New chiral liquid crystal cyclic monomers based on diosgenin: synthesis and mesomorphism

ABSTRACT

A series of new chiral liquid crystal (LC) intermediate compounds (LC-C₁~LC-C₄) containing diosgenyl groups and the corresponding cyclic LC aliphatic carbonate monomers (LC-M₁~LC-M₄) were synthesised to investigate the relationship between their structures and phase behaviour. The chemical structures of the compounds obtained in this study were characterised using FT-IR, ¹H NMR and ¹³C NMR measurement. The phase behaviour and mesophase structure were investigated with polarising optical microscopy, differential scanning calorimetry and X-ray diffraction measurement. As a result, LC-C₁ and LC-C₂ showed focal conic texture of the choleteric phase, while LC-C₃ and LC-C₄ with longer spacer length showed fan-shaped texture of a smectic A phase. The monomers (LC-M₁~LC-M₄) all exhibited focal conic texture of the choleteric phase on heating and cooling cycles. Furthermore, the effect of the spacer length on phase behaviour of the LC compounds was discussed.

GRAPHICAL ABSTRACT

KEYWORDS:

• Liquid crystal
• phase behaviour
• diosgenin
• cyclic
• aliphatic carbonate

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

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Additional information

Funding

This work was supported by the National Key Research and Development Program of China (2016YFC1000902), National Science Foundation of China (51503093), Fundamental Research Funds for the Central Universities (N160504001 and N160503001), Science and Technology Committee of Liaoning Province (201501116), and Shenyang Science and Technology Bureau (F16-205-1-37).