Chapter - II Synthesis and Characterization of

Polyaniline-Polyvinyl Alcohol-Silver Nanocomposite (PANI-PVA-Ag NC)

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2.1 INTRODUCTION:

Polyaniline (PANI) is a conducting polymer of the semi-flexible rod polymer

family. Although it was discovered over 150 years ago, only recently has polyaniline

captured the attention of the scientific community due to the discovery of its high

electrical conductivity. Amongst the family of conducting polymers, polyaniline is

unique due to its ease of synthesis, environmental stability, and acid/base

doping/dedoping chemistry [1]. However, two major shortcomings of conductive

form of polyaniline are difficult to process, since it is insoluble in common organic

solvents and unstable at melt processing temperatures, that has restricted its

applications and its poor mechanical properties. The shortcomings can be overcome

by preparing polyaniline blends and composites that possess the mechanical

properties of the insulating host matrix and the electrical properties of the

conducting polyaniline. When the host is a polymer, the resulting system is known

as a polymer blend (or polymer composite), but when the host is a non-polymer

material (e.g. metal oxides, silica), it is invariably known as a composite.

The inorganic-organic composite materials are increasingly significant due to

their extraordinary properties. There are several methods to synthesize these

materials, but the most well-known method is the incorporation of inorganic

building blocks in organic polymer matrix. The inorganic-organic composite

materials have received much interest due to the remarkable change in properties

such as mechanical [2], thermal [3-6], electrical [7] and magnetic [8] as compared to

pure organic polymers due to the presence of inorganic moieties in the nano scale.

The applications of metal nanoparticles, usually ranging from 1 to 100 nanometers

(nm), have received considerable interest in the advancement of recent research in

both scientific and technological areas due to their distinctive and unusual physico-

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chemical properties compared with that of bulk materials [9,10]. The synthesis of

metal nanoparticles has received much attention because of their electronic, optical,

magnetic and catalytic properties, which depend on their size and shape [11, 12].

Metal nanoparticles are mainly interesting because they can easily be synthesized

and tailored chemically as well as can suitably be used for device fabrication

[13-16]. The unique properties of nanoparticles are due to the increase in the ratio of

the surface area to volume, and the size of the particles. However, for application in

the field of optoelectronics and electronics, the controlled particle size and their

uniform distribution within the polymer matrix is the key to technology, based on

the nanoparticles in polymers. Moreover, metal nanoparticles show surface plasmon

resonance (SPR) absorption in the UV-visible region. The SPR peak arises as a

result of the combined oscillation of free electrons of the metal nanoparticles in

resonance with the frequency of the light wave that interacts with the metal

nanoparticles due to the small particle size [17]. Basically, SPR absorption peak

occurs in metal nanoparticles only. Hence, the existence of SPR peak is the primary

indication of metal nanoparticles formation. Among the various metal nanoparticles,

noble metal nanoparticles have drawn much attention, due to their superior physical

and chemical properties. Nanoparticles may provide solutions to technological and

environmental challenges in the areas of solar energy conversion, catalysis,

medicine, and water treatment. V.K. Sharma et al. have reported the antimicrobial

property of Ag NPs in water filter and air filter [18]. Pillai et al. [19] demonstrated

that solar cells employing metallic nanoparticles can spectacularly enhance the near

infrared absorption due to the presence of surface plasmon. Nowadays, a lot of

researches have been focused on silver nanoparticles because of their important

scientific and technological applications in colour filters [20, 21], optical switching

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[22], and optical sensors [25, 24]. In addition silver nanoparticles have applications

in catalysis, conductive inks, thick film pastes and adhesives for various electronic

components, in photonics and in photography [25-26].

