Free-radical conversions

A more versatile approach is to use a transformation reaction in which one type of active terminal species is converted into a second type. Two general reactions have been identified (1) a terminal unit anion-cation transformation by a two-electron oxidation process and (2) carbanion to free-radical conversion, which is a one-electron oxidation step. 

The rate of formation of ions is a factor of approximately 10-100 times smaller than that for free radicals. Conversely, the recombination constants are about 100 times larger for ions than for free radicals. Thus, it follows that the steady state concentration of ions is about 100 times smaller than that for free radicals. Consequently, the majority of radiation-initiated polymerizations proceed by a free radical mechanism. 

The investigations carried out earlier characterise the reactivity of different classes of polymers with NO. However, the mechanisms of free-radical processes proposed on the basis of the results considered are rather formal. As a rule, they take account of changing molecular weights and the composition of final molecular products of the nitration. In connection with this, the study of structures of free radicals forming in primary and intermediate stages of polymer conversions attracts special interest. Such research allows drawing conclusions on the mechanism of initiation of free-radical conversions dependent on the nature of functional groups of macromolecules. As... 

Free-Radical Conversions of Polymers Initiated by Nitrogen Trioxide... 

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