Berlin 2012 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 27: Poster: (Hydrogels) and Elastomers
CPP 27.2: Poster
Mittwoch, 28. März 2012, 11:00–13:00, Poster A
Rate Theory of Cyclic Structures in Polymer Model Networks — •Michael Lang1, Konrad Schwenke1,2, and Jens-Uwe Sommer1 — 1Leibniz Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069 Dresden, Germany — 2Institut f. Baustoffe (IfB), ETH Zürich, Schafmattstrasse 6, 8093 Zürich, Switzerland
A rate theory of the homo- and co-polymerization of f-functional molecules is developed, which contains the formation of short cyclic structures inside the network. The predictions of this model are compared with Monte-Carlo simulations of network formation. We find that homo-polymerizations are well captured by mean-field models at concentrations larger than one quarter of the geometrical overlap concentration. A comparison with the simulation data reveals that correlations among multiply connected molecules can be neglected for these samples. Co-polymerizations are considered in the case of a strict A-B reactions, where all reactive groups of individual molecules are either of type A or type B . For these systems we find a strong influence of density fluctuations of both species for all concentrations investigated. The effect of fluctuations is more than compensated by the lack of ring structures containing an odd number of molecules as compared to homo-polymerizations. Therefore, network formation is readily possible at concentrations one order of magnitude below the overlap concentration. Based on our data we conclude that fluctuation effects are important for co-polymerizations and that mean-field models are less appropriate for their description.