Magnetic and spin effects in the photoinitiation of polymerization

Abstract

Application of a moderate external magnetic eld increases the ef ciency of triplet photoinitiators of polymerization. The reasons for this observation are brie y outlined. Such well-documented magnetic and spin effects as the magnetic isotope effect (MIE) and chemically induced dynamic nuclear and electron polarization (CIDNP and CIDEP) have been observed under the photolysis of photoinitiators. CIDEP results are emphasized. The study of CIDEP under the photolysis of initiators allows the detection and identi cation of free radicals of initiators and the spin multiplicity of the reacting photoinitiator(triplet or singlet). The transfer of the spin polarization of the initiator free radical to monomers is a promising technique for following radical reaction pathways. The results of a CIDEP study of the sensitized decomposition of phosphine oxide photoinitiators are presented.

Spectroscopy in sculpted fields

“…Model systems include electron transfer between pyrene and dimethylaniline [78] and in photolysis of benzophenone [79] and dibenzyl ketone [80,81]. MFE on polymerization have been observed in systems where the initiator goes through a bi-radical [82,83]. Magnetic field modulation of bi-radical reactions is speculated to play a role in magnetic navigation in birds [84][85][86] and Drosophila [87], although this hypothesis remains unproved.…”

Magnetic field effects on the free radical solution polymerization of acrylamide

“…In general, the correlation between classical chemical reaction parameters and MF effects is missing. In fact, the topic was recently evaluated as deserving further studies [10]. As to the authors' knowledge, the influence of the MF on the rate coefficients of initiation, propagation, and termination has not been investigated in detail for the free radical polymerization of acrylamide.…”

Chemically Induced Dynamic Nuclear Polarization during the Thermolysis of Alkoxyamines: A New Approach to Detect the Occurrence of H-Transfer Reactions

“…[11][12][13][14]. Previously, Chemically Induced Dynamic Electron Polarization (CIDEP) [15,16] and CIDNP and its modification (CIDNP with fast switching of magnetic field) have been used in NMP research to measure the rate constants of coupling between acrylate-type radicals and the persistent nitroxide [17,18]. In those experiments, the carbon centered radicals under investigation were generated by the photolysis of ketone precursors in the presence of persistent nitroxides.…”