Malaysian Polymer Journal, Vol. 9 No. 2, p 45-53, 2014 Available online at www.cheme.utm.my/mpj
POLYANILINES PREPARED BY ULTRASOUND ASSISTED POLYMERIZATION: ELECTRICAL, THERMAL AND ANTIMICROBIAL PROPERTIES Nirmala Kumari Jangid1, Narendra Pal Singh Chauhan2,#, Samadrita Goswami3 and Pinki B. Punjabi1 Department of Chemistry, University College of Science, Mohan Lal Sukhadia University, Udaipur-313001, Rajasthan, India 2 Department of Chemistry, B. N. P. G. College, Udaipur-313001, Rajasthan, India 3 Polymer Research Laboratory, Department of Chemistry, Dibrugarh University, Dibrugarh –786004, Assam, India
1
Corresponding author’s email:
[email protected]
Abstract: Polyaniline (PANI) and ring-substituted PANIs are well-known conducting functional polymers that are routinely prepared by the stoichiometric oxidative polymerization of aniline (ANI) and its derivatives with ammonium persulphate. Electrical and thermal properties of chemically synthesized polyanilines are found to be affected by varying the protonation media. The synthesized polyanilines have been characterized by various analytical techniques like UV – visible spectroscopy, IR spectroscopy, gel permeation chromatography (GPC), Thermal gravimetric analysis (TGA) and differential thermal analysis (DTA) techniques. Temperature dependence of AC conductivity has been studied to learn about the electrical conduction behavior in the materials. The electrical conductivity of the new material is found to be in the range of 10 -7 to 10 -5 Scm-1. The conductivity has also been found to be highest for orthophosphoric acid doped polyaniline among the synthesized polyanilines. For study of antimicrobial behavior of the synthesized polyanilines different microorganisms, including the bacteria Escherichia coli (MTCC 442), Pseudomonas aeurginosa (MTCC 441), Staphylococus aureus (MTCC 96), and Staphylococus pyogenus (MTCC 443) and fungal strains Candida albicans (MTCC 227), Aspergillus niger (MTCC 282) and Aspergillus clavatus (MTCC 1323), were chosen based on their clinical and pharmacological importance. Keywords: Acidic media, thermal analysis, antibacterial and antifungal activity, AC impedance spectroscopy.
1.
INTRODUCTION
Conducting polymers have been extensively studied during the past couple of decades and they still remain the subject of intense investigations by many research groups worldwide[1–3]. Polyaniline (PANI) and ringsubstituted PANIs are well-known conducting functional polymers [4, 5] that are routinely prepared by the stoichiometric oxidative polymerization of aniline (ANI) and its derivatives with ammonium persulphate [6-8]. This reaction gives, in addition to PANI in the emeraldine salt (ES) state, a high amount of ammonium hydrogen sulfate as byproduct [9,10]. Though this byproduct does not deteriorate functional properties of PANI, its removal from neat PANI represents about one half of the PANI cost [11]. Therefore, the development of preparative processes that can reduce contamination of formed PANI with byproducts is of importance, since it can potentially bring about considerable savings. The novel properties of PANI have shown its potential in technological applications such as rechargeable batteries, electrochromic displays, high performance composites and sensors [12-14]. Although the synthetic methods to produce polyaniline are quite simple, its mechanism of polymerization and the exact nature of its oxidation chemistry are quite complex.
Because of its rich chemistry, polyaniline is one of the most studied conducting polymers of the past 50 years. PANI occurs in three different oxidation states as shown in Figure 1.
