Morphology of Highly Textured Polyethylene/ Polyethylene-PropyleneSemicrystalline Diblock Copolymers

摘要

A series of series of semicrystalline diblock copolymers of poly(ethylene) /poly(ethylenepropylene) (E/EP) were subjected to high levels of plane strain compression using a channel die. Deformations were imposed both below and above the melting point of the E block. The crystallographic and morphological textures were examined using wide-angle X-ray diffraction pole figure analysis and two dimensional small-angle X-ray scattering. The lattice unit cell orientation of the crystallized E chains with respect to the lamellar superstructure was determined, as well as the lamellar orientation relative to the specimen boundaries. When the diblocks are textured above the E block melting point at various compression ratios, the lamellae orient perpendicular to the plane of shear, while texturing below Tm causes the lamellae to orient parallel to the plane of shear. The orientation of the crystallized E chains was perpendicular to the lamellar normal, irrespective of the texturing temperature. The various shear-induced lamellar morphologies have potential applications in gas transport control to develop membranes for use in gas separations or as barrier materials. Semicrystalline polymers, Diblock copolymers.