Initial solvent driven non-equilibrium behavior of polymer nanocomposites with varying size ratios between nanoparticles and polymers

Abstract

The adsorbed polymer layer near particle surface is important in polymer nanocomposites (PNCs) as it controls particle stability and resulting polymer properties. Therefore, extensive studies have been carried out to characterize the structure of adsorbed polymers and detailed adsorbed polymer-particle interactions; the adsorbed polymer near nanoparticle surfaces is known to have different mobility and conformation from the polymer in bulk. However, most of studies are discussed in their equilibrium states although polymers and nanoparticles may not reach the equilibrium state during the processing PNC. Processing of PNC requires initial mixing of polymer and particles in solutions and subsequent solvent evaporation; thus, polymers are often kinetically trapped because of their slow dynamics. Here, we investigate the role of initial casting solvent on the adsorption layer at interfaces and the resulting rheological property of PNCs where we systemically vary the size ratios between particles and polymers and show the casting solvent changes the thickness of immobilized polymer layer and polymer conformation on nanoparticle surfaces.