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Stabilization of free radicals in filled oligoesteracrylates

A study of the formation and decay of free radicals in the process of photocuring oligocarbonatmethacrylate (OCM-2), filled by two types of silica differing in particle size and hydroxylapatite, was carried out by electron spin resonance (ESR) spectroscopy. The results were correlated with the data for molecular mobility obtained by the means of a spin probe. It was shown that the interface layers are able to stabilize free radicals that appear in the process of photocuring. The lifetime of stabilized radicals is about 20–30 min at 50°C. The existence of a wide distribution of molecular mobility in filled oligomers was established. Sorption of oligomer molecules with filler surface was accompanied by their vitrification. When the content of filler achieved 25–35 mass%, vitrification of the half-volume of polymer matrix occurred. The strongest stabilizing effect was provided by hydroxylapatite.