Features of the Electronic Structure and Chemical Bonds of Polyaniline-Based Composites Obtained by Acid-Free Synthesis

Abstract

Object. Composites based on polyaniline and CuCl₂·2H₂O/ZrOCl₂·8H₂O as modifying additives
were obtained by chemical acid-free polymerization. The chemical and electronic structure of
the samples were studied by IR spectroscopy and X-ray absorption spectroscopy. The composites
surface microstructure was studied by scanning electron microscopy. It was shown that polyaniline
is a part of the composites in a partially oxidized form. The polymer oxidation degree depends
on the type of modifying agent. The addition of CuCl₂·2H₂O/ZrOCl₂·8H₂O during the synthesis
increases the samples conductivity.
Purpose. The analysis of the electronic and chemical structure of polyaniline, synthesized by
the acid-free method with the addition of CuCl₂·2H₂O/ZrOCl₂·8H₂O modifying agent and
thermostated at low temperature (30 °C), by spectroscopic methods (XANES, IR). The investigation
of the effect of modifying agents on the electrical conductivity of composites.
Methods. PANI/Me composites (Me – Cu, Zr) were obtained by acid-free chemical oxidation of
aniline.Potassium persulfate was dissolved in distilled water and then aniline was added with
constant stirring for 15 minutes. Solutions of CuCl₂·2H₂O/ZrOCl₂·8H₂O were added as a modifying
agent. Then samples were thermostated at 30°C for 4 hours.A surface morphological study of
the samples was carried out using a scanning electron microscopy with an accelerating voltage
of 5 kV. The electronic and chemical structure of PANI/Me composites was investigated by IR
spectroscopy and X-ray absorption spectroscopy.
Results. The addition of CuCl₂·2H₂O/ZrOCl₂·8H₂O during the chemical polymerization of aniline
by the acid-free method leads to the formation of partially oxidized polyaniline. The oxidation
state of PANI depends on the type of modifying agent. The oxidation state of polyaniline in
PANI-Zr is higher than in PANI-Cu. The morphology of both samples was similar and represented
by agglomerates of lamellar (mainly) and rod-like structures. However, in PANI-Cu agglomerates
of mixed type were revealed, while in PANI-Zr agglomerates consisted of one type of
microstructures. The addition of metal-containing components improved the conductivity of
the samples. PANI-Zr contained more protonated nitrogen groups compared to PANI-Cu, which
improved its conductivity.
Conclusion. Acid-free synthesis by the chemical polymerization of aniline method in the
presence of CuCl₂·2H₂O/ZrOCl₂·8H₂O made it possible to obtain composite materials of various
morphologies with partially oxidized form of polyaniline. It was found that the oxidation state
of polyaniline in PANI-Zr is higher than in PANI-Cu. Studies of chemical and electronic structure
showed that the sample obtained with the addition of zirconium oxychloride is characterized
by a higher content of protonated nitrogen groups than the sample obtained with the addition
of copper hydrochloride. Modifi cation of polyaniline with transition metal salts (Zr, Cu) improved
the electrical conductivity of composites when compared with pure polyaniline.

REFERENCE
1. Ćirić-Marjanović G. Recent advances in polyaniline research: Polymerization mechanisms, structural
aspects, properties and applications. Synthetic Metals, 2013, v. 177, pp. 1–47. DOI: https://doi.org/10.1016/j.synthmet.2013.06.004
2. Boeva Zh. A., Sergeyev V. G. Polyaniline: Synthesis, properties, and application. Polymer Science.
Series C., 2014, v. 56(1), pp. 144–153. DOI: https://doi.org/10.1134/S1811238214010032
3. Benabdellah A., Ilikti H., Belarbi H., Fettouhi B., Ait Amer A., Hatti M. Effects of the synthesis temperature
on electrical properties of polyaniline and their electrochemical characteristics onto silver cavity
microelectrode Ag/C-EM. Int. J. Electrochem. Sci., 2011, v. 6, pp.1747 – 1759.
