Evidence of Reactions with Polymer Chains

The first observations of chain transfer come from studies of cyclic oxides. As described in Sect. 5.1, the formation of a cyclic dimer (1,4-dioxane) was observed in the polymerization of ethylene oxide and involves intramolecular attack within a peiHiltimate unit of the cludn  

This reactton is practically irrev sible and the release of 1,4-dioxane from its tonized form can proceed either by an attadr rf the oxygen atom of its own chain on the exocyclic carbon atom of the oxonmm fon, producing a new dtoxanium ion at the chain end or by a similar attack of a fore%n macromolecule. This process would result in depropaption to the dimer. 1,4-Dioxane is also formed vhen the preformed polymer is treated with an initiator of polymerizatton in the ab nce of ethylene oxide. 

Other evidence for the formation of macrocycles by similar medhanisins comes from the studies of the polymerization of oxetane and 3,3-dimethyloxetane. It was demonstrated by Rose h and confirmed by Dreyfuss, Wotsfold and Goethals ) that cyclic trimers and tetramers and higher cyclic oligomers are formed from these two monomers in polymerization. 

Other evidence stems from H-NMR studies of the polymerization of cyclic sulfides . 

The application of 300 MHz H-NMR to the polymerization of 3,3-dimethylthietane initiated with trialkyloxonium tetrafluoroborate (initiator concentration higher than 0.02 mole 1 ) permits polymeric sulfonium ions to be observed  

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