Molecular weight and properties of polyaniline

Summary form only given. Polyanifine (PAn) is fractionated through solvent dissolution into five fractions with molecular weight distribution from 2.4 to 4.7 and the molecular weight (MW) of each fraction is estimated to be from 1,000 to 40,000 by intrinsic viscosity in concentrated sulfuric acid using nylon-6 and PPTA(poly-para(phenytene terephthalamide)) as soft and stiff standard polymer, respectively. The electrical conductivity increases with MW for low MW fractions. When it reaches 10/sup 1/S/cm for NMP soluble-DMF insoluble fraction, it does not further in crease with MW. Tensile strength increases greatly with MW from 3OMPa (THF soluble acetone insoluble fraction) to 140 MPa (NMP soluble-DMF insoluble fraction), whereas that of the common polyaniline is only 55 MPa. Thus elimination of the low MW fraction is necessary to improve the tensile strength of PAn. GPC curve and intrinsic viscosity are combined to estimate the k and /spl alpha/ values in Mark-Houwink equation of PAn as 1.4 X 10/sup -4/ and 0. 93, respectively. The high a value indicates the extended molecular form of PAn in its NMP solution.