Effect of terminal polar group on self-assembly behavior of hockey-stick shaped mesogen containing biphenyl ester Schiff base derivatives with chalcone moiety

Abstract

In this study, the hockey-stick shaped mesogens H(6–16), F(6–16) and CN(6–16), based on biphenyl ester (with flexible alkoxy chain n = 6,8,10,12,14,16) and chalcone derivatives with terminal −H, −F and –CN group were designed and synthesized. The self-assembly formation of these molecules was studied using polarizing optical microscopy (POM) and differential scanning calorimetry (DSC). It is found that depending on the alkyl chain length as well as polar terminal group, nematic and smectic liquid crystalline phases were observed. Interestingly, molecules with lower alkoxy chain length in homologous series H(6–16), F(6–16) (with n = 8–12) and high polarizability of cyano group in CN(6–16), resulted in the strong intermolecular interactions and showed usual mesophase as observed by rod-like molecules (N, SmA and SmC mesophases). While longer alkyl chain length in homologous series H(6–16), F(6–16) (with n = 14–16) along with SmA mesophase, cluster of SmC mesophases were observed in cooling cycle. Further, DFT theoretical calculations are carried out to comprehend the mesomorphic behavior of studied molecules and compared them with analogous reported compounds.