On the Long-Term Stability of Colloidal Gels

Publication Reference: 
Author Last Name: 
W.C.K. Poon
Report Type: 
ARR - Annual Report
Research Area: 
Wet Systems
Publication Year: 
Publication Month: 

Executive Summary

In the first part of this report, we describe a series of simulations studying the effect of hydrodynamics on gelation dynamics, gel structure and gel sedimenta- tion. We find that hydrodynamics affects strongly the dynamics of gelation, but has little effect on gel structure. In the second, experimental, part, we first bring to a conclusion the previous four years of work on a model system consisting   of sterically-stabilised polymethylmethacrylate particles forming a gel due to the depletion attraction induced by non-adsorbing polystyrene polymers. One of the main results of our previous work was that the curved meniscus had a major effect in inducing the gravitational collapse of these gels. Here, we directly manipulate the curvature of the gel meniscus, and show that curvature of either sign speeds up collapse. We conclude by reporting preliminary experiments on a new sys- tem consisting of large, repulsive particles dispersed in a background gel of small attractive particles. The rheology of this system, which models a range of indus- trial formulations, is surprisingly complex. We find that as we change the relative amount of large spheres, the system can display time or history dependence.