Coalescence and Phase Separation During Spinodal Decomposition of Solvent Mixtures Far From Critical Point

Cuny City College, New York NY

Investigators

Abstract

Abstract CTS-0123445 Shinnar, Reuel CUNY City College The PI's main achievement so far has been to show, both experimentally and theoretically, that phase separation of low-viscosity liquid mixture is driven by the convection induced by a non-equilibrium force due to gradients of chemical potential and that this force can act over distances of a few centimeters. While the investigation has produced novel and unexpected results, much work is required to achieve the ultimate goal and model the flow of liquid mixtures during phase transition in the presence of surface-active compounds. As has been stressed, the results so far have opened a new and till now unknown area of research which they do not expect to exhaust within the time frame of the proposed investigation. What the PI's would like to do, instead, is to focus on the most needed areas, to enhance the understanding of the dynamics of phase separation and increase the applicability of its unique properties to the solution of practical problems. In fact, they expect that coalescence can be eventually retarded increasing the amount of surfactants and of thickeners, thereby increasing the viscosity of the mixtures, or when quenching the mixture into its metastable region. Therefore, they intend to determine the thresholds of the surfactant concentration and of the mixture viscosity and composition beyond which surfactants start to slow down significantly the separation process, just as they do in the absence of phase transition. In addition, the PI's want to study how mixing, which is necessary to rapidly cool the system, can counteract the effect of phase transition, causing the formation of stable emulsions. As in the past, the experimental work will be accompanied by modeling and simulation, in such a way that these two activities will interact and compliment with each other. The results should not only lead to a better understanding of spinodal decomposition and nucleation, but will also be of great value to any industrial applications of this approach to phase separation. In particular, the PI's want to focus on the following areas of research, to be addressed both experimentally and numerically.