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Producing "synthetic metals" with radiation

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This week, University Putra Malaysia's team unveiled their latest inventions and products at the 34th International Exhibition of Inventions, New Techniques and Products in Geneva (April 2-6, 2008), also known as the World's Largest Market-Place for Inventions.

This research is on a technique to transform non-conducting organic polymers into electricity conducting "synthetic metals" using radiation. These "synthetic metals" can be used for electromagnetic shielding, artificial muscles, active electronic devices, antistatic clothing, rechargeable batteries, ion exchange membranes, electrical display, chemical and biochemical sensors, electrochemical actuators, switches, and molecular electronics.

TITLE: Polymerization of PVA/PANI Conducting Polymer Blends by Radiation Technique

RESEARCHERS: Elias Saion, Muhammed Ahmed Ali Omar, Azian Osman, Khrulzaman Mohd Dahlan, Taiman Kadni, Shahril Hashim.

Department of Physics
Faculty of Science
Universiti Putra Malaysia, 43400 UPM,
Serdang, Selangor, Malaysia.
Tel: +603-89466654
Email: elias@

Most of organic polymers are insulators. However, those with conjugated ƒà-electron backbones could be transformed into conducting polymers when they are treated with strong oxidizing or reducing agents. The pi-bonds are localized structural defects in the polymer chain known as polorons that allow conducting electricity. These ¡¥synthetic metals¡¦ have been attracted much attention from both fundamental scientific concepts and potential for new technology due to their excellent optical, electronic, and electrochemical properties. They offer a wide variety of new application including electromagnetic shielding, artificial muscles, active electronic devices, antistatic clothing, rechargeable batteries, ion exchange membranes, electrical display, chemical and biochemical sensors, electrochemical actuators, switches, and molecular electronics. Among these polymers, polyaniline (PANI) generates a special interest owing to its relative high conductivity and low cost, exhibit excellent environmental stability, and its polymerization is straightforward and proceeds with high yield. Polymerization of PANI is normally achieved by chemical doping process involving charge transfer through oxidation (p-type doping) or reduction (n-type doping) and by electrochemical doping process in which electrode supplies the redox charge to the conducting polymer, while ions diffuse into the conducting polymer from the electrolyte to compensate the electronic charge. We offer a new route for synthesizing PANI by radiation method through bond scission of Cl- ions and aniline radical from aniline hydrochloride (AniHCl) blended in polyvinyl alcohol (PVA). The PVA/AniHCl blend films were prepared by solvent casting in air. The influence of the 1.25-MeV gamma-ray dose and the polymerization kinetics were investigated by means of visible absorption spectroscopy, XRD, and conductivity measurements. The polymerization of PANI was evident as the blends change colour from white to dark green, peaking at the absorption band of 780 nm, which is the colour of PANI. There is a significant reduction in the peak intensity at the diffraction angle of 19.5o, as the dose increases to 50 kGy, indicating the crystalline phase of the blends has been transformed into the amorphous phase due to the polymerization of PANI. This allows an easy passage of electrical current through the blends as the conductivity increases rapidly from 1.0 x 10-6 S/cm at 0 Gy to 3.0 x 10-1 S/cm at 50 kGy due to increase number of polarons formed in PANI. This study reveals the possibility to develop PVA/PANI conducting polymer blends from PVA/AniHCl blends by using radiation technique.

Dr Nayan KANWAL | Quelle: ResearchSEA
Weitere Informationen: www.inventions-geneva.ch/
www.putra.upm.edu.my
www.researchsea.com

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