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Melt dispersion processing-without solvents or "secondary dopants"-pushes polyaniline reproducibly to the metallic side of the IM transition, although the undispersed polyaniline is on the insulator side. This is the first time that a conductive polymer is found there without applying pressure. The transition to the metallic state is associated with a decrease of the C6-N-C6 angle from 166 • to 134 • . PACS. 71.30.+h Metal-insulator transitions and other electronic transitions -75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.) -61.10.-i X-ray diffraction and scatteringThe nature of charge transport in conductive polymers is broadly evaluated and discussed [1,2]. First products based on polyaniline are introduced into the market [3] and further technological potentials ranging from allpolymer integrated circuits [4] and light-emitting diodes [5] over drug release substrates and sensors to nanotechnological devices [6] may now become realistic. Applications like corrosion protection and final finish of printed circuit boards require two key properties to be jointly active: the noble metallic character and the catalytic capability [3]. The metallic behaviour is still a matter of debate, as polyanilines, polyacetylenes, or polypyrroles show partially metallic features, but most are on the insulator side of the "insulator-to-metal (IM) transition". Quite a few are sample dependent after solvent-borne "secondary doping" [7] in the critical regime, or cross the IM transition to the metallic side, however this is reproducible only under pressure [8,9].Processing of conductive polymers (organic metals) is a key problem for basic research and industrial applications. After the usual protonation of polyaniline (PAni) creating mobile charges, two approaches are used: i) A "secondary doping" process, e.g., with m-cresol, has been shown to increase conductivity and crystallinity of polyaniline [10].ii) Melt dispersion of PAni in an insulating polymer matrix [11]: for example, PAni protonated with p-toluenesulfonic acid (pTsA) has been dispersed in a Mailing address:

Work performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore Laboratory under Contract No. W-7405-ENG-48. This report was prepared as an account of work sponsored by the United States Government. Neither the United States nor the United States Department of Energy, nor any of their employees, nor any of their contractors, subcontractors, or their employees, makes any warranty, express or Implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference to a company or product name does not imply approval or recommendation of the product by the University of California or the U.S. Department of Energy to the exclusion of others that may be suitable.

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