Synthesis of Polyaniline HCl Pallets and Films Nanocomposites by Radiation Polymerization

Non-ionizing radiation is electromagnetic radiation that does not have sufficient energy to remove the electrons from the outer shell of the atom. Types of non-ionizing radiation are: ultra violet (U/V), Visible light, infrared (IR), microwave (radio and television), and extremely low frequency (ELF, or as they called EMF or ELF-EMF). Non-ionizing radiations produced by a wide variety of sources at homes and in the workplaces, form lasers to power lines, tanning beds to household appliances, cellular phones to home radios (Smith F. A. 2000).


Introduction
The sources of radiation are so varies, some of them are natural and others are man-made. Also the types of radiation can be categorized according to their wave length or energy or even to the ability of ionizing the media.
Non-ionizing radiation is electromagnetic radiation that does not have sufficient energy to remove the electrons from the outer shell of the atom. Types of non-ionizing radiation are: ultra violet (U/V), Visible light, infrared (IR), microwave (radio and television), and extremely low frequency (ELF, or as they called EMF or ELF-EMF). Non-ionizing radiations produced by a wide variety of sources at homes and in the workplaces, form lasers to power lines, tanning beds to household appliances, cellular phones to home radios (Smith F. A. 2000).
Ionizing Radiation: refer to the types of radiation that has capability to ionize the media directly or indirectly such as X-ray, -ray and neutron.
The common radioactive elements are I-131, . Other sources exemplar in occupational and consumption products, these implies the radiation in mines, combustible fuel (gas, coal), ophthalmic glasses, televisions, luminous, watch's dial (tritium), X-ray at air-port (detectors), smoke detectors (americium-241), road construction materials, electrons tubes, and fluorescent lamp starters, nuclear fuel cell, nuclear accidents and nuclear weapons in marshal island and war. The yield of artificial sources either as quantum represented in X-ray and gamma radiation ( ) or as particles with high energy as beta particles ( ), alpha particles ( ), neutrons and electrons. The common artificial sources are accelerators and nuclear reactors (Smith F. A. 2000).
All of the above radiation types were used in researches; today the most common radiation sources applied in researches and in man serves are: i. Co-60, as artificial source for gamma ( ) radiation. ii. Linear accelerators for photon and electron beams, with energy range of (0.3-10 MeV and up to 20 MeV).
These energies are insufficient to initiate nuclear reaction; hence the irradiated element does not exhibit any radioactivity, see the table of radiation sources (1). Ionizing radiation is a broad energetic spectrum of electromagnetic waves or high velocity atomic or subatomic particles. The radiation can be categorized according to their ability to ionize the media. Non-ionizing radiation is electromagnetic radiation that does not have sufficient energy to remove an electron of the atom. The various types of non-ionizing radiation are ultra violet (UV), visible light, infrared (IR), microwaves (radio and television), and extremely low frequency (ELF, or as they called EMF or ELF-EMF). Ionizing radiation is electromagnetic radiations, such as X-rays, -rays and charged particles (electrons, particles and -particles) which possess sufficient energy to ionize an atom by removing at least an orbital electron. According to the 1996 European Guideline of the European Atomic Energy Community (EURATOM), electromagnetic radiation with a wavelength of 100 nm or less is considered as ionizing radiation which is corresponds to ionizing potential of 12.4 eV or more (Smith, 2000). The ionization potential is dependent on the electronic structure of the target materials and generally in the order of 4 -25 eV.
The International Commission of Radiation Units (ICRU) has subdivided the ionizing radiation into direct and indirect ionizing radiation, based on the mechanisms by which they ionize the atom. Direct ionizing radiations are fast charged particles, such as alpha particles, electrons, beta particles, protons, heavy ions, and charged mesons, which transfer their energy to the orbital electron directly and ionize the atom by means of Columbic force interactions along their track. Indirect ionizing radiations are uncharged quantum, such as electromagnetic radiations (X-rays and -rays), neutrons, and uncharged mesons, which undergo interactions with matter by indirectly releasing the secondary charged particles which then take turn to transfer energy directly to orbital electrons and ionize the atom. Some properties of ionizing radiation are shown in Table 2.

