OH radical induced depolymerization of poly(methacrylic acid)

Hydroxyl radicals (generated pulse radiolytically in dilute N2O-saturated aqueous solutions) react with poly(methacrylic acid) producing two kinds of radicals. The primary radical is converted into a secondary one by H-abstraction (k=3.5x102 s-1) as monitored by changes in the UV spectrum. Subsequently, the secondary radicals undergo chain scission (k=1.8 s-1 at pH 7-9). This process has been followed both by spectrophotometry as well as by conductometry. In competition with the bimolecular decay of the radicals the ensuing end-chain radicals undergo efficient depolymerization resulting in the release of monomer. Since the lifetime of the radicals is much longer at high pH, where the polymer attains a rod-like conformation, depolymerization is most efficient in basic solution