Chemical synthesis and characterization of highly soluble conducting polyaniline in mixtures of common solvents J. Serb. Chem. Soc. 80 (7) 917–931 (2015) UDC 678.652+542.913+547.462.3: JSCS–4769 544.351.3:66.095.26 Original scientific paper 917 Chemical synthesis and characterization of highly soluble conducting polyaniline in mixtures of common solvents HICHEM ZEGHIOUD1*, SAAD LAMOURI1, ZITOUNI SAFIDINE1 and MOHAMMED BELBACHIR2 1Laboratoire de Chimie Macromoléculaire, Ecole Militaire Polytechnique, BP 17, Bordj El Bahri, Alger, Algeria and 2Laboratoire de Chimie des Polymères, Département de Chimie, Faculté des Sciences, Université d’Oran, BP 1524 El’Menouer Oran 31000, Algeria (Received 19 July, revised 29 December 2014, accepted 8 January 2015) Abstract: This work presents the synthesis and characterization of soluble and conducting polyaniline–poly(itaconic acid) PANI–PIA according to a chemical polymerization route. This polymerization pathway leads to the formation of doped polyaniline salts, which are highly soluble in a number of mixtures between organic common polar solvents and water, the solubility reaches 4 mg mL-1. The effect of synthesis parameters, such as doping level, on the con- ductivity was investigated and a study of the solubility and other properties of the resulting PANI salts were also undertaken. The maximum of conductivity was found equal to 2.48×10-4 S cm-1 for fully protonated PANI-EB. In addi- tion, the synthesized materials were characterized by various methods, i.e., vis- cosity measurements, XRD analysis and FTIR and UV–Vis spectroscopy. Fin- ally, TGA was performed to obtain some information concerning the thermal behaviour of the materials. Keywords: conducting polymer; PANI; itaconic acid; polymerization; solubility properties. INTRODUCTION The synthesis and improvement of new materials with special properties have attracted much attention in the last decade. Polyaniline (PANI) is one of the most promising polymers due to its good flexibility, low cost, oxidative stability and unique conduction mechanism.1–3 However, there are some major draw- backs, which limit its application, such as low thermal stability and poor sol- ubility in common solvents due to the stiffness of backbone and H-bonding inter- actions between adjacent chains.4,5 * Corresponding author. E-mail: hicheming@yahoo.fr doi: 10.2298/JSC140719003Z _________________________________________________________________________________________________________________________ (CC) 2015 SCS. All rights reserved. Available on line at www.shd.org.rs/JSCS/ 918 ZEGHIOUD et al. Recently a number of studies have been devoted to the search for different synthetic methods that allow PANI to be obtained with good solubility in the presence of different polymeric acids with different structures,6–9 which improve processibility, special electrical conductivity and optical and spectroscopic pro- perties. Barrios et al.10 reported the electro-synthesis of PANI in the presence of poly(itaconic acid) and they evaluated the effect of the presence of dicarboxylic acids on the electrochemical behaviour of the obtained films. Nevertheless, the electrochemical methods generated polyaniline with very low solubility that was difficult to process and had restricted application. Travas-Sejdic et al.11 studied the electrochemical properties of self-assembled multilayer films based on polyaniline and two polyanions: poly(styrene sul- phonate) (PSSA) and an oligonucleotide (ON), and found by cyclic voltammetry experiments that PANI/PSSA and PANI/ON films had different electrochemical behaviours, with PANI/ON films showing lower electroactivity. Gizdavic-Nikolaidis et al.12 recently demonstrated that a conductive poly- mer nanofibrilar network of poly(lactic acid) can be electrospun with PANI, and its copolymers with m-aminobenzoic acid (m-ABA) from DMSO/THF solutions. Abdul Rahman et al.13 found that the number average molecular weights of the copolymers decreased significantly with increasing m-ABA fraction in the copolymers, and the solubility increased with increasing proportion of m-ABA. This increase was due not only to the functional COOH groups, but also to the decrease in the average