Thermal and X-Ray Diffraction Studies of Some Liquid Crystals Having a Nitro Group at the Lateral Position

Abstract

3-Nitrophenyl 4-(4-octyloxy- and 4-(4-nonyloxybenzoyloxy)-benzoates(compound 1), 4-(4-octyloxyphenoxycarbonyl)phenyl 3-nitrobenzoate(compound 2), 4-(4-octyloxy- and 4-(4-decyloxybenzoyloxy)phenyl 3-nitrobenzoates(compound 3), and 3-nitrophenyl 4-(4-octyloxy- and 4-(4-nonyloxyphenoxycarbonyl)benzoates (compound 4) have been prepared. All the compounds show smectic A and nematic phases, where the molecular arrangement in the smectic A phase is dependent on the orientation of the ester linkages. The smectic A phase for compounds 1 and 3 has a monolayer arrangement of the molecules, while the smectic A phase for compound 3 also involves a small contribution of a partially bilayer nature near the smectic A-nematic transition. The smectic A phase for compound 2 has a bilayer arrangement, and compounds 4 probably the bilayer one. A dipole correlation within the smectic A phases has been discussed.

Key Words:

• polar liquid crystals
• smectic A modification
• x-ray diffraction
• lateral substituent effect