universiti putra malaysia electrical properties...

UNIVERSITI PUTRA MALAYSIA

ELECTRICAL PROPERTIES OF CHEMICALLY SYNTHESIZED POLYPYRROLE PELLETS AND GAMMA-RAY INDUCED

POLYPYRROLE COMPOSITE FILMS

MOHD HAMZAH BIN HARUN

FS 2007 36



By


Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia in Fulfillment of the Requirements for the Degree of Master of Science

June 2007

Dedication

To my family, relatives, colleagues, friends and lecturers aka supervisors,

who have given me all supports, love, patience and responsibility.

Thank you.

ii

Abstract of thesis presented to the Senate of Universiti Putra Malaysia in fulfilment of the requirement for the degree of Master of Science.



By


June 2007

Chairman: Professor Elias bin Saion, PhD

Faculty: Science

The polypyrrole, PPy conducting polymer pellets and PVA-PPy-FeCl3 composite

polymer films have been prepared by using pyrrole, Py monomer, polyvinyl alcohol as

polymer binder for polypyrrole composite, and iron (III) chloride, FeCl3 as oxidizing and

doping agent by conventional technique; chemical polymerization method. Further,

PVA-PPy-CH and PVA-PPy-TCA composite films have been prepared by utilizing Py

monomer and doping agents of chloral hydrate, CH and trichloroacetic acid, TCA

respectively via gamma irradiation technique. The influence of composition of doping

agent was investigated by using x-ray diffraction (XRD) for the structural analysis and by

using an impedance analyzer (LCR meter) for the electrical conductivity and dielectric

properties in frequency range from 20 Hz to 1 MHz. The temperature effect of PVA-PPy-

FeCl3 of composites and the radiation effect of PVA-PPy-CH and PVA-PPy-TCA

composites on electrical conductivity and dielectric properties were also investigated.

iii

The XRD analysis for the samples at different composition of the dopants indicated that

the redox mechanism had been taken placed particularly for polypyrrole pellets as it

clearly showed that the peak presence of the dopant. On the other hand, for PVA-PPy-

FeCl3 composite films, it was observed that the broad peak of PVA was diminished as a

result of the competition between insulating PVA and PPy formation, in which PPy yield

becomes higher at higher concentration of the dopant. The gamma ray induced PVA-

PPy-TCA and PVA-PPy-CH composite films gave the same trends for both of the

samples. The broad peak of PVA was present for all samples. New peak was observed

upon irradiation particularly for higher composition of the dopant. It was attributed to the

radiation scission of TCA and CH molecules, which do not involve in PPy

polymerization as all of the Py monomers were already consumed.

The electrical conductivity, σ for all samples increased with the increase of dopant

composition, temperature and irradiation dose. Polypyrrole pellets contained highest

conductivity among the others, as they do not contain insulating polymer binder in which

could reduce the magnitude of conductivity. Among PPy composite films, PVA-PPy-

FeCl3 gave better conductivity as compared to PVA-PPy-TCA and PVA-PPy-CH due to

factor of FeCl3 in which it is known that iron (III) chloride is reactive electron acceptor

and the reason that it is genuinely oxidation agent in which TCA and CH do not own.

Therefore, gamma-rays were used to induce the electrical properties of TCA and CH

doped polypyrrole composites. The gradual increase of the conductivity as increase the

dopant concentration and irradiation dose can be attributed to more free charges (i.e.

iv

polarons) available in the composite system whereas for temperature dependent study,

the conductivity increased as the temperature increased, was due to the high mobility of

free charges interact in composite system.

Dielectric properties in respect of relative permittivity (dielectric constant), ε’ and loss

permittivity (dielectric loss), ε” showed that the value increased as the dopant

composition, temperature and irradiation dose were increased. The number of dipoles

available became prominent as the dopant and irradiation dose were increased thus

increase the value of dielectric properties. On the other hand, the value for relative

permittivity and loss became higher as the temperature was increased, attributed to the

higher mobility of dipoles in the composite system. The trend for all samples; PPy pellets

and composites films, were almost similar as at the lower frequency region (~ 20 Hz to 1

kHz), sharp decrease were observed due to the dipoles orientation along applied electric

field and reaching almost a constant value at higher frequency (~ 1 kHz to 1 MHz)

region. It was due to the difficulty of the dipoles to orient themselves as the applied

frequency became higher. The relaxation time, τ (ω) in which represents dielectric

relaxation obtained for all samples, almost reduced with the dopant composition,

irradiation dose and temperature. Such an inconsistent value of τ (ω) might be due to the

uncertain value of the angular frequency peak, ωp and irregularity of the electrical

displacement.