length of the polymer chains. Gribkova et al.14 reported the chemical polymerization of aniline in the pre- sence of aromatic polyamides containing sulphonic groups. They observed that the presence of the flexible-chain of polyamides with a regular distribution of sulphonic groups along the polymer chain allowed the polyaniline to exhibit a random coil conformation in the presence of strong electrolytes and the for- mation of water-soluble interpolymer complexes of PANI with polyacids. Wang et al.15 prepared polyaniline nanorods by chemical oxidative poly- merization using itaconic acid as dopant. The polyaniline salt obtained, compared to the undoped form, possessed high productivity, conductivity and excellent solubility in organic solvents such as NMP, THF and DMF, which reached 19 mg mL–1. The main goal of the present work was the chemical doping of PANI in the presence of poly(itaconic acid) (PIA). PIA is a very exciting material due to its biocompatibility with natural systems. In addition, PIA is very attractive because it has two negatively charged carboxylic groups in each monomer unit. The essential advantage of the resultant PANI was the possibility of producing con- ductive PANI blends with good solubility. The spectral, thermal and electrical properties of the obtained PANI molecular composites were studied. _________________________________________________________________________________________________________________________ (CC) 2015 SCS. All rights reserved. Available on line at www.shd.org.rs/JSCS/ HIGHLY SOLUBLE CONDUCTING POLYANILINE 919 EXPERIMENTAL Materials Aniline (ANI, 99 % pure) was purchased from Fluka. Other provided materials were hydrochloric acid (35.37 %) from Organics Stinnes Chemicals, methanol (99.5 %) and ammo- nium peroxodisulphate (APS, 99 %) from Prolabo. Potassium peroxodisulphate (PPS, 99 %) was from Riedel-de Haëen, acetone (99 %) from Acros Organics, while ammonia (25 % solution), N-methylpyrrolidone (NMP, 99.5 %) and tetrahydrofuran (THF, 99 %) were from Merck. Itaconic acid (99 %) was purchased from Aldrich, dimethyl sulphoxide (DMSO, 100 %) from Analytical Reagent. Deionised water was used throughout the experiments and all chemicals were used without previous purification. Synthesis of PANI The synthesis of the PANI-EB was as follows: 4.8 g of aniline (4.75 mL) and 15 ml of HCl were dispersed in 50 mL of deionised water under vigorous stirring at room temperature for 2 h to obtain a uniform solution. Then, an aqueous solution of APS (11.8 g + 50 mL deionised water) was added to the above mixture in one portion (the mole ratio ANI:APS = 1). The resulting solution was stirred for 30 min to ensure complete mixing, and then the reaction was followed by continuous stirring at 2 °C for 4 h. The precipitate that formed was filtered off, washed with deionised water and methanol until the filtrate was colourless to remove excess acid and possible oligomers. Finally, the powder was dried under vacuum for 48 h. Then, the obtained PANI as the emeraldine salt (PANI-ES) was stirred in 1 M solution of ammonium hydroxide at room temperature for 72 h to completely convert it to emeraldine base (PANI-EB) form. Upon filtering and drying under a dynamic vacuum in an oven at 60 °C for 24 h, the base form of PANI was obtained as a blue powder. The yield of the polymer- ization was 80 %. Poly(itaconic acid) synthesis The synthesis was carried out similarly to that described in work of Larez et al.16 Thus deionised water (10 mL) was heated until boiling and left to reach ambient temperature with continuous stirring and under nitrogen bubbling. Itaconic acid (IA, 0.023 mol) and PPS (2.22×10-4 mol) were added and the system was sealed and placed in a thermostatic bath at 60 °C with continuous stirring during 48 h. A heterogeneous mixture was initially obtained due to an incomplete dissolving of IA that went transparent after 5 min. After the polymerization reaction time was over, the reactor was left to cool down to room temperature under con- tinuous stirring (about 30 min). Polymer was separated by precipitation in cool acetone. The repeat unit of the resulting polymer (PIA) is shown in Scheme 1. Scheme 1. Chemical structure of