Influence of Thiophenes on Molecular Order, Mesophase, and Optical Properties of π-Conjugated Mesogens

Abstract

Increasing interest in π-conjugated aromatic cores built essentially with thiophene rings is recognized owing to their applications in optoelectronics. In this investigation, an attempt is made to understand the influence of terminal thiophene rings on the molecular order, mesophase, and optical properties of mesogens in which phenyl benzoate is part of the core. Accordingly, mono-, di-, and terthiophene units are linked to two phenyl ring core by Suzuki cross coupling reaction. The synthesized thiophene-based π-conjugated mesogens exhibit enantiotropic nematic and smectic phases with excellent mesophase range. The tendency for smectic phases and the mesophase range enhanced with increased thiophene rings. The layer ordering in smectic A and smectic C phase is established by powder X-ray diffraction, while the orientational order of all the rings of core unit is accomplished by 13C NMR spectroscopy. Thus the 13C–1H dipolar couplings determined from 2D separated local field NMR experiments show a very high...