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.
|Titolo:||ELECTRON-PARAMAGNETIC-RESONANCE CHARACTERIZATION AND THERMAL DECAY OF RADICALS TRAPPED IN A PHOTOPOLYMERIZED TRIACRYLATE MONOMER|
SELLI, ELENA (Primo)
OLIVA, CESARE (Secondo)
|Settore Scientifico Disciplinare:||Settore CHIM/02 - Chimica Fisica|
|Data di pubblicazione:||1993|
|Digital Object Identifier (DOI):||10.1039/ft9938904215|
|Appare nelle tipologie:||01 - Articolo su periodico|