v

Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai memenuhi keperluan untuk ijazah Master Sains

SIFAT-SiFAT ELEKTRIK BAGI PELET POLIPIRROL YANG DISEDIAKAN SECARA KIMIA DAN FILEM KOMPOSIT POLIPIRROL YANG

DIRANGSANGKAN DENGAN SINARAN GAMA

Oleh


Jun 2007

Pengerusi: Profesor Elias bin Saion, PhD

Fakulti: Sains

Polipirrol, polimer pelet pengalir elektrik, PPy dan filem komposit polipirrol PVA-PPy-

FeCl3 telah disediakan dengan kaedah konvensional; teknik pempolimeran kimia,

menggunakan pirrol, Py sebagai monomer, polivinil alkohol sebagai polimer pengikat

dan ferum (III) klorida, FeCl3 sebagai agen dopan dan pengoksidaan. Selanjutnya, filem

komposit PVA-PPy-CH dan PVA-PPy-TCA disediakan menggunakan Py sebagai

monomer, asid trikloroasetik dan kloral hidrat sebagai agen dopan menggunakan kaedah

penyinaran sinar gama. Pengaruh komposisi agen dopan pengoksidaan telah dicirikan

dengan menggunakan pembelauan sinar-x (XRD) untuk menganalisis struktur sampel

dan alat penganalisa impedans (meter LCR) untuk mencirikan parameter kekonduksian

elektrik dan sifat-sifat dielektrik dari julat frekuensi 20 Hz hingga 1 MHz. Kesan

penambahan suhu bagi filem komposit PVA-PPy-FeCl3 dan kesan penambahan dos

vi

untuk PVA-PPy-CH dan PVA-PPy-TCA terhadap sifat-sifat kekondusian elektrik dan

dielektrik telah dikaji.

Daripada analisis XRD untuk sampel-sampel yang mempunyai komposisi dopan berbeza

telah menunjukkan yang mekanisma redoks wujud terutamanya bagi pellet polipirrol

dimana ia dengan jelasnya menunjukkan puncak yang mewakili dopan. Selain itu, untuk

filem komposit PVA-PPy-FeCl3, ia menunjukkan puncak yang agak mendatar mewakili

PVA semakin menghilang disebabkan wujudnya persaingan diantara PVA dan

penghasilan PPy, dimana penghasilan PPy semakin meningkat pada komposisi dopan

yang semakin tinggi. Bagi filem komposit PVA-PPy-TCA dan PVA-PPy-CH yang

dirangsangkan dengan sinaran gama, telah memberikan keputusan yang sama bagi

kedua-dua jenis sampel. Puncak yang agak mendatar mewakili PVA wujud bagi kesemua

sampel. Puncak yang baru telah wujud hasil proses penyinaran dimana ia agak jelas pada

komposisi dopan yang agak tinggi. Ia disebabkan oleh proses pemutusan ikatan bagi

molekul-molekul TCA dan CH daripada tindakbalas sinaran, dimana ia tidak melibatkan

pempolimeran PPy kerana monomer Py sebelum itu telah digunakan kesemuanya ketika

proses pempolimeran.

Kekondusian elektrik, σ bagi keseluruhan sampel meningkat dengan pertambahan

komposisi dopan, suhu dan dos penyinaran. Pelet polipirrol mempunyai kekonduksian

tertinggi jika dibandingkan dengan sampel yang lain kerana ia tidak mempunyai polimer

pengikat yang bersifat penebat yang akan menurunkan nilai kekonduksian. Diantara

vii

filem komposit PPy, PVA-PPy-FeCl3 telah memberikan nilai kekonduksian yang lebih

baik jika dibandingkan dengan filem komposit PVA-PPy-TCA dan PVA-PPy-CH

disebabkan faktor Fe(III) klorida adalah penerima elektron yang reaktif dan ia adalah

agen pengoksidaan semulajadi dimana ciri-ciri ini tidak terdapat pada TCA dan CH.

Justeru, bagi sampel komposit didopkan dengan TCA dan CH, sinaran gama telah

digunakan bagi meningkatkan sifat keelektrikannya. Peningkatan kekonduksian yang

seragam apabila komposisi dopan dan dos penyinaran ditambah adalah disebabkan oleh

bertambahnya cas-cas bebas (i.e. polarons) di dalam sistem komposit. Bagi kekonduksian

elektrik bagi suhu berbeza, nilai kekonduksian meningkat apabila suhu ditambah adalah

disebabkan oleh pergerakan cas yang semakin meningkat di dalam sistem komposit.

