Effective approaches for estimating the functionalization pattern of carboxymethyl starch of different origin

Three types of differently prepared carboxymethyl starches were analyzed by HPLC and H-1-NMR spectroscopy after chain degradation. In derivatives obta ined in the conventional manner with values of the degree of substitution ( DS) up to 0.85; glucose, mono- and di-O-carboxymethyl glucose were detected as building units. Comparison with statistic calculations revealed an even distribution of functional groups along the chain. H-1-NMR studies confirm ed a preferred substitution at the 2 position of the repeating unit. Compar able results were obtained for the carboxymethyl ether of amylose, amylopec tin and beta-cyclodextrin. The analysis of carboxymethylated starch samples prepared using a new synthesis concept via a reactive microstructure revea led a high DS achieved in a one-step synthesis as well as a nonstatistic di stribution of carboxymethyl groups along the chain. A significant amount of 2,3,3,6-tetra-O-functionalization, caused by the branched structure of sta rch, was found, Moreover, carboxymethylation of 6-O-triphenylmethyl starch and subsequent detritylation yields a regioselectively functionalized polym er consisting not only of the expected mono- and di-O-carboxymethylated rep eating units but also containing a significant amount of 2,3,4-tri-O-functi onalized anhydro-glucose units.