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Efficient Polymerization of the Aniline Dimer p- Aminodiphenylamine (PADPA) with Trametes versicolor Laccase/O2 as Catalyst and Oxidant and AOT Vesicles as Templates

The aniline dimer PADPA (= p-aminodiphenylamine = N-phenyl-1, 4-phenylenediamine) was polymerized to poly(PADPA) at 25 °C with Trametes versicolor laccase (TvL)/O2 as catalyst and oxidant and in the presence of vesicles formed from sodium bis(2- ethylhexyl) sulfosuccinate (AOT) as templates. In comparison to the previously studied polymerization of aniline with the same type of enzyme–vesicle system, the polymerization of PADPA is much faster, and considerably fewer enzymes are required for complete monomer conversion. Turbidity measurements indicate that PADPA strongly binds to the vesicle surface before oxidation and polymerization are initiated. Such binding is confirmed by molecular dynamics (MD) simulations, supporting the assumption that the reactions which lead to poly(PADPA) are localized on the vesicle surface. The poly(PADPA) obtained resembles the emeraldine salt form of polyaniline (PANI-ES) in its polaron state with a high content of unpaired electrons, as judged from UV/vis/NIR, EPR, and FTIR absorption measurements. There are, however, also notable spectroscopic differences between PANI-ES and the enzymatically prepared poly(PADPA). Poly(PADPA) appears to be similar to a chemically synthesized poly(PADPA) as obtained in a previous work with ammonium peroxydisulfate (APS) as the oxidant in a mixture of 50 vol % ethanol and 50 vol % 0.2 M sulfuric acid (J. Phys. Chem. B 2008, 112, 6976–6987). ESI-MS measurements of early intermediates of the reaction with TvL and AOT vesicles indicate that the presence of the vesicles decreases the extent of formation of unwanted oxygen-containing species in comparison to the reaction in the absence of vesicles. This is the first information about the differences in the chemical composition of early reaction intermediates when the reaction carried out in the presence of vesicles under optimal conditions is compared with a template-free system.

aniline; enzyme; laccase; liposomes; p-aminodiphenylamine; polyaniline; polymer; vesicles

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