The composition and rate behavior of free radical copolymerizations is usually described by the Mayo‐Lewis (ML) model and the associated reactivity ratios, r1 and r2. Particularly with respect to rate, a number of systems have been found to be poorly described by the simple ML model and the penultimate unit effect (PUE) model has been suggested as an explanation. A small but significant amount of work has been done with small model analogues of polymer chains and with ESR which has established the chemical feasibility of a PUE. This paper reviews recent work with pulsed laser polymerization kinetic measurements which are successfully described in terms of a modified PUE. It is concluded that the strength of the PUE correlates inversely with the monomer reactivity ratio product, r1r2. The effect is important for rate, but not for composition.
No takes yet. Share an insight, caveat, or question.
K. F. O’Driscoll (1992) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: