1.1 Introduction of Nano Technology Introduction of Nanotechnology is naturally very broad, comprise the fields of as, surface science, molecular… [301435]

INTRODUCTION

1.1 [anonimizat], [anonimizat], [anonimizat]. Generalized description of Nanotechnology was described by National nanotechnology (US) initiative, defines nanotechnology as at least one dimension sized manipulation from 1 to 100 nm. So all technology which have common trait as size name in the plural form “nanotechnologies” as well as “Nano scale technologies”. Government has invested millions of dollar due to its huge application in various industries (military & industrial use). New materials and devices with a [anonimizat], electronics, biomaterials and energy production. Bottom up technique has been used in nanotechnology for construct items. High performance products being developed by using this tools. These new techniques of nanotechnology makes different from other devices which are merely miniaturized versions of an equivalent macroscopic device; such devices are on a larger scale and come under the description of micro technology. [anonimizat]-[anonimizat], or the spacing between these atoms in a molecule, are in the range 0.12–0.15 nm, and a [anonimizat] a diameter around 2 nm. [anonimizat]-forms, [anonimizat] 200 nm in length. [1-4]

1.2 Polymer

A polymer is a large molecule (macromolecule) composed of a large number of repeating structural units typically connected by covalent chemical bonds”. In modern engineering and technology polymers are highly useful for many scientific and technological problems. Non-[anonimizat]. Now a day, [anonimizat], transportation, [anonimizat], aerospace and space technology as well as nuclear application. Homopolymers are those polymers that have only a [anonimizat] (1.1).

Figure (1.1) Simple polymer structure and polypropylene [5]

[anonimizat], or organ metallic. They are originated as polymer. [anonimizat], cloths, [anonimizat], ceramics, coatings, [anonimizat], and coatings. They are also major components in plant and soils and animal life. [anonimizat], [anonimizat], [anonimizat], and the environment. [anonimizat] (plastics) are known for their good insulating properties and widely used material. Today polymeric materials are widely used in all area of electrical and electronics device. [anonimizat], [anonimizat], equipment casing and housing. Thus, it can be concluded that polymer are widely used. Further there is a huge interest and scope of research in the study of property of conducting polymer. However, it has been discovered that there are some polymers which have conducting properties. One of the most important properties of the synthetic /conventional polymers is their ability to act as excellent electrical insulator, both at high frequency and at high voltage. Their conductivity range in 10-18 to 10-7 ohm-1 cm-1 .The typical examples are Polyethylene.[5-9]

Natural inorganic polymers include graphite, diamond, sand, asbestos, mica, quartz, and talc. Natural organic polymers include polysaccharides such as starch and cellulose, nucleic acids, and proteins are some natural organic polymer, whereas boron nitride, concrete, many superconductors, and a number of glasses. Synthetic polymers used for structural components. Their weight is considerably less than metals. They help to reduce the fuel consumption in vehicles and aircraft. They even outperform most metals when are measured on the basis of strength-per-weight. Polymers can also be used for engineering purposes such as gears, bearings, and structural members.

1.3 Basic concepts of polymer science

1.3.1 Nomenclature

In International Union of Pure and Applied Chemistry (IUPAC) many numbers of polymers have both a similar name and a structure-based name. Many polymers are usually known by their acronyms. Trade names are used by some companies to identify the specific polymeric products they manufacture. For instance, Fortrel polyester is called poly(ethylene terephthalate) (PET) fiber. Polymers are often generically named, such as rayon, polyester, and nylon..

1.3.2 Composition

Polymer structures can be represented by similar or identical repeat units. These are derived from smaller molecules, called monomers, which react to form the polymer. Propylene monomer and the repeat unit it forms in polypropylene as shown in Figure 1.2.

Figure (1.2) Propylene monomers[10]

With the exception of its end groups, polypropylene is composed entirely of this repeat unit. The number of units (n) in a polymer chain is called the degree of polymerization (DP). Moreover, proteins can be described in terms of the approximate repeat unit where the nature of R (a substituted atom or group of atoms) varies.

1.3.3 Primary structure

The sequence of repeat units within a polymer is called its primary structure. Unsymmetrical reactants, such as substituted vinyl monomers, react almost exclusively to give a “head-to-tail” product, in which the R substituents occur on alternate carbon atoms. A variety of head-to-head structures are also possible.

1.3.4 Secondary structure

This refers to the localized shape of the polymer, which is often the consequence of hydrogen bonding. Most flexible to semi-flexible linear polymer chains tend towards two structures-helical and pleated sheet/skirt like. The pleated skirt arrangement is most prevalent in polar materials where hydrogen bonding can occur. In nature, protein tissue is often of a pleated skirt arrangement type. For both polar and nonpolar polymer chains, there is a tendency toward helical formation with the inner core having “like” secondary bonding forces.

1.3.3 Molecular properties

These are used to help determine the structure and behavior of the polymer. The molecular weight of a particular polymer chain is the product of the number of units times the molecular weight of the repeating unit. Two statistical averages describe polymers, the number-average molecular weight and the weight-average molecular weight. Size is the most important property of polymers allowing for storage of information (nucleic acids and proteins). Polymeric materials remember any action that moves polymer chains or segments (such as bending, stretching, and melting). Size also accounts for an accumulation of the inter chain and intra chain secondary attractive forces called Van der Waals forces. For nonpolar polymers, such as polyethylene, the attractive forces for each repeating unit are less than that for polar polymers. Polyvinyl chloride, a polar polymer, has attractive forces that include both dispersion and dipole-dipole forces so that the total attractive forces are proportionally larger than those for polyethylene. Polymers often have a combination of ordered regions, called crystalline regions, and disordered or amorphous regions. Crystalline regions are more rigid, contributing to strength and resistance to external forces. The amorphous regions contribute to polymers' flexibility. Most commercial polymers have a balance between amorphous and crystalline regions, allowing a balance between flexibility and strength.

1.4 Classification of Polymers

E.g. Starch, Cellulose, Proteins, Nucleic acids

E.g. Polythene, PVC, Nylon, Teflon

E.g. Rayon

E.g. PVC, Polystyrene, PMMA

E.g. Rubber

Figure (1.3) Classification of Polymers [11]

1.5 Synthesis of Polymer

For polymerization to take place, monomers should have at least two reaction points or functional groups. Addition and condensation are the two main reaction routes to synthetic polymer formation. In chain-type kinetics, that result in the reaction mixture consisting mostly of unreacted monomer and polymer. Vinyl polymers derived from vinyl monomers and containing only carbon in their backbone, are formed inthis way. Examples of vinyl polymers include polystyrene, polypropylene, polyethylene, polybutadiene (Figure1.6), and poly (vinyl chloride).

Figure (1.4) Structure of Polypropylene [12]

1.6 Properties of Polymer

1.6.1 Melting point

When the changes occur from crystalline or semi-crystalline phase to a solid termed as melting point. When applied to polymers, anamorphous phase, though abbreviated as simply thermosetting polymers, they will decompose at high temperatures rather than melt.

1.6.2 Glass transition temperature

A parameter in which synthetic polymer is manufactured is the glass transition temperature (Tg), which defines that temperature at which any amorphous polymer undergo a transition from a rubbery, viscous amorphous liquid, to a brittle, glassy amorphous solid. The glass transition temperature may be altered by changing the degree of branching or cross linking in the polymer or by the addition of plasticizer.

1.6.3 Boiling point

The boiling point of a polymer substance is never defined because the polymers will decompose before reaching theoretical boiling temperature.

1.6.4 Degree of crystallinity

Due to increasing the degree of crystallinity the polymer will become more rigid. It can also lead to greater brittleness. Polymers with degree of crystallinity approaching zero or one will tend to be transparent, while polymers with intermediate degrees of crystallinity will tend to be opaque due to light scattering by crystalline / glassy regions.[13,14]

1.6.5 Crystallinity

For polymers, the term crystalline has a somewhat ambiguous usage. At some places, the term crystalline finds similar usage to that used in conventional crystallography. For example, the structure of a crystalline protein or polynucleotide, such as a sample prepared for X-ray crystallography, may be defined in terms of a conventional unit cell composed of one or more polymer molecules with cell dimensions of hundreds of angstroms or more. A synthetic polymer may be described as crystalline if it contains regions of three-dimensional ordering on atomic (rather than macromolecular) length scales, usually coming from intra-molecular folding and/or stacking of adjacent chains. For synthetic polymers which consist of both crystalline and amorphous regions; the degree of crystallinity may be defined in terms of a weight fraction or volume fraction of crystalline material. Few synthetic polymers are entirely crystalline.[15]

Figure (1.5) Structure of Nylon, Polycarbonate, Polyurethane [15]

1.6.6 Amorphousness

The chains, or their parts, which are not in the crystals and have no order to the arrangement of their chains are known to be in amorphous state. That means a crystalline polymer consists of two components: the crystalline portion and the amorphous portion. Thelamellae consists of thecrystalline portion, and the amorphous portion is outside the lamellae. Figure 1.8 shows, arrangement of crystalline and amorphous portion.

Figure (1.6)An arrangement of crystalline and amorphous portions [16].

The fibrils grow out in three dimensions, that give them a look of a spheres than wheels. The entire assembly is known as a “spherullite.

1.7 Polymerization in polymer

Polymerization is defined as a process in a chemical reaction, in which monomer molecules react together to form three-dimensional networks or polymer chains. It can either be step grow polymerization or a chain grow polymerization. The step grow polymerization involves condensation, where polymer can be called as polymer which include termination of small molecules during its synthesis, or consists of functional groups, or all the atom present in the hypothetical monomer to which it can be degraded are not contained by its repeat unit. The linking together of molecules incorporating double or triple chemical bonds is involved in Chain-growth polymerization or addition polymerization. There are extra internal bonds in these unsaturated monomers (the similar molecules which make up the polymers) which are capable to break and link up with other monomers to form the repeating chain. The polymers names are intended to reflect the monomer(s) from which they are synthesized rather than the exact nature of the repeating subunit. In both standardized conventions. For instance, polyethylene the polymer synthesized from the simple alkene ethane is known, retaining the -ene suffix even though the double bond is withdrawn during the polymerization process as described in Figure 1.10.[16]

Figure (1.7) Polymerization process [16]

1.8 Polymer characterization

Several parameters are required bythe characterization of a polymer which areto be specified. This is because in a polymer there is a statistical distribution of chains of changing lengths, and monomer residues are consisted by each chain which affect its properties.

A wide range of laboratory techniques are used to find out the characteristics of polymers. The Structural characterizations of films were carried out by XRD, which shows nature of the film. The particle size was determined by scherrer’s formula. The morphology of film were carried out by AFM ,which report shape of particle films. The absorbance of the films was measured using UV-Visible Spectroscopy .X-Ray diffraction. FTIR, NMR and Raman can be used to know composition. [16, 17]

1.9 Polymer degradation

Polymer degradation is a change in the properties – tensile strength, color, shape, etc – of a polymer or polymer based product under the influence of one or more environmental factors such as heat, light or chemicals. It is often due to the hydrolysis of the bonds connecting the polymer chain, which in turn leads to a decrease in the molecular mass of the polymer. These changes may be undesirable, such as changes during use, or desirable, as in biodegradation or deliberately lowering the molecular mass of a polymer. Such changes occur primarily because of the effect of these factors on the chemical composition of the polymer.

The degradation of polymers to form smaller molecules may proceed by random scission or specific scission. The degradation of polyethylene occurs by random scission – that is by a random breakage of the linkages (bonds) that hold the atoms of the polymer together. When heated above 450°C, it degrades to form a mixture of hydrocarbons. Other polymers – like polyalphamethylstyrene – undergo 'specific' chain scission with breakage occurring only at the ends. They literally unzip or depolymerize to become the constituent monomer.[17]

1.10 Conducting Polymers

Conducting polymer are polymer which have metallic and semiconductor characteristics a combination of properties not shown by any other known material. The presence of conjugated double bonds along the backbone of the polymer is the key property of a conductive polymer. In conjugation double bond, the bonds between the carbon atoms are alternately single and double. The type of conductive polymer which has generated much research activity in the last fifteen to twenty years fits neither intrinsic nor the conductor classification. For example structure of poly-acetylene is shown in figure ( 1.8)

Figure 1.8 Structure of Polyacetylene

these new material are generally insulator /poor conductor in their present state, but display marked increase in their conductivity on exposer to exposer to oxiding or reducing agents. Thus, one may start with an insulating material and progressively oxidize or reduce it though the conductivity ranges of a semiconductor (p or n –type respectively) in to metallic regime. The overall process which is often referred to as classification of conductive polymer.

Figure (1.9) Classification of conducting Polymer

1.10.1 Doping in Conducting Polymer

The potential usefulness of conductive polymers has been increased dramatically by discovery that their electrical conductivity could be increased by several order of magnitude of doping i.e. the addition of electron donor (n –type) such sodium or other and by addition of electron acceptor (p- type ) such iodine or other.

There are some technique are available for doping process like Chemical Doping, Electochemical Doping, Photo Doping, Iron doping etc.

Figure (1.10) some technique for Doping

1.10.2 Type of Doping

The polymer can be doped with either the electron donating or accepting molecules/group to make them either n of p type.

Figure (1.11) Type of Doping

1.11 Vinyl alcohol

Vinyl alcohol, also called ethanol (IUPAC name), is an alcohol. It is not to be confused with the drinking alcohol, ethanol. With the formula CH2CHOH, vinyl alcohol is an isomer of acetaldehyde and ethylene oxide. Under normal conditions, it converts (automatizes) to acetaldehyde:

Figure (1.12) Vinyl alcohol

1.12 Polyvinyl alcohol

Polyvinyl alcohol ( PVA) is a water soluble synthetic polymer (a popular wood glue). It has the idealized formula [CH2CH(OH)]n. It is used in paper manufacturing, textiles, and a variety of coatings. It is odorless and white (colorless). It is sometimes supplied as beads or as solutions in water.[18]

Formula: (C2H4O)x

Melting point: 230° C

Density: 1.19 g/cm³

Boiling point: 228° C

Soluble in: Water

1.12.1 Preparation

Unlike most vinyl polymers, PVA is not prepared by polymerization of the corresponding monomer. The monomer, vinyl alcohol unstable with respect to acetaldehyde. PVA instead is prepared by first polymerizing vinyl acetate, and the resulting polyvinyl acetate is converted to the PVA. Other precursor polymers are sometimes used, with format, chloroacetate groups instead of acetate. The conversion of the polyesters is usually conducted by base-catalysedtransesterification with ethanol:

[CH2CH(OAc]n + C2H5OH → [CH2CH(OH)]n + C2H5OAc

The properties of the polymer depend on the amount of residual ester groups.

1.12.2 Structure

PVA is an atactic material that exhibits crystallinity. In terms of microstructure, it is composed mainly of 1,3-diol linkages [-CH2-CH(OH)-CH2-CH(OH)-] but a few percent of 1,2-diols [-CH2-CH(OH)-CH(OH)-CH2-] occur, depending on the conditions for the polymerization of the vinyl ester precursor.[19]

Figure(1.13) Structure of Polyvinyl alcohol  Figure (1.14) PVA in powder form

1.12.3 Properties

Polyvinyl alcohol has excellent film forming, emulsifying and adhesive properties. It is also resistant to oil, grease and solvents. It has not only high tensile strength and flexibility, but also high oxygen and aroma barrier properties. However these properties are dependent on humidity, in other words, with higher humidity more water is absorbed. The water, which acts as a plasticiser, then reduce its tensile strength, but increase its elongation and tear strength.

PVA has a melting point of 230 °C and 180–190°C (356-374 degrees Fahrenheit) for the fully hydrolysed and partially hydrolysed grades, respectively. It decomposes rapidly above 200 °C as it can undergo pyrolysis at high temperatures. PVA is close to incompressible. The Poisson's ratio is between 0.42 and 0.48.

1.12.4 Use

Polyvinyl acetals: Polyvinyl acetals are prepared by reacting aldehydes with polyvinyl alcohol. Polyvinyl butyral (PVB) and polyvinyl formal (PVF) are examples of this family of polymers. They are prepared from polyvinyl alcohol by reaction with butyraldehyde and formaldehyde, respectively. In the U.S. and west Europe Polyvinyl butyral is largely used for the preparation of Polyvinyl alcohol.

Polyvinyl alcohol is used as an emulsion polymerization aid, as protective colloid, to make polyvinyl acetate dispersions. This is the biggest market application in China. In Japan its most use is vinylon fiber production.[19]

1.12.5 Safety

PVA is nontoxic. It biodegrades only slowly but up to 5% solutions are nontoxic to fish.

