THERMAL AND STRUCTURAL STUDY OF THE PHASE-TRANSITIONS IN LIQUID-CRYSTALLINE POLY(HEPTAMETHYLENE TEREPHTHALOYL-BIS-4-OXYBENZOATE)

The structure and thermal transitions of liquid crystalline poly(heptamethylene terephthaloyl-bis-4-oxybenzoate) have been studied by differential scanning calorimetry, X-ray diffraction and optical microscopy. A very important influence of different thermal treatments in the formation of crystal and mesophase has been found. The sample originating from the synthesis has a crystalline and a liquid crystalline phase at room temperature. However, by evaporation of trifluoroacetic acid solution, it is possible to obtain only the crystalline phase. By quenching the sample from the liquid crystal state into liquid nitrogen, the smectic mesophase can be 'frozen in'.