MORPHOLOGY OF HIGHLY TEXTURED POLY(ETHYLENE) POLY(ETHYLENE-PROPYLENE)(E EP) SEMICRYSTALLINE DIBLOCK COPOLYMERS/

A series of semicrystalline diblock copolymers of poly(ethylene)/poly( ethylene-propylene) (E/EP) were subjected to high levels of plane stra in compression using a channel die. Deformations were imposed both bel ow and above the melting point of the E block. The crystallographic an d morphological textures were examined using wide-angle X-ray diffract ion pole figure analysis and two-dimensional small-angle X-ray scatter ing. The lattice unit cell orientation of the crystallized E chains wi th respect to the lamellar superstructure was determined, as well as t he lamellar orientation relative to the specimen boundaries. When the diblocks are textured above the E block melting point at various compr ession ratios, the lamellae orient perpendicular to the plane of shear , while texturing below T(m) 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 te mperature.