Concentrated aqueous solutions of two samples of triple helical scleroglucan with molecular weights 1.93×105 and 1.24×105 were studied by polarizing microscopy and optical rotatory dispersion at temperatures from 11—35°C. As the polymer weight fraction w was increased, birefringent phases appeared in the continuous isotropic phase at w∼0.14 and 0.19 (for the higher- and lower-molecular weight samples, respectively) and spread over the entire region of the solution at w∼0.19 and 0.31, almost regardless of temperature. The microscopic patterns of these birefringent phases resembled those reported for cholesteric liquid crystals. The specific rotation [α]436 at 21.5°C markedly increased with increasing w between 0.14 and 0.19 and leveled off at a value about 700 times the infinite dilution value. From these findings, it was concluded that the birefringent phase of aqueous scleroglucan is cholesteric. The intrinsic birefringence of the scleroglucan triple helix in the cholesteric solution was estimated from the optical rotation data to be(1.5±0.5)×10−2.
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Yanaki, T., Norisuye, T. & Teramoto, A. Cholesteric Mesophase in Aqueous Solutions of a Triple Helical Polysaccharide Scleroglucan. Polym J 16, 165–173 (1984). https://doi.org/10.1295/polymj.16.165
- Triple Helix
- Cholesteric Liquid Crystal
- Phase Equilibrium
- Optical Rotatory Dispersion
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