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Studies of the microstructure of ethylene/1-hexene copolymers prepared over heterogeneous Ziegler-Natta catalysts

Czaja K., Białek M.

Polimery

2000

T. 45, nr 5

353-357

Three MgCl2(THF)2-supported, AlEt2Cl-activated VOCl3, VCl4 and TiCl4 Ziegler–Natta catalysts were used to copolymerize ethylene with 1-hexene in the presence of hydrogen to prepare low-M well-soluble copolymers that could be analyzed by 13C-NMR. The spectra (Fig. 1) showed resonance signals due to ethylene and 1-hexene units in positions unaffected by catalyst type and with intensities related to the degree of comonomer incorporation into the copolymer. The triad sequence distribution and comonomer reactivity ratios (r) were calculated by the Randall method [11] and Bernoulli statistics based on the known copolymer composition. The latter appeared to be the more valid in predicting the comonomer triad distribution in the copolymer. All copolymers were found to be random (rErH = 1) (Tables 4, 5). Compared with titanium, vanadium catalysts provided the higher monomer reactivity of ethylene toward alpha-olefin.