В настоящее время для синтеза большинства марок полипропилена (ПП) используют каталитические системы Циглера–Натта на основе нанесенных титан-магниевых катализаторов [1]. Известно, что полимер, полученный с использованием алкилалкоксисиланов в качестве внешнего донора представляет собой типичный изотактический ПП [2]. В [3, 4] использовали гетероциклические ароматические азотсодержащие соединения в качестве внешних доноров, что привело к образованию полипропилена с высоким содержанием синдиотактической фракции. Такие полимеры, в отличие от обычных кристаллических полимеров изотактической структуры, обладают эластомерными свойствами.

The influence of external donor nature on propylene polymerization reactions with titanium-magnesium catalyst activated with AlEt3 is studied. The use of cyclohexylmethyldimethoxysilane as the donor increases the content of isotactic polymer and the use of 2,6-dimethylpyridine promotes the formation of syndiotactic component in polypropylene. By combining different donors, it is possible to regulate the site distribution in catalytic system with respect to stereospecificity and to modify stereoregularity, molecular weight characteristics and mechanical properties of polypropylene.

A simple method for the two-stage synthesis in one reactor on one catalyst of heterophase thermoplastic elastomers based on isotactic polypropylene and an ethylene-propylene copolymer or an ethylene-propylene-1,4-hexadiene terpolymer is developed. The obtained materials, depending on the composition, have good elastomeric properties or behave like thermoplastics. Polymers in which ethylene units form long sequences have the best set of basic characteristics: high values of the elastic modulus, strength, and elongation at a break, as well as a low residual deformation.

Ethylene-propylene-5-ethylidene-2-norbornene terpolymerization is studied in a liquid propylene medium using catalysts based on metallocenes (MCs) of C-2- and C-5-symmetry, differing in the nature of bridges and ligands and activated by MAO. It is shown that the investigated MCs of C-2-symmetry do not ensure the synthesis of terpolymers combining a high molecular weight (MW) and good diene incorporation. In the presence of a MC of C-s-symmetry Ph2C(CpFlu)ZrCl2, terpolymers with an MW of 120 000 to 160 000 and a diene content of 2.0 to 5.3 wt % are obtained with a high level of activity. New heterophase compositions based on isotactic PP and ethylene-propylene-diene terpolymers, which have a good balance between strength and elasticity, are synthesized.

New bimetallic catalysts based on microspherical TiCl3 modified with vanadium trichloride to obtain its different concentrations on the TiCl3 surface were synthesized. The presence of a VCl3 crystalline phase in the catalyst was confirmed by X-ray analysis. The synthesized catalysts were applied to studying propylene polymerization in a liquid monomer medium. The kinetics of the polymerization process was determined, and the structure and properties of the synthesized isotactic polypropylene (IPP) were established. It was demonstrated that the PPI samples synthesized over the developed titanium–vanadium catalysts has enhanced freeze resistance as compared to IPP sample obtained over conventional titanium catalysts.

Предложены принципы создания новых смесевых полиолефиновых эластомеров с регулируемым комплексом свойств на основе стереоблочного эластомерного ПП, синтезированного с использованием асимметричных анса-металлоценов. Методом динамической вулканизации получены оригинальные смесевые полимерные материалы с пониженной твердостью, содержащие эластомерный ПП с различными характеристиками и 50–70 мас. % тройного маслонаполненного этиленпропилендиенового эластомера. Молекулярно-массовые характеристики ПП существенно влияют на реологические свойства полиолефиновых эластомеров. Для переработки полученных смесей исходный компонент – эластомерный ПП должен иметь Мw = (8–14) ? 104 и низкую степень кристалличности.

