Refractive Indices and Order Parameter S of Lyotropic Liquid Crystals: Hydroxypropyl Cellulose/Dimethylacetamide System

The order parameter S of a cholesteric liquid crystal of the hydroxypropyl cellulose/dimethylacetamide system was calculated using refractive index data. Two approaches were used: method 1 used solid-state data, and method 2 was Haller's extrapolation approach. The S values obtained using method 1 lay in the range of 0-0.9 and the S values calculated using method 2 were in the range of 0.4-0.5, within our experimental range. The S values depended on temperature and concentrtion, and could be generalized by a master curve. Although both approaches involved implict problems, method 2 is preferable for estimating S values of lyotropic liquid crystals.