A Pulse Radiolysis Study of the Reaction of the Sulfate Radical Ion in Aqueous Solutions of Styrene

Abstract

The ultraviolet absorption spectra of the transient species formed during the pulse radiolysis of styrene and peroxydisulfate (S2O82)solutions showed that a benzyl-type radical was formed from styrene and the SO4- radical. The effect of adding Cl- was also studied. These results are in conflict with the claim1 that a phenylethyl radical was formed from SO4-' via the styrene cation radical. That study was made on acetonitrile solutions of styrene, S2O82-, CuCl2 and LiCl and the present results suggest that up to 70% of the SO4-' radicals may have been converted into Cl2-1 radical which then reacted with styrene.

Entry in Emulsion Polymerization: Effects of Initiator and Particle Surface Charge

“…In what follows it is assumed (based on experimental evidence − ) that the initial propagation step, eq 2, is so fast that it is not rate-determining. The essence of the model is that there is no barrier to entry for a z -meric radical (i.e., I ), and thus the actual entry step is, or is close to being, diffusion-controlled.…”

“…• species to adsorb and desorb many times before undergoing true, irreversible "entry", defined here as propagation of an adsorbed radical into the particle interior; i.e., the model does not assume that "entry" and "adsorption" are equivalent (although they In what follows it is assumed (based on experimental evidence [23][24][25] ) that the initial propagation step, eq 2, is so fast that it is not rate-determining. The essence of the model is that there is no barrier to entry for a z-meric radical (i.e., IM z…”

Microemulsion Polymerization. 2. Influence of Monomer Partitioning, Termination, and Diffusion Limitations on Polymerization Kinetics

“…The reaction of a primary free radical (I • ) with a first monomer (M) is reported to occur very rapidly, essentially in the diffusion-limited regime. 14 The resulting species (IM • ) either may be amphiphilic enough to directly enter a monomer-swollen micelle and start propagating or require further propagation steps in the aqueous phase. This is mechanistically similar to the Maxwell-Morisson model 15 for radical entry in emulsion polymerizations.…”

Kinetics and Mechanism of Microemulsion Polymerization of Hexyl Methacrylate

“…If radical capture requires aqueous phase propagation, then, if only two propagation events are required Here [M] aq is the monomer concentration in the aqueous phase. A first propagation stepthe reaction of a primary initiator radical and a monomershould not be rate determining as this reaction is reported to occur in the diffusion-controlled limit …”

“…A first propagation stepsthe reaction of a primary initiator radical and a monomersshould not be rate determining as this reaction is reported to occur in the diffusion-controlled limit. 23 Alternatively, k c may be diffusion controlled. In this limit where D is the diffusion coefficient of the radical in the aqueous phase and δ is the distance a radical diffuses before encountering a droplet or particle surface.…”