**15. Conductivity of PVA/AniHCl composite at various concentrations**

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 Cl– and those of phonon assisted tunneling process that gain charge mobility at room temperature. The H+ and Cl– ions 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 Cl– ions in PVA matrix that required alternating electric field at given frequency and contributes to the conductivity by hopping between the localized sites.

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 Cl– ions.

Figure 18 shows the dc conductivity component at various AniHCl monomer concentrations. The conductivity increases significantly from <sup>8</sup> 6.61 10 S/m at 0 wt% to <sup>4</sup> 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

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

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

**15. Conductivity of PVA/AniHCl composite at various concentrations** 

the conductivity by hopping between the localized sites.

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 Cl– and those of phonon assisted tunneling process that gain charge mobility at room temperature. The H+ and Cl– ions 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 Cl– ions in PVA matrix that required alternating electric field at given frequency and contributes to

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

Figure 18 shows the dc conductivity component at various AniHCl monomer concentrations. The conductivity increases significantly from <sup>8</sup> 6.61 10 S/m at 0 wt% to <sup>4</sup> 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

**14. Electrical conductivity of composite of PVA/PANI nanoparticles** 

monomer into the conducting PANI.

and undergo irradiation.

weekly bound H+ and Cl– ions.

Fig. 17. Conductivity of the PVA/AniHCl composites versus frequency at different concentrations of AniHCl.

Fig. 18. The dc conductivity of PVA/AniHCl composites vs. AniHCl monomer concentration.

Synthesis of Polyaniline HCl Pallets and Films Nanocomposites by Radiation Polymerization 135

1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 f (Hz)

1

2

3 4 5 6

1.0E+01 1.0E+02 1.0E+03 1.0E+04 1.0E+05 1.0E+06 f (Hz)

1

2

3 4 5 6

1.0E-07

1.0E-06

1.0E-05

1.0E-04

(S/m)

 1.0E-03

1.0E-02

1.0E-07

1.0E-06

1.0E-05

1.0E-04

(S/m)

1.0E-03

a

1.0E-02

b

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.

#### **16. Conductivity of PANI composites at various doses**

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. 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 the band gap of conducting PANI decreases to about 1.0 eV for 28.6 wt% AniHCl 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).

$$
\sigma(\alpha) = \sigma\_{\text{dc}}\,(0) + \sigma\_{\text{ac}}\,(\alpha) \tag{6}
$$

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 Cl– ions in PVA/AniHCl matrix respectively. The ac conductivity at higher doses follows the universal power law of the form ( ) *ac A* <sup>s</sup> (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.

### **17. The dc conductivity of PANI composites determined from direct extrapolation method**

The dc conductivity σdc(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 σdc(0) of PANI composites deduced by the direct extrapolation. We found that the dc component for 9 wt% AniHCl monomer increases from <sup>7</sup> 6.31 10 S/m at 0 kGy to <sup>3</sup> 1.12 10 S/m at 50 kGy, while for 16.7 wt % monomer, the dc conductivity increases from <sup>6</sup> 3.63 10 S/m at 0 kGy up to <sup>3</sup> 5.75 10 S/m at 50 kGy. As for 23 wt % monomer the conductivity increases from <sup>6</sup> 4.02 10 S/m at 0 kGy to <sup>2</sup> 2.40 10 S/m at 50 kGy. The highest conductivity measured

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

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. 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 the band gap of conducting PANI decreases to about 1.0 eV for 28.6 wt% AniHCl 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

 () = dc (0) + ac () (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 Cl– ions in PVA/AniHCl matrix respectively. The ac conductivity at higher doses follows the universal power law of the

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

**17. The dc conductivity of PANI composites determined from direct** 

The dc conductivity σdc(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 σdc(0) of PANI composites deduced by the direct extrapolation. We found that the dc component for 9 wt% AniHCl monomer increases from <sup>7</sup> 6.31 10 S/m at 0 kGy to <sup>3</sup> 1.12 10 S/m at 50 kGy, while for 16.7 wt % monomer, the dc conductivity increases from <sup>6</sup> 3.63 10 S/m at 0 kGy up to <sup>3</sup> 5.75 10 S/m at 50 kGy. As for 23 wt % monomer the conductivity increases from <sup>6</sup> 4.02 10 S/m at 0 kGy to <sup>2</sup> 2.40 10 S/m at 50 kGy. The highest conductivity measured

*A* <sup>s</sup> (Johnscher, 1976). Since the ac component is limited to the lower

discarded from the further discussion.

equation (6).

form ( ) *ac* 

subsection.

