Gelation Time Depending on the Functionality and the Concentration of Monomers Simulated by a CCA Model

Abstract

We study the gelation process by simulation of a cluster–cluster aggregation (CCA) model, in which networks of gels are constructed through clustering of two-functional or four-functional monomers. We find that gelation time increases when the initial concentration of monomers decreases, while it decreases when the fraction of four-functional monomers increases. At a small initial concentration, gelation time does not markedly depend on the functionality of monomers. This can be related to the forms of clusters: for a large functionality case, the clusters should be tight and should aggregate into compact structures, while for a small functionality case, clusters should form linear chains so that they can easily associate with each other. Numerical observations are compared with experimental results on gelation time for the two types of silica gels under acidic and basic conditions.