Investigation of the physicochemical properties of aqueous solutions of sodium salt of carboxymethyl starch obtained in the solid phase by viscometric methods

Abstract

By chemical modification of corn starch with sodium monochloroacetate in the solid phase, samples of sodium salt of carboxymethyl starch (Na-CMS) with different degrees of substitution (DS) were synthesized. In the synthesis of Na-CMS, solvents such as water, methanol, ethanol, butanol, and isopropyl alcohol were used as humectants in the reaction mixture. The viscosity of dilute aqueous solutions of Na-CMS was studied by capillary viscometry. It is shown that dilute solutions of Na-CMS exhibit properties characteristic of polyelectrolytes. The rheological properties of aqueous solutions of the synthesized Na-CMS samples were studied by the method of rotational viscometry. By changing the shear rate gradient over a wide range, the values of the shear stress and the effective viscosity of the solutions at different temperatures were determined. At the same time, the obtained data showed that aqueous solutions of Na-CMS belong to non-Newtonian liquids in the entire studied temperature range. It was also found that the dynamic viscosity of Na-CMS solutions decreases with an increase in their DS. The activation energy of the viscous flow of Na-CMS solutions was determined, the value of which shows that the polymer macromolecules interact with each other through hydrogen bonds.