著者

安藤 桃子 杉村 和紀 上高原 浩

出版者

公益社団法人 日本材料学会

雑誌

材料 (ISSN:05145163)

巻号頁・発行日

vol.70, no.7, pp.547-553, 2021-07-15 (Released:2021-07-20)

参考文献数

30

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Liquid crystallinity of (hydroxypropyl)cellulose (HPC) derivative in aqueous solution was examined to develop eco-friendly liquid-crystalline system. Bulky adamantoyl group (adamantyl ester) was introduced as a substituent on HPC, and the effects of the degree of adamantoyl substitution (DSAd), polymer concentration, and temperature on the chiroptical properties, especially coloration and turbidity, of the aqueous lyotropics were investigated by circular dichroism, CD, and ultraviolet–visible–near-infrared, UV–Vis–NIR, spectrophotometry. Adamantates of HPC (Ad- HPCs) with extremely low DSAd (< 0.1) were successfully synthesized by acylation of HPC with 1-adamantanecarbonyl chloride in tetrahydrofuran. Ad-HPCs of DSAd ≤ 0.08 were highly soluble in water, and the concentrated aqueous solutions formed a right-handed cholesteric liquid-crystalline phase to impart vivid reflective colorations. The cholesteric helical pitch P, comparable to the wavelength of maximal reflectance λmax, increased with increasing DSAd of Ad-HPC and with decreasing polymer concentration. Wide-angle X-ray diffractometry, WAXD, revealed that the increases of P were attributable to the decrease of the twist angle ϕ between adjacent thin nematic layers. The aqueous Ad-HPC lyotropics were phase-separated and became turbid at an elevated temperature of > ∼30°C. Such a lower critical solution temperature (LCST)-type phase separation behavior of the Ad-HPC/water system was also affected by the hydrophobic adamantoyl group; the observed cloud point Tc was shifted to lower temperature side with increase in DSAd, presumably due to the heightening of hydrophobic interactions between the solute Ad-HPCs in water.