Effect of Template Type on the Trametes versicolor Laccase-Catalyzed Oligomerization of the Aniline Dimer p-Aminodiphenylamine (PADPA)

Abstract

Many previous studies have shown that (i) the oxidation of aniline or the aniline dimer p -aminodiphenylamine (PADPA) in a slightly acidic aqueous solution can be catalyzed with heme peroxidases or multicopper laccases and that (ii) subsequent reactions lead to oligomeric or polymeric products, which resemble chemically synthesized polyaniline in its conductive emeraldine salt form (PANI-ES), provided that (iii) an anionic “template” is present in the reaction medium. Good templates are anionic polyelectrolytes, micelles, or vesicles. Under optimal conditions, their presence directs the reactions in a positive way toward the desired formation of PANI-ES-type products. The effect of four different types of anionic templates on the formation of PANI-ES-like products from PADPA was investigated and compared by using Trametes versicolor laccase (TvL) as a catalyst in an aqueous pH 3.5 solution at room temperature. All four templates contain sulfonate groups: the sodium salt of the polyelectrolyte sulfonated polystyrene (SPS), micelles from sodium dodecylbenzenesulfonate (SDBS), vesicles from a 1:1 molar mixture of SDBS and decanoic acid, and vesicles from sodium bis(2-ethylhexyl)sulfosuccinate (AOT). Although with all four templates, stable, inkjet-printable solutions or suspensions consisting of PANI-ES-type products were obtained under optimized conditions, considerably higher amounts of TvL were required with SDBS micelles to achieve comparable monomer conversion to PANI-ES-like products during the same time period when compared to those with SPS or the two types of vesicles. This makes SDBS micelles less attractive as templates for the investigated reaction. In situ UV/vis/near-infrared, electron paramagnetic resonance (EPR), and Raman spectroscopy measurements in combination with an high-performance liquid chromatography analysis of extracted reaction products, which were deprotonated and chemically reduced, showed seemingly small but significant differences in the composition of the mixtures obtained when reaching reaction equilibrium after 24 h. With the two vesicle systems, the content of unwanted substituted phenazine units was lower than in the case of SPS polyelectrolyte and SDBS micelles. The EPR spectra indicate a more localized, narrower distribution of electronic states of the paramagnetic centers of the PANI-ES-type products synthesized in the presence of the two vesicle systems when compared to that of the similar products obtained with the SPS polyelectrolyte and SDBS micelles as templates. Overall, the data obtained from the different complementary methods indicate that with the two vesicle systems structurally more uniform (regular) PANI-ES-type products formed. Among the two investigated vesicle systems, for the investigated reaction (oxidation of PADPA with TvL and O 2 ), AOT appears a somewhat better choice as it leads to a higher content of the PANI-ES polaron form.

Effect of template type on the preparation of the emeraldine salt form of polyaniline (PANI-ES) with horseradish peroxidase isoenzyme C (HRPC) and hydrogen peroxide

“…With pinacyanol chloride the critical concentration for SDBS micelle formation (cmc) was determined in the same way as described before. 41 The value obtained in the pH ¼ 4.3 solution (data not shown) was the same as the one determined previously for the pH ¼ 3.5 solution (cmc z 0.3 mM). 41 2.3.8.…”

“…41 The value obtained in the pH ¼ 4.3 solution (data not shown) was the same as the one determined previously for the pH ¼ 3.5 solution (cmc z 0.3 mM). 41 2.3.8. SPS polyelectrolyte stock solution.…”

“…A vesicle suspension of 20 mM AOT consisting of mainly unilamellar vesicles with average diameters of about 100 nm was prepared in the same way as described before. 41 The only difference was the use of the pH ¼ 4.3 solution instead of the pH ¼ 3.5 solution. The critical concentration for AOT vesicle formation (cvc) is about 0.4 mM.…”

“…A vesicle suspension consisting of equimolar amounts of SDBS and DA, each 20 mM and mainly unilamellar vesicles of about 100 nm was prepared in the same way as described before by using the pH ¼ 4.3 solution instead of the pH ¼ 3.5 solution, with cvc z 0.4 mM. 41 The vesicle suspension was stored at RT and used within three weeks.…”

“…The rst part of this work is directly related to our previous work on the effect of different so template types on the Trametes versicolor laccase (TvL)/O 2 -catalysed oligomerisation of the linear para-NC-coupled aniline dimer PADPA (p-aminodiphenylamine) to oligo(PADPA), carried out at pH ¼ 3.5 and T z 25 C. 41 This previous work was also aimed at obtaining products with a high content of PANI-ES repeating units. In the present work we wanted to know whether the template which appeared most ideal among the tested template types for the PADPA/TvL/O 2 reaction, AOT vesicles, 41 is also the "best" one for the aniline/HRPC/H 2 O 2 reaction.…”