INELASTIC NEUTRON-SCATTERING STUDIES OF POLYANILINES AND PARTIALLY DEUTERATED ANALOGS

Inelastic neutron scattering spectra have been measured from 16 to 400 0 cm(-1) for various polyaniline samples at 30 K: the emeraldine-base and the emeraldine-salt, the ring-deuterated analogues and their hydra ted forms. The spectra of the totally hydrogenated samples are dominat ed by bands due to protons bound to the aromatic rings. The spectrum o f 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-sa lt additional protons (H+) are trapped in very shallow potential-wells with dissociation threshold similar to 300 cm(-1). At energy transfer greater than this threshold, these protons are free to recoil. The sp ectra of the hydrated samples reveal that free entities are not trappe d by water molecules. These new dynamics are tentatively related to th e electronic structure and conductivity of these polymers. These are s upposed to be determined by the position of the electronic state of '' H-0'' entities relatively to the half-filled pi-band of the metal-like form of the pernigraniline-base. In the emeraldine;base electrons tra nsferred from ''H-0'' entities to the conduction band give an insulato r with a totally-filled band and a gas of H+ entities. In the emeraldi ne-salt the electronic state of ''H-0'' entities is lowered. The struc ture is that of a metal-like half-filled band with a gas of ''H-0'' en tities and weakly bound protons.