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