Effect of processing conditions on the properties of high molecular weight conductive polyaniline fiber

Polyaniline- emeraldine base (EB) fiber with excellent mechanical and electrical properties have been spun from highly concentrated (20% w/w), EB/N-methyl- 2-pyrrolidinone (NMP)/2-methylaziridine (2 MA) solution. These solutions had gelation times, which varied from hours to days depending on the molar ratio of 2 MA to EB tetramer repeating unit in the N-methyl-2-pyrrolidinone (NMP) solvent. To better compare the mechanical and electrical properties, dense films were also prepared by thermal evaporation of less concentrated solution (1% w/w). Both fibers and films were amenable to thermal stretching with maximum draw ratios o f4:1a ndthese stretched samples exhibited the greatest tensile strength overall. Wide-angle X-ray diffraction (WAXD) of as-spun and 4-times stretched fiber showed a completely amorphous struc- ture. Fiber subjected to heat treatment at 250 °C under N2 flux for 2 h displayed further improvements in mechanical properties because of crosslinking between the polymer chains. Fibers and films were later doped by immersion in a variety of aqueous acid solutions. Room temperature DC conductivities for the doped samples ranged from 6 3 10 24 to 45 S/cm depending on the specific choice of acid. Scanning electron micros- copy of fiber samples shows the presence of macrovoid formation during fiber spinning. Continued refinement of the processing parameters and fiber post-treatment, to en- hance chain alignment and increase fiber density, will likely lead to additional improve- ments in the fiber mechanical and electrical properties. Characterization of emeraldine base (EB) powder, solution, films, and fibers by UV-Vis, DSC, TGA, and WAXD were also performed. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 194 -204, 2000