Curvature elasticity and rotational viscosity of the nematic decylammonium chloride system

Experimental data are reported on curvature elasticity and rotational viscosity of micellar nematics formed in the decylammonium chloride/NH₄Cl/H₂O system. Two mixtures of different salt concentrations were studied (DACl:NH₄Cl=10:1 and 20:1 by weight). The constants for the bend elasticity and the rotational viscosity were found to vary over nearly three orders of magnitude from 0.2×10⁻⁶ to 150×10⁻⁶ dyn and from 1 to about 1000 P, respectively. The large range is due to the divergence at the nematic–smectic transition. Both constants diverge with the same exponent. We obtained an exponent of 1.07±0.05 for a weight ratio DACl/NH₄Cl of 20 and 0.87±0.02 for a ratio of 10, but an unexpected thermal hysteresis interfered with a reliable determination of the critical properties. Overall, the elastic properties and the divergence is this micellar nematic are similar to those observed in thermotropic nematics.