1.2- insertion polymerisation

Given the success of the Grubbs-type NHC-Ru catalysts in metathesis polymerisation (Chapter 3), it is somewhat surprising that more research has not been done on mid-transition metal carbene complexes for coordination-insertion polymerisation. At this stage however, there are only a few reported attempts with the metals Co, Fe and Ir. 

In coordination polymerisation, the catalyst-monomer complex forms a heterogeneous system in which the metal ion is in the solid phase and the carbanion of the alkyl group is in the solvent phase. The monomer is inserted in between the metal ion and the carbanion and the Polymer chain formed is pushed out from the solid catalyst surface. Because of this coordination polymerisation is also known as insertion polymerisation. 

When this author realised that the pseudo-cationic polymerisations (now called cationoid insertion polymerisations) were a distinct reaction category, he started using the term cationoid to comprise both these insertions into a highly polar bond and the original cationic polymerisations which involve classical carbenium ions. 

Two further innovations are the consideration of polymerisations in which the kinetic order with respect to monomer may be different from unity, and that the very common alleged effects of counter-ions might be due to a concurrent pseudo-cationic (cationoid insertion) polymerisation. 

However, the discovery with the most far-reaching consequences arose from the close scrutiny of the results of Kunitake and Takarabe on the polymerisation of styrene by trifluoromethyl sulphonic acid. It became evident to the reviewer that in these reactions an important contribution to monomer consumption must have been made by the ester, and he was able to extract from the results the corresponding propagation rate-constants, kpu, for that cationoid insertion polymerisation. This became one of the most convincing supports for the author s views on cationoid insertions. 

Pseudocationic Polymerisation, Renamed ca. 1998 Cationoid Insertion Polymerisation ... 

It is to be added in this connection that, like alkenes, acetylene can also undergo insertion polymerisation in the presence of some coordination catalysts, following a reaction analogous to (2) [43,44],... 

Give an example of coordination insertion polymerisation. Write down the scheme. 

Activities of a-olefins in insertion polymerisation with coordination catalysts are generally related to the monomer structure both electronic and steric factors influence the activity of a-olefins in stereospecific polymerisation, but the steric factor primarily influences the rate of polymerisation, which has been especially shown for isospecific polymerisation with heterogeneous catalysts [46, 250],... 

Allene has been polymerised to high molecular weight linear polymers by various Ziegler-Natta catalysts based on compounds of such transition metals as Ti, V, Cr, Mn, Fe, Co and Ni as precursors and alkylaluminium compounds as activators [439-441], Crystalline and amorphous polymers have been produced, in various proportions, with each of the catalysts used. The crystalline polymers consist predominantly of 1,2-linked (head-to-tail) monomeric units formed by insertion polymerisation as in scheme (68), but some regioirregular-ities resulting from the 2,1-insertion, leading to head-to-head and tail-to-tail arrangements, may be present in the polymer chain ... 

Functionalised a-olefins capable of undergoing insertion polymerisation with Ziegler-Natta catalysts are, in principle, monomers in which the heteroatom (X) does not electronically interact with the double bond to be polymerised in such monomers, the heteroatom is separated from the double bond CH2=CH-(CH2)x X [326,384,518,522-528], Monomers with the heteroatom directly bound to the double bond, i.e. those of the CH2=CH-X type, may also undergo polymerization, but when the heteroatom is silicon or tin (X= Si, Sn) [522-526], Representative examples of the insertion polymerisation of functionalised a-olefins and their copolymerisation with ethylene and a-olefins in the presence of heterogeneous Ziegler-Natta catalysts are shown in Table 3.7 [2,241,326,384,518,522-528],... 

Halogen-containing monomers can undergo insertion polymerisation only when the halogen atom is situated far away from the C=C bond this concerns co-halo-a-olefins [527]. 

Pino, P., Giannini, U. and Porri, L., Insertion Polymerisation , in Encyclopedia of Polymer Science and Engineering, Wiley-Interscience, John Wiley Sons, New York, 1987, Vol. 8, pp. 147-220. 

Decomposition of the Pd M P species via /1-hydrogen elimination is unfavourable, since both /1-hydrogen atoms, H3 and Hi, are not easily accessible for a Pd-H bond forming process. The suppression of /1-hydrogen abstraction is a prerequisite for the monomer undergoing m-insertion polymerisation, leading, in this case, to poly(2,3-bicyclo[2.2.1]hept-2-ene) [10]. 

At the end of considerations dealing with the insertion polymerisation of norbornene one should mention the Pd-catalysed polymerisation of other bicyclic olefins such as exo-8,9-dihydrodicyclopentadiene (tricyclo[5.2.1.02,6]... 

The cyclohomopolymerisation of 1,6-heptadiyne by using Shirakawa [85] and related [86] catalysts is a representative insertion polymerisation of acetylenic monomers with Ziegler-Natta catalysts ... 

Paul M A, Alexandre M, Degee Ph, Calberg C, Jerome R, Dubois Ph (2003), Exfoliated polylactide/clays nanocomposites by in situ coordination insertion polymerisation, 24, 561-566. 

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