Effect of the Solvent Type on the Colloidal Stability and the Degree of Condensation of Silica Sols Stabilized by Amphiphilic Urethane Acrylate and the Properties of Their Coating Films

The colloidal stability of silica O-I hybrid sols that have a high degree of condensation could result in the formation of a hard coating film on a substrate, which could depend on the properties of solvents used in the sol-gel reaction. In this study, the effect of the solvent type on the colloidal stability and degree of condensation of the silica sols was investigated by preparing various silica O-I hybrid sols using different solvent mixtures composed of various aprotic and protic solvents in the presence of amphiphilic urethane acrylate. Silica sols prepared using the appropriate aprotic-protic solvent mixture showed a higher degree of condensation and long-term colloidal stability, which was confirmed using 29Si-NMR and DLS. Furthermore, the coating film formed from these silica sols showed a remarkable hardness of 0.97 GPa, with a thickness of 4.76 µm confirmed using nanoindentation measurements.