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CHAPTER – II

LITERATURE SURVEY AND SCOPE OF THE PRESENT INVESTIGATION

In this chapter, a literature survey on the synthesis and characterization of

polythiophene based materials and their supercapacitor applications are

presented in detail. The scope of the present investigation is given at the end.

2.1. INTRODUCTION

Polythiophene is particularly attractive because of their easy preparation,

excellent electrical properties, possible processability and stability. The structure

of polythiophene (PTh) is known as 2,4-linked five membered sulphur rings. PTh

has proved as aromatic compound due to lone pair electrons of sulphur atom and

delocalized π-electrons. The main charge carriers in polythiophenes are polarons

and/or bipolarons, associated with the formation of new quantum states in the

energy gap [1]. The various forms of polythiophene and acid doped

polythiophene [2] can be described in Figure.2.1.

Polythiophene can be synthesized by both electrochemical and chemical

oxidative polymerization pathways. In order to obtain mass production of

polythiophene, the chemical oxidative method was considered to be more useful

than the electrochemical method. The properties of polymers are based on the

degree of oxidation, and hence the present investigation was mainly focused on

the synthesis of various acids doped polythiophene by a cationic surfactant

assisted dilute polymerization method and its applications for supercapacitors.

62

H+A- = acid group; y = number of acid groups per thiophene unit.

Fig.2.1. Structures of polythiophene (a) Neutral (b) Polaron (c) Bipolaron and (d) acid doped

2.2. LITERATURE SURVEY 2.2.1. SYNTHESIS OF POLYTHIOPHENE

Entezami et al [3] synthesized highly conducting polythiophene thin film in

perchloric acid by electrochemical method and characterized for UV analysis and

CV studies.

Yue Sun et al [4] prepared conductive composites by an inverted emulsion

pathway using surfactant with FeCl3 of aqueous solution of dispersed phase and

an organic solution of host polymer used. The obtained composite had good

mechanical property and the conductivity was as high as 1.3 Scm-1. Among

thiophene, 2, 2’-bithiophene and 3-methyl thiophene, the latter one was the most

suitable for conductive composite by the inverted emulsion method.

63

Higgins et al [5] reported that polybenzo[c]thiophene-modified electrodes

by employing p-toluenesulphonate as dopant anion by electrodeposition method.

Tetraethylammonium p-toluenesulphonate (TEATos) was used as electrolyte for

electrodeposition of polybenzo [c] thiophene from CH3CN solution gives

compact, smooth films on indium-doped tin oxide electrodes. Films upto 10 μm

thick have been deposited with TEATos, but film growth is self-limiting with

tetraethylammonium tetrafluoroborate (TEAT). TEATos-grown films have a

different morphology, but can still be reversibly p-doped in the same way as

TEAT-grown films. n-doping, However, n-doping was not electrochemically

improved by using TEATos as growth electrolyte.

Toketel Yohannes et al [6] reported that the copolymer of poly (3-

methylthiophene-co-3, 4-dioxythiophene) via electrochemical oxidation method of

synthesis by fixed concentration of monomers in the mixture at various

polymerization potentials were used to produce copolymers. The electrochemical

and spectroscopic properties demonstrated the possibility of modulating

continuously the electrochemical and optical properties polymers.

Mohammed [7] synthesized electrochemically prepared polythiophene and

polypyrrole films, and the effect of ionic size was discussed by N(Bu)4BF4,

NaClO4 and LiAsF6 in propylene carbonate. An increasing order of diffusion

coefficients of electrolytes are NaSbF6 < N (Bu)4BF4 < NaClO4 < LiAsF6 at 273 K

has been observed. It proved that the ionic size was a limiting factor.

Laren Tolbert et al [8] reported that charge-transfer doping of poly (3-alkyl-

2, 2’-bithiophene). The spin-cast film of the title polymer, a highly ordered, flexible

64

and soluble polythiophene, doped with solutions of dichlorodicyanoquinone

(DDQ) to produce a highly conducting material. The doped films of the

polybithiophene exhibited strong bipolaronic absorptions, consistent with the

formation of charge-transfer polymers. The use of organic dopants of this type

provided a superior method for the production of stable conductive materials.

