Synthesis and mesomorphic properties of a series of dimers derived from thioether-terminated and cholesteryl

ABSTRACT

The synthesis and material properties of a series of new liquid crystalline compounds containing thioether and cholesteryl, these homologues with different alkyl chain lengths of 2–8, are reported. Thermal analysis shows that all oligomers have wide mesophase temperature ranges with high thermal stability. The oligomers were determined by differential scanning calorimetry (DSC) and polarising optical microscopy (POM). The molecule not only successfully exhibits strong optical properties and rainbow colours, but also the cholesteric helical pitch decreased with increasing temperature. The mesogenic incidence and tendency were found to be strongly dependent on the numbers of carbon in the flexible alkyl chain. Even members formed widely mesophase compared to odd members that showed narrower ones. The reflection wavelengths of 6S8Ch are almost across the entire visible region when they are heated, which offer tremendous potential for various optical applications. Also, it not only shows a lower transition temperature but also has a narrower cholesteric phase compared to analogues with alkoxy groups. These results not only provide practical design principles for the synthesis of new sulphur-containing LC materials with optical applications, also make a significant contribution to use as thermally sensitive liquid crystal devices requiring fast response.