Distributions of active sites of titanium-containing catalytic system in terms of stereoregulating power and kinetic nonuniformity in butadiene polymerization

Influence of the structure of the organoaluminum compound on the stereoregulating heterogeneity of catalytic systems based on TiCl4

“…With the TiCl 4 -Al(i-C 4 H 9 ) 3 system prepared in advance and kept for some time before use, sites yielding macromolecules with 50-55% content of 1,4-cis structures are formed. Such content of 1,4-cis structures is higher than that obtained with the catalytic system prepared in situ (30-45% [4]). …”

“…To compare the obtained distributions with respect to the kinetic activity of the sites with their stereoregulating ability, the polybutadiene samples synthesized using various organoaluminum compounds were fractionated. As in the case of the previously studied polybutadiene synthesized using the catalytic system prepared in situ [4,5], in the case of preliminary formation of the catalyst the molecular weights of the polydiene fractions also correlate with their stereoregularity (Fig. 1, curves 3-6).…”

“…Recently much attention has been given to the multiplesite nature of ion-coordination catalytic systems and to its dependence on such factors as catalytic system composition and conditions of the polymerization and catalyst preparation [2,3]. Studies in the fi eld of the multiple-site nature [4,5] showed that the polymerization sites are heterogeneous not only in the kinetic activity, but also in stereospecifi city of the action.…”

“…Sigaeva et al [4,5] showed previously that, in polymerization of butadiene in situ under the action of the catalytic system TiCl 4 -Al(i-C 4 H 9 ) 3 under the conditions corresponding to the maximal activity of the catalyst, formation of polybutadiene of mixed microstructure is possible as a result of formation of three types of active sites, differing in the stereoregulating power. Sigaeva et al note the relationship between the molecular weight and microstructure for all the isolated polybutadiene fractions.…”