1.13 Thiophene

Thiophene, also commonly called thiofuran, is a heterocyclic compound with the formula C4H4S. Consisting of a flat five-membered ring, it is aromatic as indicated by its extensive substitution reactions. It containg thiophene ring fused with one and two benzene rings, respectively. Compounds analogous to thiophene include furan(C4H4O) and pyrrole (C4H4NH).

Formula: C4H4S

Boiling point: 84 °C

Density: 1.05 g/cm³

Molar mass: 84.14 g/mol

1.13.1 Isolation, occurrence

Thiophene was discovered as a contaminant in benzene.[20] It was observed that isatin forms a blue dye if it is mixed with sulfuric acid and crude benzene. Victor Meyer was able to isolate the substance responsible for this reaction from benzene. This new heterocyclic compound was thiophene.

Viktor Meyer,  (born Sept. 8, 1848, Berlin—died Aug. 8, 1897, Heidelberg, Baden), German chemist who contributed greatly to knowledge of both organic and inorganic chemistry.

1.13.2 Synthesis

Reflecting their high stabilities, thiophenes arise from many reactions involving sulfur sources and hydrocarbons, especially unsaturated ones, e.g. acetylenes and elemental sulfur, which was the first synthesis of thiophene by Viktor Meyer in the year of its discovery. Thiophene is produced on a scale of ca. 2M kg per year worldwide. Production involves the vapor phase reaction of a sulfur source, typically carbon disulfide, and butanol. These reagents are contacted with an oxide catalyst at 500–550 °C.[21]

1.13.3 Properties

At room temperature, thiophene is a colorless liquid with a mildly pleasant odor reminiscent of benzene, with which thiophene shares some similarities. The high reactivity of thiophene toward sulfonation is the basis for the separation of thiophene from benzene, which are difficult to separate by distillation due to their similar boiling points (4 °C difference at ambient pressure). Like benzene, thiophene forms an azeotrope with ethanol.

1.13.4 Reactivity

Thiophene is considered aromatic, although theoretical calculations suggest that the degree of aromaticity is less than that of benzene. The "electron pairs" on sulfur are significantly delocalized in the pi electron system. As a consequence of its aromaticity, thiophene does not exhibit the properties seen for conventional thioethers. For example the sulfur atom resists alkylation and oxidation. However, oxidation of a thiophene ring is thought to play a crucial role in the metabolic activation of various thiophene-containing drugs, such astienilic acid and the investigational anticancer drug OSI-930. In these cases oxidation can occur both at sulfur, giving a thiophene S-oxide, as well as at the 2,3-double bond, giving the thiophene 2,3-epoxide, followed by subsequent NIH shift rearrangement.[22]

1.14 Polythiophene

The polymer formed by linking thiophene through its 2,5 positions is called polythiophene. Polythiophene itself has poor processing properties. Polythiophenes become electrically conductive upon partial oxidation, i.e. they become "organic metals. The monomer repeat unit of unsubstituted polythiophene.

Figure (1.15) Structure of PTs Figure (1.16) PTs in liquid form

1.14.1 Mechanism of conductivity and doping

Electrons are delocalized along the conjugated backbones of conducting polymers, usually through overlap of π-orbitals, resulting in an extended π-system with a filled valence band. By removing electrons from the π-system ("p-doping"), or adding electrons into the π-system ("n-doping"), a charged unit called a bipolaron is formed (see Figure 1.16).

Figure (1.17) Removal of two electrons (p-doping) from a PT chain produces a bipolaron.

A variety of reagents have been used to dope PTs. Iodine and bromine produce high conductivities[23] but these regents are unstable and slowly evaporate from the material. Organic acids, including trifluoroacetic acid, propionic acid, and sulfonic acids produce PTs with lower conductivities than iodine, but with higher environmental stabilities.[24][25] Oxidative polymerization with ferric chloride can result in doping by residual catalyst,[26] although matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) studies have shown that poly(3-hexylthiophene)s are also partially halogenated by the residual oxidizing agent.[27] Poly(3-octylthiophene) dissolved in toluene can be doped by solutions of ferric chloride hexahydrate which by dissolving in acetonitrile, can be cast into films with conductivities reaching 1 S/cm.[28] Other, less common p-dopants include gold trichloride and trifluoromethanesulfonic acid.

1.14.2 Synthesis

PTs can be synthesized electrochemically, by applying a potential across a solution of the monomer to be polymerized, or chemically, using oxidants or cross-coupling catalysts. Both methods have their advantages and disadvantages.

Electrochemical synthesis

In an electrochemical polymerization, a potential is applied across a solution containing thiophene and an electrolyte, producing a conductive PT film on the anode. Electrochemical polymerization is convenient, since the polymer does not need to be isolated and purified, but it can produce polymers with undesirable alpha-beta linkages and varying degrees of regioregularity.

Figure (1.18) Initial steps in the electropolymerization of thiophenes.

Chemical synthesis

Chemical synthesis offers two advantages compared with electrochemical synthesis of PTs: a greater selection of monomers, and, using the proper catalysts, the ability to synthesize perfectly regioregular substituted PTs. While PTs may have been chemically synthesized by accident more than a century ago, the first planned chemical syntheses using metal-catalyzed polymerization of 2,5-dibromothiophene were reported by two groups independently in 1980.

The first synthesis of perfectly regioregular PATs was described by McCullough et al. in 1992. As shown in Figure1.18

Figure (1.19) Cross-coupling methods for preparing regioregular PATs

Figure (1.20) conjugated polymer -thiophene

1.15.4 Applications of Polythiophene

A number of applications have been proposed for conducting PTs, but none has been commercialized. Potential applications include field-effect transistors,[29] solar cells, nonlinear optic devices,[30] batteries, electroluminescent devices diodes, photochemical resists and chemical sensors.[31]

1.16 Applications of conducting Polymers

Chemical, Biochemical and Thermal sensors:-Conducting polymer very useful in the making of sensors due to their good chemical properties. This utilizes the ability of materials to change their electrical properties during reaction in the presence of various redox agents (dopants) or via their instability to moisture and heat. An example Gas Sensors.

Electromechanical Actuators:- Polymer based actuators are a new technology. Change in the dimension property of a conducting polymer can used for actuator functioning as change in relative polymer dimension and electrode gives result in change in volume and resultant. Doping and dedoping is quite similar as that used in rechargeable batteries. The applications are micro tweezers, microvalves and actuators[32].

Light Emitting Diodes:- conducting polymer can also be used as the light sources in displays. Burroughes et al[33] first reported a light- emitting diode(LED) based on poly (p- phenylenevinylene) (PPV) in 1990. Today, PPV and its derivatives and polythiophenes (PTPs) and polyfluorenes (PFs) are the most frequently used conjugated polymers in Light –emitting diodes(LEDs) .[34,35]

Other Applications:- some of the other applications of conducting polymer that have been proposed are: Use of conducting polymer as conductive paints, tones for reprographics, printing and as components for aircraft. Commercially available applications utilizing conductive polymer also include antistatic coating for electronic packaging and electro chromic windows.[36,37]

CHAPTER-2

LITERATURE REVIEW

Somani et al[38] Poly(vinyl alcohol) (PVA) is one of most important polymeric materials, because it has several applications in industry and is of relatively low cost in manufacture (El-Sherbiny et al. 2001). For instance, it can be used as a solid polymer electrolyte when doped with phosphoric acid in solid state electrochromic display (ECD), solid state photocells (Somani et al. 2000, Somani and Radhakrishnan 2001), or as a steric stabilizer for producing conducting polymer dispersion (Somani 2002).

The PVA solution films with different amounts of AgNO3 dopant were prepared by solution casting method. 1 g of PVA powder was added to doubly distilled water and allowed to swell for 24 h at room temperature. Silver nitrate was dissolved in redistilled water and added to the polymeric solution with continuous stirring. Then the solution was poured into flat glass plate dishes.

Homogenous films were obtained after drying in an air oven for 24 h at 40 . The thickness of the films were in the range of 20 ± 0.05 µm. The optical studies were carried out using double bean spectrometer (Shimadzu UV probe Japan) in the wavelength range (300-900) nm and infrared spectra were recorded using Shimadzu FTIR-8700 spectrometer in the wavelength range (400-3000) cm-1 with a resolution of 4 cm-1.[39,40]

The Fourier Transform Infrared spectroscopy (FTIR) spectra of pure PVA films were obtained and the results are shown in Figures 2.1

Figure 2.1 FTIR spectra of pure PVA film

In recent years, doped polymers have been a subject of considerable interest because their physical and chemical properties make them useful for specific applications.

