Mesoscopic surface structures in dewetted films of liquid crystalline polymers

Upon casting from dilute solution, liquid crystalline polyacetylenes and polyesters form mesoscopic dot and line patterns. After annealing in the liquid crystalline phase, the films dewet from the substrate and form isolated micronsize dots and line structures, which exhibit a peculiar surface structure as reveiled by polarizing microscopy and atomic force microscopy. The surface structure consists of micron-size shallow dimples that are a few nanometer in depth. The lateral spacing of the dimples, which arrange in a hexagonallattice, is directly proportional to the thickness of the dot. We propose that the dimple formation is due to a convective instability.