Polyheterocycles such as polypyrrole and polythiophene were ordinarily doped

with inorganic dopants such as FeCI3 resulting in the formation of charge transfer

complexes, polarons, and bipolarons. Polarons and bipolarons were the charge

carriers in polythiophene.

Eiji Ando et al [9] reported the electric conductivity of PPy and PTh films

as a function of heat-treatment temperature. From room temperature to 150 °C,

the conductivity of polypyrrole film remained constant. From 150 to 300 °C, the

conductivity dropped due to decomposition of PPy and loss of dopant ion (ClO4-).

Above 300 °C, the conductivity increased again. Above 750 °C, the maximum

conductivity observed, this was due to the formation of carbonaceous materials.

The PTh film showed a similar tendency to the PPy film.

Jin et al [10] reported the synthesis and electro-optical properties of

polythiophene derivatives for electroluminescence displayed. The PTh derivative

synthesized by chemical oxidative polymerization method. Their chemical

structures were confirmed by UV-visible and 1H-13C-NMR spectra. The resulting

polymers were soluble in organic solvents and could be spin-cast onto ITO glass

substrate to obtain optical thin films without defects.

65

The thiophene was polymerized onto polybutadiene coated platinum

electrodes, the composites with different PTh percentages showed conductivity

in the order of 10-3 (Ωcm)-1[11]. The film characterization was performed using

FT-IR, SEM and DSC techniques. The dominant transport mechanism and the

temperature dependence of conductivity were also investigated.

Bekir Sari et al [12] synthesized polyurethane/ polythiophene conducting

copolymer by electrochemical method using LiClO4, Et4NBF4 and Bt4NPF6

supporting electrolytes at two different solvents (acetonitrile and benzonitrile) in

anhydrous medium. The CV, SEM, DSC, FTIR, TGA and conductivity studies

were carried out for all homo and copolymers.

Hussein Hosseini et al [13] investigated the chemical and electrochemical

polymerization of thiophene derivative of 3-methoxyethoxy moiety and its

copolymers with aniline, thiophene and pyrrole. The synthesized films gave

highly conductive polymeric materials and some of which were soluble in

common organic solvents. The conductivity of undoped state of the polymers

was lower than 10-4-10-3 S/cm. After doping with FeCl3/nitromethane or vapour I2,

their conductivities increased to 10-3-10-2 S/cm.

Yasemin Arslan Udum et al [14] reported the synthesis of sulphonated

PTh films by electrochemical oxidation method. The PTh films which were

soluble in DMSO and KOH. The solubility increased and conductivity decreased

with the degree of sulphonation value (decreasing C/S ratio). The polymer

characterized by CV, UV-visible, FT-IR, elemental analyzer, dry conductivity,

intrinsic viscosity measurements and thermal gravimetric analysis.

66

Park [15] synthesized nanotubes and nanowires of π-conjugated poly(3-

methylthiophene) by anodic aluminium oxide template through electrochemical

polymerization method. The nanotubes have 100-200 nm diameter and 5-10 nm

of wall thickness found out. The FT-IR, UV-visible, the structural and optical

properties have been measured.

Ming-De Lu et al [16] reported polythiophene and titania nanotube

composite by chemical oxidative polymerization method. The composite

characterized by XRD, SEM, TGA, FT-IR and XPS studies. The TGA results also

showed that phase segregation occurred when the nanocomposite contained 35

% of polythiophene.

Fumihiko saito et al [17] investigated optically active polythiophene by

chemical oxidative polymerization method, and characterized for 1H-NMR, UV-

visible and CD spectrum.

