Self-assembly of polyaniline - From nanotubes to hollow microspheres

By simply changing the molar ratio of the dopant to monomer, the morphology of salicylic acid (SA)-doped polyaniline (PANI) can be changed from one-dimensional nanotubes (similar to190-150 nm in diameter) to three-dimensional hollow microspheres (similar to1.5-3.1 mum in diameter) via a self-assembly process. Freeze-fracture electron microscopy (FFEM) proved that hollow spherical micelles composed of SA aniline act as templates in the formation of either nanotubes or hollow spheres. FTIR and X-ray diffraction measurements suggest that the hydrogen bond of the -OH group of SA with the amine group of PANI might be a driving force for self-assembling hollow microspheres, while the hydrogen bond through hydrogen and oxygen of the adjacent SA doped on the polymer chains results in the short-range order of the counter-ions along the polymer chain in the nanotubes.