Understanding the Swelling Behavior of Modified Nanoclay Filler Particles in Water and Ethanol

Abstract

Clay–polymer nanocomposite materials have gained much attention owing to their low weight ratio of filler to reinforcement properties, delivering lightweight yet resilient materials with excellent barrier properties to gas diffusion. An important process in their production is clay exfoliation, as maximum reinforcement and improvement of barrier properties occur when the clay mineral platelets are fully separated and dispersed through the polymer matrix with a preferred orientation. In this study we examine clay swelling—the first step leading to exfoliation—using molecular dynamics to generate solvation energetics, swelling curves, and atomic density profiles of three types of clay minerals—montmorillonite, vermiculite, and hectorite—with interlayer Na+ cations and/or three quaternary ammonium surfactants in water and ethanol. Analysis based on the provided simulations can help to distinguish between favorable and unfavorable swelling profiles of mineral/surfactant/solvent systems and therefore guide fur...