Domain Growth and Wetting in Polymer Mixtures

We present the results of phase-separation experiments performed on the binary polymer blend polyisoprene-poly(ethylene-propylene). Elastic light scattering and optical microscopy were used to follow the phase-separation after quenches into the coexistence region of the phase diagram. For critical quenches, we observed the well known bicontinuous infinite cluster morphology normally associated with spinodal decomposition, but with two distinct growth modes. In the bulk, we observed L(t) - t1/3 consistent with diffusion driven dynamics, whereas near the sample walls, there obtained a novel fast growth with L(t) -t 3/2, inconsistent with either diffusion or interface driven dynamics. We attribute this large exponent to wetting effects, but still lack any theoretical understanding of the phenomenon.