ORIENTATIONAL ORDERING IN FIBERS MADE OF WHOLLY AROMATIC MAIN-CHAIN LC POLYESTERS

Molecular chain orientation characterized by an order parameter in fib ers about 10(2) mu m in diameter of poly(phenyl-p-phenylene terephthal ate) and related copolyesters was investigated by means of infrared at tenuated total reflectance (IR ATR) spectroscopy. Samples had a tensil e strength of about 1 GPa, which could be increased to 2-3 GPa by a he at treatment under appropriate conditions. It has been found that the chain orientation is parallel to the fiber axis in the surface layer. At a distance of about 10-15 mu m from the surface, the orientation de creases, with the most oriented surface layer being easily detachable from the weakly oriented fiber core. The great difference between the molecular orientation in the surface layer and in the fiber bulk was s upported by wide-angle x-ray scattering (WAXS) data.