Effect of cluster deformations in the DLCA modeling of the sol-gel process

The diffusion limited cluster-cluster aggregation (DLCA) model is modified by including cluster deformations during aggregation, with a tuning flexibility parameter F. A thres-dimensional computer simulation is presented, which starts from a collection of f-functional monomers randomly distributed in a cubic box with a volumic fraction c (concentration) and which uses the highly efficient bond fluctuation algorithm to describe the cluster deformations. It is shown that, for F not equal 0, there exists a well defined threshold value of the volumic fraction below which the realization of all intra-aggregate bonding possibilities prevents the formation of a gelling network. For c > c(g), a true sol-gel transition occurs at a characteristic time t(g), after which an infinite cluster (which is self connected via the boundary conditions) appears. In contrast to DLCA, t(g) does not increase as the box size increases. The transition at c(g) is characterized by a divergence of the final clusters size for c ( cg and a divergence of the gel time for c > c(g). Several other numerical results are reported.