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 I R spectroscopy, electrophoretic and quantum chemical methods. The elec trophoretic mobility of the silica particles in aqueous suspensions de pends on the modifier concentration in a non-linear manner. The effect ive diameter of the particles of finely dispersed silica modified by M ADES (about 0.2 mu m) in aqueous suspensions is considerably smaller t han that for unmodified samples, as agglomerates (about 10 mu m) of ag gregates (0.1-0.2 mu m) are decomposed to aggregates upon the modifica tion of silica due to a reduction of hydrogen-bonding and electrostati c interactions between the modified surfaces of aggregates; in additio n, MADES molecules bound to the surface possess low solvation energy. (C) 1998 Elsevier Science B.V.