Axial chiral allenylacetates as novel ferroelectric liquid crystals

Liquid crystalline alkane-3,4-dienoates (allenylacetates) have been synthesized. Most compounds incorporate a heterocyclic 1,3,4-thiadiazole ring or a pyrimidine ring as a constituent of the rigid core. These axial chiral allene derivatives were at first obtained as racemic mixtures. Some of them were also synthesized in enantiomerically enriched form by enantioselective synthesis. The compounds were investigated by polarizing microscopy and by differential scanning calorimetry. The three-ring compounds exhibit broad regions of smectic C-phases. The optically active three-ring compounds show broad S-c*-phases with moderate values of spontaneous polarization.