Shape and diffusion of the monomer‐controlled copolymerization of ethylene and α‐olefins over Cp2ZrCl2 confined in the nanospace of the supercage of NaY

Cp₂ZrCl₂ confined inside the supercage of NaY zeolites NaY/methylaluminoxane (MAO)/Cp₂ZrCl₂] exhibited the shape and diffusion of a monomer‐controlled copolymerization mechanism that strongly depended on the molecular structure of the monomer and its size. For the ethylene–propylene copolymerization, NaY/MAO/Cp₂ZrCl₂ showed the effect of the comonomer on the increase in the polymerization rate in the presence of propylene, whereas the ethylene/1‐hexene copolymerization showed little comonomer effect, and the ethylene/1‐octene copolymerization instead showed a comonomer depression effect on the polymerization rate. Isobutylene, having a larger kinetic diameter, had little influence on the copolymerization behaviors with NaY/MAO/Cp₂ZrCl₂ for the ethylene–isobutylene copolymerization, which showed evidence of the shape and diffusion of a monomer‐controlled mechanism. The content of the comonomer in the copolymer chain prepared with NaY/MAO/Cp₂ZrCl₂ decreased by about one‐half in comparison with that of Cp₂ZrCl₂. A differential scanning calorimetry study on the melting endotherms after the successive annealing of the copolymers showed that the copolymers of NaY/MAO/Cp₂ZrCl₂ had narrow comonomer distributions, whereas those of homogeneous Cp₂ZrCl₂ were broad. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2171–2179, 2003