Surface order in thin films of self-assembled columnar liquid crystals

Abstract

The way in which alignment of hexagonal columnar mesophases depends on molecular structure, film thickness, and surface interactions is investigated. Homeotropic orientation of tapered nonpolymeric and polymeric amphiphilic columnar molecules occurs most readily on carbon substrates. The planar alignment of asymmetric dendrimers is favored on a water surface but is not possible for a symmetric dendrimer. For the polymeric material, film thickness has a significant influence on the morphology. Thick films align homeotropically, but films that are only a few column diameters in thickness are planar, and their thickness is quantized. Because they must contain an integral number of layers of cylinders, the resulting morphology is terraced.