Viscometric study of chitosan solutions in acetic acid/sodium acetate and acetic acid/sodium chloride

Abstract

A viscometric study was carried out at 25 °C to assess the physical-chemical behavior in solution and the mean viscometric molar mass (M¯ v) of chitosan solutions with different deacetylation degrees, in two solvent mixtures: medium 1 - acetic acid 0.3 mol/L and sodium acetate 0.2 mol/L; and medium 2 - acetic acid 0.1 mol/L and sodium chloride 0.2 mol/L. Different equations were employed, by graphical extrapolation, to calculate the intrinsic viscosities [η] and the viscometric constants, to reveal the solvent's quality: Huggins (H), Kraemer (K) and Schulz-Blaschke (SB). For single-point determination, the equations used were SB, Solomon-Ciuta (SC) and Deb-Chanterjee (DC), resulting in a faster form of analysis. The values of M¯ v were calculated by applying the equation of Mark-Houwink-Sakurada. The SB and SC equations were most suitable for single-point determination of [η] and M¯ v and the Schulz-Blachke constant (k SB), equal to 0.28, already utilized for various systems, can also be employed to analyze chitosan solutions under the conditions studied.