The principles of the creation of new blend polyolefin elastomers with a controlled complex of properties based on a stereoblock elastomeric PP synthesized in the presence of asymmetric ansa -metallocenes are proposed. Original blend polymer materials with reduced hardness that are based on elastomeric PPs with different characteristics and a 50–70 wt % oil-extended ternary ethylene-propylene-diene elastomer were prepared through the method of dynamic vulcanization. The molecular-mass characteristics of PP have a considerable effect on the rheological properties of polyolefin elastomers. For successful processing of the resulting blends, the pristine component, the elastomeric PP, must have a weight-average molecular mass of M w = (8−14) × 10 4 and a low crystallinity.

In recent years researchers have paid considerable attention to the creation of multifunctional polymer composite materials bearing nanoscale fillers. The introduction of nanoparticles into polymer matrices in relatively small concentrations (reaching 2.5 vol %) makes it possible to produce materials possessing better properties than the initial matrix polymers and conventional dispersion-filled composites. Carbon nanostructures are promising fillers for polymer nanocomposite materials: fullerenes, carbon nanotubes, nanofibers, and graphene nanoplatelets. A combination of structural, physicomechanical, and electrophysical properties of these fillers upon their introduction into polymer matrices affords the creation of composite materials possessing improved stress-strain, electro- and thermophysical characteristics, and noncombustibility.

The copolymerization of propylene with 1-butene and 1-pentene at 60°C in the propylene bulk in the presence of the homogeneous isospecific metallocene catalyst of the C2 symmetry rac-Me2Si(4-Ph-2-MeInd)2ZrCl2 activated by polymethylaluminoxane is studied. Copolymers containing up to 30 mol % 1-butene and up to 10 mol % 1-pentene are synthesized. For the copolymerization of the above monomers, reactivity ratios are estimated to be equal to unity, thereby indicating the azeotropic character of the process. It is found that the distribution of comonomer units in the copolymers is close to statistical. For both comonomers, the comonomer effect is observed: an increase in the rate of propylene polymerization after addition of a small amount of a less reactive comonomer. The addition of 1-butene and 1-pentene to polypropylene shows a weak effect on the stereoregularity of chains but causes a marked reduction in the molecular mass of the polymer and changes its thermophysical characteristics and mechanical properties. An X-ray diffraction study of the copolymers is performed.

Propylene-vinylcyclohexane copolymers containing 0.02–0.37 mol % vinylcyclohexane are synthesized and characterized; the copolymers are prepared via bulk copolymerization at 60°C in the presence of a metallocene catalyst with the C 2 symmetry rac -dimethylsilylidene-bis(2-methyl-4-phenylindenyl)zirconium dichloride activated by polymethylaluminoxane. The reactivity ratios are calculated to be 26.6 for propylene and 0.025 for vinylcyclohexane. The introduction of vinylcyclohexane into PP slightly affects the stereoregularity of the polymer chain but markedly decreases its molecular mass and changes the thermophysical and mechanical characteristics of the polymer. The oxidation characteristics of the prepared copolymers are estimated: The induction period of oxidation is determined from oxygen absorption, and the termination-rate constants of peroxide macroradicals is determined from the chemiluminescence of copolymers. The dependence of the kinetic characteristics of oxidation of the copolymers on the content of side cyclohexyl groups is found, and the possible mechanisms of oxidation of copolymers are considered.

The copolymerization of propylene with 1-octene in liquid propylene is carried out in the presence of a highly active homogeneous ansa-m etallocene catalyst with the C 2-symmetry rac-Me2Si(4-Ph-2- MeInd)2ZrCl2 activated by methyl aluminoxane and in the presence of ansa- metallocene C4H6Si(2-Et4- PhInd)2ZrCl2 (rac: meso = 2:1) supported on silica gel treated with methylaluminoxane. In the case of the heterogenized metallocene, (iso-C 4 H 9 )3Al is used as a cocatalyst. The copolymers of propylene and 1-octene containing up to 24 and 9.3 mol% units of the second comonomer are prepared with the homogeneous and heterogenized systems, respectively. The copolymerization of propylene with 1-octene in liquid propylene shows the azeotropic (ideal) character, and the distribution of comonomer units in the copolymers is close to statistical. The modification of PP with even small amounts of 1-octene affects the regularity of polymer chains, molecular-mass characteristics of the copolymers, their melting temperature, and the degree of crystallinity and makes it possible to vary their rigidity and elasticity in a wide range. The character of changes in thermal and mechanical properties is almost the same for the copolymers synthesized with homogeneous and heterogenized catalysts.

