Chemical synthesis of polyindole

Abstract

Polyindole is an important electroactive polymer that can be obtained by electrochemical or chemical oxidation of indole. Polyindole an important role in organic synthesis due to its catalytic properties, its use as a catalyst makes it possible to synthesize organic compounds and composites for various functional purposes. The aim of the work was to research the features of chemical polymerization of indole, as well as the structure and properties of the obtained polymer. In our work, the possibilities of chemical synthesis of polyindole by the interaction of 0.1 M indole solution with 0.1 M of oxidant (ammonium persulfate) in acetonitrile in an inert medium (Ar atmosphere) at a temperature of 0 ± 2 o C were investigated. The structure, optical and electrical properties of the obtained compounds have been studied. It is determined that during the chemical synthesis the relative yield of dark green polyindole powder is 71 %. According to electron microscopy in the polymerization process the formation of ordered structures of polyhedral type takes place, with nanosizes of 30–50 nm. When dissolving the polymer, a solvatochromic effect is observed – a change in the color of the solution and the absorption spectrum depending on the nature of the solvent in the range λ = 310…900 nm. In the optical spectra of polyindole solutions, absorption bands are observed at λ = 390 and 510 nm (dioxane), λ = 390, 440 and 510 nm (DMF) and λ = 400, 510 and 540 nm (tetrachlormethane). The color of the solutions is markedly different, the solution in chloroform is pale pink, in DMF is yellow, in dioxane is light green. The electrical conductivity of the obtained polymer was experimentally determined, which turned out to be at 5 *10 -3 S /сm. According to the temperature dependence of the resistivity (in the coordinates of the Arrhenius equation), the activation energy of conductivity E a = 0.087 eV is determined, which indicates the semiconductor properties of the synthesized polymer. Keywords : polyindole, chemical synthesis, structure, solvatochromic effect, electrical conductivity.