Study and explanation about the morphological, electrochemical and structural properties of differently synthesized polypyrrole

Polypyrrole (ppy), a conducting polymer was synthesized by four different polymerization methods viz. electrochemical polymerization (EP), interfacial polymerization (IP), chemical oxidative polymerization (COP) and template-assisted polymerization (TAP). The change in morphology that occurred due to the variation of polymerization method used was studied with scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The samples were analyzed by Fourier transform infrared (FT-IR) spectroscopy to confirm the successful polymerization of pyrrole to polypyrrole with the appearance of characteristic bands for N–H stretching, C–N stretching, ppy ring stretching, C–H and C–C bending vibrations. Optical studies were done by UV–Vis absorption spectroscopy that displayed π→π^* and polaronic/bipolaronic transitions of ppy. XRD analysis revealed amorphous nature of ppy. Examination of SEM micrographs disclosed that ppy synthesized by EP had the typical cauliflower structure while ppy formed by IP were in the form of chain like network with a thickness of 250–290 nm, COP resulted in the formation of interlinked microspheres of polypyrrole and TAP formed polypyrrole nanofibers. Electrochemical characterization showed that ppy prepared by EP had the lowest redox activity and the samples were also tested to detect Pb²⁺.