Abstract
Preparation and properties of chitosan (CS) derivatives modified with biguanido groups were examined. The melt reaction of chitosan hydrochloride with dicyandiamide gave chitosan derivatives with a degree of substitution (DS) of more than 30%. Further, a water-soluble product was readily obtained by adding copper (II) chloride to the same reaction system. However, under these reaction conditions the decomposition of the main chain took place. Chitosan pretreated with an alkaline solution was also reacted with guanyl-O-methyl isourea at room temperature, leading to the product having DS of ca. 20% and high molecular weight. The reduced viscosity of the above derivatives incresed with dilution in the acid solutions, but decreased linearly in the presence of a sodium salt. These results indicate that they were cationic polyelectrolytes. The adsorption ability increased in the order Zn (II) <Ni (II) <<Cu (II), and high affinity toward Cd (II) and Hg (II) was observed. The biguanido-containing chitosan showed a pronounced aggregation effect toward aqueous suspension of both Kaolin and acid clay.
