Structural Analysis of Copolymers of Syndiotactic Polypropylene with 13C-Enriched Ethylene

A structural analysis of copolymers of syndiotactic polypropylene with small amounts of 13 C-enriched ethylene, in the range 0.4-2.6 mol %, is reported. X-ray diffraction and solid-state C-13 NMR CPMAS data indicate that the as-prepared copolymer samples are crystallized in the conformationally disordered modification of form II of sPP containing kink bands. The disorder corresponds to the presence of portions of chains in the trans-planar conformation in chains having a prevailing 2-fold helical conformation. A direct evidence of the partial inclusion of the ethylene units in the crystalline regions of the copolymers is provided.