**extrapolation method** 

 

**16. Conductivity of PANI composites at various doses** 

Synthesis of Polyaniline HCl Pallets and Films Nanocomposites by Radiation Polymerization 137

was for 28.6 wt % monomer at which the dc conductivity increases from <sup>4</sup> 1.04 10 S/m at 0 kGy up to <sup>1</sup> 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 <sup>2</sup> 1.0 10 S/m. Recently Blinova *et al*., (2006) have successfully measured the conductivity of 15.5 S/cm or <sup>3</sup> 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 <sup>3</sup> 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

Fig. 20. Shows the dc conductivity σdc(0) by extracted from extrapolation method for PANI

10 20 30 40 50 Dose (kGy)

1

2

3 4

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

*D D* , *D*<sup>0</sup> is the dose sensitivity that can be deduce from the

composites in PVA matrix at different doses and monomer concentrations.

dc(0) versus dose.

is in the form: exp 0 0 (0) ( / ) *dc*

gradient linear slope of ln

1.0E-07

1.0E-06

1.0E-05

1.0E-04

dc(0) (S/m)

1.0E-03

1.0E-02

1.0E-01

1.0E+00

AniHCl got polymerized and the effect of binder impedance.

Fig. 19. Shows the conductivity vs. frequency of PVA/PANI nanocomposites irradiated up to 50 kGy for various monomer concentrations (a) 9.0, (b) 16.7, (c) 23.0, and (d) 28.6 wt%.

1.0E+01 1.0E+02 1.0E+03 1.0E+04 1.0E+05 1.0E+06 f (Hz)

1

2

3 4

5

6

1.0E-06

1.0E-05

1.0E-04

1.0E-03

1.0E-02

(S/m)

1.0E-01

1.0E+00

1.0E-05

1.0E-04

1.0E-03

(S/m)

 1.0E-02

c

d

1.0E-01

Fig. 19. Shows the conductivity vs. frequency of PVA/PANI nanocomposites irradiated up to 50 kGy for various monomer concentrations (a) 9.0, (b) 16.7, (c) 23.0, and (d) 28.6 wt%.

1.0E+01 1.0E+02 1.0E+03 1.0E+04 1.0E+05 1.0E+06 f (Hz)

1

2

3

5

6

4

was for 28.6 wt % monomer at which the dc conductivity increases from <sup>4</sup> 1.04 10 S/m at 0 kGy up to <sup>1</sup> 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 <sup>2</sup> 1.0 10 S/m. Recently Blinova *et al*., (2006) have successfully measured the conductivity of 15.5 S/cm or <sup>3</sup> 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 <sup>3</sup> 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.

Fig. 20. Shows the dc conductivity σdc(0) by extracted from extrapolation method for PANI composites in PVA matrix at different doses and monomer concentrations.

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 0 0 (0) ( / ) *dc D D* , *D*<sup>0</sup> is the dose sensitivity that can be deduce from the gradient linear slope of ln dc(0) versus dose.

Synthesis of Polyaniline HCl Pallets and Films Nanocomposites by Radiation Polymerization 139

Z"

0.0E+00 8.0E+03 1.6E+04 2.4E+04 3.2E+04 4.0E+04

0.0E+00

0.0E+00

0.0E+00 7.0E+02 1.4E+03 2.1E+03 2.8E+03 3.5E+03

Z"

2.0E+05

4.0E+05

Z"

6.0E+05

8.0E+05

1.0E+02

2.0E+02

Z"

3.0E+02

4.0E+02

(c)

0.0E+00 7.0E+03 1.4E+04 2.1E+04 2.8E+04 3.5E+04 Z'

4

4 = 40 kGy

0.0E+00 2.0E+02 4.0E+02 6.0E+02 8.0E+02 Z'

