Cationation of starch with an aminating reagent based on triethylamine and epichlorohydrin

Abstract

This article presents a simplified method for the preparation of cationic starches with a different degree of substitution using triethylamine and epichlorohydrin as starting materials. The optimal conditions for a starch cationation by a semi-dry method have been determined. The cationic starch with quaternary ammonium cation groups was prepared by the interaction of an aminating reagent with corn starch in the presence of sodium hydroxide. The aminating reagent, 3-chloro-2-hydroxypropyltriethylammonium chloride, was synthesized by the one-pot interaction between triethylamine and HCl followed by the reaction with epichlorohydrin in the presence of cetyltrimethylammonium bromide as a catalyst. The cationic starches were fabricated with the degree of substitution of hydrogen atoms in starch hydroxy groups equal to 0.02-0.45. The effects of molar ratios of sodium hydroxide to the aminating reagent and the aminating reagent to starch (with respect to a D-glucopyranose unit) in the initial reaction mixture on the degree of substitution were investigated. It was shown that the cationic starch with the highest degree of substitution was formed at an optimal starting molar ratio of sodium hydroxide to the aminating reagent that is equal to 1.2-2.0. An increase in the molar ratio of aminating reagent to starch significantly increases the degree of substitution when the content of sodium hydroxide is less than the optimal value. The reaction efficiency of the cationation of corn starch decreases with an increase in the molar ratio of aminating reagent to starch (in the test range of 1.0 to 6.0).