Kinetic studies of radical reactions using time-resolved EPR

摘要

The presented work has demonstrated, that TR-EPR is a powerful tool forudthe determination of the decisive structural and kinetic parameters for theudevaluation of photoinitiator efficiency. Additional insights are provided byudthe application of theoretical calculations. This combination of experimentaludand theoretical methodology provides a basis for the design and developmentudof innovative phototriggers.udOn the bases of the results presented in this thesis we can make the fol-udlowing conclusions:ud- TR-EPR allows the determination of addition rate constants in theudcases where optical spectroscopy doesn't have sufficient resolution asudwell as provides structural information of the reactive species.ud- Phosphinoyl radicals generated by photolysis of acyl and bis(acyl)phosphineudoxides, possess high rate constants of addition to n-butyl acrylate,udHDDA, styrene and 1-vynil-2-pyrrolidon. Analysis of the spin popu-udlation at the phosphorus atom supports the experimental observationsudof TR-EPR spectra that greater localization of the spin population atudthe phosphorus atom results in faster rates of addition.ud- A series of substituted benzoyl radicals have been generated by laserudflash photolysis of -amino ketones and bis(acyl)phosphine oxides. Theudbenzoyl radicals were characterized by time-resolved EPR in toluene so-udlution and their absolute rate constants for addition to n-butyl acrylateudwere determined. The experiments demonstrate two concentration do-udmains of reactivity. The reactivity of benzoyl radicals decreases at highudviscosity.udud- Benzoyl radicals react faster with oxygen than phosphinoyl radicals,udtherefore, they can be used as oxygen scavenges.ud- The fluorescence properties of the photoinitiators can be used to in-udcrease the in depth cure of the formulation.ud- DFT and ab initio calculations have shown to be in a good agreementudwith the experimental data.