Figure 1: Three different redox forms of polyaniline (a) Leucoemeraldine base (LB, colourless), (b) Emeraldine salt (ES, green) and (c) Emeraldine base (EB, blue). The emeraldine salt, the only conducting form of PANI has been extensively studied in past years. The polyemeraldine form can be doped chemically or electrochemically with various anions, resulting in a significant change in the electronic transport properties [15,16]. Ultrasound can lead to new chemical reaction and improve the reaction rate, and thus opens up a new chemistry i.e. sonochemistry [17]. Especially, high intensity ultrasound not only can accelerate the heterogeneous liquid–liquid chemical reactions, but also can break the aggregation and reduce the particle size due to its dispersion, crushing, emulsifying and activation effect, and thus has a better
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Jangid, N. K. et al. Malaysian Polymer Journal, Vol. 9, No. 2, p 45-53, 2014
2.2
Methods
All chemicals used in this study were of analytical reagent grade and used as received. The PANI was synthesized by chemical oxidative polymerization of aniline in an aqueous acidic media containing 1.0 M of each of the acids (orthophosphoric acid, hippuric acid and tosic acid) in doubly distilled water. Polymerization was initiated by the dropwise addition 1.0 M of an oxidizing agent [(NH4)2S2O8] to the acidified solution containing the aniline monomer at the room temperature under constant stirring on ultrasonic bath for ½ hour. After completion of the polymerization reaction the blue colored polyaniline was isolated by filtration and washed with doubly distilled water and
Orthophosphoric acid Hippuric acid Tosic acid Tetrahydrofuran Dimethyl sulphoxide Dimethyl formamide Toluene m-cresol
2.3
Ranbaxy, India Ranbaxy, India Ranbaxy, India Sigma– Aldrich, India Sigma– Aldrich, India Sigma– Aldrich, India Sigma– Aldrich, India Sigma– Aldrich, India
Viscosity (mPa.s at 25˚C)
The suppliers, molecular weights, viscosities and density of the materials are listed in Table 1. All the others chemicals were analytical grade commercial products and used without any additional purification. Double-distilled and de ionized (DDI) water was used throughout.
Ammonium persulphate
Merck, India Thomas Baker, India
Density (g/cm3 at 20˚C)
2. MATERIALS AND METHOD 2.1 Materials
Aniline
Molecular weight
The antimicrobial properties of conductive functionalized polyanilines have been investigated by exploring their interaction with bacterial cells. It was observed that lower concentrations (< 0.001) of PANI strongly inhibited the growth of wild-type Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus as well as several antibiotic resistant clinical pathogens [21]. Polyaniline-Zr (IV) sulphosalicylate has also been tested against various bacterial (Escherichia coli, Bacillus thuringiensis and Pseudomonas aeruginosa) and fungal strains (Aspergillus nigrus, Fusarium oxysporum and Penicillium chrysogenum) and relatively higher activities were observed than for known antibiotics [22].
Table 1: Molecular weights and densities of different chemicals Manufacturer
In this study, we develop a method, i.e. ultrasonic assisted polymerization to prepare advanced conducting polymeric materials. The method is especially useful for preparation PANI - EB because the preparation of conductive PANI needs to be in strong acid medium and PANI is an easily aggregated substance. In order to synthesize semi-conducting PANI-EB to achieve both good conductivity and thermal stability, many researchers have adopted the strategy to co-dope PANI with both inorganic acids and organic acids [18,19]. However, the influence of inorganic acids and organic acids on thermal stability of doped PANI has not been extensively investigated. In this research, inorganic (orthophosphoric acid) and organic acids (hippuric and tosic acids) doped polyanilines were synthesized by oxidative polymerization of aniline. It has been observed that the synthesized emeraldine base form of polyanilines show reasonably good room temperature conductivity and better thermal stability. A biocatalytic approach of conducting polyaniline has been studied [20].
acetone until the filtrate was colorless to ensure the complete removal of unreacted protonic acid and oxidizing agent. PANIs synthesized by this method were found dark green in color. The precipitate was allowed to equilibrate with an appropriate amount of ammonium hydroxide overnight. This process converted (dedoped) the PANI to its EB form shown in Figure 2. A free flowing powder of the polyaniline was obtained by drying it in an oven at 50–90 °C for 24 h. The dark green powder was then subjected to characterization.
Type of material
control on the morphology of particles, especially on the hard solid particle such as PANI.
93.13
1.0217
3.71
228.18
1.98
-
97.995
1.885
2.4 – 9.4
179.17
1.371
-
172.20
1.24
-
72.11
0.8892
0.48
78.13
1.1004
1.996
73.09
0.948
0.92
92.14
0.87
0.590
108.14
1.034
184.23
Characterization
The UV–visible (UV–vis) spectra of the polyaniline were recorded by using DMF as solvent. For this purpose, a Hitachi U3210 spectrophotometer was used in the range of 300–900 nm. A Perkin Elmer Spectrum-2000 Fourier transform IR spectrophotometer was used to obtain the IR spectra between 400 and 4000 cm-1. The samples were prepared in pellet form using spectroscopic grade KBr. The thermal studies were performed using a Mettler–Toledo 821 thermogravimetric analyzer in a nitrogen atmosphere from 100 ˚ C to 1000 °C at a heating rate of 10 °C/min. DTA analysis were performed using AIMIL 1600 DTA analyzer from 100 ˚ C to 1000 °C at a heating rate of 10 °C/min. The average molecular weight and its polydispersity index were determined with Gel Permeation chromatography (GPC) analysis. It was performed with a set up consisting of a Perkin- Elmer 200 pumps and 2 ultra styragel columns (104, 500 Ao) MPJ 46
Jangid, N. K. et al. Malaysian Polymer Journal, Vol. 9, No. 2, p 45-53, 2014 with THF as the eluent at a flow rate of 1 mL/min equipped with Waters differential refractometer and calibrated with the standard linear PSt.
