Controllable synthesis and characterization of polypyrrole nanoparticles in sodium dodecylsulphate (SDS) micellar solutions

• PPy nanoparticles have been synthesized by micro-emulsion method.
• The size and shape of PPy nanoparticles change with varying SDS concentration.
• TEM micrograph confirms changing of nanoparticles from spherical to cylindrical.
• The incorporation of SDS molecules as dopant in PPy is confirmed from FTIR spectra.

Polypyrrole (PPy) nanoparticles have been synthesized by chemical oxidative micro-emulsion polymerization of pyrrole monomer in the presence of ammonium persulphate (APS) as oxidant with varying sodium dodecylsulphate (SDS) surfactant concentration. High resolution transmission electron microscope (HRTEM) results show the shape change of PPy nanoparticles from spherical to elongated shape when SDS concentration is increased above its second critical micelle concentration CMC-II (0.2 M). UV–visible spectroscopy studies show formation of polaron band due to doping of PPy by SDS. A decrease of optical band gap energy (Eg) is also observed with increasing SDS concentration. The polymerization has been proposed from the thermodynamic consideration of micelle stability to explain the properties of PPy nanoparticles. Current–voltage (I–V) characteristics show an enhancement of current of PPy nanoparticles with increasing SDS dopant concentration. Thermo-gravimetric (TGA) analysis shows increase of thermal stability of PPy nanoparticles with increasing dopant concentration.