Victor Meyer[20] was able to isolate the substance responsible for this reaction from benzene. This new heterocyclic compound was thiophene. Viktor Meyer,  (born Sept. 8, 1848, Berlin—died Aug. 8, 1897, Heidelberg, Baden), German chemist who contributed greatly to knowledge of both organic and inorganic chemistry.

Meyer studied under the analytic chemist Robert Bunsen, the organic chemist Emil Erlenmeyer, and the physicist Gustav Kirchhoff at the University of Heidelberg, where he received his Ph.D. in 1867 and where he later succeeded Bunsen (1889–97). Meyer earlier had served as professor of chemistry at the Zürich Polytechnic Institute (1872–85) and the University of Göttingen (1885–89).

Many works has been done to understand the effect of different types of doping. Work carried out in past few years on different preparation methods and different dopant given below

Ertugrul Sahmetlioglu[41] were prepared Graft copolymers of poly(vinyl alcohol) with thiophene side-groups and pyrrole were synthesized by electrochemical polymerization methods. Poly(vinyl alcohol) with thiophene side-groups (PVATh) was obtained from the reaction between poly(vinyl alcohol) (PVA) and thiophene-3-acetic acid. They also showed different morphologies in different solvents. Conducting and thermally more stable copolymers were obtained than with polypyrrole. The synthesis of copolymers of PVATh in the presence of thiophene was carried out by electrochemical polymerization of thiophene on PVATh-coated electrodes. Electrolysis was run in acetonitrile containing 0.02 mol l−1 thiophene and 0.05 mol l−1 supporting electrolyte (TBAFB) at the oxidation potential of thiophene (2.0V versus Ag/Ag+ reference electrode). The electrolyses were allowed to proceed until sufficiently thick films were obtained (ca 50 μm). After electrolysis, the anode was removed from the cell and left in dichloromethane for several hours to remove the ungrafted precursor polymer.

The FTIR spectrum of PVATh (Fig 2.2) presents the usual absorption of partially hydrolyzed poly(vinylalchol) at 3398cm−1 (OH stretching), 2931 and 2856cm−1 (CH stretching), 1415cm−1 (CH2 bending), 1322cm−1 (CH bending), 1130cm−1 (CC and CO stretching). Typical absorptions for thiophene ring are present at 3104, 841, 756cm−1.

Figure 2.2 FTIR spectra PVATh

The surface morphology of the solution side ofPVATh/PPy (PTSA or TBAFB doped) copolymers were different from thatof polypyrrole, clearly indicating the presence of a different species than for homopolymers (Fig2.3).

Figure 2.3 SEM micrographs of solution side of PVATh/PPy (PTSA)

A. K. Bajpai [42] were composites of poly(vinyl alcohol)-g-poly(acrylic acid)

hydrogels impregnated with polyaniline (PANI) and prepared within the polymer matrix

by in situ polymerization of aniline. The conversion yield of aniline into PANI particles was determined gravimetrically while structural confirmation of the synthesized polymer was sought X-ray diffraction (XRD) technique.

. In a typical experiment, 1 g PVA was dissolved in 25 ml of hot double distilled water and to this solution were added precalculated amounts of acrylic acid (43.7 mM), MBA (19.45·10–2 mM) and KPS (11.10·10–2 mM). The whole reaction mixture was homogenized and kept in a petri dish (corning glass, 2.5″ diameter) maintained at 35 ± 0.2°C for 24 h. After the reaction is over, the whole mass converted into a semi-transparent film and it was purified by equilibrating it in double distilled water for a week.

Figure 2.4 Physical appearance of PVA-g-PAA gel

Figure 2.5 PANI impregnated PVA-g-PAA gel

The XRD patterns of the prepared native and PANI impregnated gels are shown in Figures 2.6 and 2.7, respectively. Figure 8a shows a prominent peakb near 20°, which corresponds to the (101) plane of the PVA crystal. Other minor peaks around 21 and 22° could be attributed to minor crystallites of grafted polyacrylic acid chains. The diffraction patterns of PANI impregnated gel are shown in Figure 8b which not only shows a characteristic peak at 20° (due to PVA) but also depicts a prominent peak at 25°, which is a characteristic peak of PANI. Thus, the XRD-patterns of impregnated gel provides an additional evidence of PANI formation within the polymer matrix.

Figure 2.6 XRD-spectra of (a) native (PVA-g-PAA) gel

Figure 2.7 PANI impregnated gel

A comparison of the peak area of the two diffractograms clearly indicates that upon PANI impregnation, the polymer matrix looses its crystallinity as evident from the increase in broadness of the XRD spectra (b).

UV-visible analysis was also carried out on a double beam UV-VIS spectrophotometer (Systronics, 2201, Ahemdabad, India). For scanning UV-spectra, thin films of samples (native and PANI impregnated) were prepared of sizes 3×1×0.05 cm3 by solution casting method and put in to the quartz cuvette in vertical orientation.

Figure 2.8 UV-visible spectra of native (PVA-g-PAA) gel PANI impregnated gel

Fgure 2.9 UV-visible spectra of PANI impregnated gel

The UV-visible analysis of PVA-g-PAA film and PANI impregnated PVA-g-PAA film carried out in the range of 200 to 800 nm. It is observed that two characteristic peaks at 334 and at 632 in impregnated PVA-g-PAA film spectra (Figure 7b). This obviously confirms the impregnation of PANI into the gel because the emeraldine form of PANI has two characteristic at 334 and 632 nm originating from π–π* transition of benzenoid rings and the exciton absorption of the quinoid rings, respectively.

CHAPTER-3

MATERIAL AND SYNTHESIS

3.1 Laboratory Methods for the Preparation of Polymer Films

Polymer films are used for various purposes, in technological or in scientific research. In most cases it is necessary to prepare samples which are highly homogeneous, flaw-free and of uniform thickness. A relative and non-porous sheet having a nominal thickness is known as a “film”. Crystallization of polymers can be done by casting films from their dilute solution on an appropriate substratum. For establishing possible relations between the process of sample preparation and the film properties various attempts have been made.

Preparation on Solid Surfaces

In solid surfaces, dissolution or dispersion of the polymeric material in a solvent or mixture of solvents is done to prepare films. The choice of solvent is very significant. It has been recognized for some time that mechanical properties of films depend on the solvent used for casting. It has been found that the film properties are influenced by the purity of the solvent. After filtering the polymer solution under pressure or vacuum techniques, entrapped air bubbles should be removed either by letting the solution stand or by vacuum application.[43]

Planar Surfaces

Use of any solid planar surface can be made when the technique developed by Blodgett for fatty acids is employed. This technique is based on oil monomolecular film and consists of dipping the solid surface beneath a water surface covered with the film and the solid is withdrawn slowly. The molecules in the film retain the orientation they had on water. Development of mechanical devices was made to remove the film without damaging it.[44]

Metallic Plates

A metallic plate is adequate as a support, whenever heat transmission is an important factor in the preparation of a polymer film. Polymers that need cure by heat treatment, such as some polyurethane, may be cast on iron plates.[45]

Plastic Plates

The films that demand curing at a reasonably high temperature, Teflon surfaces are used for their preparation, because of its inertness and heat and solvent resistance. [46]

Preparation on Liquid Surfaces

Among the benefits of a liquid surface as a support for film formation are its suitability for very adherent films and the lack of defects and imperfections due to irregular solid surfaces as well as absence of leveling problems. It is specially recommended for very thin films.

Spin or centrifugal casting

It is a convenient technique for the preparation of thin films. A cylindrical mold has been used for elastomer solutions or latexes, for thermoplastic melts, and for thermo set resins, in which case casting and curing are achieved simultaneously. [47,48]

We have chosen a solution cast technique method, out of several methods of preparation that has been used; it is relatively unsophisticated, so that sample preparation using this method is manageable within our own lab. Out of several method of preparation that have been used, we have choose a solution cast technique method is relatively unsophisticated, so that sample preparation using this method is manageable within our own lab.

Advantages of solution cast technique are as follows

No requirement for sophisticated instruments

Minimum material waste

Economical way of large area deposition

No need of handling poisonous gases likeH2Se or Se vapour

Possibility of room temperature deposition

3.2 Laboratory Preparation Details

This chapter describes the preparation of film PVAand PTs along with the details of various characterization carried out. Study of structural and morphological properties, along with the thermal characterization of films is of immense importance, which generally affects their mechanical and electrical properties. In this chapter studies related to FT-IR, XRD, SEM and UV-Visible technique nave been discussed. TGA study helps to determine thermal stability of films. FT-IR response helps to analyze and identify the chemical functional groups in the films. XRD provides the information regarding crystalline and amorphous regions in the film. SEM micrograph visualizes the phase morphology of the films.