3. RESULT AND DISCUSSION 3.1 Solubility Synthesized polyanilines are soluble in different solvents like tetrahydro furan (THF), dimethyl sulphoxide (DMSO), dimethyl formamide (DMF), toluene and m-cresol. Yield and solubility of different PANIs are depicted in Table 2. Table 2: Yield and solubility of PANI samples Polyaniline code
Yield
PANI-PA
90%
PANI-TA
80%
PANI-HA
75%
3.2
Figure 2: Scheme for the mechanism of a doping process. The electrical conductivity of the samples was evaluated from the complex impedance –admittance plots recorded at different temperatures using a HIOKI LCR HiTESTER 3522 frequency response analyzer. The experiment was carried out under a relative humidity of 57%. Humidity was controlled by using By-Air FFB Series Compact Dehumidifier (Model: FFB-170). Relative air humidity was measured from dry and wet bulb temperatures. For Antimicrobial studies following microorganisms Escherichia coli (MTCC 442), Pseudomonas aeurginosa (MTCC 441), Staphylococus aureus(MTCC 96), and Staphylococus pyogenus (MTCC 443) and fungal strains Candida albicans (MTCC 227), Aspergillus niger (MTCC 282) and Aspergillus clavatus (MTCC 1323) were chosen based on their clinical and pharmacological importance. The bacterial and fungal stock cultures were incubated for 24 h at 37˚C on Nutrient Agar and potato Dextrose Agar medium (Microcare lab., Surat, India) following refrigeration storage at 4˚C. The bacterial strains were grown in Mueller – Hinton agar (MHA) plates at 37˚C (the bacteria were grown in the nutrient both at 37˚C and maintained on nutrient agar slants at 4˚C) whereas the yeasts and molds were grown in sabouraud dextrose agar (SDA) and potato dextrose agar (PDA) media, respectively at 28˚C. The stock cultures were maintained at 4˚C.
Solubility THF, DMSO, DMF, Toluene, m-cresol THF, DMSO, DMF, Toluene, m-cresol THF, DMSO, DMF, Toluene, m-cresol
UV- Visible spectra
UV–vis absorption spectra of PANI- PA, PANI- TA and PANI – HA in DMF as a solvent. The first absorption with maxima at 321 nm is assigned to - transition of benzoid rings on the basis of studies of polyaniline [8, 23]. The second absorption with maxima at 605 nm is assigned to the transition of quinoid rings. In the spectra of these polymers, the polymer exhibits a sharp peak at 360 nm and a small shoulder at 605 nm. The sharp and intense peak at 360 nm represents the localized polarons, which are characteristics of the protonated polyanilines, whereas, a shoulder at 605 nm can be assigned to the conducting emeraldine salt phase of the polymer. A sharp peak at 605 nm present in PANI - PA is due to the polaronic peak and is characteristic of the protonated form of PANI. This clearly indicates that the polymer is composed of mixed oxidation state phases. Among the different acids used for the synthesis, PANI - PA shows the highest selectivity of all the acids in obtaining the conducting emeraldine salt phase of the polymer. 3.3
FTIR spectra
Figure 3 represents the FTIR spectra of PANI doped with different acidic media. An intense band at 829 (or 830 cm-1) cm-1 is observed in all the PANIs, which is the characteristic of the paradisubstituted aromatic rings through which the polymerization proceeds. The polymers show two intense bands at 1165 and 694 cm 1 , representing in plane and out of plane C - H bending motions of benzenoid rings. The stretching bands that are characteristics of an aromatic amine are observed in the region between 1165 and 1307 cm-1. The C - H stretching region of aromatic C - H is easily identified at 2923 cm-1. The N – H stretching region of aniline is observed on 3367 cm-1. The higher frequency vibration at 1591cm-1 has a major contribution from the quinoid rings. The lower frequency mode at 1504 cm-1 depicts the presence of benzenoid rings. The presence of both these bands clearly shows that the polymer is composed of amine and imine units. Further, it gives support to an earlier prediction of the presence of different oxidation states of the polymer. The relative intensities of these bands points toward the oxidation MPJ 47
Jangid, N. K. et al. Malaysian Polymer Journal, Vol. 9, No. 2, p 45-53, 2014 state of the material [23]. A comparison of the ratio of the relative intensity of quinoid to benzenoid ring modes (I ~ 1592/ I ~ 1504) shows the highest ratio of ~ 1.05 in PANI – PA compared to PANI – TA & PANI – HA. From the above results it can be concluded that the formation of emeraldine base is predominant in orthophosphoric acid doped PANI.
