Interfacial polar ordering and anomalous tilt angles at isotropic-nematic interfaces

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Abstract
We employ phenomenological methods to discuss the way that interfacial polar ordering of liquid crystals may affect the orientation (tilt angle) of a bulk nematic phase near an isotropic-nematic interface. The theory invokes the up-down asymmetry of the molecules to account for the anomalous behavior of substances (e.g., the n-alkyl cyanobiphenyls) that exhibit tilt angles other than 0° or 90°. In the absence of this asymmetry, the molecules in the bulk nematic phase must lie either parallel or perpendicular to a diffuse isotropic-nematic interface. We rule out several other ostensibly reasonable mechanisms by which a nematic phase might tilt at an isotropic-nematic interface.