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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 30: Polymerphysics II
CPP 30.2: Talk
Thursday, February 28, 2008, 14:15–14:30, C 130
Structure and Dynamics of silicone networks as investigated by 1H low field double-quantum NMR — •Walter Chassé and Kay Saalwachter — Martin-Luther-Universität Halle-Wittenberg, Institut für Physik, Friedemann-Bach-Platz 6, D-06108 Halle, Germany
The existence of cross-links and other topological restrictions lead to non-isotropic fast segmental fluctuations, and therefore some residual dipolar couplings persist, which are directly related to the crosslink density. Based on this principle, we have used static 1H double-quantum NMR spectroscopy to measure quantitatively these residual dipolar couplings and their distribution1.
Usually the easiest method to study network structure (crosslink density) is the swelling experiment based on Flory-Rehner-Theory. In this view we have compared the molecular weight between cross-links MC obtained from DQ-NMR with results of as well performed swelling experiments for PDMS networks with different topologies. Independently of this, the crosslink density can also be taken from 1H MAS experiments. With these results, we obtained information not only about the network structure of the rubber but also about the validity of the model used to analyze the DQ-NMR data, thermodynamics of swelling (polymer solvent interaction parameter χ), and the influence of network heterogeinities in that process. In conclusion we could show that DQ-NMR in combination with swelling experiments is a powerful method to characterize structure and dynamics of rubber.
[1] K. Saalwächter, Prog. in NMR Spectr., 2007, 51, 1-35.