Elastic and Viscosity Constants of Nematic Liquid Crystals from a New Optical Method

Abstract

Shear flow in a liquid single crystal of the nematic type (MBBA) is studied. A homeotropic layer is enclosed by two circular glass plates, one of them rotating against the other. Between crossed polarizers one observes a system of concentric dark rings. The averaged optical anisotropy is found to be a pure function of the product of shear velocity and layer thickness. This agrees with the continuum theory of Leslie. The constants k ₁₁/k ₃₃, λ₁/λ₂, and (λ₂ − λ₂)/k ₃₃ are determined.