the repeat unit of poly(itaconic acid) PIA. Doping The polymeric acid-doped PANI was prepared by mixing 0.9 g of PANI-EB (0.0025 mol, based on the approximate tetrametric repeat unit) in a THF dispersion with the appropriate quantity _________________________________________________________________________________________________________________________ (CC) 2015 SCS. All rights reserved. Available on line at www.shd.org.rs/JSCS/ 920 ZEGHIOUD et al. of poly(itaconic acid) solution of different mole ratios (based on its acidic repeat unit). The suspension was sonicated in a bath-type sonicator for 2 h followed by electromagnetic stirring (12 h) to make the dispersion homogeneous. The dispersion of PANI–PIA was filtered using poly- tetrafluoroethylene membrane filters of pore size 0.45 µm. The resultant powder was washed with large quantities of distilled water until the filtrate became colourless and the powder was dried in an oven at 60 °C for 24 h. The reaction mechanism is shown in Scheme 2. Scheme 2. Mechanism of PANI-EB doping with PIA. Characterization The Fourier transform infrared (FTIR) spectra were recorded between 400 and 4000 cm-1 from KBr pellets on an infrared Fourier transform spectrometer (Shimadzu type 8400 S). The UV– –Vis spectra of all samples dissolved in different solvents were recorded using a UV–Vis spectrometer Shimadzu UV-2401PC, in the wavelength range of 250–900 nm. The intrinsic viscosity measurements of solutions were made using a Micro-Ubbelohde Schott-Gerate viscosimeter. The X-ray powder diffraction patterns were recorded on a PANalytical X'Pert PRO diffractometer fitted with CuKα radiation (λ = 1.5404 nm) at 40 kV and 40 mA in the 2θ range 5– –60° region. Thermogravimetric (TG) analysis was performed using a Setaram MTB instrument with “10-8” sensitivity, operating at a heating rate of 10 °C min-1, from room temperature up to 450 °C under an air atmosphere. The sample mass ranged between 3 and 6 mg. RESULTS AND DISCUSSION Conductivity measurements The electrical conductivity measurements of compressed pellets of PIA- -doped PANI were made by the conventional four-point probe technique at room _________________________________________________________________________________________________________________________ (CC) 2015 SCS. All rights reserved. Available on line at www.shd.org.rs/JSCS/ HIGHLY SOLUBLE CONDUCTING POLYANILINE 921 temperature; the data are plotted in Fig. 1. The curve showing the evolution of the electric conductivity (σ) according to the doping level follows an exponential form. Indeed, the values of the electrical conductivity order of 10–4 were found for PANI–PIA, whereby a high conductivity value of 2.48×10–4 S cm–1 for the PANI–PIA was reached when the PANI-EB (conductivity value of 8.14×10–10 S cm–1) was fully protonated, showing that the resultant PANI–PIA was less conductive than the PANI–HCl, which has a conductivity of 4.6 S cm–1. This was confirmed by the narrower band gap for PANI–HCl around 3.2 eV compared with the PANI–PIA (Table I). Note that each measured value of conductivity is an average of four measurements for each face of the pellet. Fig. 1. The conductivity of PANI–PIA at different [PIA repeat unit]/[EB tetramer] mole ratio. TABLE I. Conductivity and the energy band gap of different forms of PANI Sample UV–Vis band, nm Conductivity, S cm-1 Energy band gap, eV 1 2 PANI–HCl 387 467 4.60 3.20 PANI-EB 331 626 8.14×10-10 – PANI–PIA 304 347 2.48×10-4 4.08 Fourier transform infrared spectroscopy (FTIR) FTIR spectra of IA and its polymer (PIA) are shown in Fig. 2. The assign- ments of the FTIR bands of IA, PIA, PANI-EB and PANI–PIA are given in Table II. The spectra of IA and PIA showed a broad band between 2775 and 3480 cm–1,17 which was attributed to O–H stretching vibrations. The spectrum of IA showed peaks at around 1700,18 143018 and 1220 cm–1,19 indicating the stretch- ing vibrations of C=O (carboxylic acid), C–O–H in plane and C–O, respectively. The spectrum of the PIA showed the peaks at around 1730,20 140019 and 1193 cm–1,21 indicating the stretching vibrations of C=O, C–O–H and C–O, _________________________________________________________________________________________________________________________ (CC) 2015 SCS. All rights reserved. Available on line at www.shd.org.rs/JSCS/ 922 ZEGHIOUD et al. respectively. The peak at 1629 cm−1 in the curve (t = 0 h) in Fig. 2,18 charact- erizes the presence of C=C bond coming from itaconic acid. However, this peak was absent in PIA spectrum, which confirmed the polymerization of IA. Fig. 2. Kinetics of the polymerization reaction of itaconic acid from IA (t = 0 h) to PIA (t = 48 h) determined by FTIR spectroscopy. TABLE II. Assignment of FTIR bands (wavenumber, cm-1) of IA, PIA, PANI-EB and PANI–PIA Sample Assignment IA PIA 2775–348017 2775–348017 O–H stretching vibration 170018 173020 C=O stretching vibration 162918 – C=C stretching vibration 143018 140019 C–O–H stretching vibration 122019 119321 C–O in of plane bending vibration PANI-EB PANI–PIA Assignment 343522 343522 N–H stretching vibration – 171927 C=O stretching vibration 158323 156828 N=Q=N Stretching rings 149424 148529 N–B–N stretching ring 129225 129225 C–N+ stretching in secondary amines 51126 51126 C–H out-of-plane bending 1,4 ring _________________________________________________________________________________________________________________________ (CC) 2015 SCS. All rights reserved. Available on line at www.shd.org.rs/JSCS/ HIGHLY SOLUBLE CONDUCTING POLYANILINE 923 The position of wavenumber of C=O stretching depends on hydrogen bond- ing and conjugation within the molecule. With polymerisation of IA, the C=O stretching band was shifted to higher wavenumbers, because the possibility of conjugation with a C=C band resulting in delocalization of the C=O group was eliminated on polymerisation.18 In addition, shifting of the typical bands for the C–O and C–O–H groups were detected. This effect is related to hydrogen bonding between the COOH groups of PIA. The FTIR spectrum of pure polyaniline (PANI-EB) is shown in Fig. 3. The formation of polyaniline was confirmed from the predominant peaks at the wave- number of 1583 cm–1, corresponding to C=C stretching of the quinoid ring,23 1494 cm–1 for C=C stretching of the benzenoid ring,24 1292 cm–1 for C–N+ stretching,25 and 511 cm–1 for C–H out-of-plane bending.26 After PIA doping, the quinoid and benzenoid ring bands were shifted to lower wavenumbers by 15 and 9 cm−1, respectively. This red shift phenomenon, corresponding to the transform- ation of quinoid rings into benzenoid rings, may result from conjugation effects after doping with the polymeric acid.28 Fig. 3. FTIR spectra of PANI-EB, PIA and PANI–PIA. UV–Vis spectroscopy Absorption spectroscopy is a valuable tool for detecting the presence of PANI base and its salts. All the absorption spectra of the PANI–PIA samples and the PIA spectrum, Fig. 4, showed a peak in the range of 249–285 nm, corresponding _________________________________________________________________________________________________________________________ (CC) 2015 SCS. All rights reserved. Available on line at www.shd.org.rs/JSCS/ 924 ZEGHIOUD et al. to π—π* or n—π* transitions in the carbonyl groups of the poly(itaconic acid),30 (Table III). Fig. 4. UV–Vis spectra of: a) water/NMP, b) water/THF and c) PIA and PANI–PIA salts recorded in different solvents. TABLE III. Absorption bands (λ / nm) of PIA and PANI–PIA samples in different solvents Sample (solvent) Attribution of absorption bands π–π* and/or n–π* π–π* Polaron–π* π–Polaron PIA (water) 282 – – – PANI–PIA (THF/water) 249 304 347 790 PANI–PIA (NMP/water) 285 347 410 816 The electronic absorption spectra of the PANI–PIA samples in different solvents showed bands corresponding to the following transitions: π–π* (304–347 nm), polaron–π* (347–410 nm), and π–polaron (in the region from 790 to 816 nm) of the alternating benzenoid–quinoid structures, respectively.31,32 The finding of the latter two absorption bands in the electronic spectra of all the PANI–PIA samples indicates that these polymers were well doped. When the solvent molecules interact with a PANI–PIA, its chain configur- ation may be changed depending on the structure and polarity of the solvents, which is reflected by peak shifts.33 Solubility determination PANI–PIA dispersion in THF/water mixture (20 mL) was oscillated in a bath-type sonicator