Helical vs. non-helical nematic and lamellar proper ferroelectric liquid crystal phases

Abstract

A new homologous series of mesogenic compounds with nearly linear mesogenic cores was studied, and it showed a strong discrimination between nematic and smectic phases with respect to the length of the terminal chain. For short homologues a ferroelectric nematic, N_F and a heliconical nematic, N_TBF phases were observed, while for longer ones they were replaced with ferroelectric smectic A_F and C_F phases. The n = 3 homologue exhibits a unique sequence of SmC_F and its heliconical analogue SmC^H_P. Replacing an alkyne linkage in the mesogenic core with an alkene one favoured smectic phases and led to the appearance of a modulated-type SmA_AF phase.