Using dissipative particle dynamics simulations, we study the effects of an
embedding bulk fluid on the phase separation dynamics in a thin planar liquid
film. The domain growth exponent is altered from 2D to 3D behavior upon the
addition of a bulk fluid, even though the phase separation occurs in 2D
geometry. Correlated diffusion measurements in the film show that the presence
of bulk fluid changes the nature of the longitudinal coupling diffusion
coefficient from logarithmic to algebraic dependence of 1/s, where s is the
distance between the two particles. This result, along with the scaling
exponents, suggests that the phase separation takes place through the Brownian
coagulation process.Comment: 6 pages, 5 figures. Accepted for publication in Europhys. Let