A New Director Alignment for Droplets of Nematic Liquid Crystal with Low Bend-to-Splay Ratio

Abstract

The first observation of a new director orientation within nematic droplets is reported. This orientation consists of the nematic director field arranged concentrically around a central core running through the center of the droplet, with tangential alignment of the nematic at the droplet surface. It is shown that for tangential wall alignments, the observation whether a droplet adopts the axial alignment or the previously reported bipolar droplet alignment is correlated with the k ₃₃/k ₁₁ ratio of the nematic, with a low ratio favoring the axial alignment. A qualitative argument for this preference is given. It is observed that distorting an axial droplet by placing it in a solid polymer host also distorts the director field and central core within the droplet. Droplets in the axial alignment in a polymer film can be forced into the bipolar alignment by the application of an electric field. The nature of the central core defect is discussed, with arguments made that it is a true line defect.