ESR Investigations On Polyaniline-Polyvinylchloride Blends
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ESR INVESTIGATIONS ON POLYANILINE-POLYVINYLCHLORIDE BLENDS M. Chipara, E. Goovaerts1, Magdalena Chipara2, I. Munteanu3 Department of Physics and Astronomy, University of Nebraska, Lincoln, NE 68503, USA. 1 Physics Department, University of Antwerp, Belgium, 2 Institute for Electrotechnical Researches, Bucharest, Romania 3 Faculty of Physics, University of Bucharest, Romania ABSTRACT Electron spin resonance (ESR) investigations on blends of polyaniline (PANI) and polyvinylchloride (PVC), containing different amounts of PANI, ranging from 0 to 40% (in weight), are reported. The temperature dependence of resonance line parameters, in the temperature range 150 K to 500K is analyzed. It is proved that the high spins bipolarons are not contributed to the ESR spectrum and that the resonance spectrum does not contain contributions due to extremely high conducting islands, with lengths of the order of at least 1micron. From the temperature dependence of the double integral of the resonance line, it is concluded that, the blends exhibit an almost pure paramagnetic behavior and that at short times physical processes control the behavior of these blends. At long times (102 to103 hours), the resonance spectrum is drastically reduced due to the consumption of free electrons in the chemical reactions involved by the degradation processes occurring mainly in PVC. A stationary value is reached for storage times of about 2500 hours, in air, at room temperature.
INTRODUCTION The nature of the metallic phase in conducting polymers as PANI, is presently the subject of intensive study [1,2]. The contribution of bipolarons to the charge transport as well as the possibility of highly conducting islands in such polymers, are still under debate. The high electric conductivity and the outstanding thermal and thermooxidative stability of PANI are balanced by poor mechanical properties and low processability. Blends of PANI with different polymers are investigated in order to improve the processability and the mechanical features of polyaniline [3, 4]. The low percolation threshold allows a better balance between the electrical features and the mechanical properties of the resulting blend. Dc electrical data are consistent with an one dimensional variable range hopping [5]. Electron spin resonance investigations of polyvinylchloride-polyaniline (PVC-PANI) blends, are in depth analyzed.
EXPERIMENTAL METHODS Blends of highly conducting PANI (emeraldine salt) and PVC were obtained masticating the components at 350 K, for few hours, in air. PANI (emeraldine salt) was prepared by chemical oxidation and milled up to a particle size of about 1 microns. The resulting films, with a thicknes of 1 mm were homogeneous, indicating an uniform distribution of the conducting polymer. Electron spin resonance investigations, ESR, on different PANI-PVC blends, containing 0, 5%, 10%, 15%, 20%, and 40% wt. PANI are reported. The resonance spectra were recorded using a JES-ME-3X spectrometer operating in X band. The temperature dependence of the resonance C8.8.1
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