Cationically modified 6-deoxy-6-azido cellulose as a water-soluble and reactive biopolymer derivative

Cellulose p-toluenesulfonic acid ester was obtained by conversion of cellulose with p-toluenesulfonic acid chloride and triethylamine in N,N-dimethylacetamide/LiCl solution. Further reaction with sodium azide afforded the corresponding 6-deoxy-6-azido cellulose with almost complete displacement of the sulfonate groups. Conversion of 6-deoxy-6-azido cellulose with carboxypropyltrimethylammonium chloride in the presence of N,N'-carbonyldiimidazole yielded 6-deoxy-6-azido cellulose-2,3-O-[4-(N,N,N-trimethylammonium)]butyrate chloride with the degree of substitution of cationic groups up to 0.24. Alternatively, conversion of 6-deoxy-6-azido cellulose with 4-bromobutyltrimethylammonium bromide in the presence of sodium hydroxide in 2-propanol slurry afforded 6-deoxy-6-azido-2,3-O-(4-trimethylammonium)butyl cellulose bromide with a DS of cationic groups up to 0.30. The resulting products are water soluble provided that the content of cationic groups is sufficiently high. Etherification was found to influence the degree of polymerization much more than esterification. Utilization of dimethyl sulfoxide and sodium hydride caused predominant polymer degradation.