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Assessing the RAFT Equilibrium Constant via Model Systems: An EPR Study
Author(s) -
Meiser Wibke,
Buback Michael
Publication year - 2011
Publication title -
macromolecular rapid communications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.348
H-Index - 154
eISSN - 1521-3927
pISSN - 1022-1336
DOI - 10.1002/marc.201100228
Subject(s) - electron paramagnetic resonance , raft , chemistry , equilibrium constant , reaction rate constant , thermal decomposition , chain transfer , radical polymerization , polymer chemistry , nuclear magnetic resonance , kinetics , polymer , copolymer , organic chemistry , physics , quantum mechanics
Reversible addition‐fragmentation chain transfer (RAFT) equilibrium constants, K eq , for the model system cyano‐ iso ‐propyl dithiobenzoate (CPDB) – cyano‐ iso ‐propyl radical (CIP) have been deduced via electron paramagnetic reso1494nce (EPR) spectroscopy. The CIP species is produced by thermal decomposition of azobis‐ iso ‐butyronitrile (AIBN). In solution of toluene at 70 °C, K eq has been determined to be (9 ± 1) L · mol −1 . Measurement of K eq = k ad / k β between 60 and 100 °C yields Δ E a = (–28 ± 4) kJ · mol −1 as the difference in the activation energies of k ad and k β . The data measured on the model system are indicative of fast fragmentation of the intermediate radical produced by addition of CIP to CPDB.