vii
TABLE OF CONTENTS
CHAPTER
1
TITLE
PAGE
TITLE
i
DECLARATION
ii
DEDICATION
iii
ACKNOWLEDGEMENT
iv
ABSTRACT
v
ABSTRAK
vi
CONTENT
vii
LIST OF TABLE
xi
LIST OF FIGURE
xiii
LIST OF ABBREVIATIONS
xvii
LIST OF APPENDICES
xx
INTRODUCTION
1
1.1 Percolation theory
2
1.2 Conducting blends
7
1.2.1 Blends with water-soluble polymers
8
9
1.3 Materials
1.3.1 Electrically conductive polymer
1.3.1.1 Electronic properties of conductive
9
11
polymer
1.3.1.2 Polyaniline (PAni)
13
1.3.1.3 Conduction mechanism in PAni
17
viii
1.3.2 Water-soluble polymer – Poly(vinyl alcohol)
28
(PVA)
1.3.3 Metal oxide
1.3.3.1 Titanium(IV) oxide (TiO2)
1.4 Characterization of polymer blends
2
30
31
32
1.4.1 Four-probe method
33
1.4.2 Hall Effect measurement
33
1.5 Research background and challenges
34
1.6 Research scope
36
1.7 Research objective
36
EXPERIMENT
38
2.1 Chemicals
38
2.2 Instrumentation
38
2.2.1 Vibrational spectra
39
2.2.2 Electronic spectra
39
2.2.3 Themogravimetry analysis (TGA)
39
2.2.4 Differential scanning calorimetry (DSC)
40
2.2.5 X-ray diffraction (XRD)
40
2.2.6 Scanning electron microscopy (SEM)
41
2.2.7 Transmission electron microscopy (TEM)
41
2.2.8 Four-probe resistivity measurement setup
41
2.2.9 Hall Effect measurement setup
43
2.3 Synthesis
2.3.1 Synthesis of DBSA doped PAni (PAni-
44
44
DBSA)
2.3.2 Synthesis of PAni doped with DBSA in HCl
46
medium (PAni)
2.3.3 Synthesis of PAni-TiO2 composites
48
2.3.4 Preparation of conducting blends
50
2.3.5 Preparation of free-standing films
51
2.4 XRD diffraction analysis
52
ix
2.4.1 Bragg’s law
2.5 Preparation of test samples for four-probe resistivity
52
56
measurement and Hall effect measurement
3
2.6 Four-probe resistivity measurement
56
2.7 Hall effect measurement
59
RESULT AND DISCUSSION
61
3.1 Synthesis of PAni and PAni-TiO2
61
3.2 Vibrational spectroscopic characterization of PAni
63
and its composites
3.2.1 Infrared spectra of acids doped PAni
69
3.2.2 Infrared spectra of PAni composites
71
3.2.3 PAni and its composite blends
71
3.2.3.1 Interaction between PAni and PVA
71
3.2.3.2 TiO2 incorporation in PAni/PVA
73
3.3 Electronic spectra
73
3.4 Thermal profile of PAni and its composites
75
3.4.1 Thermogravimetry analysis (TGA)
76
3.4.2 Differential scanning calorimetry (DSC)
80
3.5 Structural analysis
84
3.5.1 X-ray diffractogram (XRD)
84
3.5.2 Scanning electron microscopy (SEM)
90
3.5.3 Transmission electron microscopy (TEM)
94
3.6 Electrical properties of PAni and PAni-TiO2 blends
97
with PVA
3.6.1 Effect of TiO2/aniline weight ratio
101
3.6.2 Effect of temperature
104
3.6.3 Effect of weight fractions
107
3.6.4 Percolation threshold
110
3.7 The Hall effect
115
x
4
CONCLUSION AND SUGGESTION
124
4.1 Conclusion
124
4.2 Suggestions
126
REFERENCE
127
APPENDIX A
136
APPENDIX B
137
xi
LIST OF TABLES
TABLE NO.
