MESOGENIC BEHAVIOR OF OPTICALLY-ACTIVE ALLENES - A NEW CLASS OF FLC

Some optically active liquid crystalline 1,3,4-thiadiazole derivatives incorporating differently substituted allenic moieties providing an a xis of chirality have been synthesized. The compounds were investigate d by polarizing microscopy, by differential scanning calorimetry and b y electrooptical investigation. Thereby a common ferroelectic behavior was found in the case of two derivatives whereas a more complex S-C- polymorphism was found in the case of the other derivatives. We propos e the occurrence of an antiferroelectric, a ferrielectric and a ferroe lectric phase.