Improvements in the Strength of Visible Selective Reflection in Lyotropic Liquid Crystals Made from Cellulose Urethanes

Lyotropic liquid crystals based on mixtures of cellulose tricarbanilates (urethanes) generated stronger selective reflection in the visible range after an increase in concentration of approximately 9 wt.-% above the concentrations described by Miiller, Zentel, and Keller in "Solid Opalescent Films Originating from Urethanes of Cellulose".[2] The cellulose urethanes used were of a lower molecular weight (less than 30,000 g mol ') than the material used in [2], which had a molecular weight of approximately 50,000 g mol-'. In preparing the liquid crystal samples, the cellulose urethane was dissolved in a volatile solvent before mixing with the acrylate host. The solvent dramatically reduced sample preparation time and, as a result of its volatile nature, could be removed from the sample during film casting. Additionally, physically blending two urethane homopolymers, rather than using a copolymer, has the potential to allow for greater control over the concentrations and reproduction of lyotropic liquid crystal samples. The physical blend of homopolymers still incorporates multiple R-groups into a sample as with a copolymer. However, unlike a copolymer, new compounds do not need to be synthesized each time a new concentration of these R-groups is required to produce a different selective reflection color. This method of creating a homopolymer blend, rather than synthesizing numerous