Chemical used

3.2.1 Glutaraldehyde

Glutaraldehyde is an organic compound with the formula CH2(CH2CHO)2. A pungent colorless oily liquid, glutaraldehyde is used to disinfect medical and dental equipment. It is also used for industrial water treatment and as a preservative. It is mainly available as an aqueous solution, and in these solutions the aldehyde groups are hydrated.[49]

Structure

Figure 3.1 Structure of Glutaraldehyde

Uses

Fixative

A glutaraldehyde solution of 0.1% to 1.0% concentration may be used for system disinfection and as a preservative for long term storage. Glutaraldehyde is used in biological electron microscopy as a fixative.

Biochemical reagent

Glutaraldehyde is frequently used in biochemistry applications as an amine-reactive homobifunctionalcrosslinker. The oligomeric state of proteins can be examined through this application.

Safety

As a strong disinfectant, glutaraldehyde is toxic and a strong irritant. There is no evidence of carcinogenic activity.[50]

3.2.2 Chloroform

Introduction

Chloroform is an organic compound with formula CHCl3. It is one of the four chloromethanes.[38] The colorless, sweet-smelling, dense liquid is a trihalomethane, and is considered somewhat hazardous. Several million tons are produced annually as a precursor to PTFE and refrigerants, but its use for refrigerants is being phased out.

Occurrence

Chloroform has a multitude of natural sources, both biogenic and abiotic. It is estimated that over 90% of atmospheric chloroform is of natural origin.[51]

Industrial routes

In industry, chloroform is produced by heating a mixture of chlorine and either chloromethane or methane. At 400–500 °C, afree radical halogenation occurs, converting these precursors to progressively more chlorinated compounds:

CH4 + Cl2 → CH3Cl + HCl

CH3Cl + Cl2 → CH2Cl2 + HCl

CH2Cl2 + Cl2 → CHCl3 + HCl

Chloroform undergoes further chlorination to yield carbon tetrachloride (CCl4):

CHCl3 + Cl2 → CCl4 + HCl

The output of this process is a mixture of the four chloromethanes (chloromethane, dichloromethane, chloroform, and carbon tetrachloride), which can then be separated by distillation.

Uses

The major use of chloroform today is in the production of the chlorodifluoromethane, a major precursor to tetrafluoroethylene:

CHCl3 + 2 HF → CHClF2 + 2 HCl

The reaction is conducted in the presence of a catalytic amount of antimony pentafluoride. Chlorodifluoromethane is then converted into tetrafluoroethylene, the main precursor to Teflon. Before the Montreal Protocol, chlorodifluoromethane (designated as R-22) was also a popular refrigerant.

Chloroform is a common solvent in the laboratory because it is relatively unreactive, miscible with most organic liquids, not flammable and conveniently volatile. Chloroform is used as a solvent in the pharmaceutical industry and for producing dyes and pesticides. Chloroform is an effective solvent for alkaloids in their base form and thus plant material is commonly extracted with chloroform for pharmaceutical processing. For example, it is used in commerce to extract morphine from poppies and scopolamine from  Datura plants.

Safety

A fatal oral dose of chloroform may be as small as 10 ml (14.8 g), with death due to respiratory or cardiac arrest.

Animal studies have shown that miscarriages occur in rats and mice that have breathed air containing 30 to 300 ppm of chloroform during pregnancy and also in rats that have ingested chloroform during pregnancy. Offspring of rats and mice that breathed chloroform during pregnancy have a higher incidence of birth defects, and abnormal sperm have been found in male mice that have breathed air containing 400 ppm chloroform for a few days. The effect of chloroform on reproduction in humans is unknown.

Chloroform once appeared in toothpastes, cough syrups, ointments, and other pharmaceuticals, but it has been banned as a consumer product in the US since 1976. Cough syrups containing chloroform can still be legally purchased in pharmacies and supermarkets in the UK.

Figure 3.2 Chloroform in liquid form Figure 3.3 Structure of Chloroform

Advantages

The sampling procedure is convenient. The analytical procedure is quick sensitive and reproducible. Reanalysis of the samples is possible.

Disadvantages 
If other compounds are present, the GC run time must be lengthened so the late eluting peaks will not interfere with the next sample.

3.2.3 Iron(III) chloride

Introduction

Iron(III) chloride, also called ferric chloride, is an industrial scale commodity chemical compound, with the formula FeCl3. Iron(III) chloride, also called ferric chloride, is an indurstrial scale commodity chemical compound, with the formulaFeCl3. The colour of iron(III) chloride crystals depends on the viewing angle: by reflected light the crystals appear dark green, but by transmitted light they appear purple-red. Anhydrous iron(III) chloride is deliquescent, forming hydrated hydrogen chloride mists in moist air. It is rarely observed in its natural form, mineral molysite, known mainly from some fumaroles.

Properties

Structure and properties

Anhydrous iron(III) chloride adopts the BiI3 structure, which features octahedral Fe(III) centers interconnected by two-coordinate chloride ligands. Iron(III) chloride hexahydrate consists of trans-[Fe(H2O)4Cl2]+ cationic complexes and chloride anions, with the remaining two H2O molecules embedded within the monoclinic crystal structure.

Iron(III) chloride has a relatively low melting point and boils at around 315 °C. The vapour consists of the dimer Fe2Cl6 (c.f. aluminum chloride) which increasingly dissociates into the monomeric FeCl3 (D3h point group molecular symmetry) at higher temperature, in competition with its reversible decomposition to give iron(II) chloride and chlorine gas.

Uses

Industrial

In industrial application, iron(III) chloride is used in sewage treatment and drinking water production. In this application, FeCl3 in slightly basic water reacts with the hydroxide ion to form a floc of iron(III) hydroxide, or more precisely formulated as FeO(OH)−, that can remove suspended materials.

[Fe(H2O)6]3+ + 4 HO− → [Fe(H2O)2(HO)4]− + 4 H2O → [Fe(H2O)O(HO)2]− + 6 H2O

It is also used as a leaching agent in chloride hydrometallurgy,  for example in the production of Si from FeSi.

Other uses

Used to detect the presence of phenol compounds in organic synthesis e.g.: examining purity of synthesized Aspirin.

Used in water and wastewater treatment to precipitate phosphate as iron (III) phosphate.

Used to make printed circuit boards (PCBs).

Disadvantages

Iron(III) chloride is toxic, highly corrosive and acidic. The anhydrous material is a powerful dehydrating agent.

Although reports of poisoning in humans are rare, ingestion of ferric chloride can result in serious morbidity and mortality. Inappropriate labeling and storage lead to accidental swallowing or misdiagnosis. Early diagnosis is important, especially in seriously poisoned patients.

3.2.4 Ammonium persulfate

Ammonium persulfate (APS) (NH4)2S2O8 is a strong oxidizing agent. It is very soluble in water; the dissolution of the salt in water is endothermic. When APS dissolves in water, it is broken down into ammonia and peroxydisulfuric acid. It is a radical initiator. It is used to etch copper on printed circuit boards as an alternative to ferric chloride solution. It is also used along withtetramethylethylenediamine to catalyze the polymerization of acrylamide in making a polyacrylamide gel. In addition, a high ammonium persulfate solution can be used to leach copper from chalcopyrite under high pressure conditions.  Ammonium persulfate was prepared by H. Marshall by the method used for the preparation of potassium persulfate – by the electrolysis of a solution of ammonium sulfate and sulfuric acid.

Figure 3.4 Structure of APS

Figure 3.5 APS in powder form

Ammonium persulfate is the main component of Nochromix. On dissolving in sulfuric acid, it is used to clean laboratory glassware as a metal-free alternative to chromic acid baths.  It is also a standard ingredient in western blot gels and hair bleach.

Properties

Safety

Airborne dust may be irritating to nose, eye,  throat, lung and skin upon contact. Exposure to high levels of dust may cause difficulty in breathing.

Advantages & Disadvantages of Persulfate

Persulfate technically refers to any sulfate (or crystalized form of sulfuric acid) that has more oxygen than a normal sulfate molecule. Generally, these are formed with two oxygen atoms taking the place of one within the molecule. More generally, persulfate refers to two compounds commonly used in cleaning products and manufacturing: sodium persulfate and ammonium persulfate.

