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-hydroxybenzoi c acid/40 mol% ethylene terephthalate liquid crystalline copolyester o riented in a magnetic field (6T). The high-temperature expansion coeff icient of the oriented samples shows an anisotropy; it is negative (sh rink) to the orientation direction, while it is positive (expand) to t he direction perpendicular to the orientation. The X-ray diffraction m easurement indicates that the positive expansion coefficient is attrib uted to the increase in the mean spacing of the oriented chains.