ESR study of carboxymethyl cellulose radicals

Saiki, Seiichi; Nagasawa, Naotsugu; Tamada, Masao; Kudo, Hisaaki*; Katsumura, Yosuke*

Carboxymethyl cellulose (CMC) in a concentrated aqueous solution can be radiation-crosslinked, and OH in water radiolysis decomposition is assumed to cause radiation-crosslinking of polymer solutions. The purpose of this study is an indentification of CMC radicals formed by reactions with OH to understand the radiation-crosslinking mechanism of CMC. ESR spectra of CMC radicals formed by OH produced by photolysis of 10 mM hydrogen peroxide were measured in 0.35%CMC aqueous solution. As result, direct observation of CMC radicals in an aqueous solution were succeeded. Radical concentration increases as degree of substitution of carboxymethyl groups increases, and this implies that radicals are located on carboxymethyl groups. If radicals are located on carboxymethyl groups, ESR spectra would show Triplet Doublet, located on carboxymethyl groups linked with C6, and Doublet, located on carboxymethyl groups linked with C2 or C3. Overlapping these spectra at some proportion corresponded to experimental results accurately, and radicals on carboxymethyl groups were presumed from these results.