> (d) 10 kGy 1

0.0E+00 4.0E+04 8.0E+04 1.2E+05 1.6E+05 Z'

(d) 30 kGy

0.0E+00 5.0E+02 1.0E+03 1.5E+03 2.0E+03 2.5E+03 Z'

3

2 2 = 20 kGy (c)

0.0E+00 9.0E+03 1.8E+04 2.7E+04 3.6E+04 4.5E+04

0.0E+00 7.0E+02 1.4E+03 2.1E+03 2.8E+03 3.5E+03 4.2E+03

(c)

0.0E+00 1.2E+01 2.4E+01 3.6E+01 4.8E+01 6.0E+01

0.0E+00 3.0E+02 6.0E+02 9.0E+02 1.2E+03 1.5E+03

Z"

Z"

Z"

Z"

0.0E+00 4.0E+04 8.0E+04 1.2E+05 Z'

3 = 30 kGy (c)

3

5 5 = 50 kGy

5.0E+02 1.3E+03 2.1E+03 2.9E+03 Z'

2.0E+01 3.2E+01 4.4E+01 5.6E+01 6.8E+01 8.0E+01 Z'

20 kGy (d)

0.0E+00 8.0E+02 1.6E+03 2.4E+03 3.2E+03 4.0E+03 Z'

2

1 1 = 10 kGy (c)

### **18. The dc conductivity of PANI determined from the Cole-Cole plots**

The dc conductivity, σdc(0) can be calculated from the resistance *Z*0 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.

The dc conductivity, σdc(0) can be calculated from the resistance *Z*0 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.

> 0.0E+00 2.0E+03 4.0E+03 6.0E+03 8.0E+03 1.0E+04 1.2E+04 1.4E+04

0.0E+00 2.0E+03 4.0E+03 6.0E+03 8.0E+03 1.0E+04 1.2E+04 1.4E+04

0.0E+00

2.0E+05

Z"

4.0E+05

Z"

Z"

0.0E+00 2.0E+03 4.0E+03 6.0E+03 8.0E+03 1.0E+04 1.2E+04 1.4E+04 1.6E+04

(b)

8.6E+01

4.9E+02

8.9E+02

Z"

1.3E+03

(a)

1.7E+03

0.0E+00 5.0E+05 1.0E+06 1.5E+06 2.0E+06 2.5E+06

Z"

Z"

0.0E+00 5.0E+03 1.0E+04 1.5E+04 2.0E+04 2.5E+04 3.0E+04 3.5E+04 4.0E+04 Z'

2 = 20 kGy

0.0E+00 7.0E+02 1.4E+03 2.1E+03 2.8E+03 3.5E+03 4.2E+03 Z'

5

4

0.0E+00 1.0E+06 2.0E+06 3.0E+06 4.0E+06 5.0E+06 Z'

1 = 10 kGy

4 = 40 kGy 5 = 50 kGy

(a) <sup>1</sup>

2

0.0E+00 6.0E+03 1.2E+04 1.8E+04 2.4E+04 3.0E+04 Z'

4

5

(b)

(b)

3

(a)

3

1 1 = 10 kGy

0.0E+00 4.0E+04 8.0E+04 1.2E+05 1.6E+05 Z'

0.0E+00 3.0E+05 6.0E+05 9.0E+05 1.2E+06 Z'

2

2 = 20 kGy 3 = 30 kGy

> 3 = 30 kGy 4 = 40 kGy 5 = 50 kGy

**18. The dc conductivity of PANI determined from the Cole-Cole plots** 

Synthesis of Polyaniline HCl Pallets and Films Nanocomposites by Radiation Polymerization 141

dc conductivity 1 = 9.0

Fig. 22. Shows the dependence of dc conductivity (σdc) on the applied radiation dose theoretical method. The conductivity obeys the relation of the following form

concentration of PANI nanoparticles. The linear regressions of the "Arrhenius type plot"

 *dc* versus dose give the slope of 0 1 /*D* from which the dose sensitivity value can be determined, as shown in Table 4. The study reveals that as the monomer concentration

10 20 30 40 50

Dose (kGy)

*dc* as a function of dose for different monomer

1 2 3

4

1 2 3

4

Fig. 23. Shows the variation of ln σdc(0) versus radiation dose for different AniHCl

10 20 30 40 50

Dose (kGy)

0 0 exp( / )

1.0E-06

1.0E-05

1.0E-04

 dc (S/m)

1.0E-03

1.0E-02

1.0E-01

2 = 16.7 3 = 23.0 4 = 28.6

1.0E+00

Figure 23 shows the variation of ln (0)

increases the dose sensitivity decreases.

