ИСТИНА

The cross-metathesis reaction between various polymers containing carbon double bonds in the main chain is a new approach to the synthesis of statistical multiblock copolymers (MBC) with interesting mechanical properties and enhanced durability [1]. Through the interaction of commercial polynorbornene (“Norsorex”) and polycyclooctene (“Vestenamer”), we obtained new norbornene (NB) and cyclooctene (CO) MBC, which are difficult to obtain from the corresponding monomers [2]. Based on the study of the polynorbornene (PNB) and polycyclooctene (PCO) reaction kinetics, the sequence of individual stages was determined and a kinetic model of the process was developed [3]. In this work, new MBCs were synthesized from PNB and industrial polydienes, namely, polybutadiene (PBD) and cis- and trans- polyisoprene (PI) in the presence of Ru-carbene Grubbs’ catalysts. The conditions for obtaining copolymers with different average block lengths were determined and thermal and crystalline properties of the copolymers were studied. The kinetics of the process was investigated by in situ 1H NMR monitoring of the transformations of Ru-carbene complexes as the reaction active centers, and by ex situ 13C NMR control of the chain structure and degree of MBC blockiness. It was found that in the PNB/PBD system, along with the MBC, cyclooligomers are formed as a result of intramolecular metathesis, mainly in the chains of PBD. The cyclooligomers yield can be reduced by increasing the polymers concentration in the reaction mixture. For the first time the influence of the monomer unit stereo-structure on the cross-metathesis reaction of polymers was studied for cis - and trans- PI. It was established that the isomerization of cis-C=C to trans-C=C in cis-PI and trans-C=C to cis-C=C in trans-PI proceeded during the cross-metathesis. Trans-C=C bonds in PI are more active both in the isomerization reaction and in the cross-metathesis with PNB. Grubbs’ catalyst of the 2nd generation allows one to change the average block length in the copolymers over a wide range, up to 4.5 monomer units. PI is the least active polymer in the reaction with PNB in the series of previously studied polycycloctenes and polydienes. This could be explained by low activity of tri-substituted double C=C bonds in the metathesis reaction. The applicability of the previously developed kinetic model for the description of the studied process was shown. The constants of the elementary stages of the process were determined. The fastest of them is the interaction of Ru-PNB carbenes with double bonds in PBD chains. It proceeds two orders of magnitude faster than the interaction of Ru-PBD carbenes with double bonds in PNB chains. The reaction mechanism and possible reasons for different polymer reactivities are discussed.