Effects of pH, ionic strength, and type of anion on the rheological properties of chitosan solutions

Abstract

Abstract Changes in the rheological properties of chitosan solutions with pH, ionic strength, and type of anion were studied. Between pH 2.0 and 5.0, apparent viscosities increased with the decrease of pH in chitosan–organic acid solutions, while in chitosan–HCl solutions they behaved oppositely. In chitosan–NaOH solutions, they decreased with the increase of pH between pH 5.0 and 6.0, then increased as pH further increased to pH 6.0–6.4. The difference may be due to different interactions of counterions with macroions and also the third electroviscous effect. Relative viscosity increased with a decrease in chitosan concentrations at concentrations below 1.5 × 10 −3 M. Intrinsic viscosities changed with media pH and ionic strength.