Vadivel Murugan et al [18] synthesized the nanocomposite of PEDOT/VS2

by oxidative polymerization of EDOT with VS2 for rechargeable Li batteries. The

XRD, XPS and TEM studies showed that the change in interlayer separation is

consistent with the existence of two phases of organic and inorganic species in

the nanocomposite corresponding to the intercalation of PEDOT in the VS2

framework. The PEDOT/VS2 nanocomposite showed significant enhancement in

the discharge capacity of ~ 130 mAhg-1 compared to that of 80 mAhg-1 for

pristine VS2.

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Do Hwan Kim et al [19] reported solvent Vapour-Induced nanowires

formation in poly(3-hexylthiophene) thin films. This polythiophene derivative was

characterized by SEM and XRD studies.

Zhipan Zhang et al. [20] prepared gold core-polythiophene shell composite

nanoparticles with a diameter of 6-8 nm. The product was studied by TEM, IR

and Raman spectroscopes.

Hullathy Subhan Ganapathy et al [21] synthesized novel fluorinated ester

substituted polythiophenes by FeCl3 oxidative polymerization. The semifluoro

and perfluoroalkyl were soluble in common organic solvents. The influence of

bulky fluoroalkyl substitutions on electrical conductivity, electronic absorbance,

fluorescence and surface properties of polymer films were investigated and the

properties were compared with poly(3-octylthiophene) synthesized under similar

experimental conditions.

Jr-Shian Ji et al [22] investigated the photoluminescence of poly(3-hexyl

thiophene)/titania nanostructured hybrids by sol-gel process using titanium (IV)

isopropoxide. The chemical structure of these materials was identified by FT-IR,

1H-NMR and SEM studies. The energy levels of the hybrid materials were

determined by cyclic voltammetry and UV-Visible spectra. The

photoluminescence spectra implied that the photo-induced electron transfer was

more efficient in silane-bearing poly(3-hexylthiophene)/TiO2.

Radhakrishnan et al [23] synthesized polythiophene containing hetero

aromatic side chains, and it was analyzed using molecular orbital calculations in

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order to understand the structure-property relations. Based on theoretical

predictions, the synthesis of some model compounds were attempted.

Carlos Alemon et al. [24] reported experimental and theoretical

investigation about the influence of the dopant in the electropolymerization of α-

tetrathiophene. The theoretical results provided by quantum mechanical

calculations on 1:1 charge-transfer complexes formed by α-tetrathiophene and

X=SCN, Cl, Br, NO3 and ClO4. The consistency between experimental and

theoretical results was allowed to explain and rationalize the influence of the

dopant in the electropolymerization of α-tetrathiophene.

Mihaela Baibararac et al [25] synthesized the development of

nanocomposite materials by conducting organic polymers and carbon nanotubes.

These composite materials were in many applications such as supercapacitors,

sensors, photovoltaic cells and photodiodes, optical limiting devices, solar cells,

high-resolution printable conductor, electromagnetic absorbers and advanced

transistors.

Fouzi Mouffouk et al [26] reported 1,4,8,11-tetraazacyclotetradecane

(cyclam) derivative of 3, 4-ethylene dioxythiophene (EDOT) synthesized by

electrochemical polymerization method. The redox behaviour studied by CV of

typical functionalized PEDOT with the reversible Ni(II)-Ni(III) process of the

[Ni(cyclam)]2+ complex superimposed.

Aysegiil Gok et al [27] synthesized and characterized polythiophenes in

the presence of anionic, cationic and non-ionic surfactants by chemical oxidative

polymerization method. The prepared PThs were characterized by FT-IR,

69

elemental analysis, SEM, TGA and conductivity measurements. PThs

synthesized with a cationic surfactant showed the highest thermal stability of all

other samples.

Mokhtar et al [28] reported four kinds of PThs had been doped with

CH3SO3H in CHCl3 under air, oxygen and nitrogen. In the doping of two types of

poly(3-hexylthiophene)s, P3HexTh(Zn/Ni) and P3HexTh(Fe) with different

contents of a head to tail unit, the p-doping occurred at a similar rate. The

reaction between poly(3-dodecylthiophene), P3DodTh and the acid took place

more rapidly. P3OBuTh with a butoxy substituent undergone more facile p-

doping and received photochemical reaction with CHCl3, and this reaction

obeyed a pseudo-first –order rate at room temperature.

