Induced smectic A and C phases formed by liquid-crystalline binary systems consisting of nematic twin compounds

Abstract

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