Yu. B. Monakov

Diene polymerizations with the lanthanide coordination catalysts. I. Piperylene polymerizations effected by the type of lanthanide

The present paper concerns studies into piperylene polymerizations with the catalytic systems LnHal3· 3TBP-Al(i-C4H9)3 (Ln=Ce, Pr, Nd, Gd, Tb, Dy; Hal=Cl, Br, I; TBP=tributylphosphate) occurring in various solvents. The activity and stereospecificity of these catalysts have been found to depend on the composition of the initial lanthanide component LnHal3·3TBP and mostly on the lanthanide itself. With other conditions being equal, the highest polymerization rates are provided by the Nd catalyst, and the Gd catalyst favours the formation of polypiperylene with the maximum content of cis-1,4-units. The data obtained have proved the dependence of anti-sin isomerization of π-allyl active centres on the types of the lanthanide, halogen, hydrocarbon solvent and diene monomer used.

Lanthanide compounds—Catalysts of stereospecific polymerization of diene monomers. Review☆

The results of investigations in the field of polymerization of conjugated dienes on cis-regulating lanthanide-containing catalysts of the ion-coordination type are reviewed. The influence of the composition of the catalysts, the structure of the monomer and the conditions of polymerization on their activity and stereo-specificity is examined. The factors influencing the molecular mass characteristics of the polymers and procedures for regulating the latter are analysed. From the results of study of the plasto-elastic, physicomechanical and use characteristics of “lanthanide” polydienes and vulcanizates the authors look at the prospects for their use.

Polymerization of dienes on lanthanide containing catalytic systems. Review

The results of investigation of the polymerization and copolymerization of the dienes on lanthanide-containing catalysts are reviewed. Attention is focused on cis-regulating catalytic systems and a classification of them presented. The authors look at the influence of the composition of the lanthanide-containing catalysts and the condition of polymerization on their activity and also the microstructure and molecular mass of the polydienes. The low sensitivity of the stereospecificity of the cis-regulating catalytic systems to wide variation in their composition and the conditions of the process, especially in the case of polymerization of butadiene, is demonstrated. A general characterization of “lanthanide” rubbers and vulcanizates is presented and some of their advantages shown.

Diene polymerizations with lanthanide coordination catalysts. II. The effects of catalytic system component types and polymerization conditions on molecular characteristics of 1,4-cis-Polybutadienes

Abstract Molecular inhomogeneity has been investigated for 1,4-cis-polybutadienes obtained with a lanthanide- containing catalytic system; some kinetic parameters have been estimated for polymerizations. Gel-permeation chromatography was chosen as the main method to find out the average molecular weights (MW) and molecular weight distributions (MWD). The catalyst composition has been shown to effect MW and MWD. The molecular characteristics are determined by both the catalyst composition and the polymerization conditions (reagent concentration, temperature). The broad MWD is considered a peculiarity of butadienes prepared with lanthanide- containing catalysts. The data obtained lead to the assumption that the distribution of the polymerization centres by reactivity is responsible for the broad MWD of the polybutadienes formed.

Kinetics of oxidation of an arabinogalactan from larch (Larix sibirica L.) in an aqueous medium in the presence of hydrogen peroxide

The oxidation of an arabinogalactan in an aqueous medium under the action of hydrogen peroxide and dioxygen is accompanied by accumulation of carbonyl and carboxy groups in the oxidized polysaccharide macromolecules and derived oligomers. The addition of iron sulfate accelerates the radical oxidation of the biopolymer, while the addition of phenol inhibits the oxidation. The influence of the temperature and the initial H2O2 and arabinogalactan concentrations on the kinetics of the initial oxidation stage of the natural polysaccharide was studied.

Enhancement of the activity of the titanium catalyst for isoprene polymerization by improving the step of active site formation

Commercial microheterogeneous titanium catalyst in the step of its preliminary formation was subjected to hydrodynamic action by circulation in a tubular diffuser-confuser apparatus. As a result of such treatment, the Mooney viscosity of the high-molecular-weight polyisoprene prepared in the presence of this catalyst becomes more stable.

Effect of the concentration, distribution and degree of neutralization of the carboxyl groups, and of the nature of the cation, on the thermomechanical properties of ionomers☆

A study has been made of the effect of the concentration of carboxyl groups and their distribution along the copolymer chain on the thermomechanical and physicomechanical properties of ionomers. It is shown that when there is a random distribution and a low concentration of carboxyl groups in the polymer the degree of neutralization and the nature of the cation has little effect on the transition temperatures of ionomers. When the concentration of carboxyl groups is high the thermomechanical characteristics of neutralized samples are dependent on the concentration and nature of the cation.

Preparation of Phthalide-containing Methacrylates

Different unsaturated products of the synthesis of phthalide-containing methacrylates were obtained depending on the polarity of the reaction medium: In a donor solvent (pyridine) the phthalide ring is conserved in the product, in acetone or toluene its opening occurred.

Enzymatic degradation of modified chitosan films

The features of enzymatic degradation of modified chitosan films prepared from acetic acid solutions using Collagenase KK enzyme preparation was studied.

Transport properties of chitosan films

Effect of the history of chitosan films on their transport characteristics in relation to elimination of drugs from the body is studied.