Table 3: Molecular weights of PANI Polyaniline code
Number average molecular weight (g/mol)
Weight average molecular weight (g/mol)
Polydispersity index (PDI)
PANI-PA PANI-TA PANI-HA
19,075 30, 865 29,784
32,619 50,001 45,569
1.71 1.62 1.53
Figure 3: FT-IR spectra for (a) PANI - PA (b) PANI - TA and (c) PANI – HA 3.4
Molecular weights
The average molecular weight and its distribution for different PANIs are reported in (Table 3). The molecular weight distribution of all samples showed only one peak and thus confirmed that polyanilines were completely synthesized. Moreover, this also confirmed that the unreacted aniline was completely washed away by acetone and alcohol. The number average molecular weight (Mn) of PANI-PA, PANI-TA, and PANI-HA are 19.07, 30.86 and 29.78 kDa respectively [23, 24]. The molecular weight (M n) of PANI-PA was higher than that of PANI-TA and PANI-HA, because it has higher polyaniline segments than the others. 3.5
Thermal studies
Figure 4 depicts the thermograms of synthesized different acids doped PANIs. The thermograms of these PANIs reveal a common feature having a threestep decomposition pattern [23, 24]. The three steps in the decomposition curve can be attributed to the loss of water molecules present in the polymer matrix, loss of dopant, cross linking (Figure 5) and complete decomposition and degradation of the polymer backbone. Thermal stability measurements of these materials give two distinct stages in the thermograms and also in the differential thermal analysis.
Figure 4: TG thermograms for (a) PANI – PA (c) PANI – TA (e) PANI – HA and DTA thermograms for (b) PANI – PA (d) PANI – TA and (f) PANI – HA Figure 4(a, c and e) shows the TG curve of the PANI-PA, PANI-HA and PANI-TA, respectively. Three different weight loss steps exist, two at low temperatures are weak losses and one in high temperature the large losses. The first loss, up to 100 ˚C, corresponds to the removal of the weakly bound water, whereas, the second step at 250 ˚C corresponds to the loss of more strongly bound water between the layers. A fast and large weight loss is observed at 320˚ C in the PANI- PA which corresponds to the oxidative combustion of the organic polymer components. The weight loss corresponding to the third step (above 410 ˚ C) is mainly due to thermal decomposition of PANI into some chemical forms.
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Jangid, N. K. et al. Malaysian Polymer Journal, Vol. 9, No. 2, p 45-53, 2014 Furthermore, the DTA curve (Figure 4 b) also shows a large exotherm peak at 400 ˚C due to the deep combustion of PANI- PA. The first weak loss in Figure 4(c, e) below 100 ˚C corresponds to the removal of the bound water in PANI / hippuric acid and PANI / tosic acid composites. Both figure show PANI - TA and PANI – HA loses slowly and monotonously its weight continuously from 100 to 600 ˚C in the nitrogen atmosphere due to continual heat degradation of PANI. DTA curves Figure 4(d, f) also shows exotherm peak at 250 and 280 ˚C respectively. The main decomposition gap is observed at 150 ˚C on the basis of thermal studies. It has been suggested that the thermal stability of the PANI – PA acid composite under N2 flow is better than PANI - TA and PANI – HA. The loss of water molecules is found to be almost identical in all the PANIs. However, the second step loss (at 125 - 300 °C) that is due to the dopant ion is found to be higher in orthophosphoric acid doped PANI compared to the tosic acid and hippuric acid doped PANI.