Haeldermans et al [29] reported water soluble derivative of polythiophene

was used as photo sensitizer and a hole conductor inserted of the liquid

electrolyte, resulting in a solid state polythiophene-sensitized solar cell.

Biswa Ranjan Panda et al [30] reported the development of a reversible

pH sensor in aqueous medium based on the fluorescence properties of a

polythiopheno-gold nanoparticle composite. The composite was synthesized in

water by simultaneous reduction of HAuCl4 to AuNPs and polymerization of

thiophene in the presence of no additional reagents. This was stable for weeks

and had characteristic emissions, which changed in the pH range of 3.0 to 6.0.

This providing a mean for probing the pH of an aqueous solution. This approach

took advantage of redox chemistry in synthesizing the water-soluble composite

70

and the optical behaviour of a conjugated polymer in developing an important pH

sensor.

Wasim Alhalasah et al [1] proved the change of UV-Visible optical

absorption electropoymerised substituted poly-3-p-X-phenylthiophenes has been

followed in situ as a function of applied electrode potential in an electrolyte of

Et4NBF4 in acetonitrile. The UV-Vis spectrum showed features between 300 and

900 nm similar to those observed with many other PTh having a high degree of

conjugation. The intensity of absorption due to the π-π∗ transition around 450-

566 nm decreased, and a new broad absorption band associated with bipolaron

states appeared around 730-890 nm. On the other hand, during the oxidation (p-

doping) of the polymer films, a blue (hypsochromic) shift was observed for both

absorption bands.

2.2.2. POLYTHIOPHENE IN SUPERCAPACITOR APPLICATIONS

Arbizzani et al [31] reported that the polymer redox supercapacitor based

on poly(dithieno[3,4-b:3’,4’-d]thiophene) (pDTT) in liquid and polymer gel

electrolyte was used to study the capacity, energy density, power density and

self discharge. This electrode material was electrosynthesized under argon

atmosphere at room temperature. The symmetric type of n- and p-doped

electronically conducting polymer can be very promising electrode material for

supercapacitor. He also investigated the performance data of symmetric

supercapacitor based on p-doped poly(pyrrole), and also unsymmetrical

supercapacitor based on both p-doped poly(pyrrole) and poly(3-methylthiophene)

and compared [32].

71

Williams et al [33] reported the electrochemically synthesized bridged

dithienyl derivatives and used as the electrode materials for electrochemical

capacitors. These electronic conducting polymers (ECPs) were having low band

gap (c.a 1eV), so that the conductivity remarkably enhanced. These ECPs were

targeted for use as the active materials in electrochemical capacitors. These

materials were characterized by using cyclic voltammetry, electrochemical

impedance spectroscopy and discharge cycles.

K. Gurunathan et al [34] reviewed the electrochemical synthesis of

conducting polymers (CPs), supporting electrolytes, electrodes and structural

properties of these novel materials and the nature of the dopants which induce

electrical conductivity in conjugated organic polymers. Finally, an overview of

various applications of these materials to electronics, optoelectronics, solar cells,

p-n-semiconductors and energy storage applications like batteries and

supercapacitors had been presented.

The chemically synthesized polythiophene (PTh) and polyparafluoro

phenylthiophene (PFPT) were used as active materials in supercapacitor

electrodes [35]. The supercapacitor energy storage levels of 260 Fg-1 were

obtained with PTh and 110 Fg-1 with PFPT. The studies of the electrode

composition led to the selection of acetylene black as the electronically

conducting additive in the electrode. The best electrode composition selected

was 65 % polymer, 30 % acetylene black and 5 % binder A.

Mastragostino et al [36] focused on the data for poly(3-methylthiophene)

positive and negative electrodes, envisioned for a n/p-type supercapacitor, as

72

well as data for cycleability of supercapacitors with composite electrodes based

on such conventional polymers were reported. The capacitance and cycling

stability of poly(3-methylthiophene) were found to sufficiently high. The hybrid

configuration with pMeT as positive and activated carbon as negative electrode

may even yield a promising device both in terms of performance and cost.

