Surface science and stability of networks prepared from hydroxy-terminated polydimethylsiloxane and methyltriethoxysilane

Polydimethylsiloxane (PDMS) hybrid networks have been prepared by the reaction of PDMS(OH)2, average molecular weight 26 × 103, 43.6 × 103 and 58 × 103, and methyltriethoxysilane (MeTEOS, 10–60 wt%) using a dibutyltin dilaurate or dibutyltin diacetate catalyst. By hydrolysis and homo- and co-condensation, MeTEOS forms a siliceous domain (MeSD) and acts as a crosslinker for the PDMS domain. Kinetic studies showed that high MeTEOS and catalyst concentrations and reduction of free surface area favor fast gelation and efficiency in converting MeTEOS to the MeSD. Under the water-sparse conditions utilized, cure was slow and substantial evaporative loss of MeTEOS occurred.