Ciri-ciri dielektrik bagi pemalar dielektrik, ε’ dan lesapan dielektrik, ε” telah

menunjukkan yang nilainya meningkat dengan pertambahan komposisi dopan, suhu dan

dos penyinaran. Bilangan dwikutub terhasil semakin meningkat dengan dopan dan dos

penyinaran lalu meningkatkan nilai dielektrik. Selain itu, nilai pemalar dielektrik dan

lesapan dielektrik meningkat dengan peningkatan suhu disebabkan pergerakan dwikutub

bertambah di dalam sistem komposit. Pemerhatian bagi kesemua sampel hampir sama

dimana pada julat frekuensi rendah (~ 20 Hz ke 1 kHz), graf menurun kerana orientasi

dwikutub disepanjang medan elektrik dan agak mendatar kemudiannya pada julat

frekuensi tinggi (~ 1 kHz ke 1 MHz). Ia disebabkan oleh orientasi dwikutub berkurang

kerana terhalang dengan nilai frekuensi medan elektrik yang semakin meningkat. Masa

santaian, τ (ω) yang mewakili relaksasi dielektrik hampir berkurang dengan pertambahan

viii

komposisi dopan, dos penyinaran dan suhu. Nilainya yang tidak konsisten mungkin

disebabkan oleh nilai puncak frekuensi angular, ωp yang tidak tetap dan

ketidakseimbangan nilai penyingkiran elektrik.

ix

ACKNOWLEDGEMENTS

In the name of Allah, the most Gracious and the most Merciful

Praise is to Allah the Almighty, for thee (alone) we worship and thee (alone) we ask for

help. Praise also is upon Muhammad S.A.W. who is guidance and has led us to the path

that God has favored.

First of all, I would like to express my gratitude to my families for their support, courage

and understanding. Secondly, my acknowledgement goes to my supervisor Professor Dr.

Elias Saion for keeping his confidence and his bless to see me in a great future. For all

patience, advice, constructive comments, encouragement, in helping me to finish my

postgraduate study, my deepest gratitude goes to you. I also want to express my

appreciation to my co-supervisor, Professor Dr. Anuar Kassim and to Associate Professor

Dr. Noorhana Yahya for their moral support, technical discussion as well as contribution.

Not to forget to my research fellows in Physics Department, to name a few, Mr. Zain,

Mr. Roslim, Aris, Susilawati, Ajis, Fatma, Iskandar, Asri, Azlina, Nurizan, Azian,

Norazimah, Mr. Yousuf, Mr. Ahmad, Azhar and Sharifah for their support and help. This

appreciation also I dedicate to my office fellows and superiors in Radiation Processing

Technology Division, Malaysian Nuclear Agency for their priceless understanding and

facilities that have been provided. Finally, financial support from MOSTI IRPA Grant

(No. 09-02-04-0275-EA001) is greatly acknowledged.

x

I certify that an Examination Committee has met on 18th June 2007 to conduct the final examination of Mohd Hamzah bin Harun on his Master of Science thesis entitled “Electrical Properties of Chemically Synthesized Polypyrrole Pellets and Gamma-Ray Induced Polypyrrole Composite Films” in accordance with Universiti Pertanian Malaysia (Higher Degree) Act 1980 and Universiti Pertanian Malaysia (Higher Degree) Regulation 1981. The committee recommends that the candidate be awarded the relevant degree. Members of the Examination are as follows: …………………… Mansor Hashim, PhD. Associate Professor Faculty of Science, University Putra Malaysia (Chairman) …………………… Zainal Abidin Sulaiman, PhD. PAKAI YG TELAH DIBERI Associate Professor Faculty of Science, University Putra Malaysia (Internal Examiner) …………………… Jumiah Hassan, PhD. Associate Professor Faculty of Science, University Putra Malaysia (Internal Examiner) …………………… Ahmad Shukri Mustapha Kamal, PhD. Professor School of Physics University Science Malaysia (External Examiner)

……………….………………………… Professor Hasanah Mohd Ghazali, PhD. Deputy Dean

School of Graduate Studies University Putra Malaysia Date:

xi

This thesis submitted to the Senate of Universiti Putra Malaysia and has been accepted as fulfilment of the requirement for the degree of Master of Science. The members of the Supervisory Committee are as follows: Elias Saion, PhD Professor Faculty of Science Universiti Putra Malaysia (Chairman) Anuar Kassim, PhD Professor Faculty of Science Universiti Putra Malaysia (Member) Noorhana Yahya, PhD Associate Professor Faculty of Engineering Universiti Teknologi Petronas (Member)

__________________ AINI IDERIS, Ph.D. Professor/Dean School of Graduate Studies University Putra Malaysia

Date: 13 September 2007

xii

DECLARATION

I hereby declare that the thesis is based on my original work except for quotation and citations which have been duly acknowledged. I also declare that it has not been previously or concurrently submitted for any other degree at UPM or other institutions.

