KINETIC INVESTIGATIONS OF HYDROLYSIS AND CONDENSATION OF THE GLYCIDOXYPROPYLTRIMETHOXYSILANE AMINOPROPYLTRIETHOXY-SILANE SYSTEM BY MEANS OFFT-RAMAN SPECTROSCOPY-I/

Fourier transform Raman spectra with laser excitation in the near infr ared were recorded during the base-catalyzed sol-gel reaction of the s ystem 3-glycidoxypropyl-trimethoxysilane (GPTS)/3-aminopropyl-triethox ysilane (APTS), This combination of organo-(alkoxy)silanes is used for the synthesis of hybrid polymers. Raman bands of the trimethoxysilyl- and the epoxy-moieties were used to monitor the kinetic behaviour of the hydrolysis reaction and the ring cleavage as a function of tempera ture. A decrease of the rate of hydrolysis of GPTS at elevated tempera tures is attributed to a decrease of the pH caused by temporarily accu mulating silanol groups. After the start of the condensation reactions , the pH increases and forces hydrolysis to accelerate. The results in dicate the existence of a pentacoordinated transition state with a neg ative charge at the silicon atom during base catalyzed hydrolysis. (C) 1998 Elsevier Science B.V. All rights reserved.