4. Kelly F. M., Meunier L., Cochrane C., Koncar V. Polyaniline application as solid state electrochromic
in a fl exible textile display. Displays, 2013, v. 34 (1), pp. 1–7. DOI: https://doi.org/10.1016/j.displa.2012.10.001
5. Lobotka P., Kunzo P., Kovacova E., Vavra I., Krizanova Z., Smatko V., Stejskal J., Konyushenko E. N., Omastova
M., Spitalsky Z., Micusik M., Krup I. Thin polyaniline and polyaniline/carbon nanocomposite fi lms for
gas sensing. Thin Solid Films, v. 519 (12, 1), pp. 4123–4127. DOI: https://doi.org/10.1016/j.tsf.2011.01.177
6. Wang H., Linc J., Shen Z.X. Polyaniline (PANi) based electrode materials for energy storage and conversion.
Journal of Science: Advanced Materials and Devices, 2016, v. 1 (3), pp. 225–255. DOI: https://doi.org/10.1016/j.jsamd.2016.08.001
7. Ivanova N. M., Soboleva E. A., Visurkhanova Y. A., Kirilyus I. V. Electrocatalytic activity of polyanilinecopper
composites in electrohydrogenation of p-nitroaniline. Russian Journal of Electrochemistry, 2015,
v. 51(2), pp. 166–173. DOI: https://doi.org/10.1134/S1023193515020056
8. Matnishyan A. A., Akhnazaryan T. L., Abagyan G. V., Badalyan G. R., Petrosyan S. I., Kravtsova
V. D. Synthesis and study of polyaniline nanocomposites with metal oxides. Physics of the Solid State,
2011, v. 53 (8), с. 1727–1731. DOI: https://doi.org/10.1134/s1063783411080178
9. Zhu Y., He H., Wan M., Jiang L. Rose-like microstructures of polyaniline by using a simplifi ed template-
free method under a high relative humidity. Macromol. Rapid Commun., 2008, v. 29 (21), pp. 1705–
1710. DOI: https://doi.org/10.1002/marc.200800294
10. Konyushenko E.N., Stejskal J., Šeděnková I., Trchová M., Sapurina I., Cieslar M., Prokeš J. Polyaniline
nanotubes: conditions of formation. Polym. Int, 2006, v. 55, pp. 31–39. DOI: https://doi.org/10.1002/pi.1899
11. Trchová M., Šeděnková I., Konyushenko E.N., Stejskal J., Holler P., Ćirić-Marjanović G. Evolution of
polyaniline nanotubes: The oxidation of aniline in water. J. Phys. Chem. B, 2006, v. 110(19), pp. 9461–9468.
DOI: https://doi.org/10.1021/jp057528g
12. Bhadra S., Khastgir D. Extrinsic and intrinsic structural change during heat treatment of polyaniline.
Polymer Degradation and Stability, 2008, v. 93 (6), pp. 1094–1099. DOI: https://doi.org/10.1016/j.polymdegradstab.2008.03.013
13. Yalovega G. E., Myasoedova T. N., Shmatko V. A., Brzhezinskaya M. M., Popov Y. V. Infl uence of
Cu/Sn mixture on the shape and structure of crystallites in copper-containing fi lms: Morphological and
X-ray spectroscopy studies. Applied Surface Science, 2016, v. 372, pp. 93–99. DOI: https://doi.org/10.1016/j.apsusc.2016.02.245
14. Domashevskaya E. P., Hadia N. M. A., Ryabtsev S. V., Seredin P. V. Structure and photoluminescence
properties of SnO₂ nanowires synthesized from SnO powder. Kondensirovannye sredy i mezhfaznye
granitsy [Condensed Matter and Interphases], 2009, v. 11(1), С. 5—9
15. Baibarac M., Baltog I., Lefrant S., Mevellec J. Y., Chauvet O. Polyaniline and carbon nanotubes based
composites containing whole units and fragments of nanotubes. Chem. Mater., 2003, v. 15, pp. 4149–4156.
