The effect of spatially inhomogeneous mixing of polymer and cross-links for end-linked polymer networks

We are studying the effects caused by the spatial inhomogeneity of polymer and cross-links at the beginning of the cross-linking reaction. For this purpose we use the Bond Fluctuation Method to create the mixtures and to study the dynamics of the cross-linking process. Several structural parameters have been varied as the dilution of the system, the length of the chains, or the reaction probability for several sizes and distributions of the initial domains. The structure of the generated networks has been analysed by knot theory and graph theory as well as the density and amount of the effective material has been determined. Some of the networks show the formation of micro gels around the initial domains of the cross-linking agents and a clear displacement of the gel point. The dynamics of the cross-linking reaction is slowed down and controlled by the initial size of the domains in almost the same manner as the maximum extent of reaction. The density of the effective material is explicitly affected by the size of the domains. Dilution, decreasing probability for reaction, or decreasing length of the chains enhance the homogeneity of the network.