Research Journal of Chemical Sciences ___ ______________________________ ______ ____ ___ ISSN 22 31 - 606X Vol. 3 ( 2 ), 1 6 - 19 , February (201 3 ) Res. J. Chem. Sci. I nternational Science Congress Association 16 Dielectric Study of Polyaniline in Frequency Range 100Hz to 500 KHz a t Temperature 20 0 C and 30 0 C Saxena Dinesh 1 , Dwivedi Vivek 2 and Mishra Pankaj Kumar 2 1 Department of Physics , D.B.S. College, Kanpur, INDIA 2 Department of Physics , B.N.D. College Kanpur, I NDIA Available online at: www.isca.in Received 16 th October 201 2 , revised 23 rd October 201 2 , accepted 23 rd November 2012 Abstract The dielectric behaviour of polyaniline has been investigated in the frequency range 10 0Hz to 500KHz and at temperature 20 0 C and 30 0 C respectively. The parameters capacity, permittivity, dielectric loss and dissipation factor have been calculated. The frequency and temperature dependence of these parameters have been qualitatively explained on the basis of hopping of electrons. Keywords: Polyaniline, dielectric constant and dielectric loss. Introduction Conducting Polymers have emerged as a very important class of materials because of their unique electrical, optical and chemical properti es leading to the wide range of technological applications 1 - 3 . This class of materials provides tremendous scope for tuning of their electrical conductivity from semi conducting to metallic regime by way of doping 4 - 5 . The unique properties of conducting p olymers not only provide great scope of their applications but also have led to the development of new models to explain their observed properties; particularly various mechanisms of charge transport 6 - 8 . Among different conducting polymers, conducting pol yanilines are the most extensively studied materials due to the ease of synthesis, better environmental and thermal stabilities and greater scope of playing with chemistry to tailor their properties 9 - 10 . The common feature of almost all the electro active polymers such as polypyrole polythiophene, polyaniline etc is an extended localization in their polymer backbone. Polypyrrole (PPY) family of polymers is one of the best candidate materials for various device applications such as in solar cells electroma gnetic shielding electrodes for rechargeable batteries, sensors etc. Hence it is worthwhile to examine the mechanism of change transport in this family of polymers 11 - 12 . Among the various conducting polymers synthesized, polyaniline occupies a prime posit ion, because of its unique characteristics like inexpensiveness of monomer, ease of processing and excellent stability. It is widely investigated in both thin film and bulk forms, because its electronic and photonic properties are interesting Polyaniline i n its pure and doped forms find extensive applications in making devices like polymer light emitting diodes photovoltaic, sensors, batteries and super capacitors. The low dielectric thin films based on a.c. plasma polymerized polyaniline may find applicati ons in the microelectronics industry in the from of inter layer dielectrics 13 - 14 . Preparation of composites of conducting polymer (PANI) has been considered to provide a suitable solution to the possibility problem. These composites have the ability to enhance their material properties with desirable mechanical and physical characteristics. A review of literature suggests that not much more attention has been paid in the dielectric study of pure polyamiline (PANI) in recent years instead of doping to en hance the conductivity. We report here its dielectric constant, dissipation factor, dielectric loss as a function of frequency and temperature. Material and Methods Experiment: This chemical PANI is used for dielectric measurements was obtained in the form of disc by compressing in a die under a load 3 - 4 tons. The diameter of the pallet was 1 cm and thickness was 0.51 mm. The sample holder was made up of brass coated with nickel and had two parts. The sample was placed between the jaws of two electrodes via a spring arrangement. The temperature was measured with the help of a calibrated copper constantan thermocouple. For dielectric measurement, thin pallet mounted in between the two electrodes of the sample holder, where a vacuum near about 10 - 2 torr wa s maintained. The model No. 4255 WAYNE KER LCR capacitance measuring assembly has been used to measure the capacitance. The instrument was used in the parallel capacitance mode where parallel conductance would be measured directly. The loads were of c o - a xial wire to avoid stray capacitance effect. Lead capacitance was subtracted from the measured capacitance before calculating the dielectric constant. Research Journal of Chemical Sciences ___ _ _ _______________________________ ______________ _ ________ ISSN 22 31 - 606X Vol. 3 ( 2 ), 1 6 - 1 9 , February (201 3 ) Re s. J. Chem. Sci. International Science Congress Association 17 For the present study of dielectric behavior pallet was coated with silver paint to ensure good electric al contact between the sample and the electrodes of the sample holder. Results and Discussion The dielectric parameters were evaluated by measuring equivalent parallel