Morphology and structure of highly crystalline polyaniline films

The morphology of polyaniline films grown by self-organization on a silicon substrate, modified previously with a self-assembled monolayer, has been investigated by conductive AFM, which showed conducting crystalline domains corresponding to the well-faceted crystallites scattered over the films. The film morphology studied by conductive AFM revealed the higher conductivity crystalline domains of the film. We also use transmission electron microscopy in bright-field and dark-field imaging modes, as well as selected area electron diffraction (SAED) to study the single crystal and polycrystalline regions of the films. SAED of single crystals showed diffraction pattern with well-defined spots. Rectangular symmetry is observed for the first time for PANI single crystals. The film regions with polycrystalline domains showed diffraction pattern with sharp rings. The indexing was carried out based on the orthorhombic structure and the unit cell parameters obtained are a = 4.2 Å, b = 5.9 Å and c = 9.8 Å. The nanocrystallite size distribution obtained from C-AFM is in the range of 10–60 nm and corroborates well with the TEM data.