Epoxy-functional silicone resins via base-catalyzed hydrolytic condensation for transparent coatings with enhanced hardness and UV-aging resistance

Epoxy-functional silicone resins are promising reactive modifiers for transparent hard coatings. However, their synthesis often faces challenges such as ring-opening of epoxy groups under acidic conditions or insufficient siloxane condensation. In this work, a weak base-catalyzed hydrolytic condensation method was developed to synthesize a series of soluble epoxy-functional MDQ and MTQ silicone resins, containing M/D/Q and M/T/Q siloxane units, respectively, with tunable molecular weight. K 2 CO 3 was used as a mild catalyst to promote Si-O-Si network formation while preserving epoxy functionalities. The obtained silicone resins were introduced into a tetra-armed epoxy-functionalized phenylsiloxane (BBE-Ep 4 Si, BE) to fabricate transparent coatings through epoxy-anhydride curing. The incorporation of epoxy-functional silicone resins significantly improved the thermal stability and surface hardness of the coatings. The optimized coating exhibited the best overall performance, with a pencil hardness of 8H, an adhesion grade of 5B, a transmittance of 95.8% at 550 nm, a low surface energy of 27.92 mN m −1 , and good anti-contamination and easy-cleaning properties. After 96 h of UV aging, the coating still maintained high visible-light transmittance of 92.3% at 550 nm and good hydrophobicity with a water contact angle of 99.5°. The optimized coating shows potential as a transparent protective layer for next-generation optoelectronic devices, including foldable displays, touch panels, and cover windows.