Pitches and Phase Textures of C12TPPH2 Doped with Chiral and Non-chiral Mesogenic Additives

Abstract

Applications of thermotropic liquid crystals are mainly in display technologies. By doing so, anisotropic nematic compounds are doped with cholesteric derivatives to create twist structures, suitable for various switching modes. In this study, similar ideas are applied into a porphyrin derivative, i.e., C12TPPH2. C12TPPH2 under a polarized light microscope is known to show discotic lamella phases. In this study, C12TPPH2 was doped with the mesogenic and non-mesogenic additives, which resulted in new phase characteristics under a polarized light microscope, using a heating stage for temperature controlling. The chiral mesogenic derivatives were of oxovanadium and copper(II) complexes of chiral -diketone ligands, etc., and of pyrazole and pyroxyzole groups. C12TPPH2 was mixed well with an additive using dichloromethane as solvent. A few drops of the solution were placed onto a pre-cleaned microscope slide where the solvent evaporated. Finally, the dried sample was covered with a cover glass and placed inside a temperature controller. The sample slide was heated above clearing point and the textures were observed on cooling. Figure 1(a) shows ordinary textures of C12TPPH2 at the rim of the slide. However, at 2 mol% of chiral compound, the mixture exhibited a distinct texture showing some periodic textures similar to twist formations at the material boundary, Figure 1(b). It was also found that the pitches of the periodic textures were linearly depended on the concentrations of added chirals. Additionally, C12TPPH2 doped with some non-chiral additives were also investigated.