Phase separation in structured fluids

Trapped structures formed during the phase separation of fluids are used in a variety of engineering applications from polymer membranes for gas separations to bicontinuous structures in which the phases have complimentary properties. However, in nearly all these applications the two individual phases tend to be amorphous with no large-scale internal structure, for which the dynamics of phase separation are relatively well understood. When one of the phases is ordered, such as in a liquid crystal, the kinetics of phase separation and predictions of the structures that form are comparatively poorly understood. In this work, we introduce a computationally inexpensive coarse-grained molecular model of a liquid crystal that can form both nematic and smectic phases, allowing for the study of intermediate out of equilibrium states as the system goes through a phase separation process. By varying the volume fraction, the phase formed by the liquid crystal, and the depth of the quench into the two-phase region, we observe a variety of structures as the system undergoes phase separation. We characterize both the coarsening dynamics and the geometry of the structures formed, showcasing the development of various novel features compared to phase separation in isotropic fluids. We hope the improved understanding of this system will lead to novel materials for use in membrane technologies.