for 2 h at room temperature. The suspension was filtrated to remove undissolved polyaniline. The obtained solution was analyzed by UV–Vis spectroscopy to confirm the protonated state of PANI, then it was dried in an oven _________________________________________________________________________________________________________________________ (CC) 2015 SCS. All rights reserved. Available on line at www.shd.org.rs/JSCS/ HIGHLY SOLUBLE CONDUCTING POLYANILINE 925 at 60 °C for 12 h. The maximum solubility was the quantity of resulting poly- aniline powder after drying 20 mL of solvents mixture with an optimal volume ratio, which is measured in mg mL–1. Note that the optimal ratio was determined by the intrinsic viscosity method. The solutions of PANI–PIA in different solvents are shown in Fig. 5. The picture proves that the PANI synthesized in the present work was highly soluble in tetrahydrofuran/water and NMP/water mixtures with a dark green colour (Fig. 5a and b, respectively). Fig. 5. Photographs of solutions of PANI–PIA in mixtures, a) water/THF = 0.428 and b) water/NMP = 0.428. The carbonyl groups of extended polyacid chain of the PIA facilitate the solubility of PANI in some polar solvents.34 PANI–PIA is not soluble in pure THF and NMP. The presence of water with each organic solvent improves the solubility of the PANI–PIA significantly, which could be explained by the number of carboxylic groups that is higher than the number of hydroxyl groups in the dopant which require a solvent with more groups containing hydrogen to create hydrogen bond. These groups (C=O), more negatively charged can create a stronger hydrogen bond with the water hydrogen. This idea is presented sche- matically in Scheme 3. Scheme 3. Effect of the presence of water as co-solvent on PANI–PIA solution in THF. _________________________________________________________________________________________________________________________ (CC) 2015 SCS. All rights reserved. Available on line at www.shd.org.rs/JSCS/ 926 ZEGHIOUD et al. Intrinsic viscosity The viscosity of macromolecular substances in solution is one of the most commonly used methods for characterizations. Intrinsic viscosity is defined as the limiting value of the ratio of specific viscosity to concentration of the solute (ηsp/c), extrapolated to zero concentration. Different solutions of PANI–PIA were prepared with different volume ratios of solvents (THF or NMP)/water at room temperature. This method is based on the calculation of the difference between the efflux time of the mixture of solvents (t0) and polymeric solution (t) between two points in a capillary tube. Basing on the most recent work performed by Yilmaz et al.35 using the values of constant K and α at room temperature (26 °C) obtained for the leuco- emeraldine form in NMP solution in the presence of LiCl: K = 2.34 × 10–2 mL g–1 and α = 0.73 [η] = KM̅vα (1) If two values are introduced into the Mark–Houwink equation (Eq. (1)),36 the obtained value of the intrinsic viscosity [η] = 13.26 mL g–1 of the emeraldine salt form results in an apparent viscosity average molar mass of M̅v = 5915 g mol–1. The evolutions of the intrinsic viscosity of solutions having various (THF or NMP)/water volume ratios of polyaniline doped with poly(itaconic acid) are shown in Fig. 6. The increase in viscosity with increasing water content indicates an increase in the hydrodynamic volume of the doped polymer chains, consistent with a progressive change in molecular conformation from “compact coil” to “expanded coil”.37 This type of behaviour indicates that water interacts more strongly with the polymer chains and/or with poly(itaconic acid) (PIA) dopant Fig. 6. Relationship between the intrinsic viscosities of polyaniline doped with poly- (itaconic acid) and volume ratio of the mixtures of: a) water/THF and b) water/NMP. _________________________________________________________________________________________________________________________ (CC) 2015 SCS. All rights reserved. Available on line at www.shd.org.rs/JSCS/ HIGHLY SOLUBLE CONDUCTING POLYANILINE 927 anions than does THF. Conversely, when the value 0.428 for the volume ratio was exceeded, the intrinsic viscosity began to decrease