(723a) Modeling the Bound Polymer Layer in Polymer Nanocomposites

Polymer nanocomposites (PNCs) are usually fabricated by dispersing nanoparticles (NPs) in polymer solutions. During this process, polymer chains can be adsorbed to NPs surface and form a temporarily stable ‘bound layer’, when the polymer-NP interaction is attractive. The resulting structural and dynamical properties of this bound layer depend strongly on the formation process. Understanding this bound layer is critical to the applications of PNCs, from preventing NP aggregation to achieving superior mechanical and transport properties. In this work, we used molecular dynamics simulation and first studied the formation process of the bound layer near an amorphous NP embedded in a polymer solution. Different NP sizes, polymer chain lengths, and polymer-NP interactions are used to study their effects on the bound layer formation. We find a nonmonotonic change in the average coordination number of adsorbed chains when polymer-NP interactions are favorable enough, suggesting a two-step adsorbing process. We also employ systematic coarse-graining techniques to develop an implicit solvent model and study the polymer entanglement change during the solvent evaporation process.