Highly soluble polyaniline was synthesized from a newly designed aniline derivative, namely 2‐[2‐chloro‐1‐methylbut‐2‐en‐1‐yl]aniline. The corresponding polyanilines, PClPA‐HA, PClPA‐SA, PClPA‐NA and PClPA‐PA, were characterized by means of 1H NMR, 13C NMR, high resolution mass spectroscopy, Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy and SEM images. The elemental analysis and electrical conductivity of the polymers are also presented. It is shown that the molecular weight of the polymers obtained depends on the method of synthesis. Spectroscopic studies confirmed the emeraldine form of the polyaniline derivatives. In the work, the dependence of the current passing through resistive structures based on thin poly[2‐(2‐chloro‐1‐methylbut‐2‐en‐1‐yl)aniline] films on the relative humidity of air was studied. The results of the studies showed the prospects of using thin polymer films in the design of chemical sensors. © 2020 Society of Chemical Industry

This work is focused on modifying aniline monomers with various characteristics that allows one to study the effect of the substituent on the respective polymer.

Intramolecular acid-catalyzed cyclization was suggested for the first time for a polyaniline derivative, namely, poly­[2-(2-chloro-1-methylbut-2-en-1-yl)­aniline] (PClPA), to give hitherto unknown poly­(2-ethyl-3-methylindole) (2E3MPIn) in a high yield (81%). This is the first example of synthesizing a polymer of the indole series with 1,5-addition of monomeric units that are incorporated into the polymer structure. The physicochemical properties of the new polymer were studied. Its structure was confirmed by spectral methods and quantum-chemical calculations. The 2E3MPIn polymer showed good thermal stability compared to the starting PClPA polymer. A study of the photoluminescence of polymers showed that the emission spectrum of 2E3MPIn demonstrated a bathochromic shift (16 nm) and a considerable increase in the luminescence intensity in comparison to PClPA. The 2E3MPIn sample was found to possess photoconductivity. Irradiation of the polymer film increases the electrical conductivity by a factor of 2. The electrochemical properties obtained from the UV–vis spectrum and cyclic voltammograms suggest that 2E3MPIn has good electroactivity. A sample of 2E3MIn demonstrates a fine porous structure resembling a “sponge”. In addition, the PClPA and 2E3MPIn samples synthesized were used as sensitive materials in resistive moisture sensors. The 2E3MPIn polymer demonstrated a higher response than PClPA to changes in the environment humidity. The observed changes in the physicochemical properties of 2E3MPIn compared to PClPA confirm that the polyheterocyclization reaction occurs successfully and can be considered as an efficient way for synthesizing new functional polymers of the indole series.