Radicals trapped during the photopolymerization and photo-cross-linking of 2-ethyl-2-hydroxymethylpropane-1,3-diol triacrylic ester have been studied by EPR spectroscopy at different temperatures (25-180-degrees-C) and their thermal decay has been followed at 120-degrees-C and 150-degrees-C. Performing a fitting procedure on the EPR signals showed that they are composed of two kinds of patterns, which superimpose with the same g value. One of them is a single-line spectrum, while the other is hyperfine-structured. An exchange between two radical conformations is revealed by the latter, with the rate depending both on temperature and on the molar fraction of radicals giving the single-line spectrum. This suggests that both species are involved in the exchange mechanism. Termination occurs preferentially between radicals giving the same EPR pattern. Second-order termination rate constants depend on the photoinitiator concentration in the irradiated photoreactive mixture and give information about the microstructure of the polymer.
ELECTRON-PARAMAGNETIC-RESONANCE CHARACTERIZATION AND THERMAL DECAY OF RADICALS TRAPPED IN A PHOTOPOLYMERIZED TRIACRYLATE MONOMER / E. SELLI, C. OLIVA, A. GIUSSANI. - In: JOURNAL OF THE CHEMICAL SOCIETY. FARADAY TRANSACTIONS. - ISSN 0956-5000. - 89:23(1993), pp. 4215-4219.
ELECTRON-PARAMAGNETIC-RESONANCE CHARACTERIZATION AND THERMAL DECAY OF RADICALS TRAPPED IN A PHOTOPOLYMERIZED TRIACRYLATE MONOMER
E. SELLIPrimo
;C. OLIVASecondo
;
1993
Abstract
Radicals trapped during the photopolymerization and photo-cross-linking of 2-ethyl-2-hydroxymethylpropane-1,3-diol triacrylic ester have been studied by EPR spectroscopy at different temperatures (25-180-degrees-C) and their thermal decay has been followed at 120-degrees-C and 150-degrees-C. Performing a fitting procedure on the EPR signals showed that they are composed of two kinds of patterns, which superimpose with the same g value. One of them is a single-line spectrum, while the other is hyperfine-structured. An exchange between two radical conformations is revealed by the latter, with the rate depending both on temperature and on the molar fraction of radicals giving the single-line spectrum. This suggests that both species are involved in the exchange mechanism. Termination occurs preferentially between radicals giving the same EPR pattern. Second-order termination rate constants depend on the photoinitiator concentration in the irradiated photoreactive mixture and give information about the microstructure of the polymer.Pubblicazioni consigliate
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