C60-polymer nanocomposites:: evidence for interface interaction

Polyaniline-fullerene (PA-C-60) composites have been studied by Surface Enhanced Raman scattering (SERS) spectroscopy and X-ray diffraction. They were obtained by mixing solutions of polyaniline-emeraldine base (PA-EB) and C-60, as well as by chemical synthesis from aniline, sulfuric acid and potassium dichromate, with addition of C-60. The Raman bands peaking at 1330-1370 cm(-1). associated with a protonated structure Were used as indicative for changes of the PA-EB phonon spectrum resulting from C-60 doping. The two types of compounds show different SERS spectra, also dependent on the metallic support used (An or Ag). Variation of the SERS spectra with the type of metallic support is related to a chemical interface interaction between composite and metal. In mixture samples, a doped polymeric chain (with ionically attached C-60(-)) was evidenced by an increased fraction of quinoid rings. The SERS spectra of the chemically synthesized PA-C-60 reveals the existence of two polymeric structures: a doped PA (doped with C-60(-) ions) and an undoped one, the latter with a structure of 'pendant chain' type. Structural (XRD) data reveal the presence of C-60 nano-zones, with a lattice parameter increase of 0.3-0.6%, attributed to slight oxidation. Detailed analysis of the fcc(111) line asymmetry suggests, in mixture samples, a boundary zone with an 'expanded' lattice. induced by ionic interface effects. (C) 2002 Elsevier Science Ltd. All rights reserved.