Arbizzani et al [37] studied n/p-type of poly(3-methylthiophene) based

redox supercapacitors, the p-doped pMeT as positive electrode and activated

carbon as negative el ectrode for hybrid supercapacitors [66], with that of a

double layer activated carbon supercapacitor (DLCSs), which is representative of

the current state of supercapacitor technology. The data on the n/p-type

supercapacitor demonstrate that this device was not fully competitive with DLCSs

because of its lower discharge capacity, although all the charge was delivered at

high potentials and this made it suitable for high-voltage applications. The

results for hybrid supercapacitors demonstrated that this device was better

(DLCSs), delivering higher average and maximum specific power and

significantly higher specific energy in the potential region above 1.0 V.

Alexis Laforgue et al [38] reported chemical synthesis of fluorinated

polyphenylthiophenes and its application to supercapacitors. The

characterization of their positive and negative doping processes was performed

by cyclic voltammetry and showed high capacities, but it proved no real stability

in cycling experiments. The P-4-FPT as electroactive material in supercapacitor

systems showed interesting properties in terms of energy and power delivered.

73

The thiophene derivative of poly(alkoxythiophene) was synthesized

electrochemically and it had been studied for electron withdrawing or electron

donor groups functionalizing [39]. This study showed good stability to

voltammetry cycles and their specific capacitance for their use as electrode

materials in supercapacitors. The p-doped poly(4,4”-dipentoxy-4’-dicyanovinyl-

2,2’:5’,2”-terthiophene) pDPCT and poly(4,4”-dipentoxy-2,2’:5’,2”-terthiophene)

pDPT had been successfully used as electrode materials in supercapacitors. It

showed high capacitance values of 190 Fg-1.

Mastragostino et al [40] designed thiophene-based conducting polymers

of n/p-type supercapacitors. The result was compared to high surface area of

carbon-based composite electrodes. On the basis of capacity, capacitance and

charging resistance data of n/p-type pMeT supercapacitor. The results showed

that pMeT could be successfully used in the supercapacitor technology when a

hybrid configuration is realized.

The effect of MWCNTs with PEDOT improved supercapacitive behaviour.

This was checked by electrochemical polymerization of EDOT directly onto the

nanotubes with acetylene black [41]. The capacitance behaviour was estimated

by 2 or 3- electrode cell configuration in aqueous electrolytes such as 1M H2SO4,

6M KOH and 1M TEABF4 in acetonitrile. The capacitance values for

PEDOT/MWCNT composite ranged from 60 to 160 Fg-1 and such materials had a

good cycling performance with a high stability in all the electrolytes and the

organic medium showed higher energy stored capacitive behaviour.

74

Kwang Sun Ryu et al. [42] reported the redox and hybrid supercapacitors

based on PEDOT and MSP-20 powders as electrode materials with Et4NBF4 in

PC and LiPF6 in EC/DMC as electrolyte solutions. From the results of charge and

discharge for the hybrid type, the specific discharge capacitance of 56 Fg-1 after

1000 cycle in the range of 0-3 V was observed. This proved that hybrid system

exhibited better than that of redox type capacitor.

The symmetric supercapacitor was fabricated from ultrasonically irradiated

poly(3,4-ethylenedioxythiphene) with 1M H2SO4 as supporting electrolyte [43].

The PEDOT was prepared by chemical oxidative polymerization method using p-

toluene sulphonic acid as dopant. Due to ultrasonication the yield and specific

capacitance were increased (72 to 100 Fg-1).

Ana karina Cuentas Gallegos et al [44] reported electrodes based on

carbon nanofibers (NFC), bilayer systems of NFC and commercial polythiophene

(PEDOT-PSS), and NFC/ PEDOT-PSS based composites, for symmetric and

asymmetric electrochemical capacitor cells. The three electrode cell study carried

out to characterize the each electrode material. The swagelok cells with filter

paper as the separator were used for supercapacitor assembly, which was

characterized for CV and galvanostatic cycling to evaluate cycle life of symmetric

and asymmetric cell assemblies. The results proved that asymmetric cell

configuration doubled the capacity in comparison to NFCs symmetric cells, and

the cycle-life was compared to the symmetric cell assembled with bilayered

electrodes.

