Smectic-Aordering at a liquid-vapor interface

Publisher Website
Google Scholar
Abstract
The development of smectic-A ordering at the interface between isotropic liquid and vapor is studied using a density-functional theory, based on a mean-field approximation for the effect of attractive pair interactions and weighted-density treatment of repulsive-core contributions. In contrast to earlier microscopic theories of this phenomenon, the bulk liquid and vapor phases are in complete coexistence with each other, and no arbitrary ‘‘surface fields’’ independent of molecular pair interactions are invoked. The wetting behavior of the interface is studied as a function of the molecular-core anisotropy, which controls the relative stability of bulk nematic and smectic-A phases, under conditions where the attractive pair interactions favor complete wetting by the nematic phase. There is a change to incomplete wetting by the smectic-A phase when the latter preempts the nematic, in a process analogous to a triple-point wetting transition. This is consistent with experimental results, but the growth of smectic layers at the interface is always found to be continuous, with no evidence of the first-order layering transitions observed in experiment.