Pulse radiolysis study of diacrylate macromonomer in aqueous solution

The early stages of the polymerization of difunctional acrylate macromonomer, poly(ethylene glycol) diacrylate of average molecular weight of 700 Da (PEGDA700), were studied in aqueous solution by pulse radiolysis. The rate constant of the reaction of this monomer with OH. and hydrated electron was measured as 3.0 x 10(10) and 1.7 x 10(10) mol(-1) dm(3) s(-1), respectively. The absorption spectrum of the OH. adduct to PEGDA700 appeared to have a maximum at 275 nm. Its decay depends on monomer concentration, which was assigned to the propagation reaction, and the fast crosslinking of the macromonomer. Similar features were observed in the case of the spectrum of the H-. adduct. The shape of the absorption spectrum of electron adduct to the PEGDA700 depends on the pH of the solution. Radical anion formed at low pH undergoes protonation at carbonyl oxygen atom, giving carbon-centred radical with a maximum of absorption below 260 nm. In basic solution, protonation takes place at the beta-carbon atom, giving alpha-carboxyalkyl radical with a maximum of the absorption at 275 nm. (C) 2002 Elsevier Science Ltd. All rights reserved.