Monitoring tetraethoxysilane hydrolysis/condensation in solutions with low alcoholic content by infrared spectroscopy

Abstract

The objective of this work was to monitor the hydrolysis/condensation of tetraethoxysilane (TEOS) as a function of the silane dilution time, through infrared (IR) spectroscopy. Initially two concentrations of silane (1 and 10% by volume) were evaluated. However, it was found that at 1% of TEOS concentrations it was not possible to identify the chemical bonds of interest for the hydrolysis monitoring adequately in regions characteristic of the infrared spectrum. Once the appropriate concentration was defined, the hydrolysis/condensation monitoring was carried out using the infrared spectra obtained in solutions hydrolyzed at room temperature and extracted every 10 minutes. It was found that the hydrolysis reactions of the alkoxy groups accelerated in 40 minutes from the TEOS dilution. In parallel, the condensation of the silanols also accelerated, due to the increase in their concentration in the solution. After 70 minutes, the hydrolysis/condensation showed a deceleration through siloxane formation and due to the complete hydrolysis of the TEOS alkoxy groups. The hydrolysis of TEOS in solutions with low alcohol content (around 50% by volume) did not show any damage to the monitoring of the reactions of interest of the system, presenting reaction kinetics similar to those reported in the literature, showing up as an alternative to systems with excessive consumption of organic solvents.