Structural and Dielectric Properties of CuCl 2 and ZnCl 2 Doped Polyaniline Ersel Ozkazanc, 1 Sibel Zor, 2 Hatice Ozkazanc 2 1 Department of Physics, Kocaeli University, Kocaeli 41380, Turkey 2 Department of Chemistry, Kocaeli University, Kocaeli 41380, Turkey This article addresses the synthesis and characteriza- tion of polyaniline (PANI) both in pure and doped forms with various levels of CuCl 2 and ZnCl 2 in HCl medium where ammonium persulphate was used as an oxidant. Synthesized polymeric materials were characterized spectroscopically (UV-visible spectroscopy, Fourier transform infrared spectroscopy, and Atomic absorp- tion spectroscopy), thermally (Differential scanning cal- orimetry), and morphologically (Scanning electron mi- croscopy). Free adsorption energy was calculated via Langmuir adsorption isotherm based on the quantities of Cu 2þ and Zn 2þ cations in both pre- and post- poly- merization process where it was found that Cu 2þ and Zn 2þ are adsorbed physically on PANI surface. The dielectric measurements as a function of frequency and temperature showed that conductivity decreased with increasing doping levels of metal cations at high temperatures. POLYM. COMPOS., 31:1862–1868, 2010. ª 2010 Society of Plastics Engineers INTRODUCTION Conducting polymers have widely been investigated in the last two decades due to their unique electrical proper- ties and potential applications in various electronic devi- ces, such as sensors, light emitting diodes, and recharge- able batteries [1–17]. Among the conducting polymers, polyaniline (PANI) is one of the most popular for its easy synthesis, high electrical conductivity, and good environ- mental stability [1, 3, 6–10, 12–37]. PANI is available in four different forms, such as leucoemeraldine base (color- less), emeraldine base (blue), pernigraniline base (violet), and emeraldine salt (green) depending on the pH of the solution and oxidation potential out of which only emeral- dine salt (or protonated emeraldine) is electrically con- ducting. It can easily be synthesized through electrochem- ical or chemical oxidation of aniline with the help of oxidants like ammonium peroxidisulphate in acidic medium [1, 5, 6, 9, 10, 18, 23–26, 28, 31, 33, 35–37]. There has been a considerable effort in recent years towards improving structural and physical properties of conducting polymers synthesized with various methods and doping processes [2, 4, 6–8, 14–19, 29, 30, 33, 34]. In this study, the synthesis of PANI in pure form as well as doped with CuCl 2 and ZnCl 2 at various levels were carried out by using a simple and low-cost chemical method where ammonium persulphate (NH 4 ) 2 S 2 O 8 was used as an oxidant for aniline. We first reported results of Fourier transform infrared spectroscopy (FTIR) and UV-visible (UV-vis) spectroscopy. Different to the litera- ture, we then reported quantities of Cu þ2 and Zn 2þ remained in filtrate before and after the chemical poly- merization determined by using atomic absorption spec- troscopy (AAS). The adsorption of metal cations adsorbed to PANI surface was examined by Langmuir adsorption isotherm. Finally, Scanning electron microscopy (SEM), Differential scanning calorimetry (DSC), and dielectric measurements were performed. EXPERIMENTAL Synthesis of Polyaniline PANI was synthesized with chemical oxidation poly- merization where ammonium persulphate (Merck, Ger- many) was used as an oxidant. Aniline (5 mL) was dis- solved in 1.5 M, 70 mL HCl (Merck, Germany), 10 g of (NH 4 ) 2 S 2 O 8 dissolved in 20 mL deionized water was sub- sequently added into the above solution. The whole solu- tion was stirred at a constant speed for 5 hrs at a constant temperature of 258C. After the polymerization, the whole solution was filtered, washed, and dried leading to green emeraldine salt form of PANI granules. Doping Process CuCl 2 and ZnCl 2 (Merck, Germany) salts of various doping levels of 2, 6, and 10% each prepared in 5 mL deionized water is added into the polymerization solution Correspondence to: E. Ozkazanc; e-mail: erseloz@kocaeli.edu.tr DOI 10.1002/pc.20979 Published online in Wiley Online Library (wileyonlinelibrary.com). V V C 2010 Society of Plastics Engineers POLYMERCOMPOSITES—-2010