Showing papers on "Ring-opening metathesis polymerisation published in 1983"
01 Jan 1983
TL;DR: In this paper, the authors reviewed the literature on the composition of active centers of Ziegler-Natta catalysts and on the mechanism of propagation and chain transfer reactions and derived new data from the following trends in the study of catalytic polymerization: a) determination of the number of active centres (mainly with the use of radioactive CO as a tag); b) analysis of the microstructure of polymers with the using of 13C-NMR; c) specific features of highly active supported catalysts; d) quantum-chemical calculation of the electronic structure
Abstract: Novel data on the composition of active centers of Ziegler-Natta catalysts and on the mechanism of propagation and chain transfer reactions are reviewed. These data are derived from the following trends in the study of the mechanism of catalytic polymerization: a) determination of the number of active centers (mainly with the use of radioactive CO as a tag); b) analysis of the microstructure of polymers with the use of 13C-NMR; c) analysis of specific features of highly active supported catalysts; d) quantum-chemical calculation of the electronic structure of active centers and their reactions.
35 citations
TL;DR: In this paper, the initial carbene for ethene or propene metathesis over active fixed Mo catalysts with well defined reaction sites is formed by a 1,2-hydrogen shift via a molybdenum-n-alkenyl intermediate.
Abstract: It is indicated that the initial carbene for ethene or propene metathesis over active fixed Mo catalysts with well defined reaction sites is formed by a 1,2-hydrogen shift via a molybdenum–n-alkenyl intermediate.
23 citations
TL;DR: In this article, essential constitutional properties for a complex catalyst of olefin metathesis are derived from considerations of bond energy and kinetic stability of the transition metal carbon σ-bond on the basis of the carbene mechanism with the complex fragment X≡M(CHR) (M � Mo, W; X O, N, CR) as a model.
10 citations
5 citations
TL;DR: In this paper, a vibrational resonance between vibrating atom groups in the catalyst and the reacting molecule is used to relate the presence of oxo-ligands and the product pattern formed for reactions of terminal and internal olefins, respectively.
4 citations
03 Jun 1983
3 citations
TL;DR: In this paper, the cis-trans isomerization of polybutadiene double bonds during metathesis degradation using WCl6/(CH3)4Sn catalyst system has been estimated kinetically along with productive met athesis.
Abstract: The cis-trans isomerization of polybutadiene double bonds during metathesis degradation using WCl6/(CH3)4Sn catalyst system has been estimated kinetically along with productive metathesis. The isomerization was followed both for noncrosslinked and for crosslinked polybutadiene. Ninety-six percent cis-1, 4 units are found to isomerize into ca. 75% trans-1, 4 units. The rate of stereomutation is found to be different in the presence and absence of a low-molecular-weight olefin. The results are explained with the help of a stereo model originally proposed by Katz (Advances in Organometallic Chemistry, Academic, New York, 1977, Vol. 16.)
3 citations
TL;DR: In this paper, cyclooctene was polymerized in benzene at temperatures ranging from 10 to 80°C. The polymerization was initiated with the metathesis catalyst WCl6/C2H5)AlCl2/C 2H5OH for initial monomer concentrations varying from 0.11 to 4.0 mol/L.
Abstract: Cyclooctene was polymerized in benzene at temperatures ranging from 10 to 80°C. The polymerization was initiated with the metathesis catalyst WCl6/C2H5)AlCl2/C2H5OH for initial monomer concentrations varying from 0.11 to 4.0 mol/L. Polymerization products obtained from the metathesis reaction and the alkylation of benzene were found. The metathesis products consisted of a high molecular weight polymer and cyclic oligomers of cyclooctene. The double bond content was the same as in the monomer. The alkylation products were characterized by the presence of an aromatic nucleus and a low double bond content. Benzene was found to react with the double bond of cyclooctene and the cyclic dimer. It may also lead to the formation of saturated oligomer consisting of short chains of cyclooctyl units. Their presence is not temperature dependent and increases with decreasing initial monomer concentrations. For initial monomer concentrations above 1.0 mol/L, the alkylation reaction cannot be detected.
2 citations
TL;DR: In this paper, a comparison of the catalytic activity in olefin metathesis with the time dependence of the electrical conductivity does not give any evidence for a direct relationship between the ionic species formed during the reaction of the starting components and the catalytically active centres.
1 citations
01 Jan 1983
TL;DR: Olefin polymerization catalysts based on tetraneophylzirconium and its reaction products with submicroscopic fumed alumina are discussed in this paper, where the effect of catalyst structure on activity and oplymer properties is discussed.
Abstract: Olefin polymerization catalysts based on tetraneophylzirconium and its reaction products with submicroscopic fumed alumina are discussed. (Neophyl is the 2-methyl-2-phenylp. ropyl group). Neophylzirconium aluminate or hydridozirconium aluminate supported on alumina are extremely active catalysts for high temperature (300°C) polymerization of ethylene. The high catalyst efficiency and the innocuous nate of the catalyst residues eliminate the need for deactivation or removal of the catalyst from the resultant polymer. The effect of catalyst structure on activity and oplymer properties is discussed.
1 citations
TL;DR: A detailed study of the monometallic initiation of the polymerization of cyclopentene by WCI6 has shown that the kinetics of polymerization are extremely complex and the complexity is associated with the formation of a heterogeneous system as mentioned in this paper.