Pulse and gamma radiolysis studies of 3-sulfo propyl methacrylate in aqueous solutions

Abstract

Radiation induced polymerization of 3-sulfo propyl methacrylate (SPMA) in aqueous solution (10wt%) has been studied by steady state and pulse radiolysis techniques. The effect of radiation characteristics such as irradiation dose, dose rate and the presence of crosslinking agent on the gel formation of SPMA monomer has been investigated. In N2 -saturated solution, the gel formation doses for SPMA were found to be 70 and 258Gy at dose rates of 1.2 and 5kGyh−1, respectively. The swelling ratio results showed that the gel obtained at a constant dose of 0.8kGy dose swells ∼630 times of its dry weight at a dose rate of 5kGyh−1 whereas it is 394 times of its dry weight for the dose rate 1.2kGyh−1. The reactions of the primary radicals of water radiolysis such as eaq−, H-atom, OH radical, O−, and some oxidizing radicals like N3,Cl2−,SO4− and reducing species like CO2− with SPMA have been studied using pulse radiolysis technique. The results show that the reaction of eaq−, H-atom and OH radicals with SPMA are in the diffusion controlled limit with their respective bimolecular rate constant values being 8.6×109, 2×109 and 1.5×1010dm3mol−1s−1. The radical anion, SPMA− , (λmax=280nm) is observed to undergo fast protonation forming H-adduct, SPMA—H, (λmax=310nm) with a pKa value of 9.1. Cl2− reacts with a bimolecular rate constant of 3.5×107dm3mol−1s−1 forming solute radical cation (λmax=265nm). One-electron oxidation and reduction potentials for SPMA/SPMA+ and SPMA/SPMA− couples are estimated to be more than +1.6 and less than −1.9V, respectively.