Adhesion of Polycarbonate Blends on a Nickel Surface

Abstract

We demonstrate that the adhesive behavior of a phenol-terminated bisphenol A polycarbonate melt to a (111) nickel surface changes significantly if a small amount of short chains is present, i.e., in polydispersed melts or self-blends. Attractive interaction of the chain ends with the surface results in an adsorbed layer, made of single-and two-end attached chains. Short chains, however, diffuse from the bulk and occupy the adsorption sites much faster than the long ones. Interplay between the surface concentration of short chains, their molecular conformation, and excluded volume results in a nonmonotonic dependence of the surface coverage by long chains on the molecular weight of the additive. The smallest polycarbonate coverage is achieved for diphenyl carbonate due to its high mobility and relatively large excluded volume. We propose that self-blending can be used to modify, in a controlled fashion, the friction coefficient of a melt sheared past the nickel surface.

A hierarchical dualscale study of bisphenol-A-polycarbonate on a silicon surface: structure, dynamics and impurity diffusion

“…The densities are normalised relative to the total bulk density. There are several peaks and troughs near the surface and the density does not become constant and bulk-like until around 20 A. This value is similar to the value found for other polymer melts in contact with surfaces, for example, polystyrene on graphite 21 and poly(ethylene oxide) on TiO 2 .…”

“…This is clearly different to the case of adsorption on Ni(111), which is shown in Fig. 10 of Andrienko et al 20 In systems with longer polymer chains fewer chain ends are available and, therefore, the coverage might be expected to be lower than in the current case. However, in experiment the polydispersity can be high and it is known from simulation that short chains aggregate on the surface.…”

“…The structure and density profile is similar for each of the wall types considered and the density reaches the bulk value approximately 20 A from the surface. From the point of view of the conformations, however, the polymer does not become bulk-like until after z 60 A from the surface, which is the end-to-end distance for chains with one end attached to the surface.…”

“…However, in experiment the polydispersity can be high and it is known from simulation that short chains aggregate on the surface. 20 We would, therefore, expect that the current coverage is relevant also in experiment.…”

Simulation studies of soft matter: generic statistical properties and chemical details

“…The comparison of different chain ends shows that the melt morphology close to the surface for phenolic chain ends is significantly different from the generic dispersion force dominated structure [29]. This has also been extended to study the sliding of BPA-PC melts under shear with and without additives [30][31][32] and at a surface defect [33].…”