FACTORS AFFECTING THE REDISPERSIBILITY OF ORGANOSILICA SOLS PREPARED BY A MODIFICATION OF SILICA PARTICLES WITH A POLYOL-BASED POLYMER

Organosilica sols which were redispersible in nonpolar or less polar o rganic solvents were prepared by a chemical modification of the silica surface with a polyol-based coupling polymer; the redispersibility wa s then examined in terms of the molecular weight of the coupling polym er, charged coupling polymer/silica (mmolg(-1)) (P/S) ratio, and the s ize of modified silica particles. Fractionated coupling polymers with an M(w)/M(n) of 2.0-2.8 were used. The charged P/S ratio was a leading factor for the redispersibility. The redispersibility was achieved wh en the charged P/S ratio exceeded approximately 0.3 mmolg(-1), using c oupling polymers of various molecular weights. The particle size of th e modified silica decreased along with an increase in the charged P/S ratio and the reaction time. The presence of a free polymer was not es sential for the redispersibility when the saturation of the silica sur face with the coupling polymer was nearly completed.