Solvent effects on the copolymerization of styrene and maleic anhydride are interpreted in terms of Harwood's bootstrap effect. Earlier observations that this comonomer pair behaves according to the bootstrap effect are confirmed. Furthermore, solvent effects on stereochemical configuration can be interpreted in terms of the bootstrap effect as well. The observation that the Z / E ratio of the anhydride units versus copolymer composition is independent of solvent is attributed to monomer partitioning between the bulk of the solution and the locus of polymerization.
SYNOPSISThe Comppen model for the mechanism of free-radical copolymerization has been developed to account for both penultimate effects and the participation of 1 : 1 electron donor-acceptor complexes during chain propagation. This was achieved by incorporating penultimate effects into the existing complex participation model of Cais, Farmer, Hill, and O'Donnell, using probability theory to derive new copolymer composition and sequence distribution equations that are solely functions of the reactivity ratios, the composition of the comonomer feed, and the equilibrium constant for 1 : 1 electron donor-acceptor complex formation. The model was applied to experimental data from styrene/maleic anhydride copolymers prepared in methyl ethyl ketone a t 50°C over a wide range of comonomer feed compositions, using nonlinear least-squares curve fitting techniques to determine best estimates of the reactivity ratios. Copolymer compositions and sequence distributions for copolymers in this comonomer system were then predicted using the Comppen model and compared to those determined experimentally via 13C-NMR spectroscopy.
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