Entropic Trapping of Particles at Polymer Surfaces and Interfaces

Abstract

I consider the possibility that Gaussian random walk statistics are sufficient to trap nanoscopic additives at either a polymer interface or surface. When an additive particle goes to the free surface, two portions of the polymer surface energy behave quite differently. The purely enthalpic contribution increases the overall free energy when the additive protrudes above the level of the polymer matrix. The entropic part of the surface energy arising from constraints that segments near a surface can't cross it, is partly relaxed when the additive moves to the free surface. These two portions of the polymer surface energy determine the equilibrium wetting angle formed between the additive and the polymer matrix, the measurement of which in an experiment would allow an independent determination of each piece of the polymer surface energy.