CHAIN FOLDING IN EBEE SEMICRYSTALLINE DIBLOCK COPOLYMERS

X-ray pole-figure analysis and small-angle X-ray scattering were used to determine the lattice unit cell orientation with respect to the lamellar microstructure for semicrystalline diblock copolymers of ethylene-co-butylene-b-ethylethylene (EBEE). The X-ray data indicate that the orientation of the crystallized EB chains is perpendicular to the lamellar normals, unlike the chain folding which has been observed in semicrystalline homopolymers and proposed for semicrystalline diblock copolymers where the crystallized chains align roughly parallel to the lamellar normals. The unusual chain folding observed for EBEE is attributed to the influence of topological constraints on the EB blocks which crystallize within the amorphous lamellar microdomains present in the heterogeneous melt phase of the block copolymers.