Dynamics of nonlinear excitations in conducting polyaniline

Summary form only given. The existence of localized and mobile polarons in slightly and intermediately doped polyaniline was for the first time found at 2-mm waveband EPR. Spin density on protons was found to vary for different samples without an obvious correlation with doping level y. The relaxation times of these centers together with 1D and 3D hopping rates for mobile polarons in polyaniline with different y were evaluated. The doping of emeraldine base form of polyaniline results in the increase of a number and size of metal-like domains containing polarons and bipolarons of different mobility leading to the growth of bulk conductivity and Pauli susceptibility starting from y/spl sim =/0.02. This process stimulates the increase of a number of Pauli charge carriers and, thus, the acceleration of electron relaxation processes. The system dimensionality grows with y, that causes the replacement of Kivelson charge transfer mechanism in emeraldine base by the variable range hopping one in emeraldine salt of polyaniline. As the concentration of bipolarons is approximately 3 orders of magnitude higher than that of spin charge carriers in a polyaniline salt, one can conclude, that charges are transfered mainly by bipolarons in this polymer. The dihedral angle between the planes of neighbouring rings decreases by 23/spl deg/ at the extreme polymer doping, that evidences the more planar conformation of an emeraldine salt of polyaniline.