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Preparation And Characterization Of Spherical Monodisperse Silica Dispersions In Nonaqueous Solvents
Published 1981 · Chemistry
Abstract In two earlier papers (A. K. van Helden and A. Vrij,J. Colloid Interface Sci.76, 418 (1980);78, 312 (1980)) light-scattering measurements of organophilic silica dispersions were reported. The preparation of these dispersions is described here in more detail. Organophilic silica dispersions consisting of spherical particles of narrow size distribution were produced by a combination of two earlier described processes. First uniform silica particles were prepared by hydrolysis of ethylorthosilicate according to the method of W. Sto¨ber A. Fink, and E. Bohn (J. Colloid Interface Sci.26, 62 (1968)). Then these particles were rendered organophilic by a coating reaction with stearyl alcohol according to R. K. Iler's method (U. S. Patent 2,801,185). Stable dispersions with particle radius between 20 and 100 nm were prepared in various organic solvents, e.g., cyclohexane, n-octane, diethylether. The stability does not reduce upon storage in cyclohexane for more than 1 year. A range of systems is investigated with a number of common techniques in colloid research, e.g., electron microscopy, ultracentrifugation, static and dynamic light scattering. The results can be qualitatively explained in terms of an initially porous alcohol particle which is dehydrated to some extent in the coating reaction. At low concentrations especially in diethylether electrostatic repulsion seems to occur. At higher concentrations this effect is not observed (van Helden and Vrij,J. Colloid Interface Sci.78, 312 (1980)).