M. Hyla, J. Filipecki, J. Swiatek, R. Mervinskii, L. Gudzowska, V. Savitsky.
Journal of Non-Crystalline Solids, vol. 290, 2001, p. 20-24.
Polymerization in polymers based on acrylate oligomers was caused by exposure to ultraviolet light. Polymer specimens with different ultraviolet light exposure times have been investigated by positron annihilation lifetime spectroscopy (PALS). The longest lifetime, τ3, in observed lifetime spectra for positrons was associated with the pick-off annihilation of ortho-positronium (o-Ps) trapped by free volume in the structure. The aim of this paper was to investigate the influence of the time of UV exposure on free volume sizes in two different polymers based on acrylate oligomers. UV exposure time influences the free volume size: longer time reduces it. The concentration of the free volumes is independent of UV exposure time.