Pulsed radiolysis of poly(styrenesulfonate) in aqueous solutions

Abstract

Various radical species have been identified in the pulse radiolysis of aqueous solutions of poly(styrenesulfonate) (PSS). OH radicals react with PSS (k = (7.5 /plus minus/ 1) /times/ 10/sup 8/ M/sup /minus/1/ s/sup /minus/1/) to produce predominantly a mixture of OH adducts. An intrapolymer biradical decay of the OH adducts (2k/epsilon = (3.0 /plus minus/ 1) /times/ 10/sup 5/ cm s/sup /minus/1/) takes place when several OH radical adducts are produced on the same polymer molecule. This decay reaction competes with a first-order formation of a positive radical ion (k = 160 /plus minus/ 40) s/sup /minus/1/ at pH 5.6. The formation reaction is acid catalyzed. It is slowed down by addition of inert salts. The positive radical ion decays in the time range of hours, obeying a first-order rate law (k = (5.4 /plus minus/ 0.5) /times/ 10/sup /minus/5/ s/sup /minus/1/). This decay is attributed to an intramolecular conversion of the positive radical ion to a benzyl type radical, which subsequently decays to produce stable recombination products. The spectra and kinetics are discussed in light of the known properties of various aromatic and polymer systems. Long-lived polymeric free radicals are useful models for photochemical storage systems.