The Behavior of polymer radicals formed in irradiated carboxymethyl cellulose aqueous solutions

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

Carboxymethyl cellulose (CMC) forms gel at high concentrated solution by irradiation. It seems that polymer radicals, which produced by reactions between OH of water radiolysis products, reacts with each other to form crosslink point. To explain the mechanism of the crosslinking reaction, we investigated the behavior and the position of polymer radicals in irradiated CMC aqueous solution. In the UV absorption spectral measurement after pulse electron beam irradiation, we observed the slow decay of absorbance for about 30 minutes at 10 mM CMC concentration, and confirmed that the initial absorbance was higher with increasing dose. The decay was slower with more concentrated solution and higher molecular weight. Therefore, it seems that the initial yield of polymer radicals is affected by dose and reaction rate is by viscosity of solution. In the ESR measurement after the reaction with OH formed by photolysis of HO, we could estimate the position of CMC radical produced by OH which radical is located on secondary carbon of carboxymethyl substituent on C.