Some aspects of the radiolysis of poly(methacrylic acid) in oxygen-free aqueous solution

Hydroxyl radicals generated pulse radiolytically in dilute N2O-saturated aq ueous solutions of poly(methacrylic acid) (2.5 x 10(-3)-1 x 10(-2) mol dm(- 3), MW = 2.8 x 10(5) Da; pK(a) approximate to 7) react with this polymer wi th rate constants of 3.1 x 10(7) dm(3) mol(-1) s(-1) (protonated form) and 1.2 x 10(8) dm(3) mol(-1) s(-1) (deprotonated form). The primary and second ary carbon-centred radicals thus generated are characterized by an UV spect rum displaying a shoulder at around 320 nm. Changes in the UV spectrum in t he 10 ms time range have been attributed to an H-transfer from a methylene group to a primary radical site. The secondary radicals undergo chain sciss ion (k = 1.8 s(-1) at pH 7-9) as has been followed by purse radiolysis with conductometric detection. The ensuing end-chain radicals undergo efficient depolymerization resulting in the release of monomer. (C) 1999 Elsevier Sc ience Ltd. All rights reserved.