____________________________ MOHD HAMZAH BIN HARUN

Date: 10 August 2007

xiii

TABLE OF CONTENTS

Page

DEDICATION ii ABSTRACT iii ABSTRAK viii ACKNOWLEDGEMENTS xiv APPROVAL xv DECLARATION xvii LIST OF TABLES xxiii LIST OF FIGURES xxv LIST OF ABBREVIATIONS xxxii CHAPTER

I INTRODUCTION Fundamental of Conducting Polymers Problem Statement Objective of the Research Significance of Study Outline of the Thesis

1 1 2 3 4 5

II LITERATURE REVIEW Historical Background of Conducting Polymers The Structures of Conducting Polymers Synthesizing Techniques of Conducting Polymers Characterization Technique of Conducting Polymers Present and Future Application of Conducting Polymers

Corrosion Protection Sensors and Electromechanical Devices Batteries Electrochromic Cell Controlled-release Application Radar Application LEDs

Polypyrrole as Conducting Polymer Overview of Pyrrole Monomer History of Pyrrole Monomer The Discovery of Conducting Polypyrrole

Physical and Chemical Properties of Pyrrole Monomer Physical Properties

6 6 7 9 11 12 12 13 14 16 19 21 21 25 25 26 26 27 27

xiv

Chemical Properties Mechanism of Conduction in Polypyrrole Potential Application of Polypyrrole Conducting Polymer

28 29 30

III THEORY A Review of Conduction Mechanism in Conducting Polymers

Valence Bands, Conduction Bands and the Band Gap Electrons and Holes Conduction in Polymers Solitons, Polarons and Bipolarons Doping of Conducting Polymer Chains

Interaction of Gamma Ray with Matter Rayleigh Scattering Photoelectric Absorption Compton Scattering Pair Production

Radiation Effect on Polymer Blends Introduction on Radiation Effect Radiation and Absorbed Dose Basic Process of Radiation Chain Scission Cross-linking and Grafting Polymerization

Conductivity History and Definition Electrical Conductivity DC and AC Conductivity Thermal Conductivity

Impedance and Derivatives Inductance, Capacitance and Resistance Capacitance and Dielectric

Dielectric and its Characteristics Dielectric Polarization

Electronic Polarization Ionic Polarization Orientational or Dipolar Polarization Space Charge Polarization LCR Meter

X-Ray Diffractogram (XRD) History of X-Ray Spectroscopy Brief History of the Development of X-Ray Diffractometer

XRF and XRD and Their Differences Role of X-Ray Method in Modern Laboratory

32 32 32 34 35 36 40 41 42 43 45 47 48 48 50 52 53 56 59 60 60 61 61 63 65 65 67 69 72 74 75 75 75 76 77 77 77 78 80

xv

Properties of X-Ray Radiation Continuous and Characteristic Radiation

X-Ray Spectra and Physical Picture of X-Ray Diffractometer

81 81 82

IV MATERIALS AND METHODS Sample Preparation

Materials Preparation of Polypyrrole Conducting Polymer Pellets Preparation of Polyvinyl alcohol bulk solution Preparation of PVA-PPy Composite Films Sample Irradiation

Characterization of the Sample XRD Measurement Dielectric and Conductivity Measurement

86 86 86 87 88 89 91 94 94 96

V RESULTS AND DISCUSSION X-Ray Diffraction

Polypyrrole Pellets PVA-PPy-FeCl3 Composites PVA-PPy-TCA Composites PVA-PPy-CH Composites

Electrical Conductivity Characteristics Electrical Conductivity Properties at Different Dopant Concentrations for Polypyrrole Pellets

AC conductivity Frequency Exponent Complex Impedance DC Conductivity

Electrical Conductivity at Different Dopant Concentrations for Polypyrrole Composites

AC Conductivity Frequency Exponent Complex Impedance DC Conductivity

Electrical Conductivity at Different Temperature for PVA-PPy-FeCl3

AC Conductivity Frequency Exponent Complex Impedance DC Conductivity and Arrhenius Plot

