Synthesis of polyaniline nanofibers and nanotubes via rhamnolipid biosurfactant templating

Polyaniline (PANI) nanorods and nanotubes with average diameters in the range of 121 ± 12 nm to 152 ± 13 nm were synthesized by the oxidative polymerization of aniline using hydrochloric acid as a dopant, ammonium peroxodisulfate as an oxidant, and a rhamnolipid biosurfactant produced by Pseudomonas aeruginosa SP4 as a soft template. The reaction conditions were systematically varied with the objective to maximize the electrical conductivity and aspect ratio of the PANI nanofibers. Optimized conditions, which involved an acid concentration of 0.1 M, an ANI-to-biosurfactant weight ratio of 23:1, and a polymerization time of 6 h, afforded a material with an electrical conductivity of 25 ± 2 S/cm. This material also exhibited the highest degree of crystallinity of all studied samples and matched the electronic properties of a reference material made without the surfactant.