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EPR study of conducting polymer ; Poly(PADPA) synthesized enzymatically from the aniline dimer p-aminodiphenylamine in the presence of submicrometer-sized AOT vesicle

The synthesis of polymers with enzymes as catalysts atracts significant atention due to the potential development of energy efficient polymerisation process. Enzymatic polymerization usually are carried out under "environmentally friendly conditions" in water-rich reaction media. Furthermore, it has been shown that the presence of interfaces in the form of dissolved or dispersed structure- controlling agents, so called templates, can have considerable influence on the chemical structure and properties of the obtained polymers (polymerization reactions catalyzed by oxidative enzymes). EPR spectroscopy was used to examine the magnetic properties of an enzymatically synthesized polymer obtained in the presence of submicrometer-sized vesicles formed from sodium bis(2- ethylhexyl)sulphosuccinate (AOT) as templates. The examined polymer abbreviated as (poly(PADPA)-TvL-AOT ) was synthesized from the aniline dimer PADPA (= p-aminodiphenylamine = N- phenyl- 1, 4-phenylenediamine) with Trametes versicolor laccase (TvL)/O2 as catalyst and oxidant and AOT vesicles as templates[1]. In addition the earlier examined enzymatically synthesized polyaniline (PANI-TvL-AOT) obtained with the same enzyme, oxidant and template as well as an commercial conductive PANI sample in its emeraldine salt from (PANI ES) were used for comparison in order to correlate experimental data obtained for the two enzymatically synthesized polymers to properties of the well characterized PANI ES. For all investigated polymers linewidths and intensities of EPR spectra were analyzed at 9.5 GHz frequencies in a wide temperature interval from 5 to 300 K. It was shown that a model based on the concept of correlated polaronic bands[2] could be applied for the interpretation of the EPR spectra. It is also noted that poly(PADPA)- TvL-AOT contains the largest amounts of Curie contribution, C0, that account for noncorrelated spins, and exhibits a lower percetage of "locally disordered dimers" in comparison to PANI-TvL-AOT. The inhomogeneous complex spectrum of poly(PADPA)-TvL-AOT recorded at room temperature was decomposed in two separate Dyson– type spectral components. Presence of these spectral components was additionally confirmed by employing EPR detection at high frequency (94 GHz). Spectra detected at high frequency exhibit line broadening behaviour in comparison to spectra recorded at low frequency. This effect was used to roughly estimate the interchain spin exchange interaction. It was shown that the obtained effective distances between the polymer chains are larger for the enzymatically synthesized polymers obtained with AOT templates than for the commercial PANI ES sample. References: [1] Junker, K. et. al, in preparation. [2] Rakvin, B. et. al, J. Phys. Chem. B, 118 2205 (2014)

EPR ; Poly(PADPA) ; aniline dimer

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