Enzymatic Synthesis of Highly Electroactive Oligoanilines from a p-Aminodiphenylamine/Aniline Mixture with Anionic Vesicles as Templates

Abstract

Oligoanilines with characteristic properties of the electrically conductive emeraldine salt form of polyaniline (PANI-ES) are promising molecules for various applications. A mixture of such oligoanilines can be obtained, for example, enzymatically under mild conditions from the linear aniline dimer p-aminodiphenylamine (PADPA) with hydrogen peroxide (HO) and low amounts of horseradish peroxidase (HRP) in an aqueous pH = 4.3 suspension of anionic vesicles formed from AOT, the sodium salt of bis(2-ethylhexyl)sulfosuccinate. However, the simultaneous formation of undesired side products containing phenazine-type units or oxygen atoms is unsatisfactory. We have found that this situation can be improved considerably by using a mixture of PADPA and aniline instead of PADPA only but otherwise nearly identical conditions. The PANI-ES-like oligoaniline products that are obtained from the PADPA and aniline mixture were not only found to have much lower contents of phenazine-type units and not contain oxygen atoms but also were shown to be more electroactive in cyclic voltammetry measurements than the PANI-ES-like products obtained from PADPA only. The AOT vesicle suspension remained stable without product precipitation during and after the entire reaction so that it could be analyzed by in situ UV/visible/near-infrared, in situ electron paramagnetic resonance, and in situ Raman spectroscopy measurements. These measurements were complemented with ex situ high-performance liquid chromatography analyses of the deprotonated and reduced products formed from mixtures of PADPA and either fully or partially deuterated aniline. On the basis of the results obtained, a reaction mechanism is proposed for explaining this improved HRP-triggered, vesicle-assisted synthesis of electroactive PANI-ES-like products. The oligomeric products obtained can be further used, without additional special workup, for example, to coat electrodes for their possible application in biosensor devices.

Effect of Template Type on theTrametes versicolorLaccase-Catalyzed Oligomerization of the Aniline Dimerp-Aminodiphenylamine (PADPA)

“…Nevertheless, the HPLC analysis turned out to be very useful for analyzing the enzymatic oxidation and oligomerization of PADPA, as a complementary method to the in situ UV/vis/NIR, EPR, and Raman spectroscopy measurements. 21−24…”

How experimental details matter. The case of a laccase-catalysed oligomerisation reaction

“…23 Recently, it was shown that this phenazinetype units formation can be reduced signicantly by running the reaction instead of PADPA alone with a mixture of PADPA and aniline. 46 By using TvL/O 2 and PADPA in the presence of AOT vesicles, the amount of TvL required to reach high conversion of PADPA into the desired oligomeric PANI-ES-like products, one apparently minor detail is important to be taken in account. It is the way how the aqueous "pH ¼ 3.5 solution" is prepared from a solution of NaH 2 PO 4 .…”

“…6A). The lower absorbance at 500-600 nm most likely indicates a lower content of products containing phenazine units if the reaction is run at T ¼ 5 C instead of T ¼ 25 C. 23,46 Overall, there was no indication of a signicant improvement of the products distribution by running the reaction at T ¼ 5 C instead of room temperature. This nding is in contrast to what we had observed previously for the oxidation and polymerisation of aniline in the presence of AOT vesicles with TvL/ O 2 at pH ¼ 3.5 (ref.…”

Use of Ionic Liquids-like Surfactants for the Generation of Unilamellar Vesicles with Potential Applications in Biomedicine

“…19,20,[39][40][41][42][43] Several reports have shown data about the vesicle formation but use different methodologies to prepare them (such as extrusion). [44][45][46][47][48][49] Therefore, the chemical structure of the cationic components in the new surfactants strongly impact their aggregation process. 19,20,49 As a complementary experiment, zeta potential measurements were carried out.…”