Gamma ray (-ray) interaction and attenuation coefficients
In general the characteristic of radiation interaction with matter represented in photoelectric (Predominates for photons in the low energy range between 10 keV and 200 keV), Compton (Predominated at energies of 100 keV -10 MeV. (McGervey, 1983)), Pair production (Predominated at energies greater than twice the rest mass of an electron, i.e. 2m 0 c 2 = 1.022 MeV, where m refers to mass of electron and c refers to speed of light (Johns and Cunningham 1983)), Triplet production process (occurs when the incident photon have an energy of 2 0 4mc , i.e. it implies both the pair production at the nucleus level plus triplet production) and Raleigh scattering (predominant for photons at low energy range from 1 keV to 100 keV) The attenuation coefficient is related to the probability of interaction per atom, i.e. the atomic cross section σ a is given by equation (2) aA N A where A is the mass number and N A the Avogadro's number (6.022 x 10 23 mol/1). Table 3 briefly summarized the entire -radiation photon interactions with their possible energies required to initiate the reactions (Smith, 2000;Siegbahn, 1965).

Process
Type of interaction  Table 3. www.intechopen.com The essence of -radiation interaction with molecules and the induction of physical and chemical characteristics that leading to form new compound is ascribed to the amount of energy being transferred, which will create ion, free radicals and excited molecule. Such interaction process is termed ionization and excitation of the molecules, which can cause chemical changes to the irradiated molecule. This is due to the fact that all binding energy for organic compound in the range of 10 -15 eV. In case of low transferred energy by photon, the molecule undergoes excitation state before returning to the rest state by emitting X-ray photons or break down to release free radicals which in turn undergoes polymerization.
The ejected electron from the irradiated molecule (A + ) is subjected to the strong electric field of the formed positive charge. Therefore the recombination is a frequently occur, either during irradiation or after the end of irradiation to create energetic molecule (A ** ). Such highly energetic excited molecule will break down into free radicals and new molecule (Denaro, 1972). The fundamental of this reaction can be shown in the following scheme Figure (1).

Radiation polymerization
Radiation polymerization is a process in which the free radicals interact with the unsaturated molecules of a low molecular unit known as monomer to form high molecular mass polymer or even with different monomers to produce crosslink polymer. The formed polymer can be in different forms called homopolymer and copolymer depending on the monomer compositions link together. Radiation-induced polymerization process can be achieved in different media whether it is liquid or solid unlike the chemical polymerization which can only accomplished in aqueous media. It is also temperature independent. Radiation polymerization often continues even after removing away from the radiation source. Such condition is known as post-polymerization (Lokhovitsky and Polikarpov, 1980). Since radiation initiation is temperature independent, polymer can be polymerized in the frozen state around aqueous crystals. The mechanism of the radiation induced polymerization is concerning the kinetics of diffusion-controlled reactions and consists of several stages: addition of hydroxyl radicals and hydrogen atoms to carbon-carbon double bond of monomer with subsequent formation of monomer radicals; addition of hydrated electrons to carbonyl groups and formation of radical anion of a very high rate constant and the decay of radicals with parallel addition of monomer to the growing chain.

Cross linking
The process of crosslink occurs due to interaction between two free radical monomers which combine to form intermolecular bond leading to three dimensional net of crosslinked highly molecular polymer, more likely dominate in unsaturated compound or monomer. The crosslinked polymer show strong mechanical strength and high thermal resistance.

