• Marceau, Sandrine

Abstract

The purpose of this study is to improve the understanding of the mechanisms leading to reinforcement effects in nanocomposite materials. To do this, "model" systems were fabricated using an amorphous polymeric matrix reinforced by colloidal silica nanoparticles. The optical, physicochemical and mechanical properties of these materials were linked to their morphology. The morphological analysis of the nanocomposites showed that the silica nanoparticles were in form of dispersed aggregates for filler fractions lower than 6 %, whereas for higher fractions a percolating network of silica was evident. The study of the molecular mobility of the polymer chains showed that the nanoparticles did not induce any variation of the global mobility of the chains. The linear viscoelastic behaviour showed that the variations with temperature of the real part of Young's modules and the damping factor tan d were connected to the underlying structure of the nanocomposites. The experimental results were then compared to those obtained using two different theoretical approaches. At the mesoscopic scale, we used an adapted micromechanical model to show that the presence of the percolating network of fillers could induce a strong reinforcement effect and a shift of the main relaxation towards lower temperatures for fractions of silica higher than the percolation threshold. At the atomic scale, we analysed a PBMA-silica system by molecular dynamics. Using this model, we could show the influence of the filler on the molecular mobility of the polymer and on the mechanical properties of the nanocomposites.

Topics

• nanoparticle
• nanocomposite
• impedance spectroscopy
• polymer
• amorphous
• mobility
• molecular dynamics