3.3 Preparation of films

For preparation of films, for sample-1 is pure PVA and sample-2 and sample-3 commercially available) Polyvinyl alcohol  (HiMedia Laboratories, India) granular;Polythiophene (PT) (HiMedia Laboratories, India); Dimethylformamide (DMF) (HiMedia Laboratories, India); are used.

Materials and methods materials

Pure PVA film (Sample -1)

PVA with molecular weight of 10000 g/mol (BDH chemicals England) was used as the basic polymeric materials in this work. The PVA solution films with glutaraldehyde (GA) (25% aqueous solution) were prepared by solution casting method. 1 g of PVA powder was added to doubly distilled water and allowed to swell for 24 h at room temperature.

The polymeric solution are continuous stirring in magnetic stirrer. Then the solution was poured into flat glass plate dishes. Homogenous films were obtained after drying in an air oven for 24 h at 60. The thickness of the films were in the range of 20 ± 0.05 m.

Images(2) shows the image of films. Synthesis facility is utilised in Nanotechnology lab Gyan Ganga College of Technology, Jabalpur, M.P, INDIA.

Photograph 1: Stirring of solution on Magnetic Stirrer

Photograph 2: Thin films of Pure PVA

Polythiophene doped PVA thin film (sample -2)

Synthesis of PTh :-Two milliliter of thiophene was taken in a titration flask containing 70 ml CHCl3. 9.0 grams of FeCl3 was weighed and 180 ml CHCl3 was added to this. This solution was stirred using magnetic stirrer and added to the solution of thiophene in CHCl3. To this whole PVA thin film was added in the ratio of (1:2). The whole reaction mixture was homogenized and kept in a petri dish (corning glass, 2.5″ diameter) maintained at 35 ± 0.2°C for 24 h.

Photograph 3: Solution is cast on polythiophene doping PVA thin film

After the reaction is over, the whole mass converted into a semi-transparent film and it was purified by equilibrating it in double distilled water. The thin film was dried at room temperature, cut into rectangular size piece and stored in airtight plastic bags.

Photograph 4: Semi-transparent film

Ammonium persulfate (APS, 8.20 g) was dissolved in 20 mL deionized water. Then the ammonium persulfate solution was added dip into the rectangular size piece semi-transparent film. The mixture was heated without stirring( oven) for 5h at 70℃. Thereafter the oven switched off and allowed to cool at the room temperature. The resulting thin film was collected by filtration or centrifugation. It was washed by deionized water and then freeze-dried for 24 h. As the polymerization progresses, the semi-transparent film turns into light brown, which can be isolated by filtration. During the course of the reaction, the film changed from dark brown. The specimen obtained of having thickness of .02mm. Synthesis facility is utilized in Nanotechnology laboratory Gyan Ganga College of Technology, Jabalpur, M.P, INDIA. Figure (3.3) shows the images of thin films.

Photograph 5: Films of PTs doped PVA(sample 2)

Photograph 6: Films of PTs doped PVA (APS solution dip sample 2)

Flow chart of Synthesis of Thin film by solutions cast technique

CHAPTER-4

CHAPTER-4

CHARACTERIZATION

4.1 FT-IR (Fourier Transform Infrared Spectrometry)

To identify the chemical functional groups present and the miscibility of the polymers in film. FTIR considered to be a powerful tool and potentially very widely applicable method.

Introduction

Fourier transform spectroscopy is a measurement technique whereby spectra are collected based on measurements of the coherence of a radiative source, using time-domain or space-domain measurements of the electromagnetic radiation or other type of radiation. Fourier Transform Infrared Spectrometry (FT-IR) has been used to study the phase domain structural features of the pure and composite films. FT-IR spectrometry also helps in understanding the structure property relationship in polymers.

In FT-IR, sample is exposed to high energy electromagnetic radiation and the response is monitored .The energy of the radiation is varied over the desire range and the response is plotted as a radiation will be function of radiation energy for frequency. At certain resonant frequency, characteristics of the specific sample, the radiation will be absorbed resulting in series of peaks in the spectrum, which can then be used to identify the sample.

Figure 4.1 Fourier Transform Infrared Spectrometry (FT-IR)

Instrumental and experimental details

Image-1: FTIR, RDVV,Jabalpur(M.P.)

The Fourier Transform Infrared Spectrum (FT-IR) of films are obtained using Bruker Tensor 27 Scan Range-500-4000nm.This facility are provided by IIT, Indore, M.P, INDIA. FT-IR applications are based on the correlation between IR frequency and chemical functional group. IR group frequencies may vary considerably for a given functional group (e.g. costretch frequency can vary from 1100cm-1 to 2300cm-1). Thus, group frequency can be useful aid in identifying an unknown compound (by comparison to the same group frequency in a molecule of closely related structure).

Fig. 4.2 FTIR spectra of pure PVA thin films.

Table 1. The different parameters of Fourier transform spectroscopy of used for the FTIR analysis of PVA thin film

Fig. 4.3 FTIR spectra of polythiophene doped PVA thin film

Table 1. The different parameters of Fourier transform spectroscopy of used for the FTIR analysis of Polythiophene doped PVA thin film

The Fourier Transform Infrared spectroscopy (FTIR) spectra of pure and polythiophene doped PVA films were obtained and the results are shown in Figures 2-3. The spectra show a strong broad absorbance at 3670 cm-1 for pure PVA and 3657 cm-1 for 2 % polythiophene doped PVA. This band could be assigned to O-H stretching vibration of hydroxyl group of PVA, the band corresponding to C-H asymmetric stretching vibration occurs at 2960 cm-1 and 2949 cm-1 for the doped PVA. The band at 1753 cm-1 corresponds to C=C stretching vibration and remains the same for 2% dopant and shifted toward 1761 cm-1.[52]

Absorbance at 1556 cm-1 corresponds to an acetyl C=O group, which could be explained on the basis of intra/inter molecular hydrogen bonding with the adjacent OH group. The sharp band 858 cm-1 corresponds to C-O stretching of acetyl groups present on the PVA backbone that remains the approx. same for all the doped and undoped samples.

The corresponding bending, wagging of CH2 vibrations are at 1386 and1338 cm-1 respectively Selim et al. 2005, Shin et al. 2004, Dai et al. 2002). The shift in the corresponding bands with doping indicates that there is an interaction between PVA and polythiophene.

3.4 XRD (X-ray diffraction)

The experimental method and results of XRD study carried out on films sample-1 and sample-2 are discussed in this section. X-ray diffraction (XRD) has been utilised to detect change in crystalline and amorphous characteristics in the films. A brief account of XRD study, its application area, calculation of crystallite size, plane and other concept related to the present investigation are also presented.

3.4.1 Introduction

X-ray diffraction is based on constructive interference of monochromatic X-rays and a crystalline sample. These X-rays are generated by a cathode ray tube, filtered to produce monochromatic radiation, collimated to concentrate, and directed toward the sample. The interaction of the incident rays with the sample produces constructive interference (and a diffracted ray) when conditions satisfy Bragg's Law (nλ=2d sin θ). This law relates the wavelength of electromagnetic radiation to the diffraction angle and the lattice spacing in a crystalline sample. These diffracted X-rays are then detected, processed and counted. By scanning the sample through a range of 2θangles, all possible diffraction directions of the lattice should be attained due to the random orientation of the powdered material. Conversion of the diffraction peaks to d-spacings allows identification of the mineral because each mineral has a set of unique d-spacings. Typically, this is achieved by comparison of d-spacings with standard reference patterns. All diffraction methods are based on generation of X-rays in an X-ray tube. These X-rays are directed at the sample, and the diffracted rays are collected. A key component of all diffraction is the angle between the incident and diffracted rays.

Figure 4.4 X-ray diffraction[52]

Production of X-Ray

A cathode ray tube generates these X-rays, are then pre-colated to produce monochromatic radiation, accumulated to concentrate, and directed toward the sample.[52]

Figure 4.2 Sealed-0ff filament X-Ray tube [52]

Constructive interference (and a diffracted ray) is produced when the interaction of the incident rays with the sample occurred. The lattice spacing in a crystalline sample and the wavelength of electromagnetic radiation to the diffraction angle were related by Bragg's law. Detection, Processing and Counting of these diffracted X-rays are the next step. The sample is investigated by the range of 2θangles. Identification of the mineral is allowed by conversion of the diffraction peaks to d-spacing. Usually, Correlation of d-spacing with standard reference patterns is achieved by this. Then the diffracted rays are collected when the X-rays are directed at the sample. The angle between the incident and diffracted rays are the key part of all diffraction.

