Pulse radiolysis of aqueous solutions of N-Vinylpyrrolidin-2-one and Poly(N-vinylpyrrolidin-2-one)

Abstract

The absorption spectra of transient species produced when dilute aqueous solutions of N-vinylpyrrolidin-2-one (vp) and poly(N- vinylpyrrolidin-2-one) (pvp) are subjected to pulse radiolysis in the presence and absence of radical scavengers have been obtained and compared with those obtained from analogous compounds. The precise structure of the transients has not been established. Rate constants for the reaction of the hydroxyl radical with vp and pvp have been evaluated both by a competition kinetic method and by direct observation of the build-up of transient species: k(vp+^·OH) = (6.4-8.1) × 10⁹ dm³ mol^-1 s^-1 and k(pvp+^·OH) = (1.5-2.3) × 10⁸ dm³ mol^-1 s^-1 at 25°C. The rate constant for the reaction of the hydrated electron with vp has been determined as(1.6±0.3) × 10⁹ dm³ mol^-1 s^-1 at 25°C. Rate constants for decay of the transient species have also been evaluated at 25°C: 2k(vp- OH^·) = (8.1±1.0)× 10⁸ dm³ mol^-1 s^-1; 2k(vp-e^-) = (1.7±0.2) × 10⁹ dm³ mol^-1 s^-1 and 2k(pvp-OH^·) = (1.5±0.2) × 10⁸ dm³ mol^-1 s^-1.