Recently, a lot of research on nanoparticles dispersed within a polymer

matrix has been carried out, because these materials may have various new

properties which originate from the combination of the properties of the inorganic

components and the polymer. The polymeric matrix provides processability and

flexibility and at the same time inorganic nano sized particles not only improve the

mechanical properties of the host polymer, but also give unique properties which

differ from their bulk materials and atoms [27]. Thus polymer nanocomposite

materials represent a new alternative to conventionally nanoscopic inorganic

materials. Among the conducting polymers polyaniline is one of the most promising

polymers due to its exotic properties, environmental stability, controllable electrical

conductivity, and interesting redox properties associated with the nitrogen atoms in

PANI. Polyvinyl alcohol (PVA) being bio-degradable synthetic polymer is largely

used as fiber, film, pressure-sensitive adhesive, emulsifier, in the paper industry, in

textile sizing and as a modifier of thermosetting resins in plywood manufacture etc.

Polyaniline-metal/metal oxide (PANI-metal/metal oxide) nano composites

reportedly show enhanced sensing, corrosion resistant and catalytic capabilities, as

compared to those of pure PANI [28-30]. In the synthesis of PANI-metal

composites, metal ions are often reduced in the presence of processed PANI. In the

resulting composites, metal nanoparticles are not often effectively dispersed into

the polymer matrix, because metal ions and nanoparticles interact strongly with

the imino groups of the polymer and reduced at the point of contact [31].

Mahesh et al [32] have synthesized Pani-Ag nano composites via interfacial

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polymerization. Radhakrishnan et al [33-34] have synthesized Ag-PVA film by

using PVA as surfactant for stabilization of Ag into the polymer matrix.

Silver nanoparticles are of current importance because of its easy preparation

process and excellent optical, electrical, thermal, catalytic, sensing, and antibacterial

properties. The unique properties of Ag NPs make them ideal for numerous

technological applications such as in the field of catalysis, electronics, photography,

adhesives, optical, biomedical and antimicrobial materials etc. [8-18]. The synthesis

of silver nanoparticles with controlled morphology is essential for uncovering their

specific properties and for achieving their practical applications. However, one

major problem while synthesizing nanocomposite materials derived from the

dispersion of silver nanoparticles in polymer matrices is the aggregation of

nanoparticles. Hence, the synthesis of silver nanoparticles of desired shape and size

with uniform distribution within the polymer matrix remains extremely challenging.

Therefore, in the present research work, we have shown the synthesis of silver

nanoparticles homogeneously dispersed within the (PANI-PVA) polymer matrix

with controlled morphology without aggregation. The one step synthesis of

polyaniline-polyvinyl alcohol-silver (PANI-PVA-Ag) IPN nanocomposite by the in

situ polymerization of aniline in the PVA matrix in the presence of silver nitrate

solution is proved to be a simple and convenient method. Different characterizations

including morphological and spectral properties of the nanocomposite in the solid

state were performed and the results of the study are discussed.

2.2 SYNTHESIS OF POLYANILINE (PANI):

2.2.1 Materials and Method:

All the chemicals and reagents used were of analytical grade. Aniline,

benzene, and methanol was double distilled before use as solvents and monomer and

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hydrochloric acid supplied by SD Fine Chemicals Ltd. were used for the study.

Ammonium persulphate [(NH4)2S2O8] (APS) was used from Qualigens Fine

Chemicals. Double distilled water was used throughout the work.

Polyaniline (PANI) was synthesized by employing chemical oxidative

polymerization method using ammonium persulphate as an oxidizing agent through

established procedure [29].

2.2.2 Experimental Procedure:

0.2 g of aniline was dissolved in 10 ml of organic solvent (C6H6) and 0.1 M

ammonium persulphate (APS) was dissolved in 10 ml of 0.1 M hydrochloric acid

(HCl) at room temperature. The ammonium persulphate solution was then

transferred to aniline solution. Aniline: APS ratio was maintained as 1: 2.5.

Within few minutes after the addition of APS, the solution becomes dark green

colour indicating beginning of the polymerization of aniline. The solution was then

kept overnight so as to complete the polymerization process. The precipitate of

polyaniline (PANI) was then separated by filtration using Whatman No. 42 filter

paper and washed with 1:1 methanol/HCl mixture to remove the unreacted aniline

and acidic impurities. The PANI thus obtained was dried in vacuum oven at room

temperature (25o C ± 1o C) for 36 hours. This dried product was then used for

structural characterization and thermal studies.

