Facile synthesis and optimization of conductive copolymer nanoparticles and nanocomposite films from aniline with sulfodiphenylamine.

A new series of electrically conductive pure copolymer nanoparticles was facilely synthesized by using oxidative polymerization of aniline (AN) and sodium diphenylamine-4-sulfonate (SDP) in acidic media in the absence of stabilizer. The variation of the structure of the copolymer particles was comprehensively studied by carefully choosing several important parameters, such as the comonomer ratio, oxidant/monomer ratio, polymerization time and temperature, monomer concentration, acidic medium, and oxidant species. Analytical techniques used include IR and UV-visible spectroscopy, X-ray diffraction, laser particle analysis, atomic force microscopy, and transmission electron microscopy. It was found that the particle size varied significantly with the above-mentioned polymerization parameters, only changes in the salt concentration in the aqueous testing solution had no noticeable effect. The polymerization conditions were optimized for the formation of copolymer nanoparticles with sought-after properties. The doped copolymer particles of AN/SDP (50:50) at an oxidant/monomer molar ratio of 0.5 exhibit a minimum length of 50 nm and a minimum diameter of 44 nm. The bulk electrical conductivity of the copolymer particles increases greatly from 5.90x10(-4) to 1.15x10(-2) S cm(-1) with increasing AN content. Compared with barely soluble polyaniline, the copolymers exhibit a remarkably enhanced solubility in most solvents, including NH4OH and even water, due to the presence of the hydrophilic sulfonic groups. Nanocomposite films of the nanoparticles and cellulose diacetate exhibit a percolation threshold of down to 0.1 wt %, at which the film retains 98% of the transparency, 94% of the strength, and 5x10(7) times the conductivity of a pure cellulose diacetate film.