Electrical Conductivity at Different Dose for PVA-PPy-TCA

100 100 100 101 103 105 107 107 107 110 112 115 117 117 121 125 128 130 130 134 140 143 150

xvi

AC Conductivity Frequency Exponent Complex Impedance Dose Dependence DC Conductivity and Dose Sensitivity

Electrical Conductivity at Different Dose for PVA-PPy-CH AC Conductivity Frequency Exponent Complex Impedance Dose Dependence DC Conductivity and Dose Sensitivity

Dielectric Characteristics Dielectric Properties at Different Dopant Concentration for Polypyrrole Pellets

Dielectric Constant Dielectric Loss Dielectric Constant and Loss Factor vs Frequency Dielectric Modulus Relaxation Times

Dielectric Properties at Different Dopant Concentrations for Polypyrrole Composites


Dielectric Properties at Different Temperature for PVA-PPy-FeCl3 Composites


Dielectric Properties at Different Doses for PVA-PPy-TCA Composites


Dielectric Properties at Different Doses for PVA-PPy-CH Composites

Dielectric Constant

150 154 160 163 170 170 173 179 182 189 189 189 191 192 194 197 198 198 201 203 207 211 212 212 215 218 224 230 231 231 235 238 244 250 251 251

xvii

Dielectric Loss Dielectric Constant and Loss Factor vs Frequency Dielectric Modulus Relaxation Times

255 258 264 270

VI CONCLUSION AND SUGGESTION FOR FUTURE WORK

The Way Forward

272 278

REFERENCES 280BIODATA OF THE AUTHOR 288LIST OF PUBLICATIONS 289

xviii

LIST OF TABLES

Table

Page

2.1 Comparison of physical properties of metals, insulators and conducting polymers

8

2.2 Properties of Pyrrole

28

4.1 Specimen formulation of PPy at different concentration of dopants

87

4.2 Formulation of PVA/Py/dopant composites at different dopant concentrations

90

5.1 Value of activation energy, EA and high temperature limit, σo for the composite films of PPy at different concentration of iron (III) chloride dopant

149

5.2 Value of σo and Do for composite films PVA-PPy at different concentration of TCA dopant

169

5.3 Value of σo and Do for composite films of PVA-PPy at different concentration of CH dopants

188

5.4 Value of Intersection frequency, fT (Hz) for different concentrations of the polypyrrole pellets

194

5.5 Relaxation times for polypyrrole pellets at different concentration of dopants

197

5.6 Value of Intersection frequency, fT (Hz) for different concentrations of the composite films

207

5.7 Relaxation times for composite films of PVA-PPy at different concentrations of dopants

212

5.8 Value of Intersection frequency, fT (Hz) for different concentrations of FeCl3 for PVA-PPy-FeCl3

224

5.9 Relaxation times for composite films of PVA-PPy-FeCl3 at different temperatures

231

xix

5.10 Value of Intersection frequency, fT (Hz) for different concentrations of dopants for PVA-PPy-TCA

244

5.11 Relaxation times for composite films of PVA-PPy-TCA at different temperatures

251

5.12 Value of Intersection frequency, fT (Hz) for different concentrations of dopants for PVA-PPy-CH

264

5.13 Relaxation times for composite films of PVA-PPy-CH at different doses

271

xx

LIST OF FIGURES

Figure

Page

2.1 Comparison of conductive polymers compared to those of other materials

7

2.2 Examples of conjugated polymers

9

2.3 Electrochemical synthesis of conjugated polymers

10

2.4 General battery design

15

2.5 Electrochromic window operation

16

2.6 Selective ion transport of an electroactive bilayer

20

2.7 General design for LEDs

22

2.8 Pyrrole and derivatives

25

2.9 Mechanism of conduction of polypyrrole

29

3.1 Simple band pictures illustrate a difference in insulator, semiconductor and metal

34

3.2 Band model explaining about undoped and doped conjugated polymers

36

3.3 Polyacetylene chain

37

3.4 Soliton produced from cis polyacetylene migrates in polymer chain

38

3.5 Radical cation or polaron formed by removal of one electron on 5th carbon (a-b). The polaron migration shown in (c-e)

