Long-lived trapped radicals produced during the photopolymerization of butane-1,4-diol diacrylate (BDDA) were studied by EPR and ENDOR spectroscopy and their thermal decay was followed by EPR measurements at different temperatures (40-120-degrees-C) for kinetic study. The EPR signal showed the superimposition of two different patterns, a three-line and a single-line spectrum. Both EPR patterns decayed following first-order kinetics in the investigated temperature range. Activation parameters of the decay were obtained. The EPR patterns were attributed to the same radical species situated in fluid and in cross-linked regions of the photopolymerized BDDA. Radicals of the latter kind undergo electron spin exchange strong enough to wash out the hyperfine splitting. The single-line width is mainly determined by electron spin dipole-dipole interactions. The ENDOR response is only of the matrix kind, typical of radicals in a solid phase. The present model was also compared with recent literature reports.

EPR ENDOR STUDY OF THE DECAY OF TRAPPED RADICALS IN PHOTOPOLYMERIZED BUTANE-1,4-DIOL DIACRYLATE / C. OLIVA, E. SELLI, A. PONTI, I. BELLOBONO, R. MORELLI. - In: JOURNAL OF PHYSICAL ORGANIC CHEMISTRY. - ISSN 0894-3230. - 5:1(1992), pp. 55-61.

EPR ENDOR STUDY OF THE DECAY OF TRAPPED RADICALS IN PHOTOPOLYMERIZED BUTANE-1,4-DIOL DIACRYLATE

C. OLIVA
Primo
;
E. SELLI
Secondo
;
I. BELLOBONO
Penultimo
;
1992

Abstract

Long-lived trapped radicals produced during the photopolymerization of butane-1,4-diol diacrylate (BDDA) were studied by EPR and ENDOR spectroscopy and their thermal decay was followed by EPR measurements at different temperatures (40-120-degrees-C) for kinetic study. The EPR signal showed the superimposition of two different patterns, a three-line and a single-line spectrum. Both EPR patterns decayed following first-order kinetics in the investigated temperature range. Activation parameters of the decay were obtained. The EPR patterns were attributed to the same radical species situated in fluid and in cross-linked regions of the photopolymerized BDDA. Radicals of the latter kind undergo electron spin exchange strong enough to wash out the hyperfine splitting. The single-line width is mainly determined by electron spin dipole-dipole interactions. The ENDOR response is only of the matrix kind, typical of radicals in a solid phase. The present model was also compared with recent literature reports.
Settore CHIM/02 - Chimica Fisica
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/191055
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