Eur. Phys. J. E 5, 221-227

Structure of gels and aggregates of disk-like colloids

T. Nicolai and S. Cocard

Polymères, Colloïdes et Interfaces, UMR-CNRS, Université du Maine, 72085 le Mans Cedex 9, France

Taco.Nicolai@univ-lemans.fr

(Received 6 August 2000 and Received in final form 16 March 2001)

Abstract
The static structure factor (S(q)) of dispersions and gels of disk-like mineral colloids (Laponite) was investigated using time- and ensemble-averaged light scattering. The evolution of S(q) in time after increasing the ionic strength of well-dispersed Laponite suspensions shows that Laponite aggregates and forms fractal clusters. The structure of the aggregates does not depend on the ionic strength, but the rate of growth increases very strongly with the ionic strength. At concentrations below about 3 g/l (0.12% v/v) the aggregates sediment while at higher concentrations space-filling gels are formed. The gels are homogeneous on length scales larger than the correlation length which decreases strongly with decreasing ionic strength and increasing concentration. However, the local structure is the same, independent of the concentration and the ionic strength.

PACS
82.70.Dd - Colloids.
82.70.Gg - Gels and sols.
61.43.Hv - Fractals; macroscopic aggregates (including diffusion-limited aggregates).


© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001