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