1= 9.0 Wt 2= 16.7 wt 3= 23.0 wt 4= 28.6 wt

concentration by theoretical method.




ln dc (S/m)





0

 *dc D D*

ln (0) 

Fig. 21. Shows the Cole-Cole plots for PANI nanoparticles in PVA matrix at (a) 9 wt %, (b) 16.7 wt %, (c) 23 wt % and (d) 28.6 wt % of AniHCl monomer.

In such spectra the semicircles radius decreases with dose increment, indicating that the resistance *Z*0 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 and Mariappan and Govindaraj*.*, 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 <sup>6</sup> 5.75 10 S/m at 10 kGy and <sup>3</sup> 1.32 10 S/m at 50 kGy for 9.0 wt %. It is <sup>5</sup> 1.0 10 S/m at 10 kGy and <sup>3</sup> 2.95 10 S/m at 50 kGy for 16.7 wt %, while for 23.0 wt % it is <sup>5</sup> 2.40 10 S/m at 10 kGy and <sup>2</sup> 1.26 10 S/m at 50 kGy. For the concentration of 28.6 wt% it is <sup>5</sup> 7.76 10 S/m at 10 kGy and <sup>1</sup> 1.17 10 S/m at 50 kGy. The results are slightly different from the values determined by the extrapolating method. Previously Dutta, *et al*. (2001) measured ac and dc conductivity of chemically doped PVA/PANI blends and obtained the highest dc conductivity of <sup>2</sup> 4.8 10 S/m.

Figure 22 shows the dc conductivity (0) *dc* versus radiation dose of conducting PANI composites for different monomer concentrations. The relation between the radiation dose *D* and the dc conductivity (0) *dc* can be fitted to the empirical exponential relation of the form 0 0 exp( / ) *dc D D* where, 0 is the conductivity at zero doses, *D* is the absorbed dose and *D*0 is the dose sensitivity of the composites to radiation effect. In order to determine the dose sensitivity *D*o of the composites for irradiation, we followed 'Arrhenius type' plot of ln *dc* versus dose, as the gradient of the linear regression plot gives <sup>0</sup> 1 /*D* , where *D*0 is the dose sensitivity of the composites.

Fig. 21. Shows the Cole-Cole plots for PANI nanoparticles in PVA matrix at (a) 9 wt %,

In such spectra the semicircles radius decreases with dose increment, indicating that the resistance *Z*0 of the polymer composites decreases with dose, hence the dc conductivity

0.0E+00

3.0E-01

6.0E-01

Z"

9.0E-01

 *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 and Mariappan and Govindaraj*.*, 2002), while Lewandowski *et al.* (2000) ascribed it to non secured verticality of electrode spikes as well as

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 <sup>6</sup> 5.75 10 S/m at 10 kGy and <sup>3</sup> 1.32 10 S/m at 50 kGy for 9.0 wt %. It is <sup>5</sup> 1.0 10 S/m at 10 kGy and <sup>3</sup> 2.95 10 S/m at 50 kGy for 16.7 wt %, while for 23.0 wt % it is <sup>5</sup> 2.40 10 S/m at 10 kGy and <sup>2</sup> 1.26 10 S/m at 50 kGy. For the concentration of 28.6 wt% it is <sup>5</sup> 7.76 10 S/m at 10 kGy and <sup>1</sup> 1.17 10 S/m at 50 kGy. The results are slightly different from the values determined by the extrapolating method. Previously Dutta, *et al*. (2001) measured ac and dc conductivity of chemically doped PVA/PANI blends and obtained the highest dc

composites for different monomer concentrations. The relation between the radiation dose *D*