TITLE
PAGE
1.1
Chemical structure of some conjugated polymers
10
2.1
Different composition of polyaniline-titanium(IV) oxide
composites
50
3.1
Percentage yield of PAni and its composites
63
3.2
Observed characteristic infrared absorption bands (cm─1)
of TiO2, PVA, PAni, PAni-TiO2 (I), PAni/PVA, PAniTiO2 (I)/PVA
66
3.3
Observed electronic absorption of PAni, its composite
and their blends
74
3.4
Weight loss (%) of PAni, its composites and their blends
79
3.5
Observed glass transition temperature and melting
temperature of PVA and different content of PAni and
PAni-TiO2 (I)
84
3.6
Position of peaks of PAni, TiO2 and PAni composite
blend in Figure 3.9 and 3.10
88
3.7
The XRD data and conductivity data of PAni and PAniTiO2 blends
90
3.8
Conductivity of PAni and PAni-TiO2 composites at
various temperatures
98
3.9
Conductivity of blends films (40 wt. %) at various
temperatures
99
3.10
Conductivity of the blends films (40 wt. %) with various
weight ratio of TiO2/aniline at room temperature
101
3.11
Detailed room-temperature conductivity data of the blend
films with different PAni and PAni-TiO2 (I) composite
110
xii
loading for both blends, PAni/PVA and PAni-TiO2
(I)/PVA
3.12
The conductivity at room temperature σRT, Hall
coefficient R, carrier density n and carrier mobility µ
117
3.13
The conductivity at room temperature σRT, Hall
coefficient R, carrier density n and carrier mobility µ for
PAni-TiO2 (I)/PVA blend with various weight fractions
118
3.14
Carrier density, carrier mobility and conductivity of
iodine doped poly[(6-N-pyrrolylhexyl)hexylsilane]
(PSiPy)
123
xiii
LIST OF FIGURES
FIGURE NO.
TITLE
PAGE
1.1
Square array percolation problem. (a) First is the empty
array (b) Then, squares are randomly filled in (c) The
cluster of squares that creates a complete path across the
lattice is called the spanning or infinite cluster (d)
Parallel paths are created (Adapted from reference [7])
4
1.2
Random circle problem − demonstrate continuum
percolation (Adapted from reference [6])
4
1.3
Electrically conductive polymer blend (Adapted from
reference [8])
6
1.4
Typical percolation theory plot (Adapted from reference
[8])
6
1.5
Schematic diagram shows the energy level scheme and
optical transition for the positively charged polaron,
bipolaron and the neutral polaron-exciton (Adapted from
reference [18])
13
1.6
Various states of oxidation and protonation of
polyaniline (Adapted from reference [17, 22])
14
1.7
Protonic acid doping of PAni (emeraldine base) to PAni
(emeraldine salt) (Adapted from reference [17])
16
1.8
Chemical structures of (a) camphorsulfonic acid, CSA
and (b) dodecylbenzenesulfonic acids, DBSA (Adapted
from reference [21])
16
1.9
Defects in conjugated chains: a “physical − chemical
dictionary” (Adapted from reference [23])
19
1.10:
Polaron and bipolaron lattice. (a) Emeraldine salt in
bipolar form. (b) Dissociation of the bipolarons into two
polarons. (c) Rearrangement of the charges into a
20
xiv
‘polaron lattice’ (Adapted from reference [24, 25])
1.11