Figure 4.5 Bragg’s diffraction [52]

The nano crystalline particle size of sample-1 and sample-2 ablated by using the infinite three dimensional crystal lattice defect X-ray in a manner analogous to the reflection of visual light from a ruled grating when the particle size is the of order of the wavelength of the incident beam. The diffraction beam becomes diffused as crystallite size decreases; the diffraction beam becomes more and more diffused until it is lost in the general background as for amorphous material. Thus the width of X-ray diffraction line is able to give crystallite size. The relationship between crystallite size and diffraction ray line broadening is given by Scherrer equation 1:

(1)

Where (K) is constant which depends upon the crystalline and diffractometer set up, (λ) is wavelength of monochromatic radiation, (β) is full width at half maxima [FWHM], (θ) is the Braggs diffraction angle. The value of K = 0.9 and, λ = 1.514 Å which are equipment parameters and the value of β and θ can be obtained from the diffraction pattern.

3.4.2 Instrumental and experimental details

Images-6. XRD, IISER, Bhopal (M.P.)

X-ray diffraction (XRD) has been utilized to detect changes in crystalline and amorphous regions in the films sample-1, sample-2. Specimens were kept in aluminum sample holder in such a way that upper smooth surface was exposed to X-rays in vertical goniometry assembly. The XRD facility are provided by CIF (Central instrumentation facility) IISER, Bhopal (M.P.), India.

The pure PVA showed a characteristic peak for an orthorhombic lattice centered at 2θ, 20o C indicating a semi crystalline nature (Fig.7). Peaks at 11 and 20 were due to PVA. The amorphous nature of the PVA thin films doped with Polythiophene were investigated by XRD analysis using Smart Lab x-ray diffractometer having Cu-Kα source (1.54 Ang.).

The various specification and optimized experimental parameters of XRD system used to have the x-ray diffraction of PVA films have been tabulated in table. The amorphous characteristics of the PVA membrane is found to be three discernible peaks at 2θ~ (8.557965(14)) 0, (20.010965(16)) 0 respectively that have been clearly observed in (Fig.4.6) respectively.

Table 2: The Peak analysis of pure PVA film and Polythiophene doped PVA film

It is verified by means of XRD that the polymer possessed amorphous characteristics i.e. particle not present because the XRD pattern of film has only one peak around diffraction angle.

Fig. 4.6 XRD-spectra of pure PVA thin films.

Figure 4.7 XRD spectra of Polythiophene doped PVA thin films.

3.5 SEM (Scanning Electron Microscopy)

In recent years attention has been focused on mixtures of polymers having different properties and chemical structures to form polymers film. Many of the special properties of polymers can be explained in terms of their size (how this long chain interact with each other) and their morphological aspects. Addition of new material in polymers helps to study the changes in surface morphology of the polymer film and look effect of percentage doping.

3.6.1 Introduction

Scanning Electron Microscopy (SEM) micrographs help to study the complete chain formation with texture and other features of developed nano-domain structures, in the pure and composites. Study of polymer under the SEM can thus yield useful data on the surface morphology and phase distribution within a film, which helps in predicting the final properties of the film.

3.6.2 Instrument and experimental details

Image 3. SEM , IIITDM, Jabalpur(M.P.)

SEM is an instrument that uses electron rather than light to form an image. There are many advantages of using the SEM instead of alight microscope. The SEM has a large field of view, which allows a large amount of the sample to be in focus in one time. The SEM also provides images of high resolution which means that closely spaced features can be examined at a high magnification. Preparation of the sample is relatively easy since most SEM only require the sample to be conductive. The combination of higher magnification, larger depth of focus, greater resolution and ease of sample observation makes the SEM one of the most heavily used instrument in research areas today.[49]

The micrographs of the prepared film are recorded on a electron microscope (Carl Zesis -Supra 55) instrument, which are fully computerised. This facility is provided by CNSNT (Centre of Nano-science and Nanotechnology IIITDM, Jabalpur(M.P.), INDIA.

The surface morphology of the solution side of PVA thin film showed microstructures

The SEM images of PVA and the composite PVAThs were shown in the images (fig. 4.8,4.9) respectively. The SEM visualizes the presence of small ratio of secondary phase (PThs) which was randomly distributed and get adhered on PVA matrix.

Figure 4.8 SEM image of PVA

Figure 4.9 SEM image of Polythiophene doped PVA thin film

It is clear from the image (4.8) that the surface of the native gel is quite homogeneous and shows no cracks, voids or unevenness. This suggests that after grafting of polyacrylic acid chains onto PVA backbone, the matrix remains homogeneous in composition. However, side group polythiophene into the matrix develops heterogeneity in the matrix as evident from the SEM image (4.9). It is clear from the image (4.9) that polythiophene molecules form clusters like morphology varying in the sizes 0.5 to 2 μm.

spectroscopy has been utilised to study the absorption from ground to excited state which gives the optical characteristics.

3.6 UV (Ultraviolet) spectroscopy

3.7.1 Introduction

Ultraviolet spectroscopy has been used to study the absorption, measures transition from the ground state to excited state. In this, sample is exposed to the light in the visible and adjacent (near-UV and near-infrared (NIR)) ranges and the response is monitored. The absorption or reflectance in the visible range directly affects the perceived colour of the chemicals involved. In this region of the electromagnetic spectrum, molecules undergo electronic transitions.

Molecules containing π-electrons or non-bonding electrons (n-electrons) can absorb the energy in the form of ultraviolet or visible light to excite these electrons to higher anti-bonding molecular orbitals. The more easily excited the electrons (i.e. lower energy gap between the HOMO and the LUMO), the longer the wavelength of light it can absorb. Organic compounds, especially those with a high degree of conjugation, also absorb light in the UV or visible regions of the electromagnetic spectrum. The solvents for these determinations are often water for water-soluble compounds, or ethanol for organic-soluble compounds. (Organic solvents may have significant UV absorption; not all solvents are suitable for use in UV spectroscopy. Ethanol absorbs very weakly at most wavelengths.

“Typical” UV-VIS instrument

3.7.2 Instrumental and experimental detail

Image -6 UV SPECTROSCOPY, RDVV,Jabalpur(M.P.)

UV absorption of film sample-1 and sample-2 are obtained by UV-Spectroscopy Instrument name-Cary Varian. This facility is provided by, RDVV, Jabalpur(M.P.), INDIA. This technique is completely for absorption, measures transition from the ground state to the excited state using the wavelength of detection 200-800 nm and the methanol solvent for determination is used. Thus, thus the absorption peak can be studied with respect to wavelength. Absorption spectroscopy is a technique wherein the absorption of electromagnetic wave is measured as a function of the frequency or wavelength. The absorption process induces an interaction between electromagnetism and the sample, which can be interpreted through variations in the absorption spectra. An absorption spectrum is a fingerprint of a molecule or polymer material. UV-visabsorption is a commonly used analytical tool for studying the interactions between electrons and radiation. On the other hand, infrared absorption is widely used to analyze the interactions between the vibration energy of bonds and electromagnetic waves.

Literature on the instrumentation and technical aspects of absorption spectroscopy is extensive .We conclude that there are four basic components, namely, the light source, monochromator, sample holder, and optical detector. In general, optical absorption spectrophotometer uses either a single or double beam.[53]Figure(4.10) shows the simplest single beam which is easy to utilize and compactible. It consists of the four basic components of absorption spectroscopy.

Figure 4.10 Single channel UV-vis spectrophotometers[53]

UV radiation interacts with matter which causes electronic transition (promotion of electrons from the low energy state to high energy state) UV region falls in the range between (190-390nm). For the determination of concentrations of an absorbing species in solution this method is frequently used, using the Beer- Lambert law: log10(Io/I) Where A is the measured absorbance, in Absorbance Units (AU). UV absorption spectra of pure PVA are found wavelength 215 nm and absorption 3.4578 are shown in Figure (4.11). UV absorption spectra Polythiophene doped PVA film for sample-2 are shown in Figure(4.12).

