A KINETIC-ANALYSIS OF THE INITIAL-STAGES OF THE SOL-GEL REACTIONS OF METHYLTRIETHOXYSILANE (MTES) AND A MIXED MTES TETRAETHOXYSILANE SYSTEMBY HIGH-RESOLUTION SI-29 NMR-SPECTROSCOPY/

Si-29 solution NMR is used to follow the kinetics of the methyltrietho xysilane (MTES) homopolymerization and that of the MTES/tetraethoxysil ane (TEOS) copolymerization. Individual kinetic rate constants for the hydrolysis and dimerization reactions were obtained by fitting the co ncentration curves as functions of time for the different intermediate species. It Was found that the individual hydrolysis kinetic constant s for the MTES homopolymerization are greater than those for the TEOS homopolymerization. Using the homodimerization and codimerization kine tic rate constants for the MTES/TEOS copolymerization, reactivity rati os were calculated. These reactivity ratios suggest that the two monom ers react to form a random copolymer.