Polyaniline is useful in electronic and optical applications in part because its properties can be controlled easily by simple and reversible acid-base doping and de-doping. Synthesis of nanometer diameter fibers has only been possible via templated synthesis, using either hard templates like anodized alumina, or soft materials like micelles and liquid crystals to guide the polymerization.
Now Huang et al. have used a well-known chemical synthesis route to make polyaniline without a template. Instead of operating in a uniform aqueous solution, they ran the reaction in an immiscible aqueous-organic biphasic system so that the by-products of the reaction would naturally separate. After dialysis, the polyaniline was recovered in the form of interconnected nanofiber networks, where the fiber diameter ranges from 30 to 50 nm. In contrast to a thin film of polyaniline, the film made of the nanofibers showed a much faster electrical response upon exposure to parts-per-million concentrations of HCl and subsequent exposure of the fully doped films to NH3. The response of the nanofibers was independent of the thickness of the film made, due to their high porosity which allowed for rapid gas diffusion. -- MSL
J. Am. Chem. Soc. 10.1021/ja028371y (2002).
