Biosurfactant mediated synthesis of conductive polymeric nanoparticles

Abstract

Polyaniline (PANI) nanofibers with the average diameter of several hundred nanometers were synthesized by oxidative polymerization using an ammoniumperoxydisulfate as an oxidant and a rhamnolipid biosurfactant as a template. The biosurfactant was produced by pseudomonas SP4 isolated from petroleum-contaminated soil in Thailand. The biosurfactant reduced the surface tension of pure water to 30.1 mN/m with a critical micelle concentration (CMC) of 250 mg/L. The biosurfactant formed the vesicular structure at a concentration greater than its CMC. The entrapment ability of the biosurfactant vesicles suggested potential use as the template for aniline monomer accumulation and subsequent polymerization. The effects of aniline monomer and acid concentrations on the wesicle size were studied by the dynamic light scattering (DLS) technique. The PANI nanofibers showed the maximum electrical conductivity of 24.8 S/cm, which was consistent with the wide angle X-ray diffraction (WXRD) results. The WXRD results also indicated that the synthesized PANI nanofibers possessed a semi-crystalline structure. The UV-vis spectra revealed that the synthesized PANI existed in emeraldine salt forms. Moreover, the biosurfactant template caused only a change in the morphology of the synthesized PANI, but did not affect the chemical structure, the thermal properly and the electronic state. However, the electrical conductivity and erystallinity of HCI-doped PANI was affected by the addition of biosurfactant template and the polymerization time.