75

Randriamahazaka et al [45] reported that PEDOT based modified

electrode have been synthesized using ionic liquid. This PEDOT was performed

for two and three electrode cells. The electrochemical responses were analyzed

in terms of series of combination of a resistance (R) and a capacitor (C). This

capacitance described the chemical capacitance of PEDOT that reflected the

capability of the system to accept or release additional charge carriers on a given

variation of the chemical potential. The electrochemical response during constant

current charge/discharge experiments for two-electrode cell in which same

amount of PEDOT was deposited on each electrode showed a type I

electrochemical supercapacitor response.

Vadivel Murugan [46] investigated the synthesis and characterization of

PEDOT interleaved between the layers of crystalline oxides of V and Mo as

electrodes for Li batteries and supercapacitors. The expansion of the interlayer

spacing of crystalline oxides was consistent with a random layer stacking

structure. These hybrid nanocomposites with 1M LiClO4 in a mixture of ethylene

and dimethyl carbonate (1:1 v/v), gave higher discharge capacity than pristine

oxides. This improved electrochemical performance was attributed to higher

electrical conductivity, enhanced bi-dimensionality and increased structural

disorder. These conducting polymer-oxide hybrids delivered the higher capacity

of more than 300 mAhg-1 in the potential range of 1.3 - 4.3 V. After incorporation

of PEDOT to MoO3, the double layer capacitance increased from ~ 40 mFg-1 to ~

300 Fg-1 under same experimental condition.

76

The chemical synthesis of hybrid materials based on polyaniline and

PEDOT with polyoxometalates was tried as an electrode material for

electrochemical supercapacitors [47]. The capacitance values were as high as

168 Fg-1 for PAni/PMo12 and 130 Fg-1 for PEDOT/PMo12 hybrid materials.

Poly(3-methyl thiophene)/PVdF composite electrodes for supercapacitors

were prepared via template synthesis by an electrochemical polymerization

method [48]. The large pore size distribution in the template matrix results in

some of the poly(3-methyl thiophene) growing in a more ordered fashion than in

films synthesized without spatial restriction, and this can lead to improve

conductivity and kinetics. The CV studies performed at the potential limit of 0.7-

2.5 V. The capacitance behaviour studied by CV, ac impedance and charge-

discharge tests. The specific capacitance was 616 Fg-1; and the power density

decreased considerably up to ~ 300 cycles and then became constant about 7.3

kW kg-1.

Snook et al [49] achieved a high electrode specific capacitance with

materials of low mass specific capacitance by potentiostatically grown thick micro

and nanoporous PEDOT films. The polymer was potentiostatically grown upto

0.5 mm thick film that was porous at both micro and nano scales. The CV and

impedance study showed that specific capacitance increased linearly with the

film deposition charge approaching 5 Fcm-2.

The composite electrodes were prepared by electrochemical

polymerization of 3-methylthiophene in porous PVdF membranes of various

thicknesses [50]. It showed the biggest capacitance of 82 Fg-1 with a 27.5 µm

77

thick composite. This composite was studied for electrochemical impedance

spectroscopy, and it revealed three behaviours associated with variation in the

oxidation state of poly(3-methylthiophene) during transition from the n-undoping

to p-doping states. The best results of composites are due to more compact

morphology that reduced the frequency of defects in the poly(3-MeT) chains and

increased the surface area in contact with electrolyte.

Jie Wang et al [51] synthesized poly(3,4-ethylene dioxythiophene) on the

surface of polypyrrole modified tantalum electrodes by electropolymerization

method. The highly porous PEDOT/h-PPy horn like structure of PPy showed the

specific capacitances as 230 Fg-1 in 1M LiClO4 and 290 Fg-1 in 1M KCl solutions.