Radiation grafting
Radiation grafting is a process in which active radical sites are formed on or near the surface of an exciting polymer, followed by polymerization of monomer on these sites. Grafting is accompanied by homopolymerization of the monomer; the material to which the monomer is grafted is described as the backbone, trunk or support. Radiation grafting is used to modify the polymers texture such as film, fibers, fabrics and molding powders. The process of grafting can be expressed as follow; suppose the polymer A is exposed to -rays, thus the active free radical sites A * created randomly along the polymer backbone chain, this free radical initiate a free radical on the monomer B then undergoes grafting polymerization at that active sites. The extension of the attached monomer B upon the base polymer A is termed as the degree of grafting DOG which refers to the mass of the grafted polymer as a percentage of the mass of the original base polymer. Such process can be expressed in schematic Figure (2). Conducting polymers and their composites exhibit excellent optical, electrical, and electrochemical properties and therefore they have potential applications in enhancement the electrode performance of rechargeable batteries and fuel cells, electric energy storage systems in supercapacitors, solar energy conversion, photoelectrochromics, corrosion protection, electromagnetic interference shielding and biosensors (Malinauskas et al., 2005).
In this work attempts are made to produce conducting polyaniline (PANI) formed in pallets and dispersed in PVA matrix (films) then their structure, optical properties and electrical conductivity are investigated. However, for the first time the polymerization of pure PANI www.intechopen.com is fully achieved by ionizing radiation (Mohammed, 2007). The prime advantage of radiation processing in this work is that no oxidizing agent is used to polymerize the conducting PANI i.e. giving pure product.

Conducting polyaniline nanoparticles
PANI has high electrical conductivity that can be controlled by oxidation or protonic doping mechanism during synthesis. PANI is known for its excellent thermal and environmental stability but poor processibility due to insolubility in most common solvents and brittleness that limits its commercial applications. In the composites form with another water soluble polymers such as PVA, poly(vinyl pyrrolidone), poly(acrylic acid) and poly(styrene sulfonic acid) (PSSA) which used as stabilizers, the processibility of PANI could be improve and a functionalized protonic acid can be added into the composites to chemically polymerize PANI. The PANI dispersion can then be cast to form composite film containing PANI nanoparticles.
To improve the conductivity further, chemically and electrochemically PANI/ polymer composites have been irradiated with x-rays, gamma radiation, and electron beams (Bodugoz et al., 1998;Sevil et al., 2003;Wolszczak et al., 1996 a and b;Angelopous et al. 1990). When ionizing radiation interacts with polymer materials active species such as ions and free radicals are produced and thus, improved the PANI conductivity.
Conducting PANI has been synthesized by chemical and electrochemical methods, which the later is considered the common one because of better purity. Chemically and electrochemically synthesized polyaniline are subjected to many shortcomings such as impurities, solvent toxicity, long tedious process, poor compatibility, insoluble, expensive, low production and difficult in their preparation, etc. However, report on synthesis of PANI nanoparticles using only -irradiation has not been reported until the date of 2007. The advantages of radiation processing is that no metallic catalyst, no oxidizing or reducing agent is needed, synthesis in a solid-state condition, fast and inexpensive, and controllable acquisitions. The synthesis of PVA/PANI nanoparticles by -irradiation doping is proposed in this work.

Materials and equipments
The materials used for preparing the samples in this study, namely as polyvinyl alcohol PVA, aniline hydrochloride AniHCl, -radiation as an effective tool for polymerization process and reducing agent, Petri-dishes, micrometer, UV-spectroscopy, Raman spectroscopy and LCR-meter.

