In-situ Investigation of Annealing Effect on Higher Order Structure of Polyethylene Thin Films by Synchrotron GISWAXS Measurements.

Japan Synchrotron Radiation Research Institute (JASRI)/SPring-8, Japan* International Innovation Center, Japan** Institute for Materials Chemistry and Engineering, Japan*** The RIKEN Harima Institute/SPring-8, Japan****
â—‹Sono SASAKI* Hiroyasu MASUNAGA* Hiroo TAJIRI* Katsuaki INOUE* Hiroshi OKUDA** Atsushi TAKAHARA*** Masaki TAKATA****

We have investigated lamellar stacking structure of melt-crystallized and annealed high-density polyethylene (HDPE) thin films with a thickness of ca. 400 nm prepared on silicon wafers by synchrotron grazing-incidence small-angle and wide-angle X-ray scattering (GISWAXS) measurements at the BL40B2 in SPring-8. Figures 1 shows in-situ GISWAXS patterns measured for a melt-crystallized HDPE thin film in a stepwise annealing process. Scattering peaks relating to the long period, the average distance between stacked crystalline lamellae, were measured only in the in-plane direction near Yoneda peak of the grazing-incidence small-angle X-ray scattering (GISAXS) patterns. On the other hand, the orthorhombic (110) and (200) reflections of oriented HDPE crystals were measured in the out-of-pane direction of the grazing-incidence wide-angle X-ray scattering (GIWAXS) patterns. It was revealed that crystalline lamellae were stacked in the parallel direction to the film surface and the long period increased from ca. 25 nm to ca. 30 nm in a stepwise annealing process. Within a lamella, molecular chains were packed regularly and the chain axis (the c axis) was relatively oriented parallel to the film surface.