Project Details Critically evaluated ESR (EPR) spectra of important polymerization-related radicals

Project No.:
Start Date:
01 December 2015
End Date:
Division Name:
Polymer Division
Division No.:


The objective is to provide the ESR spectra and the complete set of the associated hyperfine splitting constants of radicals from various monomers that are relevant for both modeling of technical polymerization processes and for fundamental studies in academia and in industry. In addition, ESR spectra of radicals occurring in reversible deactivation polymerization will be collated.


Electron spin resonance (ESR) spectroscopy, also referred to as EPR, allows for the direct observation of radicals, thus being of eminent importance for detailed investigations into radical polymerization. ESR spectra provide information on the structures, properties, and concentrations of radicals. ESR detection of radicals has been difficult under stationary polymerization conditions at low radical concentration. The quality of ESR spectrometers has however been largely improved. Moreover, upon the advent of pulsed lasers, large radical concentrations may be instantaneously generated and subsequently monitored at high time resolution. Such single pulse experiments provide access to chain-length-dependent termination, to transfer and even to propagation rate coefficients. The method is also applicable toward reversible addition fragmentation transfer (RAFT) and atom-transfer radical polymerization (ATRP) kinetics. The time-resolved CIDEP ESR technique is applicable toward studies into the very initial stage of radical polymerizations. The multitude of powerful ESR techniques enables the quantitative detection of specific radicals over the entire course of a polymerization reaction. Application of these methods requires the accurate knowledge of the ESR spectra and associated hyperfine coupling constants (hfcs). No hfcs on polymerization-related radicals have been tabulated since Ranby and Rabek’s book on ESR Spectroscopy in Polymer Research (Springer, 1977).

A critically evaluated update of the available data and of recommended experimental methods is urgently required, in particular as novel monomers and polymerization techniques have been introduced. Experimentalists and theoreticians will cooperate within the project to establish a database of reliable ESR spectra for use in academia and industry.


March 2016 – Project announcement published in Chem. Int. March 2016, p. 21;

Page last updated 19 March 2016