Variable density self consistent field study on bounded polymer layer around spherical nanoparticles

Abstract

A computational study focused on the interfacial region between polymer bulk and solid surface of spherical nanoparticles is presented. Our tool is a recently developed, properly modified for curved surfaces, variable density self-consistent field method. Grafted poly(styrene) on flat or curved surfaces and physically adsorbed poly(dimethylsiloxane) macromolecular chains on silica are examined. In the poly(styrene) study the existence of a depletion layer and an associating strong elongation of the polymeric chains is observed. On the detailed investigation of poly(dimethylsiloxane)/silica interface good agreement of the numerical results with the experimental data for the dependence of the width and the structure of the rigid amorphous inter-phase on the radius of the nanoparticle is reported. Moreover, a well understood dependence of the bounded polymer layer structure on the polydispersity (mainly bipolar structures) of the polymeric sample was found. Overall, we have shown evidence for the chain immobilization in the interfacial region and found that the thickness of the interphase is sensitive to the strength of the polymer-nanoparticle interaction and strongly depends on the curvature of the surface. Based on the unique behavior of bimodal brushes in equilibrium, confirmed by our findings, we have tried to enlighten silent and unclarified polymeric characteristics, which are not experimentally observable, and point the significance of the thermodynamic factor.