Functionalization of Cellulose: Synthesis of Water-soluble Cationic Cellulose Derivatives

One of the trends of modern cellulose chemistry is the functionalization of known cellulose derivatives in order to expand their application area. In this work, water-soluble cationic cellulose derivatives containing up to 4% coupled nitrogen were obtained by the amination of hydroxyethylcellulose (HEC) with two different etherification agents, diethylepoxypropylamine (DEEPA) and (2-chlorethyl) diethylamine hydrochloride (DEAE). The influence of the composition of the reaction mixture on the degree of substitution was investigated by using mathematical planning of the experiments and was described by regression equations. The effect of the etherification agent on the composition of cationic groups of the obtained derivatives was examined. It was found that the HEC reaction with DEEPA resulted in a monofunctional cationic polyelectrolyte containing tertiary amino groups, which could be assigned to cationic groups of intermediate basicity (pKa approx. 8.2). On the contrary, the amination of HEC with DEAE gave polyfunctional derivatives containing a mixture of weakly and intermediately basic amino groups with pKa 6.0-6.2 and 8.2-8.6, respectively. The synthesized derivatives are soluble in polar aprotic solvents, as well as in water, and the solutions possess high stability at elevated temperature and a high concentration of salts.