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

<p>A series of new chiral liquid crystal (LC) intermediate compounds (<b>LC-C<sub>1</sub></b>~<b>LC-C<sub>4</sub></b>) containing diosgenyl groups and the corresponding cyclic LC aliphatic carbonate monomers (<b>LC-M<sub>1</sub></b>~<b>LC-M<sub>4</sub></b>) 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, <sup>1</sup>H NMR and <sup>13</sup>C 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, <b>LC-C<sub>1</sub></b> and <b>LC-C<sub>2</sub></b> showed focal conic texture of the choleteric phase, while <b>LC-C<sub>3</sub></b> and <b>LC-C<sub>4</sub></b> with longer spacer length showed fan-shaped texture of a smectic A phase. The monomers (<b>LC-M<sub>1</sub></b>~<b>LC-M<sub>4</sub></b>) 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.</p>