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

Abstract

The aniline dimer PADPA (= p-aminodiphenylamine = N-phenyl-1,4-phenylenediamine) was polymerized to poly-(PADPA) at 25 °C with Trametes versicolor laccase (TvL)/O 2 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.

Insight into the template effect of vesicles on the laccase-catalyzed oligomerization of N-phenyl-1,4-phenylenediamine from Raman spectroscopy and cyclic voltammetry measurements

“…Figure 3a shows the UV/vis/NIR spectroscopic changes occurring from the early stage up to 4 h of the reaction. The results presented here, with [TvL] = 64 nM and a reaction volume of 10 mL, are in good agreement with those obtained previously1 for a reaction mixture of the same composition, [TvL] = 32 nM, and a reaction volume of 15 mL, when both reactions are carried out in the same type of glass bottles (see Methods ). This confirms the high reproducibility of the reaction, despite the heterogeneity of the system, and both used enzyme concentrations (32 or 64 nM) can be regarded as optimal.…”

“…More from an application point of view, the suitability of the direct use of the “as obtained” poly(PADPA)/AOT vesicle suspension for bioelectrode fabrication needs to be investigated. At least with respect to the first CV results obtained in this work, it seems appropriate to continue research in this field, and to compare the advantages and disadvantages of the PANI-ES-like poly(PADPA)–as obtained from PADPA in the present work with TvL/O 2 and AOT vesicles–with, for example, PANI-ES as obtained from aniline with horseradish peroxidase isoenzyme C/H 2 O 2 and the same type of vesicles55, even though we know that in this latter case much more enzyme is required for the synthesis than in the case of TvL/O 2 and PADPA1.…”

“…After 120 min the initially formed radical species (most likely PADPA •+ ) disappeared, while the radical species of the (main) products clearly dominated. For the reaction without vesicles (template-free system), the total concentration of radicals never reached the levels of the reaction with vesicles1.…”

“…We showed that Raman spectroscopy is a convenient and sensitive method for in situ monitoring of the oxidation and oligomerization/polymerization of PADPA with TvL/O 2 in the presence of AOT vesicles, as well as in the absence of the vesicles. In contrast to the previously applied UV/vis/NIR and EPR spectroscopy measurements1, the present in situ Raman spectroscopy measurements of the reaction mixture during the course of reaction provide novel and detailed information on the evolution of the molecular structures of the oligomeric PADPA products through vibrational characteristics of distinct functional groups430 and through changes in their abundancies. This yields new insight into the effect of vesicles on the structural evolution of poly(PADPA).…”

Laccase-catalyzed electrochemical fabrication of polyaniline/graphene oxide composite onto graphite felt electrode and its application in bioelectrochemical system

“…The optimal pH for the catalytic activity of laccase is about 3.0-4.5, as this activity decreases when the pH is lowered [32]. What's more, most literature about aniline polymerization by laccase adopted the pH value of 3.5 and 3.6 [21,26,28,30].…”