Conductive Polymer Nanocomposites: Electrical Switching and Electrochromism

Time: 14:00~16:00

Date: May 26th, 2010
Location: The Institute for Advanced Materials and Nano Biomedicine (iNANO), 67 Chifeng Road
Reporter: John Zhanhu Guo

The electrical switching and electrochromic phenomena of nanocomposites comprising poly(p-phenylenebenzobisthiazole) (PBZT) and tungsten oxide (WO3) nanoparticles have been investigated as a function of the nanoparticle loading. Both dissolving PBZT and doping PBZT backbone structure with acid are achieved by one simple step. Chlorosulfuric acid (CSA) is used as a solvent and spontaneously transformed to sulfuric acid upon exposure to moisture. The formed sulfuric acid serves as doping agent to improve the electrical conductivity of PBZT. The most significant enhancement of electrical switching is observed in the nanocomposites with low weight fraction (5%), the electrical conductivity of 5% WO3/PBZT nanocomposite thin film is increased by about 200 times and 2 times, respectively, as compared to those of the as-received PBZT and PBZT/CSA thin films within the scanning voltage range from -1.0 V to -0.5 V. As the nanoparticle loading increases to 20% and 30%, the nanocomposites follow ohmic conduction mechanism. Stable electrical conductivity switching has been observed before and after applying a bias on the pristine PBZT and WO3/PBZT nanocomposite thin films. Electrochromic phenomena of both pristine PBZT and WO3/PBZT nanocomposite thin films with high contrast ratio have been observed after applying a bias (3 V). The mechanisms of the nanoparticles in enhancing the electrical switching and electrochromic properties are proposed. In addition, the giant magnetoresistance (GMR) from carbonized polymer nanocomposites will be presented.

Short Biography:
Dr. Guo is an Assistant Professor in Chemical Engineering Department and Director of Integrated Composites Laboratory at Lamar University. He obtained a Ph.D. from Chemical Engineering in 1996 and did three-year Postdoctoral training in Mechanical and Aerospace Engineering Department at UCLA with Dr. H. T. Hahn. He is a member of AIChE, ASC, ECS, SAMPE and TMS. Dr. Guo is a vice president of Polymer Composites Division in AIChE (2009-2010). Dr. Guo’s expertise is in the fabrication and applications of the polymer nanocomposites, magnetic nanocomposites, and nanoparticles. Dr. Guo is an Editorial board member of Journal of Nanocomposites and Nanoceramics and Science of Advanced Materials. Dr. Guo has more than thirty peer-reviewed Journal papers, four book chapters, three issued and one pending patents.


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