Transfers during polymerization of heterocyclic monomers

These are much slower than to the preceding group of monomers, evidently because of the lower reactivity of oxonium, sulphonium, ammonium, phos-phonium and siloxonium, ions. Moreover, monomers with these heteroatoms are strongly basic, and therefore cations are preferentially solvated by the monomers. This reduces the probability of other kinds of transfer to solvent, impurities, etc. Many heterocycles, e. g. A-substituted aziridines, thiethanes 

These are much slower than to the preceding group of monomers, evidently because of the lower reactivity of oxonium, sulphonium, ammonium, phos-phonium and siloxonium, ions. Moreover, monomers with these heteroatoms are strongly basic, and therefore cations are preferentially solvated by the monomers. This reduces the probability of other kinds of transfer to solvent, impurities, etc. Many heterocycles, e. g. A-substituted aziridines, thiethanes [62], tetrahydrofuran [63], under suitable conditions polymerize by a living mechanism, i. e. without transfer. In situations where transfer does occur, it is assumed to proceed by the mechanism disscussed previously, for example by transfer to the counter-ion. With regard to transfer intensity, vinyl ethers can be ordered between the hydrocarbon monomers and the heterocycles. The mechanism of transfer in their polymerization has yet to be studied. 

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