Water diffusion in a soft contact lens polymer and its tolerance to UV radiation studied by positron lifetime technique
The kinetics of water sorption, the topology or the free‐volume changes due to the presence of sorbed water in a soft contact lens polymer, poly(2‐hydroxyethyl methacrylate), were investigated by using the positron lifetime technique. It was found that the ortho‐positronium lifetime increases in the...
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Published in | Journal of applied polymer science Vol. 92; no. 2; pp. 1355 - 1366 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
Hoboken
Wiley Subscription Services, Inc., A Wiley Company
15.04.2004
Wiley |
Subjects | |
Online Access | Get full text |
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Summary: | The kinetics of water sorption, the topology or the free‐volume changes due to the presence of sorbed water in a soft contact lens polymer, poly(2‐hydroxyethyl methacrylate), were investigated by using the positron lifetime technique. It was found that the ortho‐positronium lifetime increases in the beginning of sorption because of microstructural swelling of the polymer matrix. After reaching a maximum, the lifetime decreases and becomes constant, maybe because of the filling of the free‐volume holes with water molecