The effect of terminal alkoxy chain on mesophase behaviour, optical property and structure of chiral liquid crystal compounds derived from (−)-menthol

ABSTRACT

Herein, we present the results of our extensive investigations on the synthesis and phase behaviour of nine novel (−)-menthol-based chiral liquid crystal compounds. They possess three phenyl rings and substituted with (−)-menthyl and varying length of n-alkoxy chains at one end. With the aim of exploring the fundamental relationships between molecular structural features and thermal properties, nine terminal n-alkoxy groups from ethoxy to n-octadecaneloxy group in even numbers have been used. A detailed characterisation of their properties was carried out. The characterisation results clearly illustrate that all the series compounds show the thermodynamically stable phases; the shorter chain homologues display only the BPI and N* phases, and the middle ones exhibit BPI, N* and S_A* phases while the longer chain members show the BPI, N* and S_C* phases. Besides, the BPI appeared in a narrow temperature range because of their thermodynamic disruption. Temperature range of the N* phase narrows when the length of the n-alkoxy tail increases. The reflection peak is shifted towards short wavelength region with increasing temperature due to the winding of the chiral nematic helix in the N* phase. Furthermore, their inherent reflection peak intensities of reflections were gradually weakened.

Graphical Abstract

KEYWORDS:

• (−)-Menthol
• chiral liquid crystal
• blue phase
• chain length

Acknowledgements

This work was supported by National Natural Science Foundation of China: [Grant Number 51273035] and the Fundamental Research Funds for the Central Universities [Grant Number N160504001].

Disclosure statement

No potential conflict of interest was reported by the authors.

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Funding

This work was supported by the National Natural Science Foundation of China: [Grant Number 51273035]; the Fundamental Research Funds for the Central Universities [Grant Number N160504001].