Mesoscale Modeling of Phase Separation in Structured Fluids

Phase separation of polymeric fluids yields structures used in a variety of engineering applications from gas separations to bicontinuous structures with complimentary phases. Often, the constituent phases are amorphous with no large-scale internal structure, for which the dynamics of phase separation are well established. However, 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, especially at mesoscale length scales due to compuitational constraints. We present a computationally efficient coarse-grained molecular model for liquid crystals capable of forming both nematic and smectic phases. This model allows for the study of intermediate out-of-equilibrium states as the system undergoes phase separation. By varying the volume fraction, the phase formed by the liquid crystal, and its anchoring conditions with respect to the polymer, we observe a variety of structures during the phase separation process. We studied the coarsening dynamics of the systems via structure factor analysis and characterized their interfacial geometry by quantifying the curvature of the liquid crystal-polymer interface, thereby highlighting the emergence of various novel features compared to phase separation in isotropic fluids. We hope the improved understanding of these structured fluid systems will lead to novel materials featuring tailored interfaces for use in membrane technologies.