Indian Journal of Pure & Applied Physics Vol. 46, June 2008, pp. 414-416 Structural and thermal characterization of metal halides doped polypyrrole Rashmi Saxena*, Vinodini Shaktawat, Neeraj Jain, N S Saxena**, Kananbala Sharma & T P Sharma Semi-conductor and Polymer Science Laboratory, 5-6, Vigyan Bhawan, University of Rajasthan, Jaipur 302 004 *E-mail: n_s_Saxena@rediffmail.com, rashmi_saxena29@yahoo.co.in Received 28 October 2007; accepted 7 April 2008 Polypyrrole and its metal halide composites have been synthesized by chemical oxidation polymerization technique with ammonium peroxisulphate (oxidant) in aqueous hydrochloric acid medium. structural characterization of polypyrrole samples S1 (100% Co), S2 (25%Ni -75%Co), S3 (50%Ni -50%Co), S4 (75%Ni - 25%Co) and S5 (100%Ni) has been made by XRD and FTIR spectroscopy. Thermal transport properties such as effective thermal conductivity (λ e ) and effective thermal diffusivity (χ e ) of these samples have been measured simultaneously at room temperature and normal pressure using transient plane source (TPS) technique. The values of effective thermal conductivity and effective thermal diffusivity are found higher in all the above-mentioned samples except sample S3 (50%Ni-50%Co). This result can be explained on the basis of bonding of cobalt and nickel with polypyrrole matrix during their polymerization. Keywords: Effective thermal conductivity, Effective thermal diffusivity, Metal halide 1 Introduction Polypyrrole is a hetrocyclic aromatic organic compound, a five-member ring with the formula C 4 H 5 N. In recent years, intrinsic conducting polymers with conjugated double bonds have attracted much attention as advanced materials. Among the conducting polymers, polypyrrole (PPy) is especially promising for commercial applications because of its good environmental stability, facile synthesis, and significant electrical conductivity 1 . PPy is easily prepared by either oxidative chemical polymerization or using electrochemical oxidation in aqueous or organic solutions by applying a positive potential to a monomer solution containing appropriate supporting electrolyte 1 . The oxidation of pyrrole, which involves the formation of radical anions and subsequent polymerization 2 , is given in Fig.1. Fig. 1—Oxidation of pyrrole In oxidized state, it has been found that polypyrrole contains one positive charge per three or four pyrrole rings, while the polymer is neutral in its reduced state 3 . During the polymerization, anions in the solution are incorporated in the polymer sample to maintain the charge balance. PPy and its derivatives are used as biosensors, gas sensors 4-6 , wires, micro actuators 7 , antielectrostaic coating 8 , solid capacitor, electro chromic windows and polymeric batteries. PPy coatings have an excellent thermal stability and are good candidates for use in carbon composites 9 . In the present study, thermal transport properties like effective thermal conductivity and effective thermal diffusivity at room temperature of metal halide doped PPy have been investigated. 2 Experimental Details Metal halide composites of polypyrrole were prepared by oxidative polymerization of double distilled pyrrole using ammonium persulphate (NH 4 ) 2 S 2 O 8 as an oxidant. As a typical preparation sample S1 (Co=100M%) was synthesized by taking ammonium persulphate (0.2M) and metal halide (MX) monomer ratio (0.5M), dissolved in HCl (1M) precooled to 0 °C. This aqueous solution was added to stirred solution of double distilled pyrrole (.01M) dissolved in precooled HCl (1M) solution. The temperature of this solution was maintained at 3-4°C