Alignment of a Smectic Side Chain Liquid Crystalline Polymer Using Surfaces and Alternating Electric Fields

Alternating electric fields can align the smectic A side chain liquid crystalline polymer poly(M060NS) while it cools from the isotropic phase to the smectic phase, forming an optically transparent texture. The effect occurs only above a threshold electric field strength, and depends strongly on sample thickness and cooling rate, and weakly on electric field frequency. The aligned monodomain is stable up to the smectic-isotropic transition temperature (although there is some pretransitional light scattering close to the transition), and is homeotropic, optically uniaxial, and shows strong meridional x-ray diffraction peaks due to the smectic layers. Surface fields can also align this material, producing similar monodomains, but only with samples below a certain thickness. It seems that this thickness is independent of the cooling rate.