Synthesis and physicochemical properties of (co)polymers based on aniline and its ortho-cycloalkenyl-substituted derivatives

The development of the sphere of organic electronics contributes to the emergence of new materials used in this field. An important direction in the creation of new materials is the modification of already known functional organic compounds, such as polyaniline (PANI). The introduction of a substituent into the PANI aromatic ring is one of the most popular methods for polymer modification. Therefore, the study of the influence of various structural factors on the physicochemical properties of substituted PANI derivatives seems to be an important direction in the study of polymers. In this regard, in this paper, PANI was modified by introducing alkenyl substituents into the ortho-position of the aromatic ring of the monomer with a double bond in the allyl and vinyl positions. Based on the synthesized monomers, (co)polymers with aniline in various molar ratios were obtained by classical oxidative polymerization in an acidic medium and under the influence of (NH₄)₂S₂O₈. Solubility, morphology, thermal stability, humidity sensing, optical properties, and spectral characteristics were studied for all samples. The shift of the double bond from allyl to the vinyl position led to a decrease in the quantum yield from 0.13 to 0.03. However, the thermal stability of vinyl-substituted polyaniline derivatives was higher than allyl-substituted polymer, probably due to the formation of more cross-links in the polymer. Additionally, it was reported on the performance of a humidity sensor based on polyaniline copolymers, showing sensitivity to moisture at room temperature with a response time of 2–3 s.