Preparation of high‐substituted cationic starch in presence of organic bases

Abstract

AbstractCross‐linked N‐(hydroxypropyl)–N,N,N–trimethylammonium starch chlorides (CQS) with preserved microgranules, degree of substitution (DS) from 0.18 to 1.05 are prepared by reaction of starch with glycidyltrimethylammonium chloride (GTAC) accelerated by benzyltrimethylammonium hydroxide (BTMAOH) or tertiary amines–triethylamine (TEA) and dimethylbenzylamine (DMBA). When BTMAOH instead of NaOH is used as a catalyst, the reaction of cross‐linked starch (CS) with GTAC proceeds slightly slower and with a lower efficiency (RE). DMBA unexpectedly showed similar catalyst efficiency as BTMAOH. It is suggested that the reason for such phenomena is the reaction of GTAC with tertiary amines and the formation of strong bases – quaternary ammonium hydroxides. They actually catalyse starch cationization. DMBA is more active in this reaction in comparison with TEA. It is shown that, due to a higher amount of quaternary ammonium hydroxides in the liquid phase of the reaction mixture, the yield of starch cationization decreases. Cationization in the presence of organic bases provides higher sorption capabilities to the modified polysaccharide.