title: Cross-metathesis of polynorbornene with polyoctenamer: a kinetic study.
abstract: The cross-metathesis of polynorbornene and polyoctenamer in d-chloroform mediated by the 1(st) generation Grubbs' catalyst Cl2(PCy3)2Ru=CHPh is studied by monitoring the kinetics of carbene transformation and evolution of the dyad composition of polymer chains with in situ (1)H and ex situ (13)C NMR spectroscopy. The results are interpreted in terms of a simple kinetic two-stage model. At the first stage of the reaction all Ru-benzylidene carbenes are transformed into Ru-polyoctenamers within an hour, while the polymer molar mass is considerably decreased. The second stage actually including interpolymeric reactions proceeds much slower and takes one day or more to achieve a random copolymer of norbornene and cyclooctene. Its rate is limited by the interaction of polyoctenamer-bound carbenes with polynorbornene units, which is hampered, presumably due to steric reasons. Polynorbornene-bound carbenes are detected in very low concentrations throughout the whole process thus indicating their higher reactivity, as compared with the polyoctenamer-bound ones. Macroscopic homogeneity of the reacting media is proved by dynamic light scattering from solutions containing the polymer mixture and its components. In general, the studied process can be considered as a new way to unsaturated multiblock statistical copolymers. Their structure can be controlled by the amount of catalyst, mixture composition, and reaction time. It is remarkable that this goal can be achieved with a catalyst that is not suitable for ring-opening metathesis copolymerization of norbornene and cis-cyclooctene because of their substantially different monomer reactivities.
authors.affiliation: Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Leninsky prosp. 29, 119991 Moscow, Russia.
authors.forename: Yulia I
authors.initials: YI
authors.lastname: Denisova
authors.affiliation: Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Leninsky prosp. 29, 119991 Moscow, Russia.
authors.forename: Maria L
authors.initials: ML
authors.lastname: Gringolts
authors.affiliation: Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilova str. 28, 119991 Moscow, Russia.
authors.forename: Alexander S
authors.initials: AS
authors.lastname: Peregudov
authors.affiliation: Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Leninsky prosp. 29, 119991 Moscow, Russia.
authors.forename: Liya B
authors.initials: LB
authors.lastname: Krentsel
authors.affiliation: Chemistry Department, Moscow State University, Leninskie gory 1, build. 3, 119991 Moscow, Russia.
authors.forename: Ekaterina A
authors.initials: EA
authors.lastname: Litmanovich
authors.affiliation: Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Leninsky prosp. 29, 119991 Moscow, Russia.
authors.forename: Arkadiy D
authors.initials: AD
authors.lastname: Litmanovich
authors.affiliation: Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Leninsky prosp. 29, 119991 Moscow, Russia.
authors.forename: Eugene Sh
authors.initials: ESh
authors.lastname: Finkelshtein
authors.affiliation: Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Leninsky prosp. 29, 119991 Moscow, Russia.
authors.forename: Yaroslav V
authors.initials: YV
authors.lastname: Kudryavtsev
keywords: 1st generation Grubbs’ catalyst; cross-metathesis; interchange reactions; kinetics; multiblock copolymer