Monomers alkene

The active form of a Ziegler-Natta catalyst is an alkyltitanium intermediate with a vacant coordination site on the metal. Coordination of alkene monomer... 

Vinyl monomer (Sections 7.10, 31.1) A substituted alkene monomer used to make chain-growth polymers. 

This is clo.sely related to the Tertiary radical synthesis" scheme for the preparation of organocobalt porphyrins, in which alkenes insert into the Co—H bond of Co(Por)H instead of creating a new radical as in Eq. (13). If the alkene would form a tertiary cobalt alkyl then polymerization rather than cobalt-alkyl formation is observed. " " " The kinetics for this process have been investigated in detail, in part by competition studies involving two different alkenes. This mimics the chain transfer catalysis process, where two alkenes (monomer and oligomers or... 

Methylpropene can be made to continue the process to yield high polymers—cationic polymerisation—but most simple alkenes will go no further than di- or tri-meric structures. The main alkene monomers used on the large scale are 2-methyIpropene (— butyl rubber ), and vinyl ethers, ROCH=CH2 (— adhesives). Cationic polymerisation is often initiated by Lewis acid catalysts, e.g. BF3, plus a source of initial protons, the co-catalyst, e.g. traces of HzO etc. polymerisation occurs readily at low temperatures and is usually very rapid. Many more alkenes are polymerised by a radical induced pathway, however (p. 320). 

As the alkene monomers can absorb oxygen from the air, forming peroxides (c/. p. 329) whose ready decomposition can effect autoinitiation of polymerisation, it is usual to add a small quantity of inhibitor, e.g. quinone, to stabilise the monomer during storage. When subsequent polymerisation is carried out, sufficient radical initiator must therefore be added to saturate the inhibitor before any polymerisation can be initiated an induction period is thus often observed. 

There is evidence that polymerization occurs through an insertion of the alkene monomer between the metal and the growing polymer chain. 

Cyclopolymerization of Nonconjugated Dienes. Cyclopolymerization is an addition polymerization that leads to introduction of cyclic structures into the main chain of the polymer. Nonconjugated dienes are the most deeply studied monomers for cyclopolymerization and for cyclocopolymerizations with alkene monomers 66 In general, (substituted and unsubstituted) dienes with double bonds that are linked by less than two or more than four atoms cannot undergo efficient cyclization and result in crosslinked materials.12 In fact, efficient cyclopolymerization processes have been described, for instance, for a,oo-dienes like 1,5-hexadiene, 2-methyl-l,5-hexadiene, 1,6-heptadiene, and 1,7-octadiene,67 73 which lead to formation of homopolymers and copolymers containing methylene-1,3-cycloalkane units. 

In this paper many sets of results on the polymerization of various alkenic monomers by ionizing radiations from several research groups have been re-examined by means of a... 

The first objection needs to be discussed in terms of the formation of a charge-transfer (CT) complex MSv between an alkene monomer M and the solvent Sv, with the formation constant Km. Since... 

A useful discovery was that the paradigm which had explained the phenomenology of the polymerisations of isobutene by A1C13 [112] was also useful for understanding why in the polymerisations of, for example, styrene by strong protonic acids, only a very small fraction of the acid is consumed, for which no plausible explanation had been put forward previously. It involves the formation of strong complexes also by protonic acids whith the alkenic monomers. 

A second misunderstanding concerns the nature of the propagating species in the pseudo-cationic polymerisations. The essential feature of these reactions is that the propagation involves the insertion of the alkene monomer into the heteroatomic bond of an ester, which in many instances needs to be activated in order to become sufficiently labile for the insertion. In a short discussion of pseudo-cationic polymerisations contained in a very comprehensive review [20], the statement was made Plesch did not realise, however, the necessity of activating the end-group which seems to be imperative to allow for the... 

The alkene monomer can approach the metallocene catalyst from various directions, head-on (Scheme 8.28, path A), from the same side as the anion (path B), or from a position trans to the anion, with side exchange of the alkyl ligand R (path C). 

There is a tendency toward alternation in the copolymerization of ethylene with carbon monoxide. Copolymerizations of carbon monoxide with tetrafluoroethylene, vinyl acetate, vinyl chloride, and acrylonitrile have been reported but with few details [Starkweather, 1987]. The reactions of alkenes with oxygen and quinones are not well defined in terms of the stoichiometry of the products. These reactions are better classified as retardation or inhibition reactions because of the very slow copolymerization rates (Sec. 3-7a). Other copolymerizations include the reaction of alkene monomers with sulfur and nitroso compounds [Green et al., 1967 Miyata and Sawada, 1988]. 

TRADITIONAL ZIEGLER-NATTA POLYMERIZATION OF NONPOLAR ALKENE MONOMERS... 

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