Structure of interacting aggregates of silica nanoparticles in a polymer matrix Small-angle.pdf

1 Structure of interacting aggregates of silica nanoparticles in a polymer matrix: Small-angle scattering and Reverse Monte-Carlo simulations Julian Oberdisse1, Peter Hine2 and Wim Pyckhout-Hintzen3 1 Laboratoire des Collo?des, Verres et Nanomatériaux, UMR 5587 CNRS,Université Montpellier II, 34095 Montpellier, France 2 IRC in Polymer Science and Technology, School of Physics and Astronomy University of Leeds, Leeds, LS2 9JT, United Kingdom 3 Institut für Festk?rperforschung, FZ Jülich, 52425 Juelich, Germany 13th of October 2006 Figures : 10 Tables : 3 2 ABSTRACT Reinforcement of elastomers by colloidal nanoparticles is an important application where microstructure needs to be understood - and if possible controlled – if one wishes to tune macroscopic mechanical properties. Here the three-dimensional structure of big aggregates of nanometric silica particles embedded in a soft polymeric matrix is determined by Small Angle Neutron Scattering. Experimentally, the crowded environment leading to strong reinforcement induces a strong interaction between aggregates, which generates a prominent interaction peak in the scattering. We propose to analyze the total signal by means of a decomposition in a classical colloidal structure factor describing aggregate interaction and an aggregate form factor determined by a Reverse Monte Carlo technique. The result gives new insights in the shape of aggregates and their complex interaction in elastomers. For comparison, fractal models for aggregate scattering are also discussed. 3 I. INTRODUCTION There is an intimate relationship between microscopic structure and mechanical properties of composite materials [1-5]. Knowledge of both is therefore a prerequisite if one wishes to model this link [6-8]. A precise characterization of the three-dimensional composite structure, however, is usually difficult, as it has often to be reconstructed from two-dimensional images