39

3.6 Rayleigh scattering

42

3.7 Photoelectric absorption

43

3.8 Compton scattering 45

xxi

3.9 Pair Production

47

3.10 Two large side groups in polymethylmethacrylate

54

3.11 Two large side groups in polyisobutylene

55

3.12 Crosslinking reaction of polyethylene

56

3.13 A pair of free radicals producing crosslinking formation

57

3.14 Network of molecules undergoes crosslinking formation by radiation

57

3.15 General variation thermal conductivity with temperature

64

3.16 The charges stored in capacitor plate

68

3.17 Representation of non-ideal capacitor b) Representation of the phase angle and loss tangent

71

3.18 All types of polarization: a) electronic b) ionic c) orientation d) space charge

74

3.19 The occurrence of interference or diffraction when x-ray beam is incident on lattice plane

80

3.20 Conceptual picture when incident of X-ray beam hits on the lattice plane

83

3.21 Example of sample diffractogram

84

3.22 Traditional XRD geometry

84

4.1 Polypyrrole pellets prepared by a chemical method

88

4.2 Composite polymer film of PVA/PPy composites after peeled off from the casting glass plate and ready for characterization

91

4.3 J.L. Shepherd gamma irradiator

92

4.4 PANalytical X’pert PRO X-Ray Diffraction Machine

95

4.5 Precision LCR Meter (HP 4284A) 97

xxii

4.6 Cp-G circuit mode selection for LCR meter measurement

97

4.7 Components (namely, two electrodes, composite film samples and electrical wires) to carry out AC conductivity and dielectric properties measurement

98

5.1 X-Ray Diffraction pattern of PPy pellets

101

5.2 X-ray diffraction pattern of PVA-PPy composite films at different concentration of FeCl3 1) pure PVA, 2) 0.3 g FeCl3, 3) 0.6 g FeCl3, 4) 0.9 g FeCl3 5) 1.2 g FeCl3, 6) 1.5 g FeCl3

102

5.3 XRD pattern for PVA-PPy-TCA composite film (a) 0.3 g TCA and (b) 1.5 g TCA at different doses

104

5.4 XRD pattern for PVA-PPy-CH (a) 0.3 g CH and (b) 1.5 g CH at different doses

106

5.5 AC Conductivity characteristics for polypyrrole pellets at different dopant concentrations

110

5.6 Solid lines represent the best fitted value to find parameter of s for PPy pellets at different concentrations of dopant

111

5.7 Parameter of s for PPy pellets for different concentrations of dopant FeCl3

112

5.8 Complex impedance plot of polypyrrole pellets at different dopant concentrations

115

5.9 Bulk DC conductivity for polypyrrole pellets at different dopant concentrations

116

5.10 AC electrical conductivity of composite films of PPy at different concentrations of dopants (a) FeCl3, (b) TCA and (c) CH

121

5.11 Solid lines represent the best fitted value for a) PVA-PPy-FeCl3 b) PVA-PPy-TCA and c) PVA-PPy-CH

123

5.12 Parameter of s for a) PVA-PPy-FeCl3 b) PVA-PPy- TCA and c) PVA-PPy-CH

125

5.13 Complex impedance plots for a) PVA-PPy-FeCl3, b) PVA-PPy-TCA 127

xxiii

and c) PVA-PPy-CH at different concentration of dopants

5.14 DC conductivity of (a) PVA-PPy-FeCl3, (b) PVA-PPy-TCA and (c) PVA-PPy-CH

130

5.15 AC conductivity of composite films of PVA-PPy doped with FeCl3 at different temperatures

134

5.16 Solid lines represent the best-fitted value to find parameter of s for PVA-PPy-FeCl3 at different temperatures

137

5.17 Parameter of s for composite polymer of PVA-PPy doped with FeCl3 at different temperatures

139

5.18 Complex impedance plot for composite films of PVA-PPy doped with FeCl3 at different temperatures

142

5.19 DC conductivity of composite films of PVA-PPy doped with FeCl3 at different temperatures

146

5.20 Typical Arrhenius plot for composite films of PVA-PPy doped with FeCl3 at different temperatures

149

5.21 AC conductivity of PVA-PPy composite films doped with TCA at different doses

153

5.22 Solid lines represent the best-fitted value to find parameter of s for composite polymer of PVA-PPy-TCA at different doses

157

5.23 Parameter of s for composite polymer of PVA-PPy-TCA at different doses

159

5.24 Complex impedance plot of composite films of PVA-PPy-TCA at different doses

162

5.25 DC conductivity of PVA-PPy-TCA composite films at different doses

166

5.26 Dose sensitivity of PVA-PPy-TCA composite films at different doses

169

5.27 AC conductivity of composite films of PVA-PPy-CH at different doses

173

xxiv

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