Copolymerization with Ziegler‐Natta catalysts. Part I. Monomer reactivity ratios for two α‐olefin pairs

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Abstract
Crystalline copolymers of styrene and 4‐methylpent‐1‐ene and styrene and 5‐methylhex‐1‐ene have been prepared with the catalytic system α‐TiCl3–AlEt3 in toluene. The polymerizations were carried out in dilatometers with the use of a special stirring apparatus which is described. The copolymers produced were shown to be heterogeneous in composition. Fractions soluble in cold pentane are enriched in 5‐methylhex‐1‐ene and have x‐ray diffraction patterns similar to those of crystalline isotactic poly(5‐methylhex‐1‐ene). The fractions insoluble in cold pentane are enriched in styrene and on crystallization have x‐ray diffraction patterns similar to those of crystalline isotactic polystyrene. Infrared spectra were also examined. Determination of reactivity ratios gave the values: styrene (M)‐4‐methylpent‐1‐ene, r1 = 0.89 ± 0.05, r2 = 3.67 ± 0.22; styrene (M)‐5‐methylhex‐1‐ene, r1 = 0.59 ± 0.057, r2 = 4.00 ± 0.28. Statistical analysis shows that the copolymer is probably a mixture of block macromolecules, the chain backbones consisting mainly of one monomer type with short blocks of the other.

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