with further water addition, which could be explained as follows: the PANI–PIA chains take an extended coil conformation also because there are H-bonding interactions of the hydrogen of the amine groups with the oxygen present in the molecular structure of THF. When the value of the volume ratio was more than 0.428, the water excess was used to decrease the interaction chain–organic solvent that led thereafter to decreases in the hydrodynamic volume of the chains of the doped polyaniline (compact coil). The change in intrinsic viscosity values is so large that also the quality of solvent/water mixture for PANI-EB and PANI–PIA should be considered. Namely, water in this case can act as a non-solvent. After reaching an optimal proportion between solvent and water (good solvation, intermolecular interaction), its increased share might worsen the solvent quality, which could lead to more compact random coils due to stronger intramolecular chain interaction.38 Thermogravimetry (TGA) The results of the thermogravimetric analysis of the pure PIA and PANI–PIA samples are presented in Fig. 7. Four degradation steps could be observed for PIA (Fig. 7, curve b) in the temperature range from 26–450 °C, with a residue of 30 wt. %. In the temperature region from 50–280 °C, two processes were detected; the first one is assigned to the elimination of free water adsorbed to the hydro- philic polymer and presence of residual solvent in the polymer,39 and the second to anhydride ring formation in the PIA chain.40 In the second temperature region, from 280 to 450 °C, two degradation stages were observed, probably related to some decarboxylation and carbonization processes.16,41 Fig. 7. Thermogravimetric (TG) and differential TG (DTG) curves for: a) PANI–PIA and b) PIA. _________________________________________________________________________________________________________________________ (CC) 2015 SCS. All rights reserved. Available on line at www.shd.org.rs/JSCS/ 928 ZEGHIOUD et al. In the TGA thermograms of the PANI–PIA shown in Fig. 7, curve a, there are three major stages of weight losses of PANI–PIA powder sample. The first weight loss occurred around 67–198 °C (10 %) resulting from the elimination of water and other volatiles.42 The second stage in the temperature range 198–337 °C was assigned to the decomposition of excess dopant PIA.43 The third weight loss at the higher temperature could be attributed to the detachment of doping agent and the chemical decomposition of the short chains of PANI with maximum decom- position rates at 367 and 427 °C, respectively.44 It is notable that as much of 50 % of the initial mass was preserved for temperatures up to 500 °C. This residual mass relates to the existence of reticule polymer, which is formed at high temperatures,45 and the influence of the doping agent on a real thermal stability is not clear in this temperature region. X-Ray diffraction pattern (XRD) The X-ray diffraction pattern of PANI-EB, PIA and PANI–PIA are given in Fig. 8. The crystalline (Ic) and amorphous (Ia) peaks were both integrated in 2θ space. From these integrated peaks areas (Ic, Ia), the ratio Xc/Xa can be calculated by Xc/Xa = 1.8×(Ic/Ia). A Ryland factor of 1.8 is commonly used for semi-crys- talline polymers.45 The percentage of crystallinity Xc (%) was obtained as:46 Xc (%) = 100 – 100/(1 + Xc/Xa) (2) The XRD pattern of PANI–EB (Fig. 8, curve a) contains some sharps peaks at 2θ 9.57, 15.22, 20.75 and 24.29°, representing the crystal planes of (001), (011), (100) and (110) of dedoped PANI, respectively.47 The peak intensities are listed in Table IV, indicating the pseudo orthorhombic space.26 The peak centred at 2θ 24.29° could be ascribed to periodicity perpendicular to the polymer chain Fig. 8. XRD patterns of: a) PANI-EB, b) PANI–PIA and c) PIA. _________________________________________________________________________________________________________________________ (CC) 2015 SCS. All rights reserved. Available on line at www.shd.org.rs/JSCS/ HIGHLY SOLUBLE CONDUCTING POLYANILINE 929 (π stacking),47 and the peak centred at 2θ 20.75° may be ascribed to periodicity parallel to the conjugated chain of PANI (emeraldine base).48 The sharpness of