Positron annihilation studies of chromophore-doped polymers

Citation
Cm. Huang et al., Positron annihilation studies of chromophore-doped polymers, RADIAT PH C, 58(5-6), 2000, pp. 571-574
Citations number
7
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Physics
Journal title
RADIATION PHYSICS AND CHEMISTRY
ISSN journal
0969-806X → ACNP
Volume
58
Issue
5-6
Year of publication
2000
Pages
571 - 574
Database
ISI
SICI code
0969-806X(200006)58:5-6<571:PASOCP>2.0.ZU;2-H
Abstract
Doppler-broadening energy spectra and positron annihilation lifetime have b een measured as a function of positron implantation energy in pure and chro mophore Disperse Red I (DR1)-doped poly(methyl methacrylate) (PMMA) polymer s. In pure PMMA, the S parameter increases at very short range (< 0.02 mu m ) from the surface to the bulk, while the S parameter of doped PMMA varies with a decrease from a depth of > 0.02 mu m to about 0.5 mu m after an incr ease, a short distance from the surface. The o-Ps lifetime of the polymers is found to increase from the bulk to the surface, which indicates that the hole size expands near the surface. The o-Ps lifetime distribution becomes broader near the surface. The change of the o-Ps intensity shows the same trend as the change of the S parameter. These results are interpreted as a gradient of DR1 concentration in PMMA, as a function of the depth from the surface to the bulk in the chromophore-doped polymers. (C) 2000 Elsevier Sc ience Ltd. All rights reserved.