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UNIVERSITI PUTRA MALAYSIA
ELECTRICAL PROPERTIES OF CHEMICALLY SYNTHESIZED POLYPYRROLE PELLETS AND GAMMA-RAY INDUCED
POLYPYRROLE COMPOSITE FILMS
MOHD HAMZAH BIN HARUN
FS 2007 36
ELECTRICAL PROPERTIES OF CHEMICALLY SYNTHESIZED POLYPYRROLE PELLETS AND GAMMA-RAY INDUCED
POLYPYRROLE COMPOSITE FILMS
By
MOHD HAMZAH BIN HARUN
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.
ELECTRICAL PROPERTIES OF CHEMICALLY SYNTHESIZED POLYPYRROLE PELLETS AND GAMMA-RAY INDUCED
POLYPYRROLE COMPOSITE FILMS
By
MOHD HAMZAH BIN HARUN
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
MOHD HAMZAH BIN HARUN
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 Constant Dielectric Loss Dielectric Constant and Loss Factor vs Frequency Dielectric Modulus Relaxation Times
Dielectric Properties at Different Temperature for PVA-PPy-FeCl3 Composites
Dielectric Constant Dielectric Loss Dielectric Constant and Loss Factor vs Frequency Dielectric Modulus Relaxation Times
Dielectric Properties at Different Doses for PVA-PPy-TCA Composites
Dielectric Constant Dielectric Loss Dielectric Constant and Loss Factor vs Frequency Dielectric Modulus Relaxation Times
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