Anisotropy of Self-diffusion in a Liquid Crystal Studied by Neutron Quasielastic Scattering

Abstract

Abstract The coefficient D for self-diffusion in nematic p-azoxyanisole has been determined from measurements of the energy width of quasi-elastically scattered neutrons. The directional dependence of D was studied by polarizing the substance along different directions relative to the scattering vector. For an unpolarized substance we measured D= 1.4 × 10−5 cm2 sec−1, whereas for a polarized substacnce we found D∥ = 1.8 × 10−5 cm2 and D⊥ = 1.0 × 10−5 cm2 sec−1 for diffusion parallel with and perpendicular to the optical axis, respectively. These results are in qualitative agreement with the anisotropy of the viscosity coefficient, as measured by Miesowicz (Nature 136, 261 (1935); 158, 27 (1946)).