Liquid crystalline behaviors of H-bonded dimer formed from the semi-phasmidic type carboxylic acid*

Liquid crystalline properties of acid-functionalized semi-phasmidic azo-compound were characterized by DSC, polarizing optical microscopy, and electro-optical measurements. The results suggested that this unconventional mesogenic dimer has a non-typical effective ``bend'' angle where two monomers form the hydrogen bond. To confirm this we performed electro-optical experiments in the nematic phase with strong external electric and magnetic fields. Cells with different surface geometries and treatments we used. The results reveal a behavior that is very distinct from that expected of conventional linear mesogenic dimers formed by a hydrogen bonding. The results confirm negative values of dielectric and diamagnetic anisotropies. Our observations indicate that ``bent-core-like'' dimeric mesogens are formed through an unconventional inter-molecular association. *Work supported by grant NSF/DMR-086991.