Synthesis of microscopic carboxymethylcellulose hydrogels with metal ions by radiation-induced crosslinking

Nagasawa, Naotsugu; Rokita, B.*; Ulanski, P.*; Hiroki, Akihiro; Rosiak, J. M.*; Taguchi, Mitsumasa; Tamada, Masao

no journal, , 

The chemically modified polysaccharide derivatives such as carboxymethylcellulose (CMC) are soluble in water so that have been widely used in many industrial applications. Recently, the idea of synthesis of CMC microscopic gels by means of ionizing radiation has been appeared. To obtain microscopic gels with given molecular weights and sizes the selection of proper experimental conditions should be done. However, in case of diluted CMC aqueous solutions during irradiation, the degradation is the dominant process. In order to solve this problem, we investigated a new method by adding metal ions (CaCl) to CMC solution before irradiation. The Ca ions reduce interaction of the charge for CMC molecules and makes coils structure. Therefore, macroradicals formed on such the coiled polymer chains can make possible formation of inter- and intra-molecular crosslinking. Formation of microscopic gels in this system was observed. For 0.1% CMC with CaCl at molar ratio CMC:CaCl 1:0.5-1.25 during irradiation up to 50 kGy, the increment of Ca ions and dose decrease the particle sizes from 800 nm to 50 nm. The combination of metal ions addition and radiation-induced crosslinking caused significant synthesis of nano- and micro-meter sized carboxymethylcellulose hydrogels.