Toward a simple method for the fabrication of 1D or 3D nanostructures of polyaniline

We present a one-step chemical method for the fabrication and isolation of conjugated polymer nanostructures, in particular, polyanilines (PANIs), either in the pernigraniline or emeraldine oxidation state. The polymerization is initiated by the addition of a solid oxidant into an unstirred anilinium hydrochloride solution. This step allows a slow release of the oxidant, via its solubilization and diffusion into the undisturbed solution. The formation of visible macroscopic heterogeneous seeds promotes the homogeneous polymerization and growth of bulk nanostructures in solution. The shape of the first formed heterogeneous seeds was found to be dependent on the solubility/diffusion of the oxidant, allowing the prediction and control of the nanomorphology (1D vs. 3D or granular) of the bulk polyanilines. X-ray analyses of the as-prepared nanostructured PANIs showed that, compared to the literature data, the crystallite growth in the present study is significantly enhanced, with the 1D fibrillar morphology exhibiting a higher crystallinity per volume of nanostructure than that of a 3D granular counterpart. The electrical conductivity (σ ) of pelletized HCl doped PANIs or emeraldine salts (ES) showed significant differences depending on the fibrillar or granular morphology, but a close relationship among number of unit cells, crystallite size and electrical conductivity is evidenced.