Kinetics of micelle formation and their effect on the optical and structural properties of polypyrrole nanoparticles

Polypyrrole (PPy) samples were chemically synthesized by emulsification polymerization of pyrrole in the presence of ammonium peroxydisulphate as oxidant and cetyltrimethylammonium bromide (CTAB) as surfactant, for two different concentrations of CTAB. The samples were studied using different characterization techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), ultraviolet to visible (UV–vis) and photoluminescence spectroscopy. The structural and optical properties of the two sets (for two different surfactant concentrations) were found to be vastly different. PPy nanoparticles of size ∼20 nm were obtained for one set, whereas the samples of the other set displayed properties similar to the sample prepared under non-surfactant conditions. Since the concentration of the surfactant in both the cases was greater than critical micelle concentration, we attribute the difference in properties of the samples of the two sets, to the kinetics of micelle formation. A possible polymerization mechanism has been proposed from the thermodynamic consideration of micellar stability to explain the polymer properties.