Summary: The article discusses two subjects: (a) temperature effects on the molecular weight, molecular weight distribution and stereoregularity of crystalline fractions of propylene polymers prepared with a supported TiCl4/dibutyl phthalate/MgCl2 – Al(i‐Bu)3 catalyst system, and (b) effects of different modifiers (components of cocatalyst mixtures that either greatly increase or decrease the content of the crystalline material) on the structures of the crystalline and the amorphous fraction. The principal approach of the research is the combination of GPC data for a series of polypropylene samples prepared under different conditions, the data on the distributional stereoregularity of the polymers (from analytical temperature‐rising elution fractionation (Tref) and DSC), and the 13C NMR analysis in order to produce a coherent picture of functioning of active centers. The combination of the experimental results shows that the crystalline fractions of polypropylene are produced by several families of active centers. The centers significantly differ in the average molecular weights of the polymer components they produce and in stereospecificity. The steric control exerted by the active centers of the highest isospecificity slightly decreases with temperature. In contrast, average isotacticity parameters of the crystalline fractions (estimated by NMR) increase with temperature. The latter effect is mainly the outcome of the variation in the relative contents of polymer components of low isotacticity in the crystalline fractions prepared at different temperatures. When a silane is used as a part of a cocatalyst, it not only poisons aspecific centers but poisons the centers of reduced isospecificity as well. This effect results in the increase of the average molecular weight of the crystalline fraction, narrowing of its molecular weight distribution and the increase of its average isotacticity.Resolution of GPC curves of crystalline fractions into Flory components at 50 °C.imageResolution of GPC curves of crystalline fractions into Flory components at 50 °C.

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In this study, novel carrier materials were synthesized by addition of metal dihalide compounds in the synthesis reaction of magnesium diethoxide using metallic magnesium, ethanol and iodine. Poly(propylene) polymerizations were then investigated with the MgCl2‐supported TiCl4 catalysts using these carrier materials. As results, magnesium diethoxide with extremely large particle sizes and spherical shapes were obtained and the angles of repose of PP particles obtained by using their catalysts as a flowability index showed high values. Furthermore, in order to confirm key points for excellent catalyst performance from detailed characterizations, SEM images, compositions and WAXS were measured.

Summary: Stopped‐flow polymerization of propene was first conducted at 40 °C using the TiCl4/DBP/MgCl2 catalyst (DBP = dibutyl phthalate) combined with Al(C2H5)3. An induction period was observed at the beginning of polymerization, and the resulted polymer contained a considerable amount of the isolated ethylene unit. The formation of such unusual structures was concluded to be the result of copolymerization with ethylene originating from the ethylated Ti4+ species. Catalyst washing with toluene and stopped‐flow polymerization at 70 °C brought about a drastic decrease in the contents of both Ti and DBP as well as a disappearance of both the induction period and isolated ethylene unit. The microstructures of polymers revealed that the highly stereoregular polymers are produced at the initial stage of polymerization. Changes in yield and molecular weight of polymers with polymerization time showed that the addition of tert‐butyl methyl ether (TBME) brought about an increase in the concentration of active sites, but did not affect the propagation rate of propene polymerization. Such an increase in the active site concentration caused by an external donor has hardly been reported so far in kinetic studies using the stopped‐flow method; thus, the present result is believed to be a unique example.