By using an extremely high stereospecific catalyst, three kinds of copolymerizations were carried out with combinations of monomers which differ in thecrystallinity of the homopolymers.Addition of a small quantity of comonomer to the homopolymerization systems producing very high crystalline polymers was found to cause a remarkable increase in the apparent polymerization rate as well as a marked decrease in the polymer crystallinity. Such an irregular increase in the polymerization activity was, however, not observed when a small amount of comonomer was added to the homopolymerization systems producing low-crystalline or amorphous polymers. These observations have led to the conclusion that resistance of monomer diffusion through the polymer film should be one of the significant parameters for the apparent polymerization rate when very high crystalline polymers, like high density polyethylene, isotactic polypropylene etc., are produced. ~ a) Revised manuscript from July 29, 1988.
The catalyst systems Mg (OC2H,),/benzoyl chloride (BC)/TiCl, and Mg(OC,H,),/ethyl benzoate (EB)/TiCl, were prepared for the polymerization of propene. In case of the Mg(OC,H,),/BC/TiCl, catalyst, BC changes into the internal donor EB during the in situ preparation of the catalyst and the unchanged BC acts as additional donor after reaction with triethylaluminium (TEA). Catalyst activity and isospecificity were also studied for the two catalysts by changing the amounts of BC or EB in the polymerization of propene cocatalyzed with TEA.
The recently found catalyst system, composed of Solvay-type TiCI, and (RC,),TiMe,, producing extremely high isospecific polyolefins, was used for copolymerizations of ethylene with various a-olefins (propene, 1-butene, 1 -hexene and 4-methyl-1 -pentene) to obtain monomer reactivity ratios for isospecific centers. It was found that no homopolymer was formed actually. Using the copolymer composition obtained by I3C NMR, the monomer reactivity ratios were calculated according to the Fineman-Ross and Kelen-Tud& method. For the ethylene/propene pair the same values of reactivity ratio were also obtained from the diad distribution of comonomers. The relative reactivity of these olefins was found to decrease in the following order; ethylene > propene > I-butene > I-hexene > 4-methyl-I-pentene.
Polymerization and characterization of polymers: The procedures of polymerization and characterization of polymers were described in the previous paper I). a) Part I: cf. '). a) Systematic IUPAC name of MPT = methyl 4-methylbenzoate.
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