engleski

EPR study of polyaniline synthesized enzymatically in the presence of AOT visicles

EPR spectroscopy was used to examine the magnetic properties of two enzymatically synthesized polyaniline (PANI) samples obtained in the presence of submicrometer-sized vesicles formed from sodium bis(2-ethylhexyl)sulphosuccinate (AOT) as templates. PANI-HRPC-AOT was synthesized with horseradish peroxidase isoenzyme C (HRPC) and hydrogen peroxide (H2O2) as oxidant while PANI- TvL-AOT was prepared with Trametes versicolor laccase (TvL) and dioxygen (O2) as oxidant. A commercial conductive sample of the emeraldine salt form of polyaniline (PANI-ES) was also used for comparison in order to correlate the experimental data obtained for PANI-HRPC-AOT and PANI-TvL-AOT with the properties of the well- characterized PANI-ES. It was shown that a model based on the concept of correlated polaronic bands could be applied for the interpretation of the EPR spectra of all three examined samples, although PANI-HRPC-AOT and PANI-TvL-AOT were significantly less conductive than PANI-ES. The following EPR parameters: peak to peak linewidth (Δpp), temperature dependence of the splitting parameter (ΔB), spectral intensities, decomposition of spectra and correlation time (τ0) are used for studying all three PANI samples. The magnetic properties of the PANI samples could be related to their conductivities, whereby a low conductivity was ascribed to decreased interchain spin interactions which were detectable from a splitting of the triplet spectrum at low temperatures (5 K - 10 K). The obtained effective distance between the polyaniline chains is larger for enzymatically synthesized PANI than for PANI- ES, most likely due to the presence of AOT which could not be removed completely during the workup. AOT influences the chain conformation and the average chain-chain distance.

polyaniline; conductive polymers; AOT

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