M. L. Gringolts

Comparative Reactivity of Me 3 Si-substituted Norbornene Derivatives in Ring-Opening Metathesis Polymerization

Silyl substituted norbornenes and their derivatives are effective monomers in the synthesis of new prospective polymer materials for gas separation membranes by metathesis and addition polymerization. Comparative activity of norbornenes (NB), norbornadienes (NBD) and tricyclononenes (TCN) with different spatial arrangement of one or two Me3Si substituents in ring-opening metathesis polymerization (ROMP) in the presence of Grubbs initiator Cl2(PCy3)2Ru =CHPh were studied by NMR and GC. It was shown that the rate of the initiation was lower than the propagation for all monomers and the highest activity was inherent to the exo-5-trimethylsilylnorbornene (5-NBSi) and 3-trimethylsilyltricyclononene (3-TCNSi). Disubstituted TCN turned out to be more active than NB having the same number and position of the substituents. The latter were more active than the corresponding NBD. It was found that syn- and anti-isomers of 3-TCNSi polymerized with close rates in contrast to exo- and endo-substituted 5-NBSi, for which polymerization rates were substantially different. Special behavior of monomers with bulky substituents in the geminal position was observed: 5,5-NBSi2 was inactive in the presence of the 1st generation Grubbs initiator, whereas it was polymerized in the presence of the 2nd generation one. Quantum-chemical calculations were in agreement with experimental data and evidenced the influence of energy, electronic and structural properties of the norbornene-type monomers studied on their activity in ROMP.

Regulation of the degree of blockiness of the norbornene–cyclooctene copolymer synthesized via the cross-metathesis reaction

The kinetics of the polymer cross-metathesis reaction in a mixture of polynorbornene and polycyclooctene catalyzed by the Grubbs first-generation ruthenium catalyst at room temperature is studied. The structure of the reaction product, a multiblock copolymer of norbornene and cyclooctene, is determined by a number of factors typical for a mixture of polymers reacting with each other via the interchange reaction with the participation of terminal groups. The addition of 5 mol % catalyst transforms the mixture into an almost random copolymer over a day. At a lower content of the catalyst, the maximum conversion is reached in a mixture enriched with polynorbornene. The interchain exchange results in an increase in the fraction of trans C=C bonds in polycyclooctene and cyclooctene–norbornene copolymers to 80%.

Epoxidation of Multiblock Copolymers of Norbornene and Cyclooctene

The epoxidation of double bonds in random multiblock copolymers of norbornene and cyclooctene is studied for the first time. The initial copolymers with different composition and average block length are synthesized via the cross-metathesis reaction between polynorbornene and polycyclooctene in the presence of the first-generation Grubbs catalyst. New multiblock copolymers containing oxirane fragments in the backbone are obtained with a yield of 85–92% through epoxidation conducted under the action of m-chloroperbenzoic acid in toluene. The kinetics of epoxidation of polynorbornene, polycyclooctene, and their multiblock copolymers in deuterochloroform and deuterobenzene is investigated via the in situ monitoring of transformation of double bonds using 1Н NMR spectroscopy. It is shown that on the whole the modification of cyclooctene units occurs more easily in copolymers than that in the homopolymer. The thermal properties of epoxidized homo- and copolymers are examined. It is found that upon epoxidation the glass-transition temperature and the melting temperature of multiblock copolymers increase by 40–50 and 20–30°С, respectively, wherein the degree of crystallinity and the temperature of melting grow with the length of the cyclooctene block.

Directional Synthesis of Membrane Materials by ROMP of Silyl-Substituted Norbornadienes and Norbornenes

A clarification of correlation between chemical structure of polymers and their gas transport parameters is an important task in membrane science, because it promises to solve the problem of directional construction of materials having high gas permeability and selectivity. In this respect ROMP of silylnorbornenes is a suitable subject of investigation. It allows preparing series of polymers bearing regularly changed substituents located at the desired places in the polymer backbones of a different microstructure.

Synthesis of Cyclobutane Hydrocarbons By Combination of (2+2)π-Cycloaddition and Olefin Metathesis. Their Abilities as Effective Propellants

Chemistry of cyclobutane hydrocarbons and their derivatives has been a subject of scientific attention science the beginning of the last century up to present time. The reasons of such a long attention is in special features of highly strained 4-membered ring structure and peculiar reactivity of cyclobutane compounds [1]. In application sense the compounds of this type demonstrate a range of interesting properties such as biological activity [2,3], capability to store energy [4,5], monomers activity to polymerization [1], etc. They are used as insecticides, in particular insect pheromone components [2,3], highly effective propellants [4.5] and energy accumulators [6].