Berlin 2008 – scientific programme

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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.