Straight-chain alkanediol derivatives leading to glassy cholesteric liquid crystals with visible reflection

Abstract

ABSTRACT Straight-chain alkanediols such as ethylene glycol are commonly found in our daily life as they are used to produce cosmetics, antifreezes, polyesters and polyurethanes. In this article, we report on the promising potential use of straight-chain alkanediols for rewritable full-colour imaging applications by the preparation of glassy cholesteric liquid crystals (G-CLCs). A series of straight-chain alkanediol derivatives possessing two cholesteryl groups through carbonate ester linkages (Cn-DiCh) showed thermotropic cholesteric liquid crystal phase with visible reflection. The thermally induced shifting ranges of reflection peaks were dependent on the central carbon chain length (n) of Cn-DiCh. Although the pristine Cn-DiCh showed narrow wavelength ranges of the reflection peaks by changing the temperature, we successfully prepared a mixture of two different kinds of Cn-DiCh at their equivalent weight ratio, which exhibited the reflection peak shift throughout a wide visible-wavelength range between 400 nm and 850 nm. Moreover, the binary mixtures of Cn-DiCh were rapidly cooled from the CLC temperatures to 0°C, whereupon the reflection colours could be preserved even at room temperature over 2 months. Such rapid cooling treatment enabled the straightforward preparation of solid-state G-CLCs with visible reflection characteristics, thereby leading to the applications of rewritable full-colour imaging media.