Method
The Aniline hydrochloride AniHCl monomer as 2.5, g (28.6 W/V) has been dissolved in distill deionized water of 100 ml under nitrogen atmosphere and bubbling in the solution with continuous stirring using magnetic stirrer for 3 hour. Then the solution has been irradiated with -radiation receiving 10, 20, 30, 40 and 50 kGy. The polymerized AniHCl i.e. polyaniline PANI-HCl has been precipitated filtered and collected in a form of powder. The powder (2.5g) pressed by 10 tons to form pallets.
On the other hand a polyvinyl alcohol (PVA) was supplied by SIGMA (Mw = 72,000 g/mol, 99 -100% hydrolyzed) has been prepared by dissolving 30.00 g PVA powder in 600 ml distilled deionized water at controlled temperature of 80 o C in the water-bath. The solution was magnetically stirred throughout at that temperature for 3 hours and then left to cool at room temperature. After cooling to room temperature, a weight of AniHCl, 2.5, g was added into 100 ml PVA solution, which gives the AniHCl concentrations as 28.6, wt%, by weight in comparison to the PVA. The mixtures were stirred continuously for 10 hours using a magnetic stirrer in nitrogen atmosphere. Then the PVA/AniHCl blend solution has been irradiated by -radiation receiving 10, 20, 30, 40 and 50 kGys and after irradiation the solution has been divided into Petri-dishes, each contains 20 ml and left to dry at ambient temperature and dark room for 3 days to evaporate the water. The casting film was pealed off and cut into several pieces which were eventually packed in a sealed black plastic bag. The thickness of the films was determined by a digital micrometer model Mitutoyo no: 293-521-30-Japan, The average thickness of the films was 2 mm, and then the products (Films of PANI-HCl and pallets) have been characterized using the following instrument: it shows the oily color and after an irradiation with 50 kGy the color turned to dark green solution, which is the color of polyaniline PANI. While Fig. 7-d shows the pur pallets of PANI-HCl and the formed films of PVA\ PANI-HCl (e). These obtained materials have been subjected for further characterization.
Upon irradiation, the PVA/AniHCl blend films with doses up to 50 kGy, -rays interacts with the PVA binder liberating electrons by photoelectric effect and Compton scattering and followed by ions of H + and OHfrom the bond scission. However, the contribution of these ions to the final product is not very significant. On the other hand, the interaction of -rays with the AniHCl is dominant due to the fact that HCl is easily dissociated to H + and Clions by radiation. The protonation of aniline monomer by Clproduced conducting PANI nanoparticles which can be visualized by the change of color of the un-irradiated PVA/AniHCl blend film from colorless to dark green at 50 kGy, as illustrated by the photograph pictures in Figure 5.14. As mention earlier, the formation of C=N double bonds of imines group produced green colour of PANI and the intensity increases with increasing of dose (see Raman spectrum). Before irradiation, all PVA/AniHCl blend films were colourless even exposed in air, suggesting the UV-visible radiation has no influence in the formation of conducting PANI. Only after irradiation with the dose between 20 kGy and 50 kGy, the green colour became intense.  wt% AniHCl formed as films. The optical absorption spectra of the irradiated films were measured by using UV-Visible double beam spectrophotometer with air as a reference. The optical absorption is a useful tool to study electronic transitions in molecules, which can provide information on band structure and band gap energy. The basic principle is that photons from UV-visible light source with energies greater than the band gap energy will be absorbed by the materials under study. The absorption is associated with the electronic transitions from highly occupied molecular orbital (HOMO) -band to lowly unoccupied molecular orbital (LUMO) *-band of electronic states (Arshak and Korostynska, 2002). The electronic transitions between the valence band (VB) and the conduction band (CV) start at the absorption edge, which corresponds to the minimum energy of band gap g E between the lowest minimum of the CB and the highest maximum of the VB. The spectra of irradiated films reveal two prominent absorption peaks at 315 and 790 nm assigned to the electronic transitions of chlorine Cland C=N bond respectively. The absorbance corresponds to the excitation of outer electrons through -* electronic transitions at the bands of 315 nm (3.95 eV) and 790 nm (1.57 eV). The absorbance increases with the increase of dose and AniHCl concentration and both peaks become sharper with dose increase, indicating the amount of Cland polarons formed (represented by C=N) have increased with dose increase. Both peaks shifted slightly to higher wavelengths with the increase of dose but were not very significant.
The absorbance at 790 nm is due to the creation of C=N double bond of imines group representing the polarons in conducting PANI that gives the green colour. This result is in agreement with previous study carried out by Rao, et al. (2000), in which the absorption band for the chemically prepared conducting PANI salt peaking in the range of 420 -830 nm depending on the degree of oxidation. Earlier Malmonge and Mattoso (1997) found that the absorption band of chemically synthesized PANI was 630 nm and when exposed to Xrays, the peak became sharper and shifted to 850 nm leading to an increase of the conductivity. Recent study by Cho et al. (2004) showed that the absorption bands were peaking at 740 -800 nm for PANI chemically prepared by hydrochloric acid doping and dispersed in PVA matrix.
The unirradiated PVA/AniHCl film showed a broad peak at 315 nm because of the presence of Clin AniHCl monomer and no other peak is visible in UV region. The peak increases in intensity at higher concentration of AniHCl monomer. As the dose increases the absorbance at 315 nm increases due to increased formation of chlorine Clions from the dissociation of HCl. Solid phase of HCl was present as the residual of radiation doping of imines group which can be seen from SEM micrographs in Figure 5.4. De Albuqerque, et al. (2004) measured UV-Visible spectra of emeraldine salt solution and found two absorption peaks at 320 nm and 634 nm. The presence of the absorption peak at 315 nm has been reported by Azian (2006) for irradiated PVA/AniHCl composites below 20 kGy and was confirmed by the UV-Visible spectroscopy measurements on HCl solution. Figure 9 shows the absorbance at 790 nm band for conducting PANI composites that increases exponentially with dose and can be fitted to the theoretical relationship of the form:

