Number: 2002-053-1-400
Title: Establishment of quantitative
reliability of electron spin resonance techniques for polymerization
kinetics
Task Group
Chairman: Bunichiro
Yamada
Members: Matthew
P. Tonge, Per
B. Zetterlund, Ronald
D. Sanderson, Robert
G. Gilbert, Alex
van Herk, Sabine
Beuermann, and Christopher
Barner-Kowollik
Completion Date: project abandoned
Objective:
(1) An international collaboration to identify the key sources of
error that have led to discrepancies between propagation rate coefficients
(kp(T)) measured by electron spin resonance
(ESR) and pulsed laser polymerization techniques in free radical
polymerizations.
(2) To use the results of this study to develop techniques for the
reliable quantitative use of ESR techniques in such systems to add
to the data base produced by the IUPAC projects on polymerization
kinetics.
Description:
The ability of electron spin resonance spectrometers to directly
identify the nature and environment of free radicals in free radical
polymerizations (including the propagating radicals) has long been
recognized. Appropriate treatment of the spectra of the propagating
radicals allows the measurement of the propagating radical concentration,
which in principle allows the measurement of the propagation rate
coefficient. However, other than a few exceptions, the propagation
rate coefficients (for numerous monomers) measured by this technique
have differed significantly from those measured by the IUPAC method
of choice (pulsed laser polymerization, PLP).
The establishment of reliable techniques
for the measurements of these rate coefficients by ESR is of high
importance for high weight-fraction polymer systems, where the PLP
methods are not applicable.
The objective of this project is to measure
propagation rate coefficients for a monomer (or monomers) not previously
investigated by either ESR or PLP techniques (effectively a "double-blind"
experiment), and to use this study to investigate the major sources
of error in the ESR techniques. Expected outcomes include the establishment
of techniques for the reliable measurement of the propagation rate
coefficient by ESR techniques, the development of guidelines for
experimental design that allows the avoidance of the main potential
sources of error, and guidelines for testing the consistency and
reliability of the rate coefficients thus measured.