Flory–Huggins parameter of interaction in polyelectrolyle solutions of chitosan and its alkylated derivative

The enthalpy of dilution of chitosan and alkylchitosan solutions in aqueous 0.3 M acetic acid was experimentally studied over the entire concentration range at 298 K, and the values of Flory–Huggins interaction parameter were determined with the help of a new scaling approach which took into account the electrostatic contribution to the enthalpy of dilution of polyelectrolyte solutions. That made it possible to estimate separately the excluded volume contribution to the enthalpy of dilution and, thus, to calculate the values of χ which appeared to be −0.01 for chitosan and −0.21 for alkylchitosan. It was found out that χ did not depend on the presence of salt in the solution. The hydrophobic modification of chitosan enhanced interaction with water due to the hydrophobic hydration in the aqueous solution.