THERMAL TRANSITIONS OF LIQUID-CRYSTAL POLYESTERS - POLY(DECAMETHYLENE-4,4'-DIPHENOXY TEREPHTHALATE)

The thermal transitions of liquid crystalline poly (decamethylene-4,4'-diphenoxy terephthalate) have been studied by differential scanning calorimetry, X ray diffraction and thermoptical microscopy. At room temperature a three dimensional order and a smectic mesophase coexist. The crystal-smectic mesophase transition occurs at 240-degrees-C and at higher temperature, 250-260-degrees-C, a transition from smectic C to nematic has been observed, before the isotropic transition at 290-degrees-C. The no previously known smectic C-nematic transition has been detected by microscopy, observing bars and striated textures, and by X ray diffraction patterns obtained in the whole range of temperatures.