Browsing by Subject "Polyvinyl chlorides"

Now showing 1 - 5 of 5

Open Access
Conducting polymer composites: polypyrrole and poly (vinyl chloride-vinyl acetate) copolymer
(John Wiley & Sons, Inc., 1997) Balci, N.; Bayramli, E.; Toppare, L.
Composites of a polypyrrole (PPy) and poly (vinyl chloride-vinyl acetate) copolymer (PVC-PVA) were prepared both chemically and electrochemically. An insulating polymer was retained in the blend and the thermal stability of the polymer was enhanced by polymerizing pyrrole into the host matrix in both cases. The composites prepared electrochemically gave the best results in terms of conductivity and air stability. © 1997 John Wiley * Sons, Inc.
Open Access
Doping of 2-Cl-PANI/PVC films by exposure to UV, γ-rays and e-beams
(Elsevier Sequoia SA, Lausanne, Switzerland, 2000) Sevil, U. A.; Güven, O.; Birer, Ö.; Süzer, Ş.
2-Chloro-polyaniline (2-Cl-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 μm) 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, γ-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.
Open Access
Photosensitization of PVC dehydrochlorination by hydroquinone for improved optical and electrical properties
(Elsevier, 2004) Balci, S.; Birer, O.; Süzer, Şefik
Hydroquinone (HQ) is incorporated into the PVC films containing methyl violet or polyaniline (emeraldine base) for sensitizing the UV induced optical or electrical changes, respectively. It is observed that introduction of a small amount (less than 10% by weight) of HQ not only brings the dehydrochlorination onset down to 310 nm but also sensitizes the process by more than one order of magnitude as well as leading to strong polyene formation. UV-Vis-NIR spectroscopy is used to characterize the changes and investigate the mechanism. Accordingly, it is postulated that this HQ assisted photo-dehydrochlorination involves predominantly the formation of an excited triplet via an efficient intersystem crossing in HQ followed by abstraction of hydrogen from the poly(vinyl chloride) to initiate a zipping reaction in the PVC matrix. © 2004 Elsevier Ltd. All rights reserved.
Open Access
Spectroscopic investigation of onset and enhancement of electrical conductivity in PVC/PANI composites and blends by γ-ray or UV irradiation
(American Chemical Society, 1998) Sevil, U. A.; Güven, O.; Süzer, S.
Electrical conductivity of blends and composites of poly(vinyl chloride) (PVC) with nonconducting polyaniline (PANI) increases when they are subjected to γ-rays or UV radiation. This is attributed to a radiation-induced dehydrochlorination (loss of HCl) of PVC, which in turn oxidizes (dopes) PANI 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 γ-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.
Open Access
UV-induced acid-base chemistry within the PVC matrix: Wavelength selectivity
(ACS, Washington, DC, United States, 2000) Süzer, Şefik; Birer O.
The dehydrochlorination of polyvinyl chlorides (PVC) is investigated by using it as an in-situ Bronsted acid source, in blends with pH indicators for optical changes, and with basic forms of conducting polymers to determine the electrical conductivity changes. The in-situ created HCl was responsible for the optical and electrical conductivity changes in pH indicator+PVC and nonconducting electroactive polymer (PANI) or PANI+PVC systems. It was possible to sensitized PVC and trigger polyene formation at higher wavelengths. The nature of polyene formation was strongly dependent on the wavelength of irradiation as well as the amount of energy transferred to the matrix from the sensitizer.