3.6
Conductivity analysis
Experimental observations on PANI produced in the standard fashion indicated disordered semiconductors. It is well known that disorder induces electron localization, and if the magnitude of this disorder potential is comparable to the conduction band-width, then complete localization will take place and the system will be an insulator. Weaker disorder introduces a mobility edge, separating localized electron states near the band tails from extended states further into the band. The insulator behavior of doped PANI has been explained by a number of theories, but most commonly as a phase separated mixture of metallic crystalline islands (delocalized electrons) embedded in an insulating amorphous sea (localized electrons) [25]. Molecular orientation in conducting polymers clearly is a desirable characteristic, improving both inter- and intra-chain transport. However, without any orientation, the materials have, nevertheless, been classified as disordered metals close to the critical regimes [26]. The existence of this metallic state has been attributed to the improved structural order and fewer defects of the molecular scale. The following results reveal that considerable intrinsic orientation does exist in solution cast films, and that it is this decrease in structural disorder that allows the material’s intrinsic metallic state to be partially revealed. For this reason, thickness and dopant of the polyanilines film is an important parameter to improve better transport characteristics. The conductivity of the polyanilines is measured by AC impedance spectroscopy. Figure 6 (a, b, c) presents the typical impedance plot of different polyanilines at 30 °C. As illustrated in Figure 6, the complex impedance plot is in the form of two regions: an arc and a linear region. The arc at medium-high frequencies is related to the conduction process, and the straight line inclined with respect to the real axis at lower frequencies is due to the effect of blocking electrodes.
Figure 5: Scheme for the mechanism of cross-linking of PANI during thermal treatment. Figure 6: AC impedance spectra for (a) PANI – PA (b) PANI – TA and (c) PANI – HA at 30 °C. MPJ 49
Jangid, N. K. et al. Malaysian Polymer Journal, Vol. 9, No. 2, p 45-53, 2014
The electrical conductivity is obtained from the relation, σ = t / Rb. A where, σ is the conductivity, t is the thickness, A is the area and Rb is the bulk resistance of the film, which can be estimated by the intercept of the arc with the real axis of the complex impedance spectrum [27]. The AC conductivities at 30 °C for PANI-PA, PANI-HA and PANI-TA are shown in (Table 4). As seen in the Table 4, the conductivity of PANI- PA shows an enhancement in comparison with primary polyaniline. The conductivity of PANI- PA is caused by two factors, i.e. two conductivities interfere in the total conductivity. The first is the electronic and the second is the ionic conductivity. Probably ionic conductivity is caused by phosphate ions as counter ion of the inorganic acid used for doping. Table 4 demonstrates a increases firstly and then decreases in conductivity of the blend beyond 70 oC. It has been reported that heating (annealing) of PANI samples increases their conductivity in some cases. This behavior is most likely due to a crosslinking reaction and evolution of the dopant during the heat treatment process. Ahlskog et al. [28] observed that in the case of PANI dodecylbenzenesulfonic acid (DBSA), heating accelerates the doping reaction of PANI by DBSA, accompanied by a phase transition from a paste-like material to a semi-solid material. Berner et al. [29] observed anannealing effect after moderate heating of PANI–CSA films in ambient air (typically for 30 min at 135oC), accompanied by an increase of crystallinity, while the electronic transport properties improved to more metallic behavior. Adams and coworkers [30] synthesized polyaniline films by an acid-processing route that exhibited metallic conductivity and electrical transport strongly dependent on film thickness, i.e. on intra-chain molecular dynamics. They observed that increasing film thickness results in globule formation and causes a slight decrease in conductivity behavior is most likely due to a crosslinking reaction and evolution of the dopant during the heat treatment process. Rannou et al. [31-33] attributed a decrease of conductivity of doped PANI due to its chemical degradation, caused by two main processes: (i) Dedoping and (ii) oxidation/hydrolysis/chain scission.