capacitance C p and dissipation factor tan  (D) or the equivalent resistance R p of the sample by using the equation. Where C o = 0.08854  A/t, P f . is the geometrical capacitance of vacuum of the same dimensions as the sample. A and t are the area and thickness of the sample respectively and f the measuring freque ncy. C p is the capacitance measured in P f , ' the real dielectric constant and " the imaginary dielectric constant. The dielectric constant has been measured for pallet thickness 0.51 mm. while keeping t he area and the other preparation conditions same and it was found to be independent of thickness of sample withi n the accuracy of measurement. So the observed dielectric data at higher temperature cannot be due to the electrode barriers or macroscopic in homogeneities 15 - 16 . The frequency dependence study of PANI in range 100Hz to 500 KHz at room temperature 20 0 C is given in the table 1, and in other range of frequency 300Hz - 5 KHz at 30 0 C is shown in table 2. Similarly temperature dependence nature of PA NI in the range 15 0 C to 67 0 C at fixed frequency 500Hz is shown in the table 3. We observed from the table 1 that the dielectric constant and dielectric loss both decrease with increase in frequency, but it is also evident that both increase in low frequen cy range. It is evident that the dielectric constant at a given frequency is a slowly varying function of temperature in low temperature region and the dependence increases with increasing temperature. The values of  ',  " and tan  at frequencies lover th an 1KHz increase with decreasing frequency and increasing temperature, may be attributable to free charge build up at the interface between the sample and the electrode ( s pace charge polarization) . The magnitude of  ' decreases with increasing frequencies which is a typical characteristic of disordered conducting polymer and consistent with the earlier studies 17 - 18 . At very low frequencies we have  '   s (value of the dielectric constant at quasi - static field). As the frequency increases (with  1/  ), d ipoles begin to lag behind the field and  ' slightly decreases when frequency reaches the characteristic frequency (  = 1/  ) the dielectric constant drops (relaxation process). At very high frequencies (  ��1/  ), dipoles no longer follow the field and  '    . Even at lower frequencies and higher temperatures, there is a substantial increase in the dielectric constant that is attributable to a dipolar contribution to  ' (  ) from the hopping of electrons 19 - 20 . Conclusion It is observed that the dielectric l oss tangent in case of polyaniline decreases as a function of frequency. The sample (polyaniline) used exhibits small value of dielectric loss at higher frequency. Therefore, sample of polyaniline has been used in the present study, The results clearly s uggest that there is an increased coupling among the dipolar motion (Short range order localized motion). Table - 1 Temperature 20 0 C Frequency (Hz) Cap (Pf.) C o (Pf.)  ′  ″ Dssi 100 39.61 290.45 272.790 0.9392 200 20.620 151.20 27.61 0.18264 500 18.4 34 135.17 17.290 0.12792 1KHz 17.247 126.46 15.03 0.11886 2 KHz 16.4185 120.39 15.995 0.13286 5 KHz 15.0726 110.52 15.508 0.14032 10 KHz 14.0722 103.18 13.803 0.13378 20 KHz 13.2090 96.85 11.126 0.11488 50 KHz 12.3980 90.91 7.550 0.08305 100 KHz 11. 974 87.80 5.083 0.0579 200 KHz 11.840 86.81 3.715 0.0428 500 KHz 11.685 85.68 2.613 0.0305 Research Journal of Chemical Sciences ___ _ _ _______________________________ ______________ _ ________ ISSN 22 31 - 606X Vol. 3 ( 2 ), 1 6 - 1 9 , February (201 3 ) Re s. J. Chem. Sci. International Science Congress Association 18 Table - 2 Temperature 30 0 C, Pallet Thickness = 0.51mm Frequency (Hz) Cap (Pf.) C o (Pf.)  ′  ″ Dssi. 300Hz 17.585 128.946 18.655 0.14468 500 Hz 18.522 135.817 33.918 0.24974 1 KHz 16.752 122.838 30.463 0.24800 1.5 KHz 16.0880 117.969 21.968 0.18622 2.0 KHz 15.5525 114.042 19.419 0.17028 2.5 KHz 15.1610 111.171 18.732 0.16850 3.0 KHz 14.9 292 109.472 18.203 0.16628 4.0 KHz 14.5194 106.467 17.162 0.16120 5.0 KHz 14.1988 104.116 16.516 0.15864 Table - 3 Fixed Frequency 500Hz, Pallet Thickness = 0.51 mm Temperature ( 0 C) Cap (Pf.) C o (Pf.)  ′  ″ Dssi. (tan  ) 67 23.556 172.686 93.506 0.5 4148 64 20.880 153.107 74.832 0.48876 61 20.092 147.329 65.903 0.44732 59 21.386 156.818 50.162 0.31988 56 18.450 135.289 53.109 0.39256 54 19.156 140.466 58.068 0.41340 51 18.038 132.268 47.018 0.35548 49 19.608 143.780 61.377 0.42688 46 18.038 13 2.268 52.782 0.39906 43 18.048 132.341 47.320 0.35756 41 18.750 137.489 52.144 0.37926 38 17.756 130.200 37.523 0.28820 36 16.048 117.675 23.949 0.20352 33 16.064 117.793 22.376 0.18996 31 16.754 122.852 38.750 0.31542 28 17.932 131.490 16.809 0.127 84 26 14.636 107.322 29.919 0.27878 15 15.154 111.120 12.265 0.11038 References 1. Deshpande N.G . , Gudage Y.G., Sharma R., Vyas J.C., Kim J.B. and Lee Y.P . , Journals of Sansers and Actuators , B138 , 76 - 84 ( 2009) 2. Li - Ming Huanga, Cheng - Hou chena and Ten - ch in wen , Electrochimica Acta , 51 (26) , 5858 - 5863 ( 2006 ) 3. Harsha S. , Kolla sumedh P. , Surmade Alan G. , Mac Diarmide and Sajeev K. 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