A multifrequency EPR study of poly(PADPA) synthesized with Trametes versicolor laccase from the aniline dimer p-aminodiphenylamine (PADPA) in the presence of anionic vesicles

Abstract

Poly(PADPA) synthesized with the enzyme Trametes versicolor laccase (TvL) at pH = 3.5 in aqueous solution from the aniline dimer p-aminodiphenylamine (PADPA) was studied by EPR spectrometry at X-band and W-band frequencies. For the synthesis of poly(PADPA), vesicles formed from AOT (sodium bis-(2-ethylhexyl)sulfosuccinate) were used as structure-directing templates, and TvL/O2 as catalyst and oxidant. The isolated product is abbreviated as “poly(PADPA)-TvL-AOT” to distinguish it from poly(PADPA) obtained by other means. The EPR spectrum of poly(PADPA)-TvL-AOT recorded at room temperature is complex. It can be decomposed into two separate Dyson–type spectral components. Furthermore, the spectra measured at high frequency exhibit a line broadening behavior in comparison to the spectra recorded at low frequency where there is no line broadening. This behavior was used to estimate the effective inter-chain spin exchange interaction for each monitored spectral component. The obtained effective distances between the polymer (or oligomer) chains in both identified components of poly(PADPA)-TvL-AOT can be explained by considering slightly different interactions between the chains and the AOT molecules present in the sample. Additionally, due to different average g tensor values, gav, of these components, it seems that each spectral component originates from one of two different molecular subunits (or local structural motifs) within the polymer (or oligomer) chains.