Structural investigations of thermally processable, conductive polyaniline (PANI) are presented. Free standing, compact films of conductive polyaniline were prepared by hot pressing of polyemeraldine previously protonated with diphenyl hydrogen phosphate (DPHP) in chlorobenzene. The samples were then subjected to wide-angle X-ray diffraction (WAXD) and small angle synchrotron radiation scattering studies. Additionally, the temperature dependence of their conductivity was measured. Computer modelling was used in order to facilitate the interpretation of experimentally recorded diffractograms. These approaches have led us to an orthorhombic unit cell with a, b and c lattice constants of 4.4, 5.6 and 7.2 Angstrom, respectively. Relative intensities of the diffraction peaks are strongly dependent on the temperature of pressing but show very little dependence on the time of pressing. This effect has been ascribed to the conformational changes in the polymer studied induced by external pressure at elevated temperatures, and more precisely, to the changes in the torsion angle between the phenylene rings and the zig-zag plane determined by nitrogen atoms. From two-dimensional SAXS patterns it can be concluded that the time of pressing has a strong impact on the average size of crystalline regions in the polymer whereas they do not change significantly with the temperature of pressing. It can be postulated that the decrease in the average crystallite size is associated with the cross-linking process occurring in the polymer upon extended pressing. (C) 1997 Elsevier Science Ltd.