Quantitative analysis formation of PANI composites
where y is the absorbance at dose D, 0 y is the absorbance at zero doses and 0 D is the dose sensitivity parameter.
The exponential increase of absorbance of PANI nanoparticles turns out to be of similar trend with the exponential increase of C=N formation determined from the Raman scattering measurement. This indicates the same phenomenon measured by two different methods produces almost similar result. Thus, the quantitative analysis of polarons could be extracted by either the Raman scattering or the optical absorbance method. The values of 0 D from the absorbance of PANI composites at different AniHCl concentrations were determined from the inverse of the gradient ln y vs. dose, as shown in Figure 9 and plotted for different AniHCl concentrations. The result shows a decrease in the D 0 value with the increase of AniHCl concentration. Thus, the PVA/PANI composites became more radiosensitive at higher AniHCl concentration as shown in Figure 10. The linear relationship between D 0 and AniHCl concentration C is D 0 = -0.29C + 23.7.    Figure 12 shows the absorbance at 315 nm band due to the formation of HCl versus radiation dose. The absorbance increases exponentially following the radiation dose increment and leading to saturation at doses higher than 50 kGy, indicating chlorine ions Clwere being consumed for the formation of conducting PANI composites. The relation between the absorbance of Cland dose could be fitted to the relation of the form:

Quantitative analysis of HCl formation
where y is the absorbance at the applied dose D for each concentration, A 0 is the difference between the absorbance at 50 kGy and 0 Gy for each concentration.

Band gap of PANI nanoparticles
At high absorption level,  > 10 4 cm -1 , the absorption coefficient (ν)hν is related to the band gap g E according to the Mott and Davis (1979) using the following relation: where, hν is the energy of the incidence photon, h is the Planck constant, E g is the optical band gap energy, B is a constant known as the disorder parameter which is dependent on composition and independent to photon energy. Parameter m is the power coefficient with the value that is determined by the type of possible electronic transitions, i.e.1/2, 3/2, 2 or 1/3 for direct allowed, direct forbidden, indirect allowed and indirect forbidden respectively. The band gap denotes the energy between the valence bands (VB) and the conduction band (CB). The direct allowed band gap at different doses were evaluated from the plot of (α(v)hν) 2 vs. hν. By extrapolation a straight line of α(v)hν) 2 versus hν curves for (α(v)hν) 2 = 0, the band gap can be determined as shown in Figure 15. The results showed that band gap E g value decreases with the increase of the radiation dose shown in Figure 16. The decrease in the band gap energy with increasing dose is attributed to more conducting PANI nanoparticles formed and as more polarons in the irradiated composite reduce the band gap between VB and CB for the  -* electronic transition. We found that when the doses were increased from 10 to 50 kGy the band gap decreases from 1.36 to 1.18 eV for 9 wt %, from 1.28 to 1.09 eV for 16.7 wt %, from 1.21 to 1.04 eV for 23 wt % and from 1.12 to 1.00 eV for 28.6 wt %.

