Coarsening of two-dimensional island emulsions on smectic liquid crystal bubbles in microgravity*

Two-dimensional island emulsions in molecularly thin, tethered smectic liquid crystal bubbles in microgravity are observed to coarsen via coalescence and Ostwald ripening in both the smectic A and smectic C phases. We report here on the observed dynamics of island growth and disappearance in the absence of coalescence at locations in the island emulsion far from the meniscus around the bubble inflation needle. This Ostwald ripening occurs as a result of the system’s tendency to reduce its energy through a decrease in the total length of the island boundaries, a process that is generally dependent on the surface and line tensions and the disjoining pressure of the islands. Smaller islands generally have a higher disjoining pressure than their larger neighbors, which results in permeative flow from the smaller to the larger islands. We will also describe emulsion coarsening by island coalescence and compare the experimentally observed coarsening dynamics with simulations.