Experimental and computational study on hydrolysis and condensation kinetics of γ-glycidoxypropyltrimethoxysilane (γ-GPS)

Since the amount of silanol units in the hydrolysis solution directly determines the interfacial adhesive strength and corrosion resisting property of self-assembled silane films, therefore, it is very essential to have a deep understanding of hydrolysis behaviors of SCAs (silane coupling agents). Conductivity measurement, RA-IR measurement and density functional theory (DFT) calculation was applied to the study of the hydrolysis and condensation kinetics of γ-glycidoxypropyltrimethoxysilane (γ-GPS) under near-neutral and acidic conditions. The results indicated that a critical point existed at about 50 h, dividing the entire hydrolysis period into two stages: Stage 1 (S1) and Stage 2 (S2). In S1, the first step hydrolysis reaction prevailed, while the second and third step hydrolysis reactions only played minor roles. The pH value of the hydrolysis solution imposed little influence on the reactions occurring in the solution. However, in S2, pH value exerted a significant influence on the hydrolysis and condensation reactions, based on which there was an optimum pH value range. The results of DFT calculation were consistent with the experimental measurements. Hitherto, a validate method was proposed to simulate the reactions occurring in the hydrolysis solution.