EPR Characterization of Peroxy Perfluoroalkyl Radicals in Irradiated PTFE

The formation of peroxy radicals in polytetrafluoroethylene (PTFE) during the industrial production of low molecular weight PTFE is a key factor influencing the generation of oxygenated species such as perfluorooctanoic acid (PFOA). The aim of this thesis was to investigate the nature, formation mechanisms, and behavior of these radicals under different irradiation conditions and to correlate radical chemistry with structural modifications in the polymer. This work addresses industrially relevant materials using a comprehensive spectroscopic and analytical approach. Electron paramagnetic resonance (EPR) spectroscopy, in both continuous-wave and pulsed modes, was employed to characterize radical species, complemented by infrared and Raman spectroscopy, differential scanning calorimetry, melt flow rate analysis, and quantum-chemical calculations. Continuous-wave EPR provided direct evidence of radical species and allowed assessment of how irradiation conditions affect radical formation and PFOA-related pathways. Pulsed EPR, including electron nuclear double resonance (ENDOR), enabled the detailed study of peroxy radicals, revealing their electronic structure, orientation, and local environment. Complementary IR, Raman, DSC, and MFR analyses correlated microscopic radical structures with macroscopic chemical and physical modifications in the polymer. Overall, this work provides a molecular-level understanding of radical formation in PTFE and offers guidance for minimizing persistent perfluoroalkyl species in industrial processes, representing a significant methodological and practical contribution to the field.