The copolymers of propylene and methyl vinyl ketone are synthesized at 60°С by copolymerization in the propylene bulk in the presence of the polymethylaluminoxane-activated metallocene catalysts, namely, the isospecific С 2 -symmetric metallocene catalyst rac -Me 2 Si(2-Me-4-PhInd) 2 ZrCl 2 and the syndiospecific Сs-symmetric metallocene catalyst Ph 2 ССpFluZrCl 2 , and characterized. It is shown that a noticeable insertion of methyl vinyl ketone into a polypropylene chain is possible during copolymerization initiated by the syndiospecific catalytic system, whereas in the case of the isospecific system, the insertion of methyl vinyl ketone is hindered. The thermal oxidation of the resulting polymers is studied. With the use of chemiluminescence, the accumulation of peroxy macroradicals under the action of daylight in samples based on isotactic and syndiotactic polypropylene is detected. It is found that even a low (0.2 mol %) content of methyl vinyl ketone endows polypropylene with the capability to undergo rapid and controlled degradation under natural conditions.

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.

This work is devoted to a study of the properties of copolymers of polypropylene with a content of octene units of 1.5–8.4 mol%. A study was made of the kinetics of oxidation of nascent specimens of polypropylene and its copolymers with octene at temperatures of 90–130°C. At all temperatures, both the oxidation rates and the induction periods of oxidation depend extremally on the composition of the copolymer. It seems that the observed effects are connected with change in the chemical or physical structure of the amorphous regions.

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.

Ethylene/1-hexene copolymers, which differ significantly in 1-hexene content (from 1.9 to 37.0 mol %), are studied by Raman spectroscopy. The copolymer spectra are compared with the Raman spectra of polyethylene at elevated temperatures. We have found that the phase and conformational order of the copolymer macromolecules depends strongly on the 1-hexene content. In particular, an increase in 1-hexene content leads to a decrease in content of the PE-like orthorhombic crystalline phase and in content of trans-conformers in the amorphous phase. The Raman signature at about 800 cm−1 provides information about the end conformers for the ethylene/1-hexene copolymers with high 1-hexene content.

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.