Real space observation of dynamic scaling in a critical polymer mixture

We have studied the growth of the wetting layer formed at the surface of a critical mixture of poly(ethylene propylene) and perdeuterated poly(ethylene propylene) during spinodal decomposition. The wavelength of the surface spinodal wave is found to grow as ${\mathit{t}}^{1/3}$ over the entire range of times accessible in the experiment. The composition profiles exhibit universal scaling behavior in the near-surface region. These results are in excellent agreement with a recent numerical study on surface-directed spinodal decomposition.