Electrical conductivity of composite of PVA/PANI nanoparticles
Polymers are commonly insulators as they have no significant mobile charges to serve the electrical conductivity. One of the requirements for polymers to exhibit good conductivity is the existence of π-electrons, which overlaps along the conjugated chain to form πconjugated band. The conductivity of conjugated polymers or pure polymers can be increased after suitable oxidization or reduction process (Kanazawa et al., 1979;Blythe, 1979) by doping or blending with charge donors of several organic groups (El-Sayed et al., 2003) like hydroxyl, amine, carboxylate, sulfonate, and quaternary ammonium (Blanco et al., 2001) or by radiation induced doping (Park et al., 2002). In this work, the PVA was first blended with the organic monomer, AniHCl and then followed by  irradiation to oxidize the monomer into the conducting PANI.
The conductivity of polymer composites, generally consist of free or weakly bound electronic and ionic charges and trapped ionic charges in the polymer matrix. The free charges are free to move in electrical field, independent of frequency and contribute to the direct current (dc) conductivity. While charge carriers that are trapped in the polymer matrix require alternating electric field at certain frequency to liberate the ions from one site to another site in succession by hopping mechanism and contribute to the alternating current (ac) conductivity. Realizing this, the electrical conductivity of un-irradiated and irradiated PVA will be measured and discussed first. This allows us to determine the conductivity values and identify the type of charge carriers in the un-irradiated and irradiated PVA before blending the PVA with AniHCl monomer at various concentrations and undergo irradiation. Figure 17 shows the conductivity measured at different frequencies from 20 Hz to 1 MHz for the PVA/AniHCl composites with different concentrations of AniHCl. At low AniHCl concentrations both the dc and ac conductivity are clearly seen. The dc conductivity is frequency-independent served by weakly bound electrons, H + , and Cland those of phonon assisted tunneling process that gain charge mobility at room temperature. The H + and Clions were derived from dissociation of HCl which is weakly attached to the phenyl group of aniline monomer. The ac conductivity at high frequencies is due to trapped H + and Clions in PVA matrix that required alternating electric field at given frequency and contributes to the conductivity by hopping between the localized sites.

Conductivity of PVA/AniHCl composite at various concentrations
The conductivity increases with the increase of AniHCl concentration until 28.6 wt% before the conductivity drops to the lower values at higher concentrations of 33.0 and 38.0 wt%. The conductivity of higher concentrations is mainly the dc conductivity contributed from weekly bound H + and Clions. Figure 18 shows the dc conductivity component at various AniHCl monomer concentrations. The conductivity increases significantly from 8 6.61 10   S/m at 0 wt% to 4 1.04 10   S/m at 28.6 wt% and there is subsequently dropped in conductivity at 33.0 wt% and 38.0 wt%. A decrease in conductivity may be due to the increase of crystallinity in the polymer matrix as more crystalline chlorine are present within the composite films. It may also be due to high viscosity and caused resistance or impedance to oppose ion mobility in www.intechopen.com   www.intechopen.com the composites (Guo et al., 2004;Bidstrup, 1995). It has been shown that the ionic mobility is inversely proportional to viscosity as in the theoretical relation given by Richard (2002). For this reason, the conductivity of PVA/AniHCl composites decreased in values at monomer concentrations of 33.0 and 38.0 wt%. Subsequently, the analysis of these samples was discarded from the further discussion. Figure 19 shows the conductivity of PANI composites dispersed in PVA matrix polymerized at doses up to 50 kGy for various AniHCl concentrations from 9.0 to 28.6 wt%. The results show that the conductivity increases with the increase of dose and monomer concentration.

