Pyridine-based chiral smectogens: effects of polar end groups on liquid crystal properties

In this study, novel chiral pyridine-based rod-like mesogens, consisting of a chloro or bromo group substituted pyridine head core which is connected to one or two aromatic rings through ester linkers and a flexible (S)-2-methylbutoxy or (S)-3,7-dimethyloctyloxy chiral end chain have been synthesised. The liquid crystal properties of new compounds were investigated by various experimental techniques such as DSC, POM and SAXS. Depending of the nature of the halogen end group, the derivatives with two aromatic rings are non-mesogenic compounds whereas a smectic A phase (SmA) enantiotropically occurs for the members with three aromatic rings of the series. Additionally, chloro group substituted compound composed of three aromatic rings carrying a (S)-2-methylbutoxy end chain exhibits an enantiotropic chiral nematic phase (N*).