s (OEGs; <i>n</i> = 2-6 and <i>n</i> = 2-4) at the feed functional group ratios (carboxy groups in PSQ-2C/hydroxy groups in OEG) of 10:1 and 4:1, respectively, onto oxygen plasma-treated glass substrates, followed by heat drying, water immersion, and room-temperature drying. The formation of ester bonds in the resulting coatings, indicating the presence of a cross-linked structure, was confirmed via Fourier-transform infrared/attenuated total reflectance spectroscopy. Notably, the coating prepared using PSQ-2C and tetraethylene glycol (OEG; <i>n</i> = 4) at a feed functional group ratio of 10:1 demonstrated no peeling or dissolution even after water immersion for 1 h, and its surface hardness, which was evaluated via the pencil scratch test, was 4H. Additionally, when exposed to water vapor generated from warm water at 40 °C at a distance of 2 cm, the coating maintained transparency for up to 85 s, confirming its excellent antifogging performance. Finally, the coating exhibited self-healing properties, as evidenced by the disappearance of scratches induced by a 5H pencil when the coating was left standing at 25 °C and 30% relative humidity for 5 min.