No absorption in the range 316-500 nm was observed for the undoped PVA films but as the doping percentage increase, the absorbance was also increased showing a broad peak appeared at 325 nm.The absorption coefficient can be represented by the Tauc model as (Zong et al. 2006):

(αhυ) = B (hυ – Eg)r…………….(1)

Where α is the absorption coefficient his the photon energy, Eg is the optical energy gap, Β a constant known as the disorder parameter which is nearly independent of the photon energy and r is the parameter measuring type of transition.

If r = 2 or 3 the transition is indirect allowed and forbidden, so in order to get the property of the band we need to test the above transition where could be found that r=3 fitted with our results. Fig. (4.13) shows the absorption coefficient (αhυ)1/3 plots of PVA and Polythiophene doped PVA films as a function of the photon energy (hυ). The optical band gap is determined through extrapolating the linear portion to αhυ= 0. As can be seen from Fig. (4.13) and the doped films show a red shift behavior.

The UV visible spectra of the films are presented in sample-1 and sample -2 in table 3.

Table 3: Absorption and Wavelength of Sample-1 and Sample-2.

Figure 4.11 UV-visible spectrum of Pure PVA sample-1

Figure 4.12 UV-visible spectrum of Polythiophene doped PVA film (sample-2)

Figure 4.13 Absorptance versus wavelength for pure PVA (samples-1), Polythiophene doped PVA (sample-2)

The UV-Vis spectroscopy valuable and simple method for quantative- analysis is offered by Beer-Lambert- law. The UV spectroscopy is widely used in determining equilibrium constant, rate constant, acid base dissociation constant etc. for chemical reactions. The UV-Vis spectroscopy has many applications in the pharmaceutical and drugs industry. The use of UV-Vis spectroscopy in evolution of enzymatic assays has become very common.

CHAPTER-5

CHAPTER-5

RESULTS AND DISCUSSION

A easier and more efficient methodology for the synthesis of films by Solution Cast technique, where polythiophene doped PVA thin film keeping PVA constant and increasing the concentration of polythiopene of two different ratios. To develop films of PVA film ratio of polythiophene by Solution Cast Technique and carried out detail studies through different characterization and effects. Like structural and morphological characterization studied through FTIR, SEM. Films obtained in the form of .01mm thickness. The FTIR, XRD and SEM studies enables to understand the issues related to the processing and structure properties relationship for polymer PVA and polythiophene This issue induced the relationship between crystallization, particle size analysis and nano-domain structure.

FT-IR (Fourier Transform Infrared Spectrometry)

The Fourier Transform Infrared spectroscopy (FTIR) spectra of pure and polythiophene doped PVA films were obtained and the results are shown in Figures 1-3. The spectra show a strong broad absorbance at 3670 cm-1 for pure PVA and 3657 cm-1 for 2 % polythiophene doped PVA. This band could be assigned to O-H stretching vibration of hydroxyl group of PVA, the band corresponding to C-H asymmetric stretching vibration occurs at 2960 cm-1 and 2949 cm-1 for the doped PVA. The band at 1753 cm-1 corresponds to C=C stretching vibration and remains the same for 2% dopant and shifted toward 1761 cm-1

Fig. 1. FTIR spectra of pure PVA thin films.

Fig. 2. FTIR spectra of polythiophene doped PVA thin film

The Fourier Transform Infrared spectroscopy (FTIR) spectra of pure and polythiophene doped PVA films were obtained and the results are shown in Figures 1-2. The spectra show a strong broad absorbance at 3670 cm-1 for pure PVA and 3657 cm-1 for 2 % polythiophene doped PVA. This band could be assigned to O-H stretching vibration of hydroxyl group of PVA, the band corresponding to C-H asymmetric stretching vibration occurs at 2960 cm-1 and 2949 cm-1 for the doped PVA. The band at 1753 cm-1 corresponds to C=C stretching vibration and remains the same for 2% dopant and shifted toward 1761 cm-1 .

Absorbance at 1558 cm-1 corresponds to an acetyl C=O group, which could be explained on the basis of intra/inter molecular hydrogen bonding with the adjacent OH group. The sharp band 856 cm-1 corresponds to C-O stretching of acetyl groups present on the PVA backbone that remains the approx. same for all the doped and undoped samples..

5.1.2 XRD (X-ray diffraction)

The amourphous characteristics of the PMMA thin films doped with RH-B were investigated by XRD. The various specification and optimized experimental parameters of XRD system used to have the x-ray diffraction of PVA films have been tabulated in table. The amorphous characteristics of the PVA membrane is found to be three discernible peaks at 2θ~ (8.557965(14)) 0, (20.01096514)) 0 respectively that have been clearly observed in (Fig.8) respectively.

Fig. 3. XRD-spectra of pure PVA thin films.

Fig. 4. XRD spectra of Polythiophene doped PVA thin films

SEM (Scanning Electron Microscopy)

The combination of higher magnification, larger depth of focus, greater resolution and ease of sample observation makes the SEM one of the most heavily used instrument in research areas today.

The surface morphology of the solution side of PVA thin film showed microstructures

The SEM images of PVA and the composite PVAThs were shown in the images 4,5 respectively. The SEM visualizes the presence of small ratio of secondary phase (PThs) which was randomly distributed and get adhered on PVA matrix.

Figure 5. SEM image of PVA

Figure 6. SEM image of Polythiophene doped PVA thin film

It is clear from the image (fig.5) that the surface is quite homogeneous and shows no cracks, voids or unevenness. This suggests that after grafting of polyacrylic acid chains onto PVA backbone, the matrix remains homogeneous in composition. However, side group polythiophene into the matrix develops heterogeneity in the matrix as evident from the SEM image (fig.6). It is clear from the image (fig.6) that polythiophene molecules form clusters like morphology varying in the sizes 0.5 to 2 μm.

UV (Ultraviolet) spectroscopy

UV absorption of film sample-1 and sample-2 are obtained by UV-Spectroscopy Instrument provided by, RDVV, Jabalpur(M.P.), INDIA. Where A is the measured absorbance, in Absorbance Units (AU). UV absorption spectra of pure PVA are found wavelength 215 nm and absorption 3.4578 are shown in Figure(8). UV absorption spectra Polythiophene doped PVA film for sample-2 are shown in Figure(8). No absorption in the range 316-500 nm was observed for the undoped PVA films but as the doping percentage increase, the absorbance was also increased showing a broad peak appeared at 325 nm. It is observed that two characteristic peaks at 215 and at 405 in Polythiophene doped PVA film spectra.

Figure 7. Absorptance versus wavelength for pure PVA (samples-1), Polythiophene doped PVA (sample-2)

5.2 Conclusion

polythiophene into poly(vinyl alcohol) results in a composite which shows fair electroconductive and electroactive behaviors. The FTIR spectra of polythiophene show characteristic peaks of polythiophene and other functional groups of constituent polymers, i. e., PVA and PThs. The Fourier Transform Infrared spectroscopy (FTIR) spectra of pure and polythiophene doped PVA films were obtained and the results are shown in Figures 1-3. The spectra show a strong broad absorbance at 3670 cm-1 for pure PVA and 3657 cm-1 for 2 % polythiophene doped PVA. The polythiophene within the polymer matrix brings about a loss in crystallinity as confirmed by the XRD spectra of the native. The composite shows cluster like morphology varying in size between 0.5 to 2.0μm. The amorphous characteristics of the PVA membrane is found to be two discernible peaks at 2θ~ (8.557965(14)) 0, (20.01096514)) 0 respectively that have been clearly observe SEM micrographs report the size and shape of the developed cluster micro and nano domain structure of PThs on the PVA which mainly affects the electrical and optical properties of the polymer films. The polythiophene particles show a wide variation in their sizes ranging from 1 to 100 μm. The UV-Vis spectroscopy valuable and simple method for quantative- analysis is offered by Beer-Lambert- law. It is noticed that with increasing PVA, APS concentration, the amount of polythiophene increases up to a certain range and thereafter decreases.

5.3 Future scope

We know that nanostructures and nanomaterial’s have high surface area. Conducting polymer very useful in the making of sensors due to their good chemical properties. An example Gas Sensors.

In this dissertation work, the developed specimens with varying concentration of PThs on the PVA and studied the structural, morphological, optical properties. Further we want to prepare these method by other method like Spin or centrifugal casting.

This unique combination of properties has given these polymers a wide range of applications in the microelectronics industry, including battery technology, photovoltaic devices, light emitting diodes, and electro-chromic displays and more recently in the biological field.

These unique characteristics are useful in many biomedical applications, such as

Light –emitting diodes (LEDs) .

Biosensors

Neural probes

Drug-delivery devices

Bio-actuators