Orthoconic antiferroelectric liquid crystals containing a terphenyl rigid core

Four homologous series of orthoconic (45 degree tilt) antiferroelectric liquid crystals, containing either a terphenyl or fluorosubstituted terphenyl core as mesogenic unit, have been synthesized and their mesomorphic behaviour investigated by the DSC and polarized light microscopy were discussed. X-ray diffraction studies have shown that above the ferroelectric smectic C* phase or antiferroelectric there was a de Vries-type smectic A phase. Some correlations between phase transition temperatures and positions of fluorosubstitution of rigid core are discussed. Temperature dependence of the helical pitch was measured for three different cores.