Nanostructure Evolution of Homogeneous Poly(ethylene‐co‐1‐octene) as a Function of Strain

Abstract

AbstractPolyolefin elastomers with varying 1‐octene content and different thermal history are studied by wide‐angle X‐ray scattering (WAXS) and small‐angle X‐ray scattering (SAXS) during drawing and after relaxation. The multidimensional chord distribution function (CDF) reveals the nanostructure made from crystallites in the amorphous matrix. Both lamellae and granular crystals are found. Lamellae do not form stacks. The SAXS peak is observed because each lamella is covered by an amorphous layer of well‐defined thickness. Arrangement, rotation, fine chain slip and failure of the domains are directly observed as a function of elongation. During straining and relaxation a well oriented macrolattice with colloidal dimensions but short‐ranging order is formed. Two processes are generating microfibrils, namely (1) arrangement of granular crystallites, and (2) irreversible disruption of lamellae (coarse slip) followed by arrangement of their fragments. The second process stabilizes the colloidal lattice permanently. The higher the comonomer content, the later the irreversible process starts. Quenching from the melt shifts the onset to lower deformation. Deformation of microfibrils is not homogeneous. Instead, there is a limiting long period that cannot be exceeded without disruption. It is related to the position of the maximum in the SAXS pattern (which is almost constant).Long periods in the CDF z(r12, r3) of an ethylene‐octene block copolymer after relaxation from drawing.magnified imageLong periods in the CDF z(r12, r3) of an ethylene‐octene block copolymer after relaxation from drawing.