Radiation-chemical reduction of 4,4'-bipyridinium salts in solid polymers

The influence of temperature on radiation induced reduction mechanism of alkyl substituted derivatives of 4,4'-bipyridinium salts (viologens) was studied in solid matrices of polyvinyl alcohol (PVA), polyvinyl purrolidon (PVP), polyvinyl butyral (PVB) and polymethyl methacrylate (PMMA) by means of pulse radiolysis. Activation energy values (EA) of 1,1'-dihepthyl-4,4'-bipyridinium dibromide of radiation induced reduction by radical intermediates were determined in PVA, PVP and PVB. It was found out that the EA values did not depend on the length of alkyl substituents (methyl-, hepthyl- and hexadecyl-) in viologen molecules. The reaction rate of reduction was limited by the mobility of macromolecule segment having unpaired electrons on carbon atoms. (author)