Ostwald ripening of two-dimensional islands in thin, spherical bubbles of smectic liquid crystal in microgravity*

We have recently made experimental observations of 2D coarsening in which thickness islands grow via coalescence and Ostwald ripening in molecularly thin, tethered smectic liquid crystal bubbles. We report here on the dynamics of island growth and collapse without coalescence in island emulsions at locations far from the meniscus around the bubble inflation needle. This Ostwald ripening of essentially 2D smectic A and C islands occurs as a result of the system’s tendency to reduce its energy through a decrease in the total length of the boundaries of the islands, a process that is generally dependent on the surface and line tension, the disjoining pressure of the island, and the excess air pressure inside the bubble. 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 describe our observations of Ostwald ripening behavior in smectic bubbles and compare these with the dynamics of island coarsening dynamics in flat smectic films.