Dilute solution viscosity properties of high molar mass poly(acrylonitrile-co-itaconic acid)

The intrinsic viscosities [η] and viscosity constants of high molar mass poly(acrylonitrile-co-itaconic acid) copolymer in DMF were obtained by the methods of Huggin, Fuoss, Martin and Schulz-Blaschke. The values of [η] by averaging procedures suggested by Sakai were close to those from Huggins method. There was an abnormal positive deviation from the rectilinearity of the reduced viscosity (ηred) versus concentration (c) plot in all the cases in the dilute regime, which was attributed to the polyelectrolytic effect. This was further confirmed by the analysis by Fuoss method. The deviation from the Huggins dependence is discussed for a good solvent (DMF) alone and in the presence of a non-solvent, methanol. The deviation cross-over points c′ and c″ changed with molecular weight, and the concentration range greater than c″ and less than c* was taken for a more reliable determination of intrinsic viscosity. The non-solvent played a key role in determining the polymer–polymer interactions. The Huggins coefficient increased and the cross-over points c′ and c″ shifted to higher concentration regime as the mixed solvent became poorer. The inter- and intra-polymer interactions increased in the presence of methanol. In poor solvent, the enhanced intramolecular interactions caused the polymer to shrink in size, causing a reduction in [η] and hydrodynamic volume. Copyright © 2003 Society of Chemical Industry