Study of phase separation of a binary fluid mixture in confined geometry.

Small angle neutron scattering experiments were performed to measure the structure factor [ital S]([ital q]) for a binary fluid water/lutidine mixture imbibed inside porous Vycor glass at concentrations both near and away from critical. In both cases, the results can be interpreted as a combination of a lutidine-rich wetting layer coating the internal surfaces of Vycor and random single-phase domain growth with temperature. This result does not support the random field Ising model predictions for the phase separation behavior, but is in good agreement with theories based on pore confinement of the imbibed fluid mixture.