Structure of interacting aggregates of silicananoparticles in a polymer matrix: small-angle scattering and reverse Monte Carlo simulations

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.

Silica nanoparticles dispersed in a self-assembled viscoelastic matrix: structure, rheology, and comparison to reinforced elastomers

“…The scattering experiment allows thus to access directly the structure factor, which is nothing but the Fourier transform of the pair correlation functions of the silica particles. Detailed analysis of the scattering data has been performed in the past [35], and the following, simplified picture was found to be compatible with the scattering experiment: silica particles, which interact mainly through electrostatic repulsion, carry more electrostatic charges at higher pH in solution. This mechanism leads to a better dispersion of the nanoparticles in the polymer matrix, i.e.…”

“…At intermediate solution pH, around 7, particles aggregate in clusters of approximately one hundred, but the remaining repulsion between particles induces a strong liquid-like ordering of the clusters within the matrix. This leads to a characteristic peak in q-space, the position of which can be used to estimate the average aggregation number with good precision; in any event, such a structure is compatible with the scattering data, as shown by Reverse Monte Carlo simulations [35] .…”

“…Several papers have been published on the silica-latex model system, and in particular on the structure of the silica in this particular polymer matrix [34,35]. For the sake of comparison with the hydrogel system, important results are recalled and put into perspective.…”

Analysis of structures of rubber-filler systems with combined scattering methods

“…For rubber-filler systems, the aggregation of primary silica particles has been investigated with the reverse Monte Carlo method, and real space images were obtained for the aggregations of silica particles. [56][57][58][59][60] Hagita et al 61,62 developed a 2D pattern reverse Monte Carlo method for the analysis of 2D scattering patterns. They applied the method to the investigation of structural changes in silica particle filler under uniaxial elongation.…”

Preparation, characterization and properties of polycaprolactone diol-functionalized multi-walled carbon nanotube/thermoplastic polyurethane composite

“…However, the application of CNTs to fabricating polymer-based composite with enhanced properties is strongly limited, [17,18] which is mainly due to the following two factors: first, raw CNTs tend to aggregate because of van der Waals forces, consequently making CNTs very difficult to homogeneously disperse in polymer matrices; second, lack of sufficient interfacial interaction between the two phases makes CNTs easily slide in the matrices under external forces. One effective way to improve both the dispersion and interfacial bonding is to chemically functionalize CNTs [17,19,20].…”