Inelastic neutron scattering studies of polyanilines and partially deuterated analogues

Inelastic neutron scattering spectra have been measured from 16 to 4000 cm −1 for various polyaniline samples at 30 K: the emeraldine-base and the emeraldine-salt, the ring-deuterated analogues and their hydrated forms. The spectra of the totally hydrogenated samples are dominated by bands due to protons bound to the aromatic rings. The spectrum of the ring-deuterated base reveals that most of the remaining protons are not bound to nitrogen atoms. There is a continuum of intensity due to the recoil of free particles with mass 1 amu. In the emeraldine-salt additional protons (H +) are trapped in very shallow potential-wells with dissociation threshold ≈ 300 cm −1. At energy transfer greater than this threshold, these protons are free to recoil. The spectra of the hydrated samples reveal that free entities are not trapped by water molecules. These new dynamics are tentatively related to the electronic structure and conductivity of these polymers. These are supposed to be determined by the position of the electronic state of “H 0” entities relatively to the half-filled π-band of the metal-like form of the pemigraniline-base. In the emeraldine-base electrons transferred from “H 0” entities to the conduction band give an insulator with a totally-filled band and a gas of H + entities. In the emeraldine-salt the electronic state of “H 0” entities is lowered. The structure is that of a metal-like half-filled band with a gas of “H 0” entities and weakly bound protons.