Electron spin resonance quantitative monitoring of five different radicals in γ-irradiated polyvinylidene fluoride

The complex superimposition of electron spin resonance (ESR) signals of the five different radicals generated on PVDF upon γ-rays exposure is fully simulated for the first time, including g factors as well as aα and aβ hyperfine splitting constants of proton or fluorine in α or β positions from the radical. The starting parameters were selected based on a thorough literature survey on their better-known fluorocarbons and perhydrogenated radical analogs and discussed in terms of correspondence with radicals in PVDF. In particular, the electronegativity difference between F and H atoms is taken into account since it directly affects the electron delocalization in the radical. The finally obtained ESR parameters are consistent with the spectroscopic characteristics and the chemical stability of the radicals. Since the absolute concentration of each radical is accessible, the simulation was also applied to monitor their stability upon annealing for different exposure times at 373 K. The resulting trend is in full adequacy with the expected relation between electron delocalization, mobility and stability.

► Simulation of the ESR signal of γ-irradiated poly(vinylidene fluoride).
► ESR parameters of each radical are discussed and modeled for the first time.
► The quantization of each radical species is presented.
► Concentration of a radical is related to its intrinsic stability, and depends on its chemical structure and chain localization.