2.3 CHARACTERIZATION TECHNIQUES:

The Fourier transform infrared (FTIR) spectrum of the sample was recorded

on a Perkin-Elmer FTIR (Model No.1000) in the range 4,000-400 cm-1 and at a

resolution of 4 cm-1. UV-Visible absorption spectrum of the polymer solution was

recorded over the wave length range of 200-800 nm using double beam UV-Visible

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spectrophotometer-UV5704SS (Electronics Corporation of India Limited).

The powder X-ray diffraction (XRD) patterns were recorded on Ultima IV X-ray

diffractometer using Cu Kβ radiation (1.54 Ǻ) at 40 kV and 30 mA. Thermo

gravimetric analysis (TGA) and differential scanning colorimetric (DSC) analysis of

PANI was carried out in the temperature range 30-4500 C in a LINSEIS STA PT

1600 system thermal analyzer with a heating rate of 10o C/min under nitrogen

atmosphere at a flow rate of 100 ml/min. Scanning electron microscope (SEM)

images of the polymer were taken on the Leica instrument (Model No.440) operated

at 20 kV.

2.4 RESULT AND DISCUSSION:

2.4.1 Ultraviolet-Visible (UV-Vis) Spectroscopy:

The UV-visible spectrum of pure PANI (Figure 2.1) shows a shoulder at

320 nm, a sharp intense peak at 420 nm and a groove at 550 nm with an extended

free carrier tail characteristic of an extended coil confirm the increasing absorbance

in the range of 850 – 1,100 nm [32]. The shoulder at 320 nm corresponds to the

π – π* transitions of the benzenoid rings, while the sharp intense peak at 420 nm is

assigned to the localized polarons transition which are characteristics of the

protonated PANI [35-36]. A weak peak at 550 nm can be attributed to the n – π*

transitions of the benzenoid ring together with extended tail representing the

conducting form of polyaniline because the free carrier tail in the IR region is the

characteristics of metallic conductive materials [32].

2.4.2 Fourier Transform Infrared Spectroscopy (FTIR):

Figure 2.2 shows FTIR spectrum of PANI. In the spectrum of PANI

characteristic bands are observed at 3735, 1564, 1496, 1299, 1147, 877, 811, 678,

621 and 503 cm-1. A small peak at 3735 cm-1 is assigned to the free N-H

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stretching vibrations of an amino group. The high frequency strong bands at

1564 and 1496 cm-1 are due to the presence of the quinoid ring and the benzenoid

ring respectively [37]. The intense peak at 1299 cm-1 in the spectrum corresponds to

the C–N stretching vibrations of the secondary aromatic amine [38]. A very strong

and broad band at 1147 cm-1 has been assigned to the B – NH+ = Q vibration,

indicating that the PANI is conductive and is in the form of emeraldine salt [32].

The remaining peaks at 877, 811 and 503 cm-1 corresponds to bending vibrations of

C – H out of plane, in-plane and C – Cl stretching vibrations respectively [39].

2.4.3 X-ray Diffraction (XRD):

The crystallinity and chain packing of the synthesized polyaniline was

studied by X-ray diffraction analysis. Figure 2.3 shows the XRD patterns of virgin

PANI. The figure shows the broad peak at 2θ value of 25.3o, which is characteristic

peak of PANI [40] and is ascribed to the periodicity in parallel and perpendicular

directions of the polyaniline chain [41, 42]. It is characteristics of van der Waals

distances between stacks of phenylene rings (polyaniline rings) [43-45].

2.4.4 Scanning Electron Microscopy (SEM):

The SEM image of pure PANI is shown in Figure 2.4. The figure shows the

individual ultrafine PANI particles uniformly packed. The particles are rod shaped

with uniform particle size of about 100 nm to 200 nm. It is reported that PANI

synthesized from other synthetic routes possess irregular morphology with high

heterogeneity in chain dimensions [46]. A uniform morphology and chemical

homogeneity is observed in the present case.

