3,5-Dinitrosalicylic acid-assisted synthesis of self-assembled polyaniline nanorods

Self-assembled polyaniline nanorods were synthesized by the oxidation of aniline with ammonium peroxydisulfate in an aqueous solution in the presence of 3,5-dinitrosalicylic acid, using the template-free falling-pH method. The effects of the mole ratio of 3,5-dinitrosalicylic acid to aniline, i.e., of starting pH, monomer concentration, and reaction time on the yield of polymerization, molecular-weight distribution, molecular structure, morphology, and conductivity of the prepared polyanilines have been studied by gel-permeation chromatography, elemental analysis, FTIR and Raman spectroscopies, scanning and transmission electron microscopies, and conductivity measurements. The weight-average molecular weights and polydispersity index were in the range 36,400–54,900 and 3.7–7.6, respectively. Synthesized polyaniline nanorods have a diameter of 25–280 nm and a length of 0.2–1.3 μm, and conductivities in the range (1.2–4.6) × 10−2 S cm−1. The formation mechanism of self-assembled polyaniline nanorods has been discussed.