Refractive Index and Deuterium Resonance Measurements on Nematic Decylammoniumchloride, Ammoniumchloride, Water Mixtures

Abstract
Mixtures of decylammoniumchloride and NH4Cl in a molar ratio of 2.76: 1 with H2O or D2O were studied. The water concentration varied between 89 and 91 mole %. Refractive index and deuteron resonance measurements were made as a function of temperature covering the nematic range. The transition temperatures for samples with D2O were about 8°C higher than those with H2 at the same molar composition. The birefringence and the deuteron resonance splittings of D2O are a relative measure for the orientational order in the nematic phase. The two methods give results which are in good agreement. On a reduced scale the temperature dependence of the order follows for all studied mixtures approximately the same curve. The curve is similar to that found with typical thermotropic nematics.