Influence of modification of fine silica by organosilicon compounds on particle-particle interaction in aqueous suspensions

Fumed silica modified by methacryloyloxymethylenemethyl diethoxysilane (MADES) was studied and compared with unmodified fumed silica using IR spectroscopy, electrophoretic and quantum chemical methods. The electrophoretic mobility of the silica particles in aqueous suspensions depends on the modifier concentration in a non-linear manner. The effective diameter of the particles of finely dispersed silica modified by MADES (about 0.2 mu m) in aqueous suspensions is considerably smaller than that for unmodified samples, as agglomerates (about 10 mu m) of aggregates (0.1-0.2 mu m) are decomposed to aggregates upon the modification of silica due to a reduction of hydrogen-bonding and electrostatic interactions between the modified surfaces of aggregates; in addition, MADES molecules bound to the surface possess low solvation energy. (C) 1998 Elsevier Science B.V.