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Laser Flash Photolysis of Caboxymethylcellulose in Aqueous Solution
Summary
The method of laser flash photolysis with excitation at 248 nm was used to study photochemically derived changes of carboxymethylcellulose (CMC) of various degree of substitution in aqueous solution. The absorption spectra of solutions after the flash revealed a broad band with the maximum about 720 nm, which can be ascribed to the formation of hydrated electron. Kinetics of the reaction of polymer with hydrated electron and hydroxyl radical were investigated. It has been considered that interactions of with CMC are slow (< 107 dm3mol-1s-1) and OH reacts with polymer with a high rate (9.5 ´ 106 dm3mol-1s-1). The rate constants of the reactions between CMC and hydroxyl radicals decrease at low pH and in the presence of inorganic salt, which is determined by coiled conformation of macromolecule. Sa a result of OH attack long-life radicals on CMC were formed. An increase in absorbance was recorded at l < 370 nm for CMC solutions photolyzed at the presence of H2O2. It was found that recombination of macroradicals leads to the formation of crosslinking bonds between side chain groups, since insoluble gel appeared at solutions of low pH.
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