UV-induced electrical and optical changes in PVC blends

2-Chloro-polyaniline (2-Cl-PANI) in its non-conducting (emeraldine base, EB) form, prepared by a chemical route, was dissolved together with poly-(vinylchloride) (PVC) in THF for casting into thin (10-50 μm) films. Upon exposure to UV radiation, the electrical conductivity of these films increased by more than 4 orders of magnitude (from 10-6 to 10-2 S/cm). This is attributed to the dehydrochlorination of PVC by exposure to energetic photons and subsequent doping of 2-Cl-PANI (i.e. conversion to emeraldine salt, ES) by in situ created HCl. The doped films could be returned to their undoped form by exposure to NH3 vapours. The UV-induced doping/NH3 undoping cycles could be repeated several times. Various spectroscopic techniques were employed to follow the changes in the films upon exposure to UV radiation. The same photo-dehydrochlorination process has also been utilized for optical and/or lithographic purposes by preparing PVC blends containing methyl violet, and acid-base indicator dye. The photo-dehydrochlorination can be effectively sensitized by incorporating hydroquinone into the PVC blends containing methyl violet

Spectroscopic Investigation Of Onset And Enhancement Of Electrical Conductivity In Pvc/Pani Composites And Blends By Gamma-Ray Or Uv Irradiation

Electrical conductivity of blends and composites of poly(vinyl chloride) (PVC) with nonconducting polyaniline (PANI) increases when they are subjected to gamma-rays or UV radiation. This is attributed to a radiation-induced dehydrochlorination (loss of HCl) of PVC, which in turn oxidizes (dopes) PANT within the PVC matrix causing the increase in electrical conductivity of these films. XPS, UV-vis-NIR and FTIR spectroscopic methods are used to characterize and verify this novel process. After the films are subjected to gamma-rays (or UV radiation) the intensities in the XPS spectra of both -N+- and Cl- peaks increase, confirming the increase in charged species within the PVC matrix. Similar observations attributable to radiation-induced electrical conductivity are also observed in both the UV-vis-NIR and FTIR spectra. This radiation-induced conductivity can also be reversed to some extent by further exposing the films to NH3 vapors, where the oxidized centers are partially reduced (undoped). Several UV/NH3/UV cycles can be performed without much loss in conductivity-and/or conductivity-related spectroscopic features. The onset of the photoinduced conductivity both in PVC-only and PVC/PANI composite films is determined to be 300 nm (4.1 eV), which coincides with the first UV absorption band of PVC.Wo

Doping Of 2-Cl-Pani/Pvc Films By Exposure To Uv, Gamma-Rays And E-Beams

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.Wo