The Kinetics of the Synthesis of Polyaniline Nanoparticles Stabilized by Branched Polyvinyl Alcohol

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ABSTRACT Narrowly dispersed nanoparticles with a diameter below 200 nm were synthesized by oxidative polymerization of aniline in aqueous solutions of branched polyvinyl alcohol, since it is challenging in the presence of linear polyvinyl alcohol. According to IR spectroscopy data, the obtained particles consist of polyaniline and branched polyvinyl alcohol chains interacting through hydrogen bonding. The detected thermotropic change in the order of the catalytic stage of aniline polymerization in aqueous solutions of branched polyvinyl alcohol at 5°C–15°C is due to the reaction's heterogeneous autocatalytic nature. The rate constant growth in the catalytic stage with an increase in the molecular weight and concentration of branched polyvinyl alcohol is shown. On the contrary, the rate constant of the non‐catalytic stage of the aniline polymerization decreases with a rise in the stabilizer concentration. The obtained results are explained by the formation of hydrogen bonds between the hydroxyl groups of the polyvinyl alcohol and the monomer, as well as by shielding the surface of dispersed phase particles containing the catalytically active oxidized units of polyaniline chain with a macromolecular stabilizer. Thus, by varying the molecular weight of branched polyvinyl alcohol, it is possible to control the particle size and the rate of aniline dispersion polymerization.

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