Received October 12, 2005

In Final Form: November 28, 2005

Abstract:

We study the temporal growth pattern of surface fluctuations on a series of spinodally unstable polymer films where the instability can be adjusted with the film thickness, h₀. For the most unstable film studied (whose (h₀ - h_sp)/h_sp = 0.988; h_sp is the thickness where the second derivative of the interfacial potential of the film equals zero), the growth rate function of the surface modes as a function of the wavevector fits well to the mean-field theory. When the film thickness is increased such that (h₀ - h_sp)/h_sp 0.977, the mean-field theory demonstrates marked disagreement with experiment, notwithstanding the provision of the known corrections from nonlinear effects and thermal noise. We show that the deviations arise from large-amplitude fluctuations induced by homogeneous nucleation, which are not considered in the conventional treatments.

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