INTERFERENCE OF SPINODAL WAVES IN THIN POLYMER-FILMS

We have studied the thickness dependence of the spinodal decomposition in thin films of a binary polymeric mixture. Nuclear reaction analysi s (NRA) and time-of-flight forward recoil spectrometry (TOF-FRES) have been used to monitor the phase separation in thin films of poly(ethyl enepropylene) (PEP) and perdeuterated poly(ethylenepropylene)(dPEP) af ter a quench into the two-phase region. The composition profiles are m odeled by two distinct spinodal waves originating from the two surface s of the films, and interference effects are observed as the film thic kness is varied. Below a critical film thickness the coarsening of the phase structure is found to be severely altered with respect to the t hick film behavior. Cell-dynamical simulations have been performed whi ch closely resemble the experimental findings.