Scalable and Low Cost Synthesis of Highly Conducting Polypyrrole Nanofibers Using Oil-Water Interfacial Polymerization under Constant Stirring.

In the present work, we report a low cost and scalable oil-water interfacial polymerization method to synthesize one-dimensional (1-D) highly conducting polypyrrole (PPy) nanofibers doped with p-toluenesulfonic (p-TSA) and hydrochloric (HCl) acids. Polymerization of pyrrole (monomer) has been carried out at the interface formed between the immiscible oil and aqueous water droplets under constant magnetic stirring at room temperature. Formation of smaller diameter (16-20 nm) PPy nanofibers has been confirmed from the high resolution transmission electron microscopy (HRTEM) studies, and the average diameter of p-TSA doped PPy nanofibers is found to be smaller than that of HCl doped nanofibers. The polymer chain ordering or crystallinity of both p-TSA and HCl doped PPy nanofibers have been studied with X-ray diffraction (XRD). Studies of Fourier transform infrared (FTIR) spectra suggest the presence of all the characteristic vibration bands in doped PPy nanofibers. The doping of PPy nanofibers has been confirmed from the formation of polaron and bipolaron bands in their UV-vis spectra. The optical band gap energy (Eg) and Urbach energy (EU) for PPy nanofibers doped with p-TSA and HCl doped PPy nanofibers were determined from their UV-vis absorption spectra. The red shift of the polaron absorption band in p-TSA doped PPy nanofibers confirms a higher conjugation length of the polymer nanofiber chains than that in the HCl doped PPy nanofibers. Thermogravimetric (TGA) and derivative plots of TGA studies predict that PPy nanofibers doped with p-TSA are thermally and structurally more stable as compared to HCl doped PPy nanofibers. Current-voltage (I-V) characteristics exhibit nonlinear behavior with voltage in both p-TSA and HCl doped PPy nanofibers.