THE STRUCTURE OF HIGHLY TEXTURED QUASI-SINGLE-CRYSTALLINE HIGH-DENSITY POLYETHYLENE PROBED BY ATOMIC-FORCE MICROSCOPY AND SMALL-ANGLE X-RAY-SCATTERING

Previous texture evolution experiments carried out on high-density pol yethylene to an equivalent strain of epsilon(e) = 1.86 have indicated the development of a quasi-single-crystalline long-range coherence in the principal direction of molecular alignment parallel to the directi on of extensional flow, in which the differentiation between crystalli ne and amorphous components is substantially weakened. The present inv estigation probes the long-range coherence of the macromolecular order with atomic force microscopy (AFM) with molecular-level resolution. T he AFM findings support the earlier studies and reveal a remarkable le vel of long-range coherence in the chain direction with few regions of imperfection - consisting mostly of isolated molecular kinks, flip-ov er of molecules and gradual coherent twists, but no readily discernibl e phase-separated amorphous layers. These structural characteristics a re consistent with the radical weakening of small-angle X-ray scatteri ng images and the high level of hexagonal coordination of molecules in the stretched 'amorphous' material, which was revealed by X-ray pole figures.