Chain ordering and molecular orientational order in liquid crystals

Abstract

We have extended the scheme for computing deuterium quadrupolar splittings of a flexible solute in a nematic solvent[Ferroelectrics30, 83 (1980)] to study chain ordering in the 4‐n‐alkyl‐4′‐cyanobiphenyl liquid crystals (nCB). All possible configurations {φ} of the nCB molecule are generated by the rotational isomeric state model of Flory. Each {φ} has a separate ordering matrix whose diagonal elements are assumed to scale with the shape anisotropy of the molecule as prescribed by the principal moments of inertia of the configuration I{φ}. Two models for identifying the molecular‐fixed‐frame are considered: (1) The frame diagonalizes I{φ}; (2) the frame is stationary on the nCB core. The variation of deuterium quadrupolar splittings along the alkyl chain can be satisfactorily explained by the calculations, however, the detailed behavior of the computed splittings are sensitive to the assumptions about the placement of the molecular‐fixed‐frame.