The supercapacitor studies showed the ideal behaviour in 1M KCl solution.

Further, the specific power of composite reached 13 kWkg-1 with good cycle

stability.

Patra et al [52] electronically deposited PEDOT on stainless steel

substrate in presence of sodium dodecylsulphate (SDS) in 0.1 M H2SO4. It

showed the higher specific capacitance than the electrodes prepared from

neutral aqueous electrolyte. The influence of various experimental variables such

as concentration effects of H2SO4 and SDS, deposition potential and the nature

of supporting electrolytes used for capacitor studies were also discussed.

Krishna Bhat et al [53] prepared n- and p-doped PEDOT coating on

stainless steel to use as electrode materials for redox supercapacitor. The

electrochemically synthesized polymer was studied for CV and ac impedance

78

analysis. The supercapacitor showed a maximum specific capacitance of 121 Fg-

1 at 10 mV/s scan rate.

Selvakumar et al [2] reported the composite electrodes had been prepared

via electrochemical deposition of β-naphthalene sulphonate doped PEDOT onto

activated carbon (AC) electrodes. The characteristics of the electrodes and the

fabricated supercapacitor were investigated using cyclic voltammetry and AC-

impedance studies. The electrodes showed a maximum specific capacitance of

158 F/g at a scan rate of 10 mV/s. This indicated that the in-situ

electropolymerization of ethylenedioxythiophene onto AC could improve the

performances of carbon electrodes for use in supercapacitors.

Uniform nanomaterials of polythiophene using various surfactants had

been prepared by polymerization at an organic phase. Migration of the product

into organic phase was hypothesis to suppress uncontrolled polymer growth by

isolating the nanomaterials from excess reagent. The addition of some

surfactants leads to further control the sizes of nanomaterials. To compare the

effects of surfactants-free PTh showed globular structure with particle size of 1

µm, but some fibrils were also present. When anionic surfactant (SDS) assisted

PTh showed the ribbon structure, the layered structure was obtained by cationic

surfactant and also the smooth surface with small deformed globules were visible

in the PTh-nonionic surfactant assisted products.

Omastov’a et al [54] synthesized highly conducting and stable polypyrrole

by chemical polymerization in aqueous solution containing an oxidant, FeCl3 or

Fe(SO4)3 and an anionic surfactant (sodium dodecylbenzenesulpphonate). The

79

polymer synthesized in the presence of the anionic surfactant and higher

conductivity than the same synthesized in the presence of an oxidant only.

2.3. SCOPE OF THE PRESENT INVESTIGATION

It is proposed to synthesis various acids doped polythiophene

nanoparticles by a cationic surfactant assisted dilute polymerization method in an

aqueous medium. The polymerization to be carried out using ferric chloride as

the oxidant by varying the carboxylic acid dopants, such as tartaric acid (TA),

citric acid (CA), p-toluene sulphonic acid (p-TSA) and anthraquinone sulphonic

acid (AQSA).

The PVdF-co-HFP based polymer electrolyte containing 1M LiPF6-EC: PC

(1:1 v/v) to be used for this redox supercapacitor. The voltage limit to be applied

for the cell would be -1.0 to +1.0 V.

The following physical and electrochemical characterizations are to be

carried out for the synthesized products.

The molecular conformation of acids doped polythiophenes are to be carried

out by FT-IR spectroscopy.

The structural identification of acids doped polythiophenes are to be studied

by UV-Visible spectroscopy.

The crystallinity properties of the polymer-acids are to be confirmed by XRD

studies.

The surface morphology of the synthesized products to be observed using

scanning electron microscope (SEM) studies.

80

The conductivity of the products are to be identified by four probe resistance

measurements.

The specific capacitive behaviour of the capacitors are to be measured by

cyclic voltammetry studies.

The resistance properties of the capacitors are to be measured by impedance

spectroscopy.

The specific capacitance, energy & power densities and coulombic efficiency

of the capacitors are to be measured by charge-discharge studies.

81

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