Crystallization and Chain Conformation of Semicrystalline and Amorphous Polymer Blends Studied by Wide-Angle and Small-Angle Scattering

ABSTRACT: We examine the crystallization and chain conformation behavior of semi-crystalline poly(ethylene oxide) (PEO) and amorphous poly(vinyl acetate) (PVAc) mix-tures with wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS), and small-angle neutron scattering (SANS) experiments. For blends with PEO weight fractions (wtPEO) greater than or equal to 0.3, below the melting point of PEO, the WAXD patterns reveal that crystalline PEO belongs to the monoclinic system. The unit-cell parameters are independent of wtPEO. However, the bulk crystallinity deter-mined from WAXD decreases as wtPEO decreases. The scattered intensities from SAXS experiments show that the systems form an ordered crystalline/amorphous lamellar structure. In a combination of WAXD and SAXS analysis, the related morphological parameters are assigned correctly. With the addition of amorphous PVAc, both the average amorphous layer thickness and long spacing increase, whereas the average crystalline layer thickness decreases. We find that a two-phase analysis of the corre-lation function from SAXS, in which the scattering invariant is linearly proportional to the volume fraction of lamellar stacks, describes quantitatively the crystallizatio