Spin-charge inversion of a conjugational defect. Charged
solitons are spinless; neutral solitons carry a magnetic
moment [26]
20
1.12
Scheme of the protonation process leading to formation
of polaron and bipolaron in doped PAni (a) Emeraldine
salt in bipolar form (b) Dissociation of the bipolarons
into polarons (c) Rearrangement of the charges into a
“polaron lattice” (Adapted from reference [21, 27 – 28])
22
1.13
Propagation of polaron through a conjugated polymer
chain by shifting of double bonds (alternation) that give
rise to electrical conduction (Adapted from reference
[30])
25
1.14
Energy band diagrams and defect levels for polarons and
bipolarons in undoped, lightly doped and heavily doped
conducting polymers (Adapted from reference [30])
25
1.15
(a) Hopping transport: a man crossing the river by
jumping from stone to stone and (b) Electronic level
scheme of disordered PAni to demonstrate the hopping
conductivity (CB = conduction band, VB valence band,
EF = Fermi energy, W = energetic distance between
states, R = local distance between states, Eg = energy
gap) [26]
26
1.16
Conducting network of a conducting polymer with A
indicating intrachain transport of charge, B indicating
interchain transport, C indicating interparticle transport
and arrows showing path of charge carrier migrating
through the material [26]
28
1.17
Structure of PVA
29
2.1
Diagram of the Four-Probe Set-Up
42
2.2
Diagram of the Hall Effect Set-Up
43
2.3
Synthesis of PAni-DBSA
45
2.4
Synthesis of PAni
47
2.5
Synthesis of PAni-TiO2
49
2.6
Preparation of PAni/PVA and PAni-TiO2/PVA blends
into conducting films
51
2.7
Deriving Bragg’s Law using the reflection geometry and
applying trigonometry. The lower beam must travel the
54
xv
extra distance (PQ + QR) to continue traveling parallel
and adjacent to the top beam
2.8
Model for the four probe resistivity measurements
57
2.9
Circuit used for resistivity measurements (Four Probe
Set-up)
58
2.10
Schematic diagram of sample placement in constant
magnetic field (H) to measure the Hall voltage as a
function of current (I)
60
3.1
Structure of acid doped PAni (Adapted from reference
[21])
62
3.2
FTIR spectra of (a) PAni (b) PAni-TiO2 (I) (c) TiO2
64
3.3
FTIR spectra of (a) PVA (b) PAni-TiO2 (I)/PVA (6 wt.
%) (c) PAni/PVA (6 wt. %)
65
3.4
Interaction between PAni and PVA (intermolecular Hbonding) (Adapted from reference [70])
72
3.5
Absorption bands of (a) PVA, (b) PAni/PVA and (c)
PAni-TiO2(I)/PVA
74
3.6
TGA curves of (a) PAni (
(
)
77
3.7
TGA curves (a) PVA (
), (b) PAni/PVA (40 wt. %)
(
) and (c) PAni-TiO2 (I) /PVA (40 wt. %) (
)
78
3.8
DSC curves of (a) PAni-TiO2 (I)/PVA (6 wt. %) (b)
PAni/PVA (0.4 wt. %) (c) PAni-TiO2 (I)/PVA (0.4 wt.
%) (d) PVA
81
3.9
XRD patterns of (a) TiO2 (b) PAni (powder form) (c)
PVA (d) glass
86
3.10
XRD patterns of (a) PAni-TiO2 (IV)/PVA (6 wt. %) (b)
PAni-TiO2 (I) /PVA (6 wt. %) (c) PAni-TiO2 (I)/PVA
(0.4 wt. %)
87
3.11
SEM micrographs of (a) PAni-TiO2 (I)/PVA (10 wt. %)
(b) PAni-TiO2 (I)/PVA (40 wt. %) (c) PAni/PVA (40 wt.
