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Polymeric transfer reagents solution

Schrock, Gibson et al. [52d] found that styrene and 1,3-pentadiene could be used as chain transfer reagents for the living ring-opening olefin metathesis polymerization of norbornene with molybdenum based catalyst 35a. Renewed norbornene addition to a polymerization mixture containing initiator 35a and 30 equivalents of styrene resulted in the formation of polynorbomene with a low polydispersity and a molecular weight controlled by the number of norbornene equivalents in each of the individual monomer solutions, Eq. (38). This method allows a more efficient use of the catalyst. [Pg.63]

The commercially available 3-amino-1,2,4-dithiazole-5-one, (3), has been attached to a hydroxyl resin via a succinic acid linker, and has been used as an efficient sulfur-transfer reagent for the solution-phase synthesis of phos-phorothioates. DNA synthesis scale-up to lOOg of a 20-mer phosphorothioate has been examined " key to this was the purification of the product, which was carried out using a high efficiency polymeric anion exchange chromatographic media. [Pg.431]

In principle, the appearance of electron donor groups near the double bond of the monomer leads to a cationic mechanism, while positive groups that withdraw electrons mostly lead to the anionic process. An increase of temperature usually leads to a decrease in rate of reaction or length of the chain. Polymerization always occurs in solution, wherein the solvent acts as separator of the ion-pair, and quite often as a transfer reagent. As already mentioned, most monomers undergo polymerization via free radicals, mainly when conjugated double bonds are present or substitute groups that withdraw electrons. [Pg.22]

It has generally been accepted that aryloxy radicals are intermediates in the polymerization, largely because the effective reagents are those capable of one-electron transfer. This assumption has been confirmed recently by the identification of both monomeric and polymeric aryloxy radicals in the ESR spectra of polymerizing solutions of 2,6-xylenol (21). The first step in the reaction is the oxidation of the phenol to the aryloxy radical by Cu(II). Carbon-oxygen coupling of two aryloxy radicals yields the cyclohexadienone, which tautomerizers to the dimer (II) (Reaction 3). [Pg.678]


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See also in sourсe #XX -- [ Pg.244 ]




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Polymeric solutions

Polymeric transfer reagents

Polymerization solution polymerizations

Reagent solutions

Solution polymerization

Transfer reagent

Transferring solution

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