The Interplay of Bent-Shape, Lateral Dipole and Chirality in Thiophene Based Di-, Tri-, and Tetracatenar Liquid Crystals

A range of mesogenic mols. varying in both bend angle and strength of lateral dipole were synthesized, and their phase behavior was characterized by polarizing microscopy, thermal anal., x-ray diffraction, and electrooptical measurements. The authors find the general destabilization of the liq. crystallinity caused by strong lateral dipolar groups and the bent mol. shape are off-set in mesomorphic tetracatenars, which display stable nematic, smectic, columnar, and cubic mesophases. The broad mesomorphism of the tetracatenars contg. lateral dipoles and their incompatibility with chiral induction are explained by considering that loosely correlated dimers exist within the mesophases. Chiral mesophases of derivs. with strong lateral dipoles were achieved by attaching fewer or different side chains to each end of the mesogen. [on SciFinder(R)]