Dynamiccal Theory of Gelation Process

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Gelation is a phenomena that a material transforms from a fluid state (the state that flows under infinitesimal strees) to a solid state (the state that cannot flow). The phenomena has been identified as the formation of an infinite network, and has often been discussed in the framework of the percolation theory, where it has been studied when and how an infinite network is formed when monomers or bonds are placed randomly on a lattice \ cite {Family}. However, in such set up of the problem the actual molecular dynamics is not taken into account.Tostudy the structural evolution associated with gelation, we performed a computer simulation for the gelation process of telechelic polymers which have two reaction sites (stickers) at both ends of the chain. We assume that (i) when stickers contact with each other, they form a cluster and move together then after, and that (ii) there is a maximum number of stickers in the cluster. The structural evolution of the system before and after the gelation point is studied.It is found that (i) as the gelation proceeds, a large concentration inhomogeneity is created as in the case of spinodal decomposition, (ii) this structural evolution take place very slowly over the period long after an infinite network is formed, and (iii) the structural evolution is stopped by the elastic effect of the network.