13C CPMAS solid state NMR of polyaniline salts with increasing dopant concentrations

C. J. CATTENA; E. M. ERRO; R. IGLESIAS; G. A. MONTI; H. M. PASTAWSKI

Rosario

Workshop; Frontiers in Magnetic Resonance, from materials to biological systems; 2013

The attention given to conducting polymers have not yet declined since their discovery, more than thirty years ago. In spite of the enormous technological advances and the increasing interest in their use as organic components in nanocomposites and nanodevices, the metal-insulator transition still presents a strong scientific challenge, since it is not well understood from the point of view of basic science [1]. Recent   theoretical results give important insights to the conceptual basis of this field, emphasizing the fundamental role of disorder and decoherence processes on the transport properties for these kind of one-dimensional systems [2]. In this work, we report on 13C solid state nuclear magnetic resonance measurements of carefully prepared samples of polyaniline emeraldine base and emeraldine salts, with increasing HCl dopant concentrations, near the critical point of the metal-insulator transition. A simple fitting function, built upon two free parameters, describes surprisingly well the experimental data. We provide a simple and convenient explanation for the observed displacement in the first moment of the spectra with increasing dopant concentrations of the emeraldine salts. Our results shows meticulously that all relevant chemical shifts contribute to a single average and uniform (inhomogeneous) broadening, enforcing the role of disorder as a decisive ingredient in the electronic transport mechanism in polyanilines.REFERENCES1. A. J. Heeger, Rev. Mod. Phys. 73, 681 (2001).2. C. J. Cattena, R. A. Bustos-Marún, and H. M. Pastawski, Phys. Rev. B 82, 144201 (2010).