%) (d) PAni-TiO2 (IV)/PVA (10 wt. %) with
magnification of 10,000 x
91
3.12
SEM micrographs of particles (a) PAni (b) PAni-TiO2 (I)
(c) PAni-TiO2 (IV)
93
3.13
TEM micrographs of PAni/PVA blends at (a) 0.2 wt. %
(b) 0 4 wt %
95
) and (b) PAni-TiO2 (I)
xvi
(b) 0.4 wt. %
3.14
Conductivity of films (40 wt. %) at various temperatures
100
3.15
Variation of room temperature conductivity of films
102
(40 wt. %) with the weight ratio of TiO2/aniline
3.16
Conductivity of blends as a function of 1/T1/2
106
3.17
Conductivity of PAni/PVA and PAni-TiO2 (I)/PVA
blends at room temperature with various weight fractions
109
3.18
(a) Plot of electrical conductivity of PAni vs weight
fractions in PAni/PVA films, (b) Plot of log
(conductivity) vs log (f – fc)
113
3.19
(a) Plot of electrical conductivity of PAni-TiO2 (I) vs
weight fractions in PAni-TiO2 (I)/PVA films, (b) Plot of
log (conductivity) vs log (f – fc)
114
3.20
Hall Voltage, VH OF (a) PAni-DBSA/PVA (b)
PAni/PVA (c) PAni-TiO2 (I)/PVA (d) PAni-TiO2
(II)/PVA (e) PAni-TiO2 (III)/PVA (f) PAni-TiO2
(IV)/PVA
116
3.21
The samples (40 wt. %) plotted against (a) conductivity
and carrier density, (b) carrier mobility and density and
(c) conductivity and carrier mobility of the samples
120
3.22
The samples with various weight fractions plotted
against (a) conductivity and carrier density, (b) carrier
mobility and density and (c) conductivity and carrier
mobility of the samples
122
xvii
LIST OF ABBREVIATIONS
PA
-
Polyacetylene
PAni
-
Polyaniline
PEO
-
Poly(ethylene oxide)
PT
-
Polythiophene
PPY
-
Polypyrrole
PPV
-
Poly(phenylenevinylene)
PPS
-
Poly(phenylene sulfide)
PPP
-
Poly(p-phenylene)
Eg
-
Energy gap
eV
-
Elektron volt
LEB
-
Leucoemeraldine
PNB
-
Pernigraniline
EB
-
Emeraldine base
ES
-
Emeraldine salt
Cl−
-
Ion chloride
CSA
-
Camphorsulfonic acid
DBSA
-
Dodecylbenzene sulfonic acid
APS
-
Ammonium persulphate
S/cm
-
Siemen per cm
HCl
-
Acid hidrochloric
Na
-
Sodium
K
-
Kalium
Li
-
Lithium
Ca
-
Calcium
xviii
BF4
-
Boron tetrafluoride
PVA
-
Poly(vinyl alcohol)
TiO2
-
Titanium(IV) oxide
UV
-
Ultra violet
SEM
-
Scanning electron microscopy
TEM
-
Transmission electron microscopy
AFM
-
Atomic force microscopy
FTIR
-
Fourier transform infrared
TGA
-
Thermal gravimetry analysia
DSC
-
Differential scanning calorimetry
XRD
-
X-ray diffraction
Ge
-
Germanium
ρ
-
Resistivity
σ
-
Dc conductivity
W
-
Sample thickness
S
-
Probe distance
DC
-
Direct current
I
-
Current
V
-
Voltage
VH
-
Hall voltage
RH
-
Hall coefficient
n
-
Carrier density
µ
-
Carrier mobility
H
-
Magnetic field
q
-
Electron charge
PAni-TiO2
-
Polyaniline-titanium(IV) oxide composite
PAni-TiO2/PVA
-
Polyaniline-titanium(IV) oxide composite blend
with poly(vinyl alcohol)
PAni/PVA
-
Polyaniline blend with poly(vinyl alcohol)
Å
-
Angstrom
2θ
-
Angle of incidence of X-rays diffracting planes
CB
-
Conduction band
VB
-
Valence band
xix
EF
-
Fermi energy
Tg
-
Glass transition temperature
Tm
-
Melting temperature
σdc
-
Conductivity of direct current
Wt.
-
Weight
VRH
-
Variable range hopping
I2
-
Iodine
PSiPy
-
Poly[(6-N-pyrrolylhexyl)hexylsilane]
xx
LIST OF APPENDICES
APPENDIX
TITLE
PAGE
A
Equations and calculations for the resistivity and
conductivity of PAni/PVA (40 wt. %, 30 oC) by using
four-probe method
136
B
Sample calculation of Hall Effect measurement for
PAni/PVA (40 wt. %, 30 oC) by using Hall Effect
measurement
137