Thesis presented November 18, 2004

Abstract:
This report deals with a multi-scale study of structural and electronic properties of doped and non-doped π-conjugated systems. The first part is devoted to a comparative study of polyaniline and one model oligomer, the tetraniline, both of them being HCl-doped. It is mainly based on spin dynamics methods which allow one to probe the charge carrier (polarons) motion at a microscopic scale via their spin:
1/ NMR : measurement of the longitudinal nuclear relaxation time T1 as a function of frequency,
2/ ESR : measurement of the linewidth as a function of temperature and adsorbed oxygen amount.
We have demonstrated the existence of a metallic behaviour of the microscopic conductivity in the polymer, which is not present in the tetramer. This result closes the debate about the origin of the ESR linebroadening observed in the polymer at high temperature. In addition, it appears that the microscopic conductivity is quasi-1d in both compounds, while considerably higher in the polymer. The second part deals with the self-organization of π-conjugated polymers, the regioregular poly(3-alkylthiophenes. Monolayers of poly(3-hexylthiophene) and poly(3-dodecylthiophene) deposited on graphite (HOPG) have been studied by scanning tunnelling microscopy (STM). We have shown that the structuration at different scales (organized parts vs. disordered parts, nanocrystal size, chain bending,....) Depends on the deposit and post-deposit parameters. Finally, some electronic properties are deduced from 2d scanning tunnelling spectroscopy (STS) measurements performed on regioregular poly(3-dodecylthiophene).

Keywords:
Conjugated polymer, conductor polymer, electronic properties, metallic state, spin dynamic, NMR, ESR

On-line thesis.