DPPH as sensitizer

More detailed investigations by Rabek and Pajak [508] show that DPPH (concentration 10-3—10-4 mole l-1) added to a solution of cis-l,4-polyisoprene in benzene or n-heptane accelerates the photodegradation in the presence as well as in the absence of oxygen. It was discovered that the products of photochemical decomposition of DPPH have stronger sensitizing properties with respect to the photodegradation of diene polymers than has the undecomposed DPPH. 

Mayo et al. [404] found that phenylhydrazine catalysed markedly the degradation of polyisoprene in solution with oxygen. The effect increases with the amount of phenylhydrazine. Considering the above results it seems possible that hydrazines formed during the photolysis of DPPH catalyse the polyisoprene oxidation [508]. It was also found that the addition of hydrazine hydrate accelerated the thermal oxidation of polyimides [187]. 

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