Chemical synthesis of polypyrrole: structure–properties relationship

Nanostructures composed of polypyrrole (PPy) are obtained by chemically synthesizing PPy within the pores of microporous and nanoporous Particle Track-etched Membranes (PTM). Hollow tubules are formed because polypyrrole initially deposits on the surface of the pores walls. By running successive syntheses, we have obtained wires (filled tubules). These nanoscopic materials show enhancements in electronic conductivity compared to analogous polymer bulk conductivity. This work highlights the difficulty in obtaining an absolute value of the electronic conductivity. Pores shape and pores filling must be well tailored because these parameters are absolutely required to determine the conductivity. So, the morphologies and the structures of the nanomaterials have been carefully analyzed by Field-Effect Scanning Electron Microscopy (FE-SEM). The Raman spectroscopy was used to correlate the molecular structure of the nanoscopic tubules with their conducting properties by determining the relative conjugation length in the PPy chains. Raman data show that the ordering of the polymer chains is improved when the pores diameter decreases and is responsible for the enhancement in conductivity.