PROTON NMR RELAXATION IN HIGHLY CONDUCTING POLYANILINES

Measurements of the conductivity and proton spin-lattice relaxation ti mes T1rho and T1 in polyanilines (PANI) prepared through a novel polym erization-condensation synthesis are presented. The new method of prep aration yields a significant increase in the electrical conductivity, which may be related to the lesser amount of decomposition products, l eading to a more uniform distribution of dopant protons along the chai n, thus allowing the charge carriers to move along a longer path. The effects of the increase of the effective length of the chains on the r elaxation rates are studied in terms of their frequency and temperatur e dependences. From an analysis of the data in the light of a diffusio n equation for the magnetization, it appears that the intra-chain diff usion rate is larger than that in conventional PANI, Whereas the cut-o ff frequency calculated by comparing T1rho and T1 gives an upper limit ing value of the inter-chain diffusion rate of about 10(7) rad s-1. Th e temperature dependence of T1 is also modified.