抄録
The structure of an aromatic copolyester [I] containing _??_70 mol% p-hydroxybenzoic acid (HBA) and _??_30 mol% 2-hydroxy-6-naphthoic acid (HNA) was studied by means of wide-angle X-ray diffraction (WAXD). Highly oriented fibers of I spun from the nematic melt were annealed at 100_??_300°C for 1_??_80 hours. The WAXD patterns of samples annealed sufficiently at higher temperatures showed six reflections on the equator and two reflections on the first layer line in addition to three meridional ones. Assignment of these reflections was carried out by assuming an orthorhombic crystal system for [I]. The lattice parameters were: a=0.796nm, b=0.549nm, and c=1.354nm. The density of the unit cell was calculated to be 1.47g/cm3, whereas the observed density was 1.43g/cm3. The cross sectional area of the unit cell of I was intermediate between those of homopolymers of HBA and HNA. These results indicated that cocrystallization of the comonomers (HBA and HNA) took place in spite of their random distribution along the molecular chain of I.
