TY - JOUR
T1 - Revealing model dependencies in "assessing the RAFT equilibrium constant via model systems
T2 - An EPR study"
AU - Junkers, Thomas
AU - Barner-Kowollik, Christopher
AU - Coote, Michelle L.
PY - 2011/12/1
Y1 - 2011/12/1
N2 - In a recent article (W. Meiser, M. Buback, Assessing the RAFT Equilibrium Constant via Model Systems: An EPR Study, Macromol. Rapid Commun. 2011, 18, 1490-1494), it is claimed that evidence is found that unequivocally proves that quantum mechanical calculations assessing the equilibrium constant and fragmentation rate coefficients in dithiobenzoate-mediated reversible addition fragmentation transfer (RAFT) systems are beset with a considerable uncertainty. In the present work, we show that these claims made by Meiser and Buback are beset with a model dependency, as a critical key parameter in their data analysis - the addition rate coefficient of the radicals attacking the C=S double bond in the dithiobenzoate - induces a model insensitivity into the data analysis. Contrary to the claims made by Meiser and Buback, their experimental results can be brought into agreement with the quantum chemical calculations if a lower addition rate coefficient of cyanoisopropyl radicals (CIP) to the CIP dithiobenzoate (CPDB) is assumed. To resolve the model dependency, the addition rate coefficient of CIP radicals to CPDB needs to be determined as a matter of priority.
AB - In a recent article (W. Meiser, M. Buback, Assessing the RAFT Equilibrium Constant via Model Systems: An EPR Study, Macromol. Rapid Commun. 2011, 18, 1490-1494), it is claimed that evidence is found that unequivocally proves that quantum mechanical calculations assessing the equilibrium constant and fragmentation rate coefficients in dithiobenzoate-mediated reversible addition fragmentation transfer (RAFT) systems are beset with a considerable uncertainty. In the present work, we show that these claims made by Meiser and Buback are beset with a model dependency, as a critical key parameter in their data analysis - the addition rate coefficient of the radicals attacking the C=S double bond in the dithiobenzoate - induces a model insensitivity into the data analysis. Contrary to the claims made by Meiser and Buback, their experimental results can be brought into agreement with the quantum chemical calculations if a lower addition rate coefficient of cyanoisopropyl radicals (CIP) to the CIP dithiobenzoate (CPDB) is assumed. To resolve the model dependency, the addition rate coefficient of CIP radicals to CPDB needs to be determined as a matter of priority.
KW - ab initio quantum mechanical calculations
KW - intermediate radical termination
KW - kinetics (polymer)
KW - model dependency
KW - rate coefficients
KW - reversible addition fragmentation transfer (RAFT)
UR - http://www.scopus.com/inward/record.url?scp=82455175731&partnerID=8YFLogxK
U2 - 10.1002/marc.201100494
DO - 10.1002/marc.201100494
M3 - Article
SN - 1022-1336
VL - 32
SP - 1891
EP - 1898
JO - Macromolecular Rapid Communications
JF - Macromolecular Rapid Communications
IS - 23
ER -