Analysis of the complex-dissociation model for free-radical copolymerization

Abstract

Probability theory has been used to derive equations for the complex-dissociation model for free-radical copolymerization showing how the composition, the triad fractions, and the number fractions of sequences in the copolymer are related to the comonomer composition through the reactivity ratios and the equilibrium constant for complex formation. It is shown how these equations can be used to estimate "best" values of the reactivity ratios and the equilibrium constant using experimentally determined copolymer compositions. This model has been applied to the data of Dodgson and Ebdon for the styrene-maleic anhydride copolymerization in bulk at 60 °C. The complex-dissociation model, the penultimate model, and the complex-participation model fit the copolymer/comonomer composition data equally well. However, the predicted styrene sequence distributions of the three models are quite different, and experimental determinations, for example, by 13C NMR, would enable discrimination between the models.

A mechanistic study of the radical copolymerisation of p‐methoxystyrene with citraconic anhydride via 13C NMR spectroscopy

“…3,5,9) finding that the comonomer units in these copolymers displayed a similar tendency to alternate compared with the copolymerisation of ST with MA in bulk at 60 "C. It was concluded from this work that the complex-participation model should not be discounted when describing the mechanism of copolymerisation of p-MST with MA under these conditions. Hence it would appear that the role of the charge-transfer complex in these types of copolymerisations warrants further investigation.…”

Grafting of maleic anhydride onto styrene–butadiene–styrene triblock copolymer using supercritical CO2 as a swelling agent

“…The reason is that increasing of MA concentration increases the reaction probability of MA and SBS, and the grafting ratio increases. Because the homopolymerization of MA is difficult,17 and the quantity of reactive double‐bonds in SBS is invariable, increase of MA concentration continuously will lead the grafting ratio to saturation.…”

A general kinetic method to predict sequence length distributions for non-linear irreversible multicomponent polymerizations

“…Several experimental works for the quantification of sequence length distributions are based on the use of NMR [21e25]: the copolymer/co-monomer composition relationship and the sequence distributions were experimentally measured using 13 C NMR by Hill et al [21] for the copolymerization of styrene and acrylonitrile. Alternative models to the terminal model (penultimate model, complex participation, complex dissociation) were also tested by the same authors [21,22]. The sequences formed in the styrenee methylmethacrylate copolymer were also experimentally investigated using proton and carbon NMR spectra [23] and for the study of the copolymerization system methacrylic acid/ poly(ethylene glycol)monomethacrylate 1 H NMR was employed [24].…”