Characterization of polypyrrole-fibre composites by time-of-flight secondary ion mass spectrometry and vibrational spectroscopy

Abstract

We have examined polypyrrole-polyester and polypyrrole-quartz fibre composite samples using time-of-flight secondary ion mass spectrometry (TOF-SIMS). This technique has allowed us to confirm that in each composite the conducting polymer overlayer of cationic polypyrrole chains is doped with 5-sulphosalicylate dopant anions, at least to a sampling depth of 10 Å. Surprisingly there is no detectable presence of the second aromatic sulphonate dopant anion utilized in the Milliken synthetic procedure (1,5-naphthalenedisulphonic acid, disodium salt). Our Fourier transform ( FT) Raman spectra of these polypyrrole-fibre composite contain strong spectral bands due to the cationic polypyrrole chains, several weak features due to the underlying fibre substrate (particularly in the case of the polyester fibres), and no bands attributable to the dopant anions. These observations suggest that the Raman scattered light from the substrate component is largely reabsorbed by the polypyrrole overlayer. Thus we conclude that there must be extensive coverage of the fibre substrate by the conducting polymer with few, if any, ‘bare’ patches. Finally, our FTi.r. microscopy studies on these coated composites produced good quality spectra of the underlying substrate with few features attributable to the polypyrrole overlayers.