Structure and properties of novel three-armed star-shaped liquid crystals

A series of novel three-armed star-shaped liquid crystals based on 1,3,5-trihydroxybenzene as a core and u-[4-(p-alkoxybenzoloxy) phenoxycarbonyl]valeric acid as mesogenic arms were synthesized. Their chemical structures were confirmed by FTIR and 1H NMR spectra, their mesomorphic properties and phase behavior were investigated using differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffraction (XRD) measurements. The results show that the three-armed star-shaped liquid crystals exhibit a broad range of liquid crystalline phases at moderate temperature, no crystallization but vitrifying to form glass-forming mesogens during cooling from the isotropic melt. The formed crystals are glassy liquid crystals. The three-armed molecules are highly thermal stable and the mesomorphic ranges (DT) become wider as the terminal alkoxy chains become longer. Threadlike texture, a typical nematic phase, can be observed in the liquid crystalline state. q 2005 Elsevier B.V. All rights reserved