Abstract
Semi-rigid polyesters having nitro- or methoxyazobenzene unit in the side chain and calamitic mesogen (biphenyl or 2,5-diphenyl-1,3,4-thiadiazole unit) in the main chain were prepared by melt polycondensation of diethyl isophthalates composed of the azobenzene units with three dioxydiundecanol derivatives of the mesogenic units and their thermotropic liquid crystalline (LC) and optical properties were evaluated. The assigned structures of polymers were characterized by FTIR and 13 C NLR spectroscopy and elemental analyses. Differential scanning calorimetry (DSC) measurements, optical texture observation, powder X-ray analyses and miscibility tests indicated that most of the polyesters form thermotropic LC (smectic B, C, and E) phases and the polymer having the nitroazobenzene in the side chain forms the most stable LC phase. Absorption spectra of the polyesters in solutions and in films showed absorption maxima based on the azobenzene or the 2,5-diphenyl-1,3,4-thiadiazole unit, whereas their emission spectra were not observable.
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