Radicals formed by a charge-transfer mechanism

The observed chain scission and/or crosslinking reactions occur subsequently, by a free radical mechanism, and are accompanied by free radical oxidation and singlet oxygen ( 02) oxidation. 

There is very limited information on polymer degradation by charge-transfer mechanisms. However, it has been reported that crosslinking of poly(2-phenylbutadiene) is induced by photoexcitation of the polymeric charge-transfer complex with tetracyanobenzene in polar solvents, and that ionic species such as the radical cation of the polymer contribute to the primary processes of the crosslinking [1159]. 

Photodegradation of poly(a-methyl styrene) through a charge-transfer complex with tetracyanobenzene has also been described [1160]. A tentative mechanism for this type of photodegradation may be presented by the following reactions  

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