Effect of temperature and hydrochloric acid on the intrinsic viscosity of poly(acrylic acid) in aqueous solutions

In this work, the intrinsic viscosities of poly(acrylic acid) were measured in water and aqueous hydrogen chloride solutions from (288.15 to 313.15) K. Poly(acrylic acid) are ionized in water and hence intensification of the intramolecular repulsive interactions was arising between ionized groups along the polymer chain and polymer chains were expanded. Whereas adding hydrogen chloride acid in PAA solutions suppressed the ionization of ionizable groups and PAA became as neutral polymers; therefore polymer chains were shrunk. The expansion factors of the polymer chains were calculated from the intrinsic viscosity data. The thermodynamic parameters (entropy of dilution parameter, the heat of dilution parameter, theta temperature, polymer-solvent interaction parameter and second osmotic virial coefficient) were derived by the temperature dependence of the polymer chain expansion factor. The thermodynamic parameters indicate that aqueous hydrogen chloride solutions are changed to the good solvents for poly(acrylic acid) by increasing temperature.