Efficient formation of difluoramino (NF2) groups within the polymer matrix upon exposure of polyamides (PA6 and PA12) to elemental fluorine is reported. The reaction was assessed on bulk and thin-film samples by means of RA-FTIR (reflection-absorption FTIR), XPS (X-ray photoelectron spectroscopy), and NMR (nuclear magnetic resonance) techniques. Direct fluorination causes cleavage of the amide C-N bond and concomitant formation of the NF2 chain-end functionalities as evident from an exceptionally large shift (+5 eV) of the N 1s binding energy and an increase of the ν(CO) frequency by about 80 cm(-1). The structural model is supported by the F-19 NMR spectra of volatile reaction products that clearly reveal the presence of the NF2 group.