Pulse Radiolysis of Methacryloyl-L-proline Methyl Ester in Dilute Aqueous Solution

The reactions of hydroxyl radical, hydrogen atom and hydrated electron intermediates of water radiolysis with a hydrogel-forming monomer, methacryloyl-L-proline methyl ester (MA-ProOMe), were studied by pulse radiolysis in dilute aqueous solutions and compared with the reactions of the acrylic derivative (A-ProOMe). The spectral and kinetic characteristics of the first step of OH, H and e aq - reactions with the two monomers are very similar. There are considerable differences in the next steps. In neutral solutions, the electron adduct of A-ProOMe decays in slow radical-radical reactions. The adduct of MA-ProOMe, however undergoes a fast irreversible protonation resulting in α-carboxyalkyl radical. The oligomerization reactions occurring in MA-ProOMe solutions are slow, and under adopted pulse radiolytic conditions, they are observable only at high monomer concentrations. In A-ProOMe solutions the reaction is significantly faster.