2-Chloro-polyaniline (2Cl-PANI) is chemically prepared in its non-conducting (Emeraldine Base, EB) form and dissolved together with polyvinylchloride (PVC) in THF for casting into thin (10-50 mu m) composite films. The electrical conductivity of these films increases by more than four orders of magnitude (from 10(-6) to 10(-2) S/cm) when they are exposed to UV, gamma-rays and e-beams. This is attributed to the dehydrochlorination (loss of HCl) of PVC by exposure to energetic particles and subsequent doping of the 2-Cl-PANI (i.e., conversion to Emeraldine Salt, ES) by the in-situ-created HCl. The doped films can also be returned to their undoped form by further exposure to NH3 vapours. The UV (or other particles)-induced doping/NH3 undoping cycles can be repeated several times until almost total dehydrochlorination of the PVC matrix. UV-Vis-NIR, Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopic (XPS) techniques are employed to follow the changes in the composite films upon doping by exposure to these energetic particles. (C) 2000 Elsevier Science S.A. All rights reserved.