Free volumes in UV-cured polymers based on acrylate oligomers

Polymerization in polymers based on acrylate oligomers was caused by exposu re to ultraviolet light. Polymer specimens with different ultraviolet tight exposure times have been investigated by positron annihilation lifetime sp ectroscopy (PALS). The longest lifetime, tau (3), in observed lifetime spec tra for positrons was associated with the pick-off annihilation of ortho-po sitronium (o-Ps) trapped by free volume in the structure. The aim of this p aper was to investigate the influence of the time of UV exposure on free vo lume sizes in two different polymers based on acrylate oligomers. UV exposu re time influences the free volume size: longer time reduces it. The concen tration of the free volumes is independent of UV exposure time. (C) 2001 El sevier Science B.V. All rights reserved.