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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 30: Polymerphysics II

CPP 30.1: Vortrag

Donnerstag, 28. Februar 2008, 14:00–14:15, C 130

Study of rubber network structure by low field ¹H double-quantum NMR experiments — •Juan Lopez Valentin and Kay Saalwachter — Martin-Luther-Universität Halle-Wittenberg, Institut für Physik; Friedemann-Bach-Platz 6, D-06108 Halle (Germany)

Elastic properties of rubber are closely related with the network structure, and Solid-state nuclear magnetic resonance (NMR) is a successful tool to obtain this local information. Proton double-quantum (DQ) is one of the most recent and versatile approach towards the measurement of weak residual dipolar couplings (the NMR observable) associated with ”NMR submolecules” (related to the Kuhn segments). It provides in the same experiment not only quantitative information on semi-local chain order (thus cross-link density) and its distribution, but also about chain dynamics [1].

Based on this methodology, natural rubber networks, which were vulcanized with different cure systems (sulphur and organic peroxide), were studied. Important variations in the quantity of non-coupled network defects (which are not elastically active), crosslink distribution as well as chain dynamics were found according to the different vulcanization reactions. They could partially explain the variation in the elastic properties of these samples. Note that we never observe any influence of Gaussian chain statistics on network chain dynamics. Cooperativity between polymer chains reduces and homogenise the conformational space that ultimately governs the chain entropy.

[1] K. Saalwachter. Prog. NMR Spectrosc., 2007, 51, 1-35.