Conductivity of PANI composites at various doses
As the dose and AniHCl concentration increased more polarons were formed and thus, increase the conductivity of conducting PANI composites. Moreover, as the dose increased t h e b a n d g a p o f c o n d u c t i n g P A N I d e c r e a s e s t o a b o u t 1 . 0 e V f o r 2 8 . 6 w t % A n i H C l concentration and radiation dose at 50 kGy. This is closed to the silicon semiconductor band gap of about 0.8 eV. The conductivity comprises of the dc and ac components given equation (6).
At low doses below 10 kGy, the composites behave like insulators, where the dc and ac components are due to weakly bound and trapped H + and Clions in PVA/AniHCl matrix respectively. The ac conductivity at higher doses follows the universal power law of the Johnscher, 1976). Since the ac component is limited to the lower concentrations of AniHCl and at lower doses as shown in Figure 18, we suspected that the conductivity is not related to polarons in this situation. The ac component occurs at higher frequency region and becomes less important at higher doses. This indicates that at higher doses the conductivity is dominated entirely by the dc conductivity due to polarons. Therefore, detail analysis of the ac conductivity will not be discussed further. The species of polarons are considered the main criteria of conducting polyemeraldine salt that results in a remarkable shift of the dc conductivity to higher values with increasing dose and monomer concentration up to 28.6 wt%. Detail analysis of the dc conductivity is given in the following subsection.

The dc conductivity of PANI composites determined from direct extrapolation method
The dc conductivity σ dc (0) of conducting PANI composites was deduced from direct extrapolation of dc portion Figures 19 and from calculation using the resistance Z 0 obtained from the Cole-Cole plots. Figure 20 shows the dc conductivity σ dc (0) of PANI composites deduced by the direct extrapolation. We found that the dc component for 9 wt% AniHCl monomer increases from 7 6.31 10   S/m at 0 kGy to 3 1.12 10   S/m at 50 kGy, while for 16.7 wt % monomer, the dc conductivity increases from    1.17 10   S/m at 50 kGy. The obtained values were compared with previously published data for chemical and electrochemical doping methods. MacDiarmid et al. (1987) have successfully prepared conducting PANI by HCl doping and obtained a conductivity of 1.0 S/cm or 2 1.0 10   S/m. Recently Blinova et al., (2006) have successfully measured the conductivity of 15.5 S/cm or 3 1.55 10   S/m for PANI prepared by chemical doping with 1 M phosphoric acid. The PVA/PANI-HCl composites of polyaniline were prepared and the maximum conductivity achieved was 3 2.0 10   S/m at 60 wt% PANI (Cho et al., 2004). The difference in conductivity between PANI-Radiation doping and PANI-(chemical/electrochemical doping) is that radiation interaction occurs randomly i.e. not all AniHCl got polymerized and the effect of binder impedance. The dc conductivity of conducting PANI composites seems to begin at dose of 10 kGy. Referring to the absorption spectra Figure (2), the absorbance at 790 nm band for conduction PANI showed up at 10 kGy for all monomer concentrations, confirming that the formation of PANI begins at 10 kGy as measured by conductivity measurement. This minimum dose might be the threshold of radiation dose to start polymerizing the conducting PANI for all AniHCl concentrations. The general relationship between the dc conductivity and the dose is in the form: exp www.intechopen.com

The dc conductivity of PANI determined from the Cole-Cole plots
The dc conductivity, σ dc (0) can be calculated from the resistance 0 Z obtained from the Cole-Cole plots. Figure 21 shows the Cole-Cole plot curves for various AniHCl monomer concentrations that display similar semicircle characteristics, a typical impedance spectra of synthetic-metal or metallic-polymer film composites (Vorotyntsev et al., 1999;Tarola, et al., 1999). At low frequency region for certain dose and monomer concentration, there is a straight line spike due to interstitial effect of the electrodes. It has been reported by Mariappan and Govindaraj. (2002) that the depressed semicircle at the low frequency region is related to characteristics of parallel combination of the bulk resistance and capacitance phase element of the samples. While Chen et al. (2003) ascribed the presence of straight line at low frequency region due to the capacitive characteristics of conducting polymer film.  In such spectra the semicircles radius decreases with dose increment, indicating that the resistance 0 Z of the polymer composites decreases with dose, hence the dc conductivity (0) dc  increases with dose (Kobayashi et al., 2003). The increase of dc conductivity of the PANI composites is due to polaron species caused by radiation beginning at 10 kGy. The inclined straight line appear at the end of the semicircles was due to electrode polarization or space effect (Hodge et al., 1976 andMariappan andGovindaraj., 2002), while Lewandowski et al. (2000) ascribed it to non secured verticality of electrode spikes as well as to capacitance interface between the electrode and the dielectric.
We found that the dc conductivity obtained from the Cole-Cole plots are quite typical with those deduced from the direct extrapolation method. The dc conductivity is    Table 4. The study reveals that as the monomer concentration increases the dose sensitivity decreases.   Table 4. Shows the relation between monomer concentration and dose sensitivity D 0 Figure 24 shows the dose sensitivity versus AniHCl concentration which reveals a decrease in dose sensitivity with the increase of monomer concentration i.e. as the dose increases the composites become more radiosensitive to produce conducting PANI nanoparticles. The correlation between the dose sensitivity and the concentration of monomer is given by the formula: D 0 = -5.1C + 7.8, where C refers to the AniHCl concentration. The increasing of radiosensitivity by increasing the AniHCl concentration is attributed to higher density of the monomer to be irradiated, thus, producing more polarons in conducting PANI.

