8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P7.50Thu 811:10-14:00Phase-separation kinetics of mixtures undernanoconfinement in the presence of concentrationgradients in the initial statePrabhat K. Jaiswal, 1 Kurt Binder, 1 and Sanjay Puri 21 Institute of Physics, Johannes Gutenberg University, Staudingerweg 7 55128, Maniz,Germany2 School of Physical Sciences, New Delhi, IndiaWe study the kinetics of phase separation of binary mixtures in confined geometries. If a homogeneousmixture in equilibrium is quenched below the miscibility curve, it becomes spontaneouslyunstable and decomposes into its components. This far-from-equilibrium evolution of the systemis usually nonlinear and is characterized by complex spatio-temporal pattern formation. The systemapproaches to its new equilibrium state via the emergence and growth of domains enrichedin the preferred state. This non-equilibrium dynamics is often referred to as domain growth orcoarsening kinetics or phase-ordering dynamics. In this work, we use Langevin simulations tostudy the effect of concentration gradient in the initial configuration of a homogeneous state onthe phase-separation kinetics of mixtures confined in a thin-film geometry between two parallelexternal surfaces. In particular, we focus on the emerged pattern formation due to the small filmthickness, as finite-size effects play a significant role on the growth kinetics. We find that thesystem undergoes a phase separation with a morphology that distinctly depends on the magnitudeof the initial concentration gradient: if the gradient is small, domains separated by domain wallsperpendicular to the two parallel external surfaces form. Larger gradients lead to a extremely longlived metastable state, where a single domain wall parallel to the external surfaces persists. Whilethe thickness of the film controls the magnitude of the gradient where the phase behavior changes,the lateral size of the film has no essential influence. Our work points towards the possibilityto stabilize metastable morphologies of materials by appropriately chosen non-equilibrium initialconditions of phase separation processes.50