Study by FT-IR Spectroscopy of the reaction of hydrolysis and polycondensation of TEOS in presence of PDMS.

In this work, we have studied, by FT-IR Spectroscopy, the influence of the molecular weight of organic polymers (polydimethylsiloxane, PDMS) in the hy drolysis and polycondensation reactions of tetraethylortosilicate (TEOS) in acid medium. Following of the bands located at 880, 1180 and 850 cm(-1), t he hydrolysis and selfcondensation of TEOS process and copolymerization bet ween TEOS and PDMS respectively can be studied. The rates of hydrolysis and self-condensation of TEOS are not affected by the presence of the polymer. However, the reaction of copolymerization between TEOS and PDMS decreases when the molecular weight of polymer increase, and this is due to both the diferences in the concentration of silanol end groups of polymer and polyme r viscosity. The materials obtained from high molecular weight (18000 and 2 6000 g/mol) have gelification times as TEOS. On the other hand the gelifica tion time decreases when polymers of lower molecular weight ( 550 and 1700 g/mol) are used. This work shows that FT-IF: Spectroscopy can be applied to investigate the sol-gel reactions.