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Colloidal Aggregation in a Binary Mixture Near its Demixing Temperature

Published online by Cambridge University Press:  15 February 2011

Michael L. Broide
Affiliation:
Lewis & Clark College, Department of Physics, Portland, OR 97219, USA.
Daniel Beysens
Affiliation:
Service de Physique de l'etat Condensé, Centre d'Etudes de Saclay, F-91191 Gif-sur-Yvette Cedex, France.
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Abstract

We have investigated temperature-induced aggregation of silica colloids in a binary mixture of 2,6-lutidine and water. Aggregation occurs in the one-phase region of the binary mixture and can be reversed by cooling the sample.

Using low-angle light scattering, we have determined the growth kinetics and aggregate structure for this system. We find that the time dependent scattered intensity is well described by I(q, t) = ¯(t)/[1 + (q¯R(t))2/10]2\, where the weight-average cluster mass ¯I(t) ⋧ t, and the average cluster radius ¯(t) -çt1/3.

Our results indicate that this experimental system generates compact clusters, ¯ ⋧ ¯ 3, and that the rate of aggregation is diffusion limited. The dense, non-fractal, structure we observe suggests that the bonds between the silica spheres are not rigid, and supports the hypothesis that aggregation is induced by the adsorption of lutidine on the silica surface.

Type
Research Article
Copyright
Copyright © Materials Research Society 1993

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