*D*0 is the dose sensitivity of the composites to radiation effect. In order to determine the dose sensitivity *D*o of the composites for irradiation, we followed 'Arrhenius type' plot of

*dc* versus dose, as the gradient of the linear regression plot gives <sup>0</sup> 1 /*D* , where *D*0 is the

*dc* versus radiation dose of conducting PANI

1.2E+00 1.6E+00 2.0E+00 2.4E+00 2.8E+00 3.2E+00 Z'

50 kGy (d)

5

*dc* can be fitted to the empirical exponential relation of the form

0 is the conductivity at zero doses, *D* is the absorbed dose and

(b) 16.7 wt %, (c) 23 wt % and (d) 28.6 wt % of AniHCl monomer.

4

40 kGy

1.0E+01 1.5E+01 2.0E+01 2.5E+01 3.0E+01 3.5E+01 Z'

to capacitance interface between the electrode and the dielectric.

(0) 

0.0E+00

3.0E+00

Z"

6.0E+00

9.0E+00

(d)

conductivity of <sup>2</sup> 4.8 10 S/m.

and the dc conductivity (0)

*dc D D* where,

dose sensitivity of the composites.

0 0 exp( / )

ln  

Figure 22 shows the dc conductivity (0)

Fig. 22. Shows the dependence of dc conductivity (σdc) on the applied radiation dose theoretical method. The conductivity obeys the relation of the following form 0 0 exp( / ) *dc D D*

Figure 23 shows the variation of ln (0) *dc* as a function of dose for different monomer concentration of PANI nanoparticles. The linear regressions of the "Arrhenius type plot" ln (0) *dc* versus dose give the slope of 0 1 /*D* from which the dose sensitivity value can be determined, as shown in Table 4. The study reveals that as the monomer concentration increases the dose sensitivity decreases.

Fig. 23. Shows the variation of ln σdc(0) versus radiation dose for different AniHCl concentration by theoretical method.

Synthesis of Polyaniline HCl Pallets and Films Nanocomposites by Radiation Polymerization 143

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

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

Fig. 25. Shows the Raman spectra showing Raman shifts of covalent bond species in the 28.6%-AniHCl nanocomposites of PVA/PANI nanoparticles induced by radiation doping at

1500 1700 1900 2100 2300 2500 2700 2900 3100 3300 3500 Raman shift cm-1

C=O

CH

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

**19. The SEM morphology of PANI nanoparticles** 

C=N C=C

and provide quantitative information of the samples of interest (Barnes, 1998).

cm-1 assigned to C-H bending.

1 2

3

4 5

6

different doses

Raman intensity


Table 4. Shows the relation between monomer concentration and dose sensitivity *D*<sup>0</sup>

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 = -5.1*C* + 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.

Concentration of AniHCl %

Fig. 24. Shows the variation of dose sensitivity *D*0 versus the concentration of AniHCl within the PVA film by theoretical method.

#### **18. 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

*D*0 (the Cole-Cole method) (kGy)

9.0 7.3 7.3 16.7 7.0 6.8 23.0 6.7 6.1 28.6 5.6 5.7

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 = -5.1*C* + 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

Fig. 24. Shows the variation of dose sensitivity *D*0 versus the concentration of AniHCl within

0.09 0.12 0.15 0.18 0.21 0.24 0.27

Concentration of AniHCl %

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

Table 4. Shows the relation between monomer concentration and dose sensitivity *D*<sup>0</sup>

monomer to be irradiated, thus, producing more polarons in conducting PANI.

*D*0(extrapolating method) (kGy)

*D*<sup>0</sup> = -5.1*C* + 7.8

AniHCl concentration (Wt %)

the PVA film by theoretical method.

6.2

6.4

6.6

6.8

Dose sensitivity D0

7

7.2

7.4

**18. Raman scattering analysis of PANI nanoparticles** 

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.

Fig. 25. Shows the Raman spectra showing Raman shifts of covalent bond species in the 28.6%-AniHCl nanocomposites of PVA/PANI nanoparticles induced by radiation doping at different doses

#### **19. 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

Synthesis of Polyaniline HCl Pallets and Films Nanocomposites by Radiation Polymerization 145

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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.
