THERMAL-EXPANSION OF A 60 MOL-PERCENT PARA-HYDROXYBENZOIC ACID 40 MOL-PERCENT ETHYLENE TEREPHTHALATE LIQUID-CRYSTALLINE COPOLYESTER ORIENTED IN A MAGNETIC-FIELD

The thermal expansion is investigated for a 60 mol% para-hydroxybenzoic acid/40 mol% ethylene terephthalate liquid crystalline copolyester oriented in a magnetic field (6T). The high-temperature expansion coefficient of the oriented samples shows an anisotropy; it is negative (shrink) to the orientation direction, while it is positive (expand) to the direction perpendicular to the orientation. The X-ray diffraction measurement indicates that the positive expansion coefficient is attributed to the increase in the mean spacing of the oriented chains.