SYNTHESIS AND MESOMORPHIC PROPERTIES OF AZO-COMPOUNDS DERIVED FROM PHENYL-1,3,4-THIADIAZOLE AND THIENYL-1,3,4-THIADIAZOLE

The synthesis and mesomorphic behaviour of new series of liquid crysta ls containing 1,3,4-thiadiazole and thiophene rings with azo central b ond are reported (series 5a and 5b). All compounds of series 5a exhibi t enantiotropic nematic mesophase and the higher homologues (n = 9-10) also show a monotropic smectic C phase. Series 5b show dimorphism S-C -N (for n = 5-7 the S-C is monotropic). These series are compared with the Schiff's bases analogues, the imine bond gives rise to similar li quid crystals phase but larger mesomorphic range.