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.

Keywords

• полианилин
• композиты на основе полианилина
• бескислотный синтез
• рентгеновская спектроскопия поглощения
• ик спектроскопия.