Diversified alpha-phase nanostructure of isotactic polypropylene under cylindrical confinement via cross diffraction analysis

摘要

Understanding polymer nanostructures is a prerequisite to manipulate their physical properties. Molecular self-assembly under confinement effectively generates novel polymer nanostructures. However, in one confined system, diffraction signals of different nanostructures are merged in a typical two-dimensional (2D) wide-angle X-ray diffraction (WAXD) measurement. For comparison, selected-area electron diffraction (SAED) of transmission electron microscopy can precisely capture the "local" diffraction signal of an individual nanoscale entity. Here, using isotactic polypropylene (i-PP) as a model polymer, we have demonstrated a cross-analysis of global X-ray and local electron diffraction results to fully reveal the structural details of i-PP nanorods. For the first time, we have decomposed completely the "mixed" 2D WAXD patterns of i-PP nanorods into five types of alpha-phase nanostructures: (a). Left-tilted daughter crystals; (b) Right-tilted daughter crystals; (c) Double-tilted daughter crystals; (d) a*-axis oriented crystals; (e) b-axis oriented crystals.