Add time:08/10/2019         Source:sciencedirect.com

The hydrodynamic behavior of chitosan hydrochloride macromolecules in aqueous solutions of D- and l-ascorbic acid in a temperature range 25–45 °C was studied by capillary viscometry. The intrinsic viscosity, the Huggins constant, and the temperature coefficient of viscosity were estimated. The effect of the ionic strength of the solvent mixture, predetermined by varying the acid concentration or introducing NaCl, on the hydrodynamic volume of macromolecules and their manifestation of polyelectrolyte properties was revealed. It was established that an increased temperature had led to the macromolecular coils getting more compact and the thermodynamic quality of the water-acid medium as a polymer solvent getting poorer. Despite the close values of pH and ionic strength of the aqueous solutions of D- and l-ascorbic acid, chitosan hydrochloride in the d-ascorbic acid solution is characterized by larger macromolecules and the polymer interaction with the solvent mixture components is energetically more favorable. It is suggested that the conformational state of chitosan hydrochloride is affected not so much by the macrochain stiffness as by the isomeric form of ascorbic acid. A comparison was made of the viscometric parameters of the aqueous solution of the aminopolysaccharide in ascorbic acid with its traditional solvent media, namely: water, acetic and hydrochloric acids, and sodium acetate buffer.

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