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2.4.5 Thermal Studies:

2.4.5 a) Thermogravimetric analysis (TGA):

Thermal stability of the synthesized PANI was studied by simultaneous thermo

gravimetric analysis (TGA) and differential scanning calorimetry (DSC) measurements

under a dynamic flow of nitrogen gas at a flow rate 100 ml/min with a heating rate of

10oC/min. the TGA/DSC trace of pure PANI is shown in Figure 2.5(a). The following

features are observed with the increasing temperature. The weight loss of 12% occurs

within the temperature range of 30-110oC owing to the release of moisture, HCl and

other volatile matter associated during the synthesis of PANI. No considerable change

in weight loss is observed from 110-290o C. This indicates the thermal stability of the

polymer. Thereafter a continuous loss is noticed in the temperature range from

290-450oC showing a maximum of 61% leaving ~27% residue. This weight loss is

attributed to the decomposition as well as degradation of the polymer as also reported in

our earlier work and by other authors [32, 38, and 47].

2.4.5 b) Differential Scanning Calorimetry (DSC):

In the DSC trace, Figure 2.5 (b) PANI shows a weak endotherm around

80-100o C due to release of dopant, moisture and other volatile matter. The trace is

then followed by a broad endotherm around 270-290o C relating to starting of

decomposition at high temperatures. PANI completely decomposes above 400o C,

showing a broad exothermic peak. PANI shows an irregular weight loss and absence

of a clear dehydration step when synthesized employing chemical oxidation

routes [48]. A clear dehydration and loss of volatiles step followed with a slow and

steady weight loss for decomposition is an important feature, which helps in

employing this method to synthesize functionalized PANI for specific applications.

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2.5 SYNTHESIS OF PANI-PVA-Ag IPN NANOCOMPOSITE:

2.5.1 Materials and Methods:

All chemicals and reagents used were of analytical grade. Aniline and

methanol was double distilled before use as monomer and solvent and hydrochloric

acid supplied by SD Fine Chemicals Ltd. were used for the study. Polyvinyl alcohol

(PVA), ammonium per sulphate (APS) and silver nitrate (AgNO3) were used from

Qualigens Fine Chemicals. Double distilled water was used throughout the work of

the study. Polyaniline-polyvinyl alcohol-silver (PANI-PVA-Ag) IPN nanocomposite

was synthesized by employing chemical oxidation polymerization method using

ammonium persulphate as an oxidizing agent as explained.

2.5.2 Experimental Procedure:

The synthesis of polyaniline-silver (PANI-Ag) and polyaniline-gold (PANI-Au)

nano composites by interfacial polymerization method using ammonium persulphate as

an oxidizing agent was reported in our earlier research work by Mahesh et al.

PANI-PVA-Ag nanocomposite was synthesized by chemical oxidative

polymerization of aniline in the PVA matrix in the presence of silver nitrate

solution. Freshly distilled 0.2 M aniline was polymerized in the aqueous solution of

PVA (0.2 g in 10 ml H2O) in the presence 1x10-3 M AgNO3 solution by the usual

technique of chemical oxidative polymerization using aqueous acidic solution of

ammonium persulphate with constant stirring. Here aqueous acidic solution of

ammonium persulphate (APS) acts as an oxidizing agent. Aniline: APS mole ratio

was maintained 1:2.5. After 5 min. dark reddish brown color was formed indicating

the formation of the silver nano-particles in the solution. The reaction mixture was

kept undisturbed for 18 hours so as to complete the reaction. The precipitate was

then separated by centrifuging and washed with 1:1 methanol/HCl mixture to

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remove the unreacted aniline and acidic impurities. The nano composite thus

obtained was dried in vacuum oven at 40o C for 36 hours. This dried polymer-metal

nanocomposite sample was then used for structural characterization and thermal

studies.

