Synthesis and phase behavior of mesogen-jacketed liquid crystalline polymer with triphenylene discotic liquid crystal mesogen unit in side chains

Abstract

A novel mesogen-jacketed liquid crystalline polymer (MJLCP) containing two triphenylene (Tp) units in the side chains, named poly[bis(3,6,7,10,11-pentakis(hexyloxy)triphenylen-2-yl)2-vinyl terephthalate] (PBTCS), was designed and successfully synthesized via conventional free radical polymerization. The chemical structure of the monomer was confirmed by ¹H/¹³C NMR and high-resolution mass spectrometry. The molecular characterization of the polymer was performed with ¹H NMR, gel permeation chromatography (GPC) and thermogravimetric analysis (TGA). The phase structure and transition of the polymer were investigated by the combination of techniques, including differential scanning calorimetry (DSC), polarizing optical microscope (POM), 1D/2D wide-angle X-ray diffraction (1D and 2D WAXD) and 1D small-angle X-ray scattering (1D SAXS). The results showed that the PBTCS reached a relatively high glass transition temperature and formed a higher symmetry hexagonal columnar (Φ_H) phase due to the strong coupling effect between the Tp moieties and the MJLCP main chain.