Characteristics of Nanohybrid Coating Films Synthesized from Colloidal Silica and Organoalkoxysilanes by Sol–Gel Process

Abstract

Organic–inorganic hybrid sols were synthesized using colloidal silica and organoalkoxysilane using the sol–gel process. Hybrid sols were functionalized using methyltrimethoxysilane (MTMS) and γ-glycidoxypropyltrimethoxysilane (GTMS). Coating films were formed on a glass substrate using a spin coating procedure. The hybrid sols were evaluated for stability and thermal degradation. Viscosity increased markedly when the hybrid sols were reacted for 10 d. It was found that the hybrid sols reacted over 10 d were difficult to be used as coating agents. The thermal degradation of a colloidal silica (CS)/MTMS sample occurred at 650 °C owing to the decomposition of a methyl group. Two CS/MTMS/GTMS samples degraded at 400 °C owing to the decomposition of an epoxy group. Coating films were characterized in terms of hydrophobicity, surface morphology, and electrical resistance. CS/MTMS coating films showed a high contact angle, indicating hydrophobic character. The contact angle of the CS/MTMS/GTMS coating film decreased owing to epoxy group when a large amount of GTMS was added. The roughness of all coating films was less than 20 nm. The surface resistance of the coating films reacted for 7 d was measured. The surface resistance of the coating films was more than 1013 Ω.