J. L. Valentín, I. Mora-Barrantes, J. Carretero-González, M. A.
López-Manchado, P. Sotta, D. R. Long, K. Saalwächter.
Experimental Approach To Evaluate Filler-Elastomer Interactions.
Macromolecules 43, 334-346 (2010). DOI 10.1021/ma901999j.
Novel information on filler-elastomer interactions is obtained by combining
solid-state 1H low-field NMR spectroscopy and
equilibrium swelling experiments. Multiple-quantum (MQ) NMR experiments provide
detailed quantitative molecular information on the cross-link density of the
elastomer matrix in a variety of filled systems, indicating generally weak
filler effects on the overall cross-link density and on the network homogeneity.
Swelling experiments, as well as mechanical data, are additionally influenced by
the matrix-filler and filler-filler interactions. Our approach is based on
comparing crosslink densities fromNMRand (Flory-Rehner) swelling experiments,
for which a masterline is always found in unfilled elastomers. In filled
elastomers two different scenarios are observed. If there are no interactions
between the polymer chains and the filler surface, no deviations from the
masterline are detected because the swelling capacity of the composite is
governed by the bulk polymer. Deviations from the masterline (reduced swelling)
are exhibited by those composites that have strong rubber-filler interactions.
In these cases, some fraction of the polymer is connected to the filler surface,
which thus behaves like a giant cross-link, and the overall degree of swelling
is thus reduced as compared to the bulk polymer. The novel experimental approach
was used to evaluate filler-elastomer interactions in different composites and