Aqueous solutions, containing disolved oxygen, of sodium salt of carboxy-methyl cellulose and of polyacrylic acid and so on were irradiated with γ-rays from Co
60 or with 90
KV X-rays, and the degeneration of molecules in the solutions brought about under various conditions was studied by viscometric, ultracentrifugal, and electrical measurements.
Ideal indirect kinetics of main chain fractures through activated water has been recognized in all the cases from highly concentrated solutions to fairly diluted ones. In the case of extremely diluted solutions, however, free-radical recombination seems to make the reaction inefficient.
From a simple consideration of these fact, a certain information as to the molecular extension and form in the solution has been derived.
Inclusion of salts and alcohols in the solution protects effectively the degeneration due to irradiation, which can be explained satisfactorily likewise on the assumption of “
indirect effect”.
The molecular contraction and change of molecular form caused by the inclusion of salts have been estimated.
The irradiation effect on dilute solutions of non-electrolyte polymers was also investigated. The efficiency of chain fractures comes out not much smaller than in the case of polyelectrolyte molecules in the same concentration range. Here the rate of fracture seems to indicate again the “
indirect effect”.
It may therefore be concluded that electrical charges on polyelectrolyte molecules, in a certain range, are not essential for degradation and their extension is not much different from that of non-electrolyte molecules.
It has been observed that, in the case of concentrated polyelectrolyte solutions containing oxygen, irradiation does not give rise to formation of gel, although micro-gel may be formed.
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