Дан краткий обзор исследований гомо- и сополимеризации пропилена с этиленом и высшими олефинами (бутеном-1, гексеном-1, 4-метилпентеном-1, октеном-1) в среде жидкого пропилена под действием гомогенных металлоценовых катализаторов различного типа. Обсуждаются основные кинетические закономерности процессов и свойства синтезированных полимеров. Описаны оптимальные условия получения с высокой активностью изотактического, синдиотактического, геми-изотактического и стереоблочного ПП. Показана перспективность использования комбинированного сокатализатора – полиметилалюмоксана совместно с (i-Вu)3Al. При сополимеризации пропилена с этиленом в зависимости от типа используемого катализатора образуются сополимеры с блочным, статистическим или близким к альтернантному распределением звеньев сомономеров в полимерной цепи. Показано, что сополимеризация пропилена с высшими олефинами в массе мономера на высокоактивных стерически затрудненных изоспецифических каталитических системах носит идеальный характер с константами сополимеризации r1 r2 1, т.е. состав сополимера при всех соотношениях равен составу мономерной смеси. Проведенные исследования показали перспективность синтеза гомо- и сополимеров пропилена в массе мономера при использовании современных гомогенных катализаторов для высокоэффективного получения как традиционных, так и новых полимерных материалов с уникальным набором физико-механических и теплофизических свойств.

Studies devoted to the homo-and copolymerization of propylene with ethylene and higher olefins (1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene) in liquid propylene under the action of homogeneous metallocene catalysts of various types are surveyed in brief. The main kinetic features of the processes and the properties of the polymers are discussed. The optimal conditions for the highly efficient syntheses of isotactic, syndiotactic, hemiisotactic, and stereoblock PPs are described. It is shown that the combined cocatalyst—polymethylaluminoxane coupled with (i-Bu)3Al—shows promise for the processes under consideration. Depending on the type of catalyst used, the copolymerization of propylene with ethylene yields copolymers with a block, random, or close to alternating distribution of comonomer units in a polymer chain. The copolymerization of propylene with higher olefins in the monomer bulk initiated by highly active sterically hindered isospecific catalytic systems shows an ideal character, and the reactivity ratios are r 1 ≈ r 2 ≈ 1; that is, the composition of the copolymer is equal to the composition of the monomer mixture at all comonomer ratios. It is demonstrated that the synthesis of homo-and copolymers of propylene in the monomer bulk in the presence of modern homogeneous catalysts is promising for highly efficient production of both traditional and new polymer materials with a unique combination of mechanical and thermal properties.

The copolymerization of ethylene with propylene in the liquid propylene initiated by ansa -metallocenes of the C 1 symmetry, rac -[1-(9-η 5 -fluorenyl)-2-(5,6-cyclopenta-2-methyl-1-η 5 -indenyl)ethane]zirconium dichloride and rac -[1-(9-η 5 -fluorenyl)-2-(5,6-cyclopenta-2-methyl-1-η 5 -indenyl)ethane]hafnium dichloride, activated by methylaluminoxane has been studied. Triisobutylaluminum has been used as a cocatalyst. The propylene-ethylene copolymers thus prepared contain 5–60 mol % ethylene units. The reactivity ratios have been measured. In the case of the zirconocene-based catalyst, the molecular mass of the copolymers decreases with an increase in the content of ethylene units. The reverse situation is observed in the case of the hafnocene-based catalytic system. The copolymers are characterized by the low T g values (down to −45°C). Incorporation of a small amount of ethylene units (5 mol %) results in a rise in the elastomeric behavior of the polymers.