THE HYDROLYSIS OF [OSI(OCH3)2]4 - A NEW PRECURSOR FOR THE SOL-GEL PROCESS

The hydrolysis of octamethoxycyclotetrasiloxane was carried out in the absence of a catalyst and Si-29-NMR spectra were measured. It is shown that under these conditions the siloxane ring stays intact. Due to the many possible isomers in partially hydrolysed cyclic tetramer silicic acid esters, assignment of the Si-29 chemical shifts in the NMR spectra to individual species was not possible in most cases. However, the general shift area for the building units of rings > Si(OCH3)2, > Si(OCH3)(OH) and > Si(OH)2 was obtained by observing the proton coupled Si spectra. The rate constants for the formation of the ring units > Si(OH)(OCH3) and > Si(OH)2 were determined.