Anisotropy of Binary Mass Diffusion Constants in Nematic, Smectic A and Smectic B Phases Studied by Forced Rayleigh Scattering

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Abstract
The binary mass diffusion constants of methyl red in p-butoxybenzylidene-n-octylaniline have been measured by forced Rayleigh scattering. Because of the different activation energies between the diffusion constants D // and D ⊥ in the smectic A (SA) and B (SB) phases, the anisotropy D ///D ⊥ drastically changes from 0.028 to 1.67 with the phase sequence through SB, SA and nematic (N). In SB, D // is much smaller than D ⊥, while D // gets larger than D ⊥ in SA near the phase transition temperature to N, T AN. The anomalous behavior at T AN is also discussed.