POLY(ETHYL ACRYLATE) LATEXES ENCAPSULATING NANOPARTICLES OF SILICA .1. FUNCTIONALIZATION AND DISPERSION OF SILICA

Silica (Aerosil A200 V) has been functionalized by reaction with metha cryloylpropyltrimethoxysilane (MPTMS) in toluene. The grafting yield f irst increases with the ratio MPTMS/SiOH and then levels off after ful l monolayer coverage, each molecule of MPTMS covering 71 Angstrom(2). A greater amount can be grafted if the MPTMS is first hydrolysed and p artly condensed, and then reacted with the silica. A high degree of fu nctionalization is needed to get complete dispersion of the silica in toluene. The redispersion of the functionalized silica in water is dif ficult; the best results are obtained in the presence of isobutanol as dispersing agent, after three days of treatment at pH 9.5, which caus es the hydrolysis of the remaining methoxy groups.