DOI: https://doi.org/10.1021/cm021287x
16. Okotrub A. V., Asanov I. P., Galkin P. S., Bulusheva L. G., Chehova G. N., Kurenja A. G., Shubin Ju. V.
Composites based on polyaniline and aligned carbon nanotubes. Polymer Science - Series B, 2010, v. 52 (1–2),
pp. 101–108.
17. Wang S., Tan Z., Li Y., Suna L., Zhang T. Synthesis, characterization and thermal analysis of polyaniline/
ZrO₂ composites. Thermochimica Acta, 2006, v. 441, pp. 191–194. DOI: https://doi.org/10.1016/j.tca.2005.05.020
18. Ullah R., Bowmaker G. A., Laslau C., Waterhouse G. I. N., Zujovic Z. D., Ali K., Shah A.-U.-H. A.,
Travas-Sejdic J. Synthesis of polyaniline by using CuCl₂ as oxidizing agent. Synthetic Metals, 2014, v. 198,
pp. 203–211. DOI: https://doi.org/10.1016/j.synthmet.2014.10.005
19. Izumi C. M., Constantino V. R., Temperini M. L. Spectroscopic characterization of polyaniline formed
by using copper(II) in homogeneous and MCM-41molecular sieve media. J. Phys. Chem. B, 2005, v. 109,
pp. 22131–22140. DOI: https://doi.org/10.1021/jp051630w
20. Magnuson M., Guo J.-H., Butorin S. M., Agui A., Sеthe C., Nordgren J. The electronic structure of polyaniline
and doped phases studied by soft x-ray absorption and emission spectroscopies. J. Chem. Phys., 1999,
v. 111, pp. 4756–4761. DOI: https://doi.org/10.1063/1.479238
21. Domashevskaya E. P, Storozhilov S. A. Turishchev S. Yu. Kashkarov V. M., Terekhov V. A., Stogney
O. V., Kalinin Yu. E., Sitnikov A. V., Molodtsov S. L. XANES and USXES studies of interatomic interactions
in (Co₄₁Fe₃₉B₂₀)x(SiO₂)_1-x nanocomposites. Physics of the Solid State, 2008, v. 50 (1), с. 139–145.
22. Gaur A., Klysubun W., Sonic B., Shrivastav D., Prasad J., Srivastava K. Identifi cation of different coordination geometries by XAFS in copper(II) complexes with trimesic acid. Journal of Molecular Structure,
2016, v. 1121, pp. 119–127. DOI: https://doi.org/10.1016/j.molstruc.2016.05.066
23. Fulton J. L., Hoffmann M. M., Darab J. G., Palmer B. J. Copper(I) and сopper(II) сoordination
structure under hydrothermal conditions at 325 °C: an X-ray absorption fi ne structure and molecular dynamics study. J. Phys. Chem. A., 2000, v. 104, pp. 11651–11663. DOI: https://doi.org/10.1021/jp001949a
24. Porto A. O., Pernaut J. M., Daniel H., Schilling P. J., Martins M. C. Alves X-ray absorption spectroscopy
of iron-doped conducting polymers. Synthetic Metals, 1999, v. 104, pp. 89–94. DOI: https://doi.org/10.1016/S0379-6779(99)00025-9
25. Zhang Y., Addison O., Gostin P. F., Morrell A., Cook A. J. M. C., Liens A., Wu J., Ignatyev K., Stoica M.,
Davenport A. In-situ synchrotron X-ray characterization of corrosion products in Zr artifi cial pits in simulated
physiological solutions. J. Electrochem. Soc, 2017, v. 164(14), pp. 1003–1012. DOI: https://doi.org/10.1149/2.0671714jes