This title appears in the Scientific Report : 2010 

Strain induced anisotropies in silica polydinethylsiloxane composites
Schneider, G.J.
Göritz, D.
JCNS; Jülich Centre for Neutron Science; JCNS
Neutronenstreuung; IFF-5
Streumethoden; IFF-4
The @journal of chemical physics, 133 (2010) S. 024903
Melville, NY American Institute of Physics 2010
Journal Article
Großgeräte für die Forschung mit Photonen, Neutronen und Ionen (PNI)
BioSoft: Makromolekulare Systeme und biologische Informationsverarbeitung
Journal of Chemical Physics 133
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Structural changes of silica in polydimethylsiloxane rubber induced by external forces were studied by means of small-angle X-ray scattering experiments. The silica fraction varies from 9 up to 23 vol% and the elongation ratio from 1 to 3. Within the q-range of 0.02 nm(-1)<q<1 nm(-1) the primary particles and the clusters which consist of these basic units could be resolved. The scattering diagrams of the samples without external deformation are radially symmetric and, in particular, the mass fractal dimension does not depend on the silica fraction. Due to the deformation the contours of the two-dimensional scattering diagrams become elliptic. A model independent analysis of the intensity as a function of the q-vector perpendicular and parallel to the deformation axis revealed that the microscopic cluster size is systematically increased by the macroscopic external deformation. In particular, the deformation ratio at the microscopic and the macroscopic length scale is very similar. The mass fractal dimension, as obtained by the slope of the scattering curve, increases significantly with growing deformation ratio, but is the same in vertical and horizontal directions. A simple relation derived for the crossover from self-similar to self-affine fractals can be used to relate the cluster sizes perpendicular and parallel to the deformation and the mass fractal dimension. By that means, it is demonstrated that the mean number of particles within each aggregate is constant, although the rubber was stretched up to a factor of 3.