We investigated the effect of temperature on conductivity of non-irradiated PANI taking inorganic acids and organic acids. We have observed a slightly increase initially and after that decrease in conductivity as temperature increased. This is a very common observation for semi-conductor materials. In general, when temperature of a semiconductor raises, more bonds break and intrinsic conduction increases because more free electrons and holes are produced; thus resistance of a semiconductor decreases, resulting in increasing conductivity. One reason is suspected to be that when the pellet was subjected to the higher temperature the dedoping occurs, leading to decrease in concentration of doped PANI. There is large decrease in p electron delocalizaion due to deprotonation of primary and secondary dopants and hence destruction of polaron structure. 3.7
Antimicrobial properties
The antimicrobial activity of PANI –PA, PANI –TA and PANI – HA were studied in different concentration (5µg/ml, 25µg/ml, 50µg/ml, 100µg/ml) against four pathogenic bacterial strains (E. coli MTCC 442, P. aeurginosa MTCC 441, S. aureus MTCC 96 and S. pyogenus MTCC 443) and three fungal strains (C. albicans MTCC 227, A. niger MTCC 282 and A. clavatus MTCC 1323). Antibacterial and antifungal activity of PANI –PA, PANI –TA and PANI – HA were assessed in terms of Minimal Inhibition Consecration (MIC). The results of antibacterial activity and antifungal activity are presented in Table 5 and Table 6 respectively. As compared to standard drugs, the results revealed that in PANI (PA, TA, HA) for bacterial activity, S. aureus were more sensitive as compared to E. coli, P. aeurginosa and S. pyogenus, and for fungal A. clavatus shows good result as compared to C. albicans and A. niger. PANI – PA found to be more active for S. aureus as compared to standard drugs (Chloramphenicol and Ciprofloxacin and Amphicilin), PANI – TA and PANI – HA found to be more active for S. aureus as compared to standard drugs (Amphicilin) which is shown in Figure 7. PANI – PA found to be more active for C. albicans and A. clavatus as compared to standard drugs (Nystatin and Greseofulvin), PANI – TA and PANI – HA found to be more active for C. albicans as compared to standard drugs (Greseofulvin) which is shown in Figure 8.
Table 4: Temperature vs. conductivity data at 30 °C for different PANI PANIs
σ (S cm-1) 30 oC
40 oC
50 oC
60 oC
PANI – PA
3.70×10-5
4.31×10-5
9.23×10-5
6.74×10-5
PANI – TA
2.8×10-7
4.42×10-7
6.35×10-7
PANI – HA
3.29×10-7
5.54×10-7
6.58×10-7
70
C
80 oC
90 oC
4.62×10-5
2.52×10-5
2.84×10-5
8.26×10-7
3.98×10-7
2.57×10-7
4.48×10-7
2.04×10-7
5.88×10-7
4.43×10-7
5.9×10-7
o
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Jangid, N. K. et al. Malaysian Polymer Journal, Vol. 9, No. 2, p 45-53, 2014 Table 5: Antibacterial activity
1. 2. 3. 4. 5. 6. 7. 8.
PANI – PA PANI – TA PANI – HA Gentamycin Amphicilin Chloramphenicol Ciprofloxacin Norfloxacin
200 125 62.5 0.05 100 50 25 10
62.5 200 250 1 100 50 25 10
25 70 200 0.25 250 50 50 10
S. pyogenus
S. aureus
P. aeruginosa
Compounds E. coli
S. No.
Minimal Inhibition Concentration (microgram/mL)
50 90 200 0.5 100 50 50 10
Table 6: Antifungal activity
4.
CONCLUSION
A. clavatus
PANI – PA PANI – TA PANI – HA Nystatin Greseofulvin
A.niger
1. 2. 3. 4. 5.
C. albicans
S. No.
Minimal Inhibition Concentration (microgram/mL) Compounds
90 110 150 100 500
150 190 130 100 100
80 120 95 100 100
Synthesized polyanilines (PANI –PA, PANI – TA and PANI HA) are not studied previously by any researchers and scientists. Spectroscopic studies of synthesized polyanilines showed that complete polymerization takes place by oxidative polymerization method. Thermal studies showed that orthophosphoric acid doped polyaniline is more thermally stable as compared to PANI – TA and PANI – HA because in PANI – PA more cross inking are present. These results were further by molecular weight and conductivity measurements. Among these acids, orthophosphoric acid was found to be more suitable as a protonic acid medium in order to have a PANI with high conductivity. Conductivity was observed in the range of 10 -7 to 10-5 S /cm depending on the acid used for polymerization. The initial increase in conductivity was due to better charge transfer. In this current investigations found that synthesized polyanilines have good antibacterial and antifungal activity as compared to standard drugs. 5.
ACKNOWLEDGEMENTS
One of the authors (Nirmala Kumari Jangid) is thankful to Council of Scientific and Industrial Research, New Delhi for providing financial assistance in the form of SRF.
Figure 7: Antibacterial activity against (E. coli MTCC 442, P. aeurginosa MTCC 441, S. aureus MTCC 96 and S. pyogenus MTCC 443).
Figure 8: Antifungal activity against (C. albicans MTCC 227, A. niger MTCC 282 and A. clavatus MTCC 1323). 6.
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