Higher-order Structure Analysis of Polyethylene Thin Films by In-situ Synchrotron Grazing-incdence Small-angle and Wide-angle X-ray Scattering Measurements

Abstract

The higher-order structures of high-density polyethylene (HDPE) thin films on Si wafers have been investigated on lamellar and molecular levels by synchrotron grazing-incidence small-angle and wide-angle X-ray scattering (GISWAXS: GISAXS and GIWAXS) measurements, respectively. Annealing effect on molecular orientation and lamellar stacking structure of the thin films was clarified by in-situ GISWAXS measurements at BL40B2 in SPring-8 for the thin films in a stepwise annealing process from 378 K to 393 K under vacuum. The thin films with a thickness of ea. 400 nm were prepared by a dip-coating method. The two-dimensional GISAXS patterns of the thin films suggested that crystalline lamellae were alternately stacked with amorphous in the parallel direction to the substrate surface and the long period increased from ea. 26 nm to ea. 36 nm during annealing. Their two-dimensional GIWAXS patterns measured at the same time indicated that HDPE chains formed the orthorhombic crystal and the chain axis in a crystalline lamella oriented relatively parallel to the film surface.