Rotational Viscosities of Nematic Sodium Decylsulfate, 1-Decanol, D2 O Mixtures

Abstract

The studied mixtures of sodium decylsulfate, 1-decanol and D 2 O show a sequence of three nematic phases, a low temperature uniaxial phase N L , a biaxial phase N bx , and a higher temperature uniaxial phase N C . We report rotation experiments in magnetic fields to determine the anisotropy of the diamagnetic susceptibility and the rotational viscosity, electrical conductivity measurements to study micellar order and realignment in magnetic fields, and birefringence measurements and relaxation studies on thin surface aligned films. The measured rotational viscosities in N C range from a few poise to nearly 100 poise. There is a strong pretransitional decrease of the viscosity with decreasing temperature at the N C -N bx transition. The data in the N L range indicate also a pretransitional decrease as the N L -N bx transition is approached. Near the transition the viscosity is considerably smaller in the lower temperature N L -phase than in N C . The conduction anisotropy and birefringence in N C show some differences in the temperature dependence. Both decrease slightly as the uniaxial-biaxial transition is approached but the decrease of conduction anisotropy is more pronounced