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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 vesicles

Synthesis of polymers with enzymes as catalyst attracts significant attention due to potential for the development of energy efficient polymerisation process. It is expected that these reactions usually are carried out under ’’environmentally friendly conditions’’ in water- reach reaction media. The presence of interfaces in the form of dissolved or dispersed structure- controlling agents, so called templates, has also considerable influence on the chemical structure and properties of the obtained polymeric forms. EPR spectroscopy was used to examine the magnetic properties of an enzymatically synthesized polymer sample obtained in the presence of submicrometer- sized vesicles formed from sodium bis(2- ethylhexyl)sulphosuccinate (AOT) as templates for polymerisation. The examined conductive polymer (poly(PADPA)-TvL-AOT ) was synthesized from aniline dimer PADPA (= p-aminodiphenylamine = N- phenyl-1, 4-phenylenediamine) with Trametes versicolor laccase (TvL)/O2 as catalyst and oxidant and AOT as templates1. In addition the earlier examined enzymatically synthesized polyaniline (PANI-TvL-AOT) obtained with the same catalyst, oxidant and template as well as an commercial conductive polymer sample of the emeraldine salt from polianiline (PANI ES) were used for comparison in order to correlate experimental data obtained for enzymatically synthesized polymer with AOT template to properties of the well characterized PANI ES. For all monitored polymers linewidths and intensities of EPR spectra have been analyzed at 9.5 GHz frequencies in the wide temperature interval from 5 K to 300 K. It was shown that model based on the concept of correlated polaronic bands2 could be applied for interpretation of these spectra. It is also noted that poly(PDPA)- TvL-AOT contains the largest amount of Curie contribution, C0, that account for noncorrelated spins, and exhibits a lower percentage of ‘’locally disordered dimmers’’ in comparison to PANI-TvL-AOT. The inhomogeneous complex spectrum of poly(PDPA)-TvL-AOT has been decomposed on two separate Dyson–type spectral components at room temperature. Presence of these spectral components has been 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 estimate an approximate interchain spin exchange interaction. It was shown that the obtained effective distances between polyaniline chains are larger for enzymatically synthesized polymers with AOT template than for PANI ES.

Polyaniline; PADPA; EPR; AOT vesicles

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