Kinetics of gel formation in dilute dispersions with strong attractive particle interactions

We report a combined experimental and modeling study to investigate the kinetics of the transformation of a colloidal dispersion with strong attractive particle interactions into a gel. In the model, a two step mechanism is proposed, where an initial aggregation step is followed by an interconnection step leading to a particle network spanning the entire system volume. Using the Smoluchowski aggregation equation for the first step, we introduce a criterion to determine when the aggregation process is arrested and clusters become caged. In the second step the caged clusters diffuse over short distances and interconnect to form the particle network. The reliability of the gelation times computed by the model has been tested by comparison with a suitable set of experimental data. In addition, we show that the concept of mathematical gelation within the Smoluchowski aggregation equation is not appropriate for the description of the entire gel formation process in this system.