Synthesis and Characterization of Organically Soluble Polyaniline and Polyaniline Block Copolymers

An emulsion process has been developed for the direct synthesis of the emeraldine salt of polyaniline (PANI) that is soluble in organic solvents. The process entails forming an emulsion composed of water, a water soluble organic solvent (e.g., 2-butoxyethanol), a water insoluble organic acid (e.g., dinonylnaphthalene sulfonic acid) and aniline. The resulting product is truly soluble in organic solvents such as xylene and toluene, of high molecular weight (Mw >22,000) and film forming. The emulsion polymerization process was also employed to synthesize ABA triblock polymers of polyaniline where the B block is a diamine terminated polymer and the A block is polyaniline. As cast, PANI films were only moderately conductive (10−5 S/cm). However, PANI conductivity could be enhanced by up to five orders of magnitude by treatment of the films with surfactants or low molecular weight alcohols and ketones. Blends of PANI and plasticizers such as toluenesulfonamide were found to exhibit conductivities up to 100 S/cm. X-ray diffraction studies of cast PANI films help to explain the conductivity enhancement by showing that surfactant and solvent treatments significantly increase the crystallinity and long range ordering of the polymer.