Electronic Conduction in Biphenyl Liquid Crystals

Abstract

A series of 4-alkyl-4′-alkoxylbiphenyls, which are one of the representative calamitic liquid crystals having a small aromatic core moiety, has been synthesized and their charge carrier transport properties are characterized in order to examine how small the core size can be for a high mobility. The biphenyls exhibit both smectic B and E phases and the hole transport characterized by a high mobility of 10−3 cm2 V−1 s−1 in the smectic mesophases. The mobility depends on temperature in both smectic phases, and furthermore it depends on the electric field in the smectic E phase. The fact that such a small molecule of biphenyl exhibits the mobility comparable to those of triphenylenes and TPD (N,N′-diphenyl-N,N′-bis(3-methylphenyl)[1,1′-biphenyl]-4,4′-diamine) gives an insight into the molecular design of high mobility liquid crystalline materials.

Revisiting Smectic E Structure through Swollen Smectic E Phase in Binary System of 4-Nonyl-4′-isothiocyanatobiphenyl (9TCB) and n-Nonane

“…Smectic E (SmE) phase is a liquid crystalline mesophase having a layer structure like smectic A (SmA) phase. The SmE phase has no fluidity and is the closest to an ordered crystal among orthogonal mesophases exhibited by calamitic mesogens. , Recently, the SmE phase attracts great attention because the mesogens showing the SmE phase are favorably applied to organic semiconductors. − For their development and improvement, it is important to know fundamental properties such as their structure. However, the fundamental investigation of their properties has progressed less so far, in comparison with other liquid crystalline phases, such as nematic and SmA phases.…”