From amorphous to crystalline: Practical way to improve electrical conductivity of water-borne conducting polyaniline

Water-borne conducting polyaniline (cPANI) films were prepared using phosphonic acids containing different numbers of (m) repeating -CH2CH2O- units (m = 1-16) as dopants, and the influence of phase transition on the electrical conductivity of these cPANI films was investigated. The influence of the side chain length of the dopant on the chain packing of cPANI was found to be highly dependent on the m value in dopant side chain, when m decreased from 16 to 2, cPANI film changed slowly from amorphous to partially crystalline, as indicated from the increasing relative intensity of peak at 25.7°, in the meantime, its electrical conductivity increased from 5.9 × 10−6 S/cm to 4.5 S/cm, and the average diameter of cPANI particle in the dispersion decreased from 950 nm to 100 nm. Especially, when m equaled to 1, a much more crystalline phase was formed in that a new sharp diffraction peak at 7.45° and a new peak at 12.6° appeared, electrical conductivity as high as 27 S/cm was obtained, and the diameter of cPANI particle in the dispersion was reduced to 42 nm. The transition from disorder to order structure may provide a new insight for preparation of highly conducting polyaniline by means of highly crystalline or regular stacking.