J. Phys. IV France 03 (1993) C4-241-C4-247
Interplay between electron affinity and free volume on positronium formation in polyimidesY. ITO1, K.-I. OKAMOTO2 and K. TANAKA2
1 Research Center for Nuclear Science and Technology, The University of Tokyo, Tokai, Ibaraki 319-11, Japan
2 Faculty of Engineering, Yamaguchi University Japan
Our recent PAL results on a series of polyimides (Pl) are summarized. It is shown that Pls are properly grouped according to whether there is long-lived o-Ps or not, and that those that do not produce o-Ps have strong electron affinities. Secondly the pore size was changed by ex-posing Pls to 50 atm CO2 gas. I3 was increased substantially for the Pls that have moderate I3 values. For the Pls that have large o-Ps yield the increase in I3 was small, and for those having no o-Ps the o-Ps component did not appear. In a third experiment where the pore structure was changed by introducing vapor molecules, both [MATH]3 and I3 were reduced. This contrasts to low density polyethylene for which , τ3 and I3 were increased. These results are viewed as an aspect of the spur model in which both electron affinity and pore size are affecting Ps formation.
© EDP Sciences 1993