ON THE MEASUREMENT OF STRUCTURAL RELAXATION IN POLYMERS USING POSITRON-ANNIHILATION LIFETIME SPECTROSCOPY

Authors
Citation
Xs. Li et Mc. Boyce, ON THE MEASUREMENT OF STRUCTURAL RELAXATION IN POLYMERS USING POSITRON-ANNIHILATION LIFETIME SPECTROSCOPY, Journal of polymer science. Part B, Polymer physics, 31(7), 1993, pp. 869-873
Citations number
19
Categorie Soggetti
Polymer Sciences
ISSN journal
08876266
Volume
31
Issue
7
Year of publication
1993
Pages
869 - 873
Database
ISI
SICI code
0887-6266(1993)31:7<869:OTMOSR>2.0.ZU;2-0
Abstract
Positron annihilation lifetime spectroscopy has been identified as an effective means of characterizing the free volume content of amorphous polymers. The lifetime and intensity of the ortho-positronium (o-Ps) pick-off annihilation has been found to correlate with the average siz e and density of free volume sites, respectively. Recently, PALS has b een used to evaluate and monitor the physical aging and structural rel axation of polymers in terms of both initial state and evolution in st ate with time. However, during extended PALS measurements in insulatin g materials, an electric field can build up due to positron-electron a nnihilation and can effectively reduce the probability of positronium formation. In this paper, an observed decrease in intensity associated with the o-Ps annihilation component in the glassy polymers polycarbo nate and polystyrene is found to be unrelated to structural relaxation of the materials over the time periods examined as reported earlier b y others, and, instead, to be more likely a result of electric charge build-up.