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EPR Study into Cross‐Termination and Fragmentation with the Phenylethyl–Phenylethyl Dithiobenzoate RAFT Model System
Author(s) -
Meiser Wibke,
Buback Michael,
Ries Oliver,
Ducho Christian,
Sidoruk Alana
Publication year - 2013
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.201200668
Subject(s) - raft , chain transfer , chemistry , fragmentation (computing) , radical polymerization , reversible addition−fragmentation chain transfer polymerization , polymer chemistry , polymerization , photochemistry , radical , styrene , organic chemistry , polymer , copolymer , computer science , operating system
The reversible addition–fragmentation chain transfer (RAFT) equilibrium constant of the phenylethyl–1‐phenylethyl dithiobenzoate model system is deduced via EPR spectroscopy to be 31 ± 4 L mol −1 at 110 °C. The difference in activation energies of addition and fragmentation, E a ( k ad ) – E a ( k β ) ≈ −45.6 kJ mol −1 , is close to that of the polystyryl–polystyryl dithiobenzoate system. Significant amounts of products from cross‐termination and from “missing step” reaction of the cross‐termination product with the phenylethyl radical demonstrate that intermediate radical termination, rather than slow fragmentation of the RAFT intermediate radical, is responsible for the rate retardation in the dithiobenzoate‐mediated styrene polymerization.