Dual Resolution Molecular Simulation of Bisphenol-A Polycarbonate Adsorption onto Nickel (111): Chain Length Effects

Summary

We discuss results of molecular dynamics simulations of dense liquids of BPA-PC adjacent to (111) nickel surfaces. The BPA-PC molecule is modeled using a dual-resolution coarse-grained representation, in which the chemical repeat unit is represented by four spherical beads, each roughly corresponding to a comonomeric functional group, except at the chain ends, where the terminal carbonate groups are represented atomistically. This dual resolution scheme is necessary to give access to an orientational degree of freedom upon which the polymer/surface interaction potential sensitively depends. The results expand upon those of Ref. [Abr03b], in which chains of length N = 10 repeat units were considered, by considering chains of length N = 20. We observe that the structure of the liquid near the wall is sensitively affected by the strong attraction of the chain ends to the surface for both chain lengths. The liquid forms two layers: in the innermost layer near the wall, most chains have both ends adsorbed, while in the outermost layer, most chains have a single end adsorbed. This structure leads to an interesting profile in chain orientation, where chains are flattened in the innermost layer and stretched in the outermost layer. The overlap between these two layers is more diffuse in the case of the N = 20 chains.