A new class of star-shaped cholesteric liquid crystal containing a 1,3,5-trihydroxybenzene unit as a core

A new class of star-shaped cholesteric liquid crystals were designed and synthesized, which used 1,3,5-trihydroxybenzene unit as a core and ω-cholesteric alkyl diacid monoester as mesogenic arm. Their chemical structures were confirmed by element analyses, FT-IR, and 1H NMR. The mesomorphic properties and thermal stability were investigated by differential scanning calorimetry, thermogravimetric analysis, polarizing optical microscopy, and X-ray diffraction measurements. The experimental results demonstrated that the mesogenic arm structures strongly affected the phase behavior. 4a did not show any liquid crystallinity, while 4b, 4c and 4d revealed reversible cholesteric phase transition. As the intermedius alkyl chain of the star-shaped compounds lengthened (from n = 2 to n = 8), their melting points decreased but mesomorphic temperature ranges increased. Focal conic texture, one of cholesteric phase can be observed in the liquid crystalline state.