2.5.3 Characterization Techniques:

The Fourier transform infrared (FTIR) spectrum of the sample was recorded

on a Perkin-Elmer FTIR (Model No.1000) in the range 4,000-400 cm-1 and at a

resolution of 4 cm-1. UV-Visible absorption spectrum of the composite was recorded

over the wave length range of 200-800 nm using double beam UV-Visible

spectrophotometer-UV5704SS (Electronics Corporation of India Limited).

The powder X-ray diffraction (XRD) patterns were recorded on Ultima IV X-ray

diffractometer using Cu Kβ radiation (1.54 Ǻ) at 40 kV and 30 mA. Thermo

gravimetric analysis (TGA) and differential scanning colorimetric (DSC) analysis of

PANI-PVA and PANI-PVA-AgNP composite were carried out in the temperature

range 30-450o C in a LINSEIS STA PT 1600 system thermal analyzer with a heating

rate of 10o C/min under nitrogen atmosphere at a flow rate 100 ml/min. Scanning

electron microscope (SEM) images of the composite were taken on the Leica

instrument (Model No.440) operated at 20 kV.

2.6 RESULTS AND DISCUSSION:

2.6.1 UV-Visible Spectroscopy:

The UV-visible spectrum of PANI-PVA-Ag nanocomposite in the aqueous

phase is shown in Figure 2.6. The absorption spectrum of PANI-PVA-Ag

nanocomposite shows five absorption bands. A broad band appears at 326.5 nm,

sharp intense peaks at 419.5, 443.5 and 448.0 nm and a medium peak 552.0 nm.

A broad band at 326.5 nm corresponds to the π-π* transition of the benzenoid ring of

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the PANI. The absorption peaks at 419.5 and 552.0 nm are assigned to the polaron-

π* and n-π* transitions of the protonated form of PANI. The peak owing to

polaron/bipolaron transition is also observed at 443.5 nm with little blue shift due to

the presence of silver nanoparticles. The sharp intense peak at 448.0 nm is assigned

to the surface plasmon resonance (SPR) absorption of the electrons in the

conduction bands of silver which confirms the formation of nano sized silver

particles. Since surface plasmon bands appearing in the visible region are

characteristics of the noble metal nanoparticles [32]. The result is consistent with

previous reports [49].

2.6.2 Fourier Transform Infrared (FTIR) spectroscopy:

The PANI-PVA-Ag nanocomposite was further characterized by infrared

spectroscopy. Figure 2.7(a, b) shows the FTIR spectrum of pure PVA and PANI-

PVA-Ag NC. The infra red spectrum of PVA Figure 2.7 (a) shows the

characteristic bands at 3296, 2940, 1714, 1423, 1252, 1087 and 832 cm-1. The very

strong broad band at 3296 cm-1 can be assigned to O – H stretching due to the strong

hydrogen bonding of intramolecular and intermolecular type [50]. The C – H

stretching and bending vibrations are observed at 2940 and 1423 cm-1. The small

peak at 1374 cm-1 is due to – CH2 – wagging and intense peak at 1087 cm-1 is due to

C – O stretching vibrations. The peaks at 1714 and 1252 cm-1 are due to C = O and

C – O – C bonds of the non hydrolyzed vinyl acetate group of the polyvinyl acetate.

The IR spectrum of PANI-PVA-Ag NC Figure 2.7 (b) exhibits all the peaks

corresponding to PANI and PVA network. A shoulder at 3359 and 2922 cm-1

correspond to free N –- H stretching vibrations of an amino group of PANI and

C – H stretching vibrations of PVA segment respectively. The very strong broad

band of PVA at 3296 cm-1 due to O – H stretching vibrations is splitted into more

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peaks. The intense peak at 3264 cm-1 is assigned to O – H stretching due to the

strong hydrogen bonding of intramolecular and intermolecular type [50]. This peak

is shifted to 32 cm-1 lower frequency than in the PVA spectrum. The bands at

3197 and 3050 cm-1 are due to the presence of hydrogen bonding between the PANI

and PVA networks [51]. The presence of quinoid (Q) ring stretching vibrations at

1580 cm-1 and benzenoid (B) ring stretching vibrations at 1505 cm-1 are typical

features of a semi-quinoid structure of emeraldine salt form of PANI. The bands at

