Hybrid Silica Microgels Sols as Precursors of Sol-Gel Coatings.

ALICIA DURÁN; YOLANDA CASTRO; MARIO APARICIO; ISABEL SOBRADOS; JESÚS SANZ; ROBERTO WILLIAMS; SERGIO PELLICE

Sunderland, UK.

Congreso; 8th ESG / ICG Annual Meeting / SGT Annual Meeting; 2006

ESG / ICG

In organic-inorganic hybrid coatings bearing organic polymerizable groups it is often difficult to advance both the organic and inorganic polymerizations to high conversions. In this work we show that it is possible to synthesize a sol consisting of a solution of crosslinked particles (microgels) exhibiting a complete conversion in the organic polymerization together with a fraction of free SiOH and SiOR groups. Sols were synthesised following a two-step process. In a first step, the hydrolysis and condensation of tetraethoxysilane (TEOS) and 3-methacryloxypropyltrimethoxysilane (MPMS) dissolved in isopropanol, was advanced in the presence of HNO3. In a second step, 2-hydroxyethylmethacrylate (HEMA) and 2,2’-azobis(isobutyronitrile) (AIBN) were added to the pre-condensed sol, and the organic polymerization was carried out. The conversion in the organic polymerization was followed by FTIR and 13C NMR spectra and the conversion in the inorganic polymerization was monitored from 29Si NMR spectra. When the dilution was equivalent to a concentration of 40 g L-1 SiO2 no gelation was observed after completing the organic polymerization. At this concentration the resulting sol was a solution of microgels whose dimensions were characterized by scanning electron microscopy after solvent evaporation. The sol was used to produce transparent coatings of excellent quality over glass and metallic substrates.