Mesophase Structure in Salt-containing Solutions and Gels of Liquid-Crystalline Cellulose Derivatives and Electrical Control of their Optical Properties

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Cellulosic polymers possess inherently the semirigidity and chirality in the carbohydrate backbone, and therefore, they are capable of forming a 'cholesteric' liquid-crystalline phase in a condensed fluid state and often colored due to selective reflection of visible light. Concentrated aqueous solutions of (hydroxypropyl)cellulose (HPC) exhibit such a typical cholesteric character.This polymer solution system is also known to show an LCST-type of phase diagram and therefore becomes turbid at an elevated temperature. In the present research project, we investigated 1) mesophse behavior in salt-containing solutions of HPC and related polysaccharides, 2) conditions for preparing gels and films with a cholesteric arrangement of these polymers, and 3) a new method to control the optical properties coming from the liquid crystallinity and phase diagram characteristic of cellulose derivatives. The following results are worth noting :1. For the aqueous HPC/salt lyotropic system, it was shown … More clearly that the cholesteric periodicity parameter as well as the cloud point increased with an increase in strength of a so-called chaotropic effect of the additive salts. The orientation order in the liquid crystallne phase was, nevertheless, insensitive to the salt addition, as evidenced by a deuteron NMR study.2. We designed and constructed. a device desirable to produce a dynamic variation in the cholesteric coloration and optical turbidity of the aqueous HPC/salt solutions by electrical stimulation. The electrification process was examined quantitatively to clarify the mechanism.3. Colored films were prepared successfully via polymerization of HPC solutions in a methacrylate monomer/water/methanol mixted solvent. When the crosslinked cholesteric films were immersed and swollen in aqueous salt solutions, the coloration and turbidity of the samples changed depending on the sort of the coexistent salt.4. A novel network formation and phase structure were studied for a few related polysaccharides. Less