1303 and 1299 cm-1 are attributed to C–N deformation modes and stretching

vibrations of aromatic amine. The absorption peaks at 1444 and 1207 cm-1 are due to

C-H bending and C-H waging vibrations respectively. The peaks at 905, 860 and

486 cm-1 corresponds to bending vibrations of C – H out of plane, in-plane and

C – Cl stretching vibrations [39]. The medium peaks at 739 and 694 cm-1 are

attributed to the out of plane deformation of C – H aromatic ring and the C – H

stretching vibrations respectively. The absence of the strong and broad band at

1147 cm-1 due to protonated chain (B – NH+ = Q) vibration of the conductive

emeraldine salt form of PANI in the composite is noteworthy [32]. The band due to

protonated chain vibration of the conductive emeraldine salt form of PANI is

weakened when silver nanoparticles are incorporated in the polymer matrix and is

shifted to 1173 cm-1. For the reason that Ag+ is reduced to Ago and the amine

(–NH–) group of the polyaniline chain is oxidized to imine (–N=) group [32].

Additional frequencies and shift in frequencies are found in nanocomposite

spectrum compared to PVA indicating the formation of nano composite.

2.6.3 X-ray Diffraction Studies:

The crystallinity and chain packing of the synthesized polymer and its

composite were studied by XRD analysis. Figure 2.8 (a, b) shows the X-ray

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diffraction (XRD) pattern of pure PVA and PANI-PVA-Ag nanocomposite.

The X-ray diffraction pattern of PVA (Figure 2.8 a) shows an intense diffraction

peak at around 2Ѳ = 20o indicating the presence of a typical semi crystalline

structure. The X ray diffraction pattern of PANI-PVA-Ag composite (Figure 2.8 b)

exhibits intense diffraction peaks at 2Ѳ = 38.38o, 45.18o and 65.3o with

corresponding diffraction signals to (111), (200) and (220) planes of silver,

respectively that match with the JCPDS pattern of Ag nanoparticles, JCPDS File

No. 04-0783 indicating the presence of silver nanoparticles in the composite.

As reported by Desong Wang et. al the reflection peaks can be indexed to face-

centered cubic silver [52]. Thus, the XRD spectrum confirms the crystalline

structure of silver nanoparticles with a face-centered cubic structure. From this we

can infer that the crystallinity of the PANI-PVA-Ag nanocomposite is mainly due to

silver nanoparticles rather than PVA. The size of the silver nanoparticles as

calculated from XRD data is 34. 926 nm.

2.6.4 Morphology Studies:

Scanning Electron Microscopy:

The SEM images of PANI-PVA-Ag nanocomposite at low and high

resolution are shown in Figure 2.9 (a, b). The SEM images show that the Ag

nanoparticles are homogeneously distributed within the PANI-PVA IPN matrix. As

shown in SEM image (Figure 2.9), the silver nanoparticles (Ag NP) are well

embedded in the PANI-PVA IPN composite matrix due to strong affinity of silver

for nitrogen of the polyaniline. It can also be noticed that the globular shaped Ag

nanoparticles are clearly mono dispersed. An interpenetrating network structure of

silver nano particles within the PANI-PVA matrix is proposed with the schematic

sketch as shown in Figure 2.10. Thus it proves that the PANI-PVA polymer

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composite matrix is an excellent host matrix to avoid the aggregation of silver

nanoparticles and is helpful for encapsulation of silver nanoparticles acting as a

good capping agent and providing chemical and environmental stability as well.

The size of the silver particles is < 50 nm and is spherical in shape. The SEM

morphology shows that Ag nanoparticles possess the same particle size.

