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Fabrication of Polypyrrole Nanotubes Using Electrospun Hydrophobic Polymer Nanofiber Templates

Sujith Nair and Seong H. Kim. Penn State University, 123 Fenske Laboratories, Penn State University, University Park, PA 16802

We have investigated the possibility of coating conducting polypyrrole (PPy) onto electrospun polystyrene (PS) poly (styrene co- maleic anhydride)(PSMA) nanofiber templates by a two-step method which involves (1) electrospinning of PS-PSMA nanofibers containing ferric chloride (FeCl3) followed by (2) vapor phase polymerization by exposure to pyrrole vapors. The FeCl3 polymerizes pyrrole to polypyrrole by an oxidative polymerization mechanism. Since the FeCl3 is polar in nature, selection of an optimized solvent system that is able to facilitate the dissolution of the hydrophobic PS-PSMA and the FeCl3 is a critical issue involved in this study. The SEM image of the electrospun FeCl3 containing PS-PSMA fibers showed a meshed like network structure indicating that the FeCl3 was precipitated on the surface of the PS-PSMA nanofibers. When exposed to pyrrole vapors, polypyrrole (PPy) was formed on the surface of the PS-PSMA nanofibers. The SEM of the PS-PSMA-PPy nanofibers after polymerization showed a smooth morphology with the absence of the meshed structure, thus indicating that the outer surface might have been covered with PPy. The growth of polypyrrole was monitored as a function of polymerization time using fourier transform infrared (FTIR) spectroscopy. The formation of PPy was also confirmed by x-ray photoelelectron spectroscopy (XPS). The PS-PSMA-PPy nanofiber composite is inert in aqueous solutions and serve as ideal candidates for enzyme immobilization studies. Also, the PS-PSMA matrix can be dissolved in organic solvents, such as tetrahydrofuran, to yield PPy nanotubes.