INDUCED SMECTIC-A AND SMECTIC-C PHASES FORMED BY LIQUID-CRYSTALLINE BINARY-SYSTEMS CONSISTING OF NEMATIC TWIN COMPOUNDS

The binary systems consisting of di[4-(4-substituted phenylazo)phenyl] alkanedionates, which are twin liquid crystals, were prepared. The twi n liquid crystals having a nitro or a butyl terminal substituent exhib ited only a nematic phase with a schlieren texture. The liquid-crystal line binary system (BS-8-n) containing di{4-[4-(nitro)phenylazo]phenyl }sebacate and di{4-[4-(butyl)phenylazo]phenyl}sebacate which involve a n even number of central methylene units, exhibited an induced smectic A phase with a fan texture. However, the liquid-crystalline binary sy stem (BS-7-m) containing di{4-[4-(nitro)phenylazo]phenyl}azelate and d i{4-[4-(butyl)phenylazo]phenyl}azelate, which have an uneven number of central methylene units, showed an induced smectic C phase with broke n fan and schlieren textures, as well as a nematic phase. This differe nt liquid crystal formation can be related to the molecular shapes of the twin liquid crystals, due to the conformation of the central methy lene chain.