Stability of colloids and wetting phenomena

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Abstract
Light scattering and interferometry techniques are used to demonstrate the influence of wetting phenomena on the stability of silica colloids when immersed in a homogeneous two-component fluid (2,6-lutidine and water). A reversible flocculation is observed for both fused quartz and Stöber silica particles. Its location in the fluid phase diagram is different according to the origin of the particles and corresponds only to the ‘‘wetting’’ side of the coexistence curve. The flocculation is preceded by the growth of adsorption layers whose composition is that of the expected wetting phase. A number of mechanisms, related to wetting transitions, that can explain these observations are discussed.