Thermotropic liquid crystalline polymers containing five-membered heterocyclic groups IX. Synthesis and optical properties of liquid crystalline semi-rigid polyesters composed of a quinquephenyl analogue containing 1,3,4-thiadiazole and aliphatic chains†

Abstract

Novel semi-rigid polyesters containing a quinquephenyl analogue containing 1,3,4-thiadiazole and a central 1,3-phenylene unit in the main chain were synthesized by high temperature solution polycondensation of a dimethyl ester derivative of 1,3-bis(5-phenyl-1,3,4-thiadiazol-2-yl)benzene with an aliphatic (octa-, deca- and dodecamethylene) diol. The proposed structures were confirmed using FTIR and 1H NMR spectroscopies, and elemental analyses; their liquid crystalline and photoluminescent (PL) properties were examined by means of differential scanning calorimetry, optical texture observations using polarizing microscopy, powder X-ray diffraction, and UV-vis and PL spectra measurements. These measurements showed that the polymers not only show a monotropic solid smectic or disordered crystal phase, but also PL properties with blue emission in HFIP solutions and in the solid phase, Stokes shifts of 116.5–119 nm being observed.