the peaks represents the degree of orientation of the polymer chains in that particular crystal plane, and the intensity represents the population of crystallites in that plane.49 This result suggests a low degree of crystallinity of 9.64 %. TABLE IV. The 2θ values, intensity and indexation (hkl) of PANI-EB, PIA and PANI–PIA Sample 2θ / ° Intensity, a.u. d / Å (hkl) Crystallinity, Xc / % 09.57 167.46 09.23 001 9.64 PANI–EB 15.22 176.44 05.82 011 20.75 202.06 04.28 100 24.29 203.40 03.66 110 PIA 11.80 016.88 07.50 – 9.50 PANI–PIA 19.99 008.60 04.44 100 2.03 37.27 005.71 02.41 110 As shown in Fig. 8, curve c, the poly(itaconic acid) showed a moderate degree of crystallinity (Xc = 9.5 %, broad peaks in the spectrum) and a single sharp peak at 11.8°. On the other hand, the diffractogram of PANI–PIA powder, presented in Fig. 8, curve b showed two peaks; the first at 19.99° and the other at 37.27° with a characteristics distances of 4.44 and 2.41 Å, respectively. It should be noted that the chains of the PANI–PIA were less ordered than those of the PANI-EB, which was confirmed by the value of Xc = 2.03 % for PANI–PIA. CONCLUSIONS Soluble conducting polyaniline salts were successfully synthesized via che- mical polymerization. Undoped and poly(itaconic acid)-doped polyaniline were characterized by a number of methods. The doped polyaniline had good solubil- ity in mixtures of NMP/water and THF/water with a maximum solubility of 4 mg mL–1 in the latter mixture at room temperature; on the other hand, this polyani- line salt was not soluble in the pure polar organic solvents (THF and NMP) except when the temperature is above 60 °C. The optimum volume ratio of 0.42 between water and THF was determined by intrinsic viscosity measurements. The electrical conductivity of the doped form of polyaniline presents a pro- portional relationship with the concentration of the doping agent (PIA). A dec- rease in crystallinity was detected in the new PANI salt due to the presence of poly(itaconic acid) in the composite. _________________________________________________________________________________________________________________________ (CC) 2015 SCS. All rights reserved. Available on line at www.shd.org.rs/JSCS/ 930 ZEGHIOUD et al. И З В О Д СИНТЕЗА И КАРАКТЕРИЗАЦИЈА ПРОВОДНОГ И У СМЕШИ РАСТВАРАЧА ВЕОМА РАСТВОРНОГ ПОЛИАНИЛИНА HICHEM ZEGHIOUD 1 , SAAD LAMOURI 1 , ZITOUNI SAFIDINE 1 и MOHAMMED BELBACHIR 2 1Laboratoire de Chimie Macromoléculaire, Ecole Militaire Polytechnique, BP 17, Bordj El Bahri, Alger, Algeria и 2Laboratoire de Chimie des Polymères, Département de Chimie, Faculté des Sciences,Université d’Oran, BP 1524 El’Menouer Oran 31000, Algeria У раду је приказана синтеза и карактеризација растворног и проводног полиани- лина PANI–PIA добијеног хемијским поступком тј. полимеризацијом. На овај начин је добијена со полианилина допираног поли(итаконском киселином), која је веома рас- творна у бројним смешама поларних органских растварача и воде, при чему је достиг- нута растворљивост од 4 mg mL-1. Анализиран је утицај параметара синтезе, као што је степен допирања, на проводљивост, растворљивост и друга својства синтетисаних PANI– –PIA соли. Максимална проводљивост у износу од 2,48×10-4 S cm-1 је остварена при потпуном протоновању полианилина у облику емералдинске базе (PANI-EB). Поред тога, синтетисани материјали су додатно карактерисани вискозиметријом разблажених раствора, UV–Vis спектроскопијом, дифракцијом X-зрака (XRD), инфрацрвеном спек- троскопијом и термогравиметријском анализом (TGA) за анализу њихових термичких својстава. (Примљено 19. јула, ревидирано 29. децембра 2014, прихваћено 8. јануара 2015) REFERENCES 1. Y. G. Han, T. Kusunose, T. Sekino, J. Polym. Sci., B 47 (2009) 1024 2. A. Rahy, D. J. Yang, Mater. Lett. 62 (2008) 4311 3. F. G. Souza Jr., B. G. Soares, J. C. Pinto, Eur. Polym. J. 44 (2008) 3908 4. M. G. Mikhael, A. B. Padias, H. K. Hall Jr., J. Polym. Sci., A 35 (1997) 1673 5. J. Q. Dong, Q. Shen, J. Polym. Sci., B 47 (2009) 2036 6. K. Shannon, J. Fernandez, J. Chem. Soc. Chem. Commun. 5 (1994) 643 7. L. Sun, H. Liu, R. Clark, S. C. Yang, Synth. Met. 84 (1997) 67 8. G. L. Yuan, N. Kuramoto, S. J. 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