Synthesis, Characterization, and Effects of Molecular Structure on Phase Behavior of 4-Chloro-1,3-Diazobenzene Bent-Core Liquid Crystals with High Photosensitivity

Abstract

In this study, a series of novel compounds were synthesized by adding azo functional groups and chlorine substituent to the central bent-cores to form a 4-chloro-1,3-dizaophenylene bent-core. The structure, mesogenic properties, and photosensitivity of these synthesized compounds were evaluated experimentally. The results show that these compounds exhibit a broad temperature window up to 63.8 °C for nematic phase and fast <i>trans – cis</i> photoisomerization in seconds with 80% conversion. Quantum mechanics modeling confirms that using azos as the central linkages can effectively reduce the molecular dipole moment, which appears to promote favorable mesogenic behaviors and photonic characteristics. Moreover, varying the carbon number in the terminal alkyl chains can alter molecular dipole, especially the polarizability anisotropy, of which the variation is strongly correlated with the phase transition temperature and temperature range of nematic phase. These findings suggest that reducing molecular dipole can promote favorable mesogenic and photonic properties.