Semicrystalline polyvinylidene fluoride (PVDF) films have been irradited with different ion beams and energies ranging between 0.1 keV/amu and 6 MeV/amu. Polymer modifications induced by the ion irradiation, for electronic and nuclear energy stopping, have been investigated in situ by a highly sensitive quadrupole mass spectrometer. Ion irradiation of PVDF produced ejection of H 2 and HF molecules with a high chemical yield. Switching on the ion beam, the measured yields show a prompt (for H 2) and a slow (for HF) component of the molecular emission, which depends on the ion energy, ion fluence and polymer temperature. Along the ion track, the energy deposition produces a high density of active species, which give rise to desorbed molecules, to cross-linking processes and to a very stable residual carboneous film. At room temperature, the diffusion coefficient of HF molecules measured in irradiated PVDF is of the order of 10 -8 cm 2/s. The structural modifications of the irradiated films have been investigated ex situ by X-ray diffraction and optical absorption. The ion energy deposition along the ion track can be useful to realize active bio-membranes through the polymer grafting process.