Effect of dose and subsequent annealing on radicals distribution in γ-irradiated PVDF as quantitatively monitored by ESR: Correlation between network features and radical type

A simulation model which takes into account the molecular structure, the localization and the chemical environment of radicals is used to quantitatively monitor the five radical species generated on PVDF upon γ-irradiation at different dose ranging from 100 to 500 kGy. While from 150 kGy to upper dose the overall concentration of radicals is similar, the distribution differs due to their chemical structure and localization (mid-chain versus end-chain). The changes obtained with an annealing at 373 K on the total amount of radicals and in the relative proportions of each species are presented. The observed differences are not only related to intrinsic reactivity of radicals but also to the characteristics of the network (gel fraction, crosslink density) obtained along radiation, as the mobility of polymeric segments is all the more reduced with increasing dose.

► Effects of irradiation dose and annealing on ESR signal of Poly(vinylidene fluoride) are presented.
► While global concentration of radicals is constant from 150 kGy and more, the distribution of radicals varies.
► Mobility of chain-segment containing radical and chemical structure effect are crucial parameters.
► Relationship between the distribution of radicals and crosslinking is evidenced.