  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.
