Regensburg 2004 – scientific programme

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CPP: Chemische Physik und Polymerphysik

CPP 8: Physics of Polymers II

CPP 8.1: Talk

Monday, March 8, 2004, 15:45–16:00, H 37

The effect of spatially inhomogeneous mixing of polymers and cross-links for end-linked polymer networks — •Michael Lang, Dietmar Göritz, and Stefan Kreitmeier — Fakultät für Physik, Universität Regensburg, 93040 Regensburg

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 these mixtures and to study the dynamics of the crosslinking process. The structure of the generated networks has been analyzed by knot-theory and graph-theory. The density and amount of the elastically active material has been determined. Several structural parameters have been varied as the dilution of the system or the length of the chains or the probability of any reaction for several sizes and distributions of the initial domains.

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 is controlled by the initial size of the domains in almost the same manner as the maximum extent of reaction. The densitiy of the elastically active material is clearly affected by the size of the domains and the distance to the next domain. Diluted systems form more short cycles but result in a more homogeneous network. The homogeneity is also enhanced by decreasing probability for reaction or decreasing length of the chains.