Studies on graft copolymerization onto cellulose derivatives. (Part 34). Preparation of Carboxymethyl-Chitin Graft Polymer and its Characterization.

Abstract

Graft copolymerization of methyl methacrylate (MMA) onto carboxymethyl-chitin (CM-Chitin) and the characterization of graft copolymer were carried out. Chitin was first carboxymethylated with monochloroacetic acid in alkali medium. Degree of carboxymethylation (DS) increased with increasing monochloroacetic acid concentration and prolonging reaction time. At the same time, alkali solution also caused deacetytation of chitin. CM-Chitins with various DS were grafted with MMA using ammonium peroxodisulfate (APS). Degree of grafting increased with increasing APS concentration. Addition of crosslinking agent to the system extremely increased degree of grafting. The chain length of grafts of CM-Chitin decreased compared with that of chitin. Degree of grafting and the apparent number of grafted chains also increased with increasing DS and then decreased DS around 0.6. These results indicate that carboxyl groups participated in not only initiation reaction but also termination reaction. Samples having higher degrees of grafting adsorbed less amount of water.Cation exchange capacity of the graft copolymer depended on pH of solution and was affected by ion species. From pH 4 to 5, the cation exchange capacities for divalent ions were the following order; Cu2+>Ca2+>Cd2+, those for different charge ions were the following order; Fe3+>Cu2+>Ag+. Since the graft copolymers could be used repeatedly, these are considered to be useful ion exchangers.