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Transfer and Termination Involving the Polymer Backbone

With more basic nmnomers the importance of termination deareases, as has ak dy been discussed for the polymerization with initiators bearing simple anions (e.g. halide anion. Sect. 3). Thus, tw) factors have to be taken into account simultaneously, the nucleophilicity and inherent stability of the anion as well as the nucleophilicity of the monomer involved. The higher the nucleophilicity of the monomer, the less important becomes termination involving anions. [Pg.97]

Apparently, the lymerization of some threemembered cyclic ethers, for example a-epi-chlorohydrin which undergoes incomplete monomer conversion, proceeds with efficient decomposition of the macroin pairs. It seems, that the limited converaons observed in Ref. 239 are also due to termination and not to the thermodynamic equilibrium, proposed in the cited paper and leading to the uruealistically low ring strain of o-epichlorohydrin. [Pg.97]

In the majority of cationic polymerizations of heterocyclic monomas, chain propagation immlves a nucleophilic attack of a monomer molecule on the strained onium ions, e.g.  [Pg.97]

Both reactions, namely tte intermolecular process (131) and the intramolecular one (132) can be either reversible or irreversible (termination). In the case of reversible reactions true chain transfer takes place vdien the rate constant of the backward reaction (kj ) becomes comparable with the rate constant of M-opaptun. This applies to the polymerization of cyclic acetals where the product of chain traiKfer is equally active in propaption. [Pg.98]

transfer or termination which involve reaction of the powing center with its own backbone are inherent features of the cationic polymerization of heterocyclic monomers, and cannot be completely avoided. (For exceptions and their origin see p. 104.) [Pg.98]


Transfer and Termination Involving the Polymer Backbone. The polymer chain contains the same heteroatora as the parent monomer. Therefore, the nucleophilic attack of a monomer molecule on the strained onium ion can be replaced by the attack of a polymer chain. The polymer chain can react with active species of a foreign macromolecule or of its own macromolecule (back biting). [Pg.109]


See other pages where Transfer and Termination Involving the Polymer Backbone is mentioned: [Pg.97]    [Pg.99]    [Pg.103]    [Pg.107]    [Pg.109]    [Pg.111]    [Pg.115]    [Pg.119]    [Pg.97]    [Pg.99]    [Pg.103]    [Pg.107]    [Pg.109]    [Pg.111]    [Pg.115]    [Pg.119]    [Pg.212]    [Pg.75]    [Pg.145]    [Pg.1976]    [Pg.383]    [Pg.157]    [Pg.3240]    [Pg.481]    [Pg.292]   


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Polymer backbone

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