Controlled morphology of conducting polymers: Formation of nanorods and microspheres of polyindole

Abstract

One-dimensional nanotubes and nanowires have attracted attention because of their unique electronic and mechanical properties, resulting in the promising applications in electrical, electronic and nanodevices or three-dimensional hollow spheres because of drug delivery, encapsulations and biosensor applications. For the first time we report the formation of nanorods and microspheres of polyindole conducting polymer based on chemical synthesis using two immiscible (interfacial) and two miscible solvents respectively (without surfactant). Interfacial polymerization of polyindole is carried out by taking oxidizing agent in mild acid (HCl) and monomer in dichloromethane phases and polymerization in two miscible solvents is carried out by taking monomer in ethanol and oxidizing agent in mild acidic solution. Scanning electron microscope and atomic force microscope images of polyindole confirmed the formation of hollow spheres and nanorods. The possible mechanism for controlled morphologies is discussed based on formation of metastable micelles (for microspheres) and unstable micelles (for nanorods) in absence of surfactant. The mechanism is also supported by in-situ AFM studies. FT-IR data supported the 2,3 position polymerization of polyindole in both the morphologies. XRD data revealed that nanorod are more crystalline than microspheres, however, quite different from the amorphous conventional polymer obtained by electrochemical polymerization technique.