Domain Growth and Wetting in a Low Molecular Weight Binary Fluid System

We present the results of phase-separation experiments performed on the pseudo-binary fluid system guaiacol-glycerol-water. 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, at early times we observed L(t) ∼ t1/3 consistent with diffusion driven dynamics, crossing over to L(t) ∼ t1 at later times, as hydrodynamics became important. Near the sample walls, there obtained a novel fast growth with L(t) ∼ t3/2, just as in the case of recent studies with polymer blends, inconsistent with either diffusion or interface driven dynamics. We attribute this large exponent to wetting effects, and the observation of the same phenomenon in such disparate systems as polymer blends and polar organic solvents is strong evidence that the phenomenon is generic to binary systems.