2.6.5 Thermal Studies:

Thermogravimetric Analysis (TGA):

Thermal stability of the synthesized IPNs was studied employing

simultaneously TGA and DSC techniques. Figure 2.11 (a, b) shows the thermal

plots of PANI-PVA and PANI-PVA-Ag nanocomposite. The TGA curve of

PANI-PVA composite Figure 2.11 (a) shows three steps due to release of dopant

over 30-100o C, moisture and bound water in the range 180-240o C, and degradation

of the components over 400o C. The TGA plot of the for PANI-PVA-Ag IPN

nanocomposite Figure 2.11 (b) shows two step decomposition patterns. The first

weight loss of 21% occurs in the range of room temperature to 300o C which is

attributed to the release of moisture, dopant, and degradation of the PVA molecule

to form low molecular weight fragments. No considerable change in weight loss is

observed from 300 to 540o C, which indicates the increase in the thermal stability of

the polymer-metal nanocomposite due to the presence of silver nanoparticles.

The continuous weight loss is noticed in the second step which starts at 540o C and

continues up to 700o C. This weight loss is due to the decomposition of the

nanocomposite. Thus, silver nano particles may act as stabilizer for the IPN so that

the decomposition temperature is increased for PANI-PVA-Ag IPN when compared

without silver for PANI-PVA IPN (discussed in Chapter – III).

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Differential Scanning Calorimetry (DSC):

The DSC curves of PANI-PVA composite Figure 2.11 (a) shows one broad

endotherm around 200o C, due to the fact that some of the vinyl segments were

subject to dehydration to form a conjugated unsaturated structure. The moisture and

dopant release endotherm is disappeared as a result of the formation of the hydrogen

bonding between PANI and PVA components. Ultimately over 400o C both the

components of the composite decompose to volatile products. The DSC profile of

PANI-PVA-Ag composite Figure 2.11 (b) shows a broad exotherm at 140o C which

is mainly attributed to the crystallization of silver nanoparticles, an endotherm

around 270o C relating to morphological changes at high temperatures and a broad

exothermic peak at 630o C due to the decomposition of IPN in the temperature

region of 540 to 700o C. The increased thermal stability of the polymer composite

may be attributed to the formation of interpenetrating polymer network embedded

with silver nanoparticles. It is observed from thermal studies that residue exists for

PANI-PVA IPN Figure 2.11 (a) but in case of PANI-PVA-Ag Figure 2.11 (b)

residue goes to 0 % above 800o C.

2.7 CONCLUSION:

It has been concluded with the synthesis of PANI-PVA-Ag IPN

nanocomposite that the PANI-PVA polymer IPN matrix is helpful in avoiding the

aggregation of globular shapes silver nanoparticles with homogeneous distribution

of the particles. Thermal study of the nanocomposite shows that there is increase in

the thermal stability of the polymer composite due to the presence of silver

nanoparticles and catalytic effect is observed after dehydration. This indicates that,

catalytic decomposition during thermal analysis of the PANI-PVA-Ag

nanocomposite.

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Figure 2.1: UV-visible spectrum of Polyaniline

Figure 2.2: FT-IR Spectrum of Polyaniline

80

Figure 2.3: XRD pattern of Polyaniline

Figure 2.4: SEM image of Polyaniline

81

Figure 2.5 (a): TGA trace of Polyaniline

Figure 2.5 (b): DSC trace of Polyaniline

82

Figure 2.6: UV-Visible Spectrum of PANI-PVA-Ag nanocomposite

Figure 2.7 (a): -FT-IR spectrum of PVA

83

Figure 2.7 (b): FT-IR Spectrum of PANI-PVA-Ag Nanocomposite

Figure 2.8 (a): XRD pattern of PVA

84

Figure 2.8 (b): XRD pattern of PANI-PVA-Ag nanocomposite

Figure 2.9 (a): SEM image of PANI-PVA-Ag nanocomposite at low resolution

85

Figure 2.9 (b): SEM image of PANI-PVA-Ag nanocomposite at high resolution

Figure 2.10: Structural representation of PANI-PVA-Ag interpenetrating network (IPN)

86

Figure 2.11 (a): TGA/DSC trace of PANI-PVA composite

Figure 2.11 (b): TGA/DSC trace of PANI-PVA-Ag Nanocomposite

87