INELASTIC NEUTRON-SCATTERING STUDY OF PROTON DYNAMICS IN POLYANILINES

The inelastic neutron scattering (INS) spectra between 16 and 4000 cm( -1) of chemically prepared non-doped (PANI 2A) and 50% protonated (PAN I 2S) polyaniline at 20 K are reported. Band frequencies are compared to those estimated from the IR reflectivity. Different types of proton s are distinguished in the spectra: (i) For the 'water-containing' 2S sample, INS features are consistent with the presence of a crystalline arrangement of the H2O network within the PANI lattice. (ii) The spec tra of the 2S and 2A samples are dominated by bands assigned to vibrat ions of the benzoic and quinoidal protons. (iii) A continuum of intens ity, underneath the bands of the aromatic protons, is tentatively attr ibuted to the recoil of 'quasi-free' protons. These protons could be o f great relevance to the explanation of the correlation between the pr otonation degree and the electronic and protonic conductivity.