Banana-shaped mesogens: effect of 2-methylresorcinol as the central unit on the mesomorphic properties of five-ring esters

Abstract

Three homologous series of banana-shaped five-ring esters and one series of seven-ring esters derived from 2-methylresorcinol have been synthesized. This has been carried out to understand the effect of chemical structure on the mesomorphic properties of such compounds. It is shown that the 2-methyl substituent in the central phenyl ring destabilizes the mesophases when they are compared with those of the analogous unsubstituted compounds. Replacement of a phenyl ring by a biphenyl moiety (seven-ring esters) in the two arms of the bent-core molecule enhances the thermal range of the mesophases as well as the clearing temperatures. The mesophases have been characterized using techniques such as polarizing optical microscopy, differential scanning calorimetry, and X-ray diffraction, and by electro-optical investigations. In the 32 compounds investigated, two mesophases, B₁ and B₂, have been identified.