III International Conference

PP-II-89The stereospecificity of polymer produced with МС is closely related to the symmetry ofthe ligands attached to the active transition metal. MC catalytic systems allowed synthesizingof all kinds of PP stereoisomers: isotactic, syndiotactic, hemiisotactic and stereoblock PP withhigh activity. Depending on the type of a metallocene used one may produce polymers fromamorphous structure to the samples that have up to 85 % crystallinity degree. High monomerconcentration at polymerization in bulk results in different influence on PP regularity independence of metallocene type. For MC C 2 - and C S - symmetry the increasing of propyleneconcentration lead to increasing of PP stereoregularity. At the same time for MC C 1 -symmetry the increasing propylene concentration lead to decreasing of PP stereoregularity.Metallocene produced propylene-ethylene copolymers have a tendency to alternating orrandom comonomer distribution in the polymer chain, in contrast to the heterogeneouscatalysts which have a tendency to form the long crystallizable ethylene sequences.Propylene copolymerization with higher α-olefins - 1-butene, 1-hexene and 1-octene inliquid propylene medium in presence of homogeneous MAO-activated high effectiveisospecific C 2 -symmetry ansa-zirconocene and propylene copolymerization with 1-octene inpresence of silica supported metallocene catalyst activated by iso-Bu 3 Al has been studied.General kinetic characteristics of propylene/higher α-olefin copolymerization were evaluated.In contrast to earlier investigations in toluene [1] we found for the copolymerization in theliquid propylene medium the proximity of comonomer relative reactivity ratios (r 1 ~ r 2 ~ 1)that indicates ideal nature of copolymerization processes in studied conditions [2]. Thethermo-physical and mechanical properties of synthesized copolymers were investigated.Polypropylene modification with insignificant comonomer content (1-6 mol. %) allows tochange mechanical properties of copolymers dramatically. For the 1-octene copolymers astronger influence of the comonomer on the thermal and mechanical properties of the polymerwas found. The use of metallocene catalysts provides obtaining of copolymers with theproperties combining high strength and relatively high elongation at break.This work was financially supported by the Russian Foundation for Basic Research(Projects NN 05-03-32872 и 06-03-81036).References1. L.А. Rishina, N.M. Galashina, P.M. Nedorezova, A.N. Klyamkina, A.M. Aladyshev,V.I. Tsvetkova, A.O. Baranov, V.A.Optov, and Yu.V. Kissin. Vysokomol. Soed. А, V. 46, № 9,2004, P. 1493-1504.2. Koval’chuk A.A., Klyamkina A.N., Aladyshev A.M., Nedorezova P.M., Antipov E.M. 2006,Polymer Bulletin. 56. P. 145-156.325