Raman scattering analysis of PANI nanoparticles
The Raman scattering analysis was performed on the PVA/PANI nanocomposites before and after -irradiation up to 50 kGy and for all monomer concentrations. The significant of Raman spectroscopy study is that it can be used to investigate particular covalent bonds of some molecular species where the amount is expected to change after -irradiation. In this www.intechopen.com method, the vibrational transitions of particular molecular bonds could provide information on the chemical structure of the materials, which might be modified by ionizing radiation. Thus, Raman scattering (inelastic scattering) method is vital for the identification of substances by targeting at particular bonds which can become a chemical finger printing and provide quantitative information of the samples of interest (Barnes, 1998). Figure 25 shows Raman spectra of 28.6%-AniHCl composites of PVA/PANI composites at different doses and reveal the prominent peak originated at Raman shift 1637 cm -1 assigned to C=N bond stretching of imines group which gives the PANI color and represents the polaron species. In addition to the formed polarons of imines group, the Raman spectra also show Raman shift at 2100 cm -1 and 2527 cm -1 assigned for the π-bonds between double bond carbon C=C stretching within the aromatic ring and C=O stretching of aldehyde derivative from PVA bond scission respectively. Also shown is the weak intensity of Raman shift 3023 cm -1 assigned to C-H bending.

The SEM morphology of PANI nanoparticles
The morphology and particle size of the conducting PANI nanoparticles were studied by means of a scanning electron microscope (SEM). Figure 26 shows the SEM image of PANI nanoparticles polymerized 'in situ' by radiation doping with the dose of 50 kGy for AniHCl concentration of 28.6 wt%. The micrograph was taken at the electron operating voltage of 15 kV and 10,000 times magnification. It reveals the formation of conducting PANI nanostructures distributed almost uniformly and the diameter of spherical PANI nanoparticles was estimated to be in the range of 50 -100 nm. The micrograph also reveals some fibrous clusters made up from aggregates of many PANI nanoparticles. The PANI cluster size is about 100 -200 nm in diameter and 300 -400 nm in length. There have been reported that the diameters of the PANI nanoparticles polymerized chemically with hydrochloric acid were about 100 to 150 nm for PVA/PANI nanocomposites (Cho et al., 2004) and 40 nm for PVP/PANI nanocomposites (Dispenza et al., 2006). This suggests that the type of binder determined the diameter of spherical nanoparticles. Fig. 26. Shows SEM image of PANI nanoparticles polymerized by 50-kGy Co-60 -rays for 28.6 wt% monomer.
The formed pallets of pure PANI-HCl ( Fig. 1) were characterized with Voltmeter and LCRmeter. It is conductivity was obviously higher than that of PVA\PANI-HCl, which is ascribed to the presence of PVA within the composites, the conductivity was 1 S/m and it is UV-spectrum was peaked at 790 nm which is same as in PANI\PVA composites.

Conclusion
The ionizing -radiation could be used successfully to obtain the polymerization of monomers such as aniline hydrochloride AniHCl and the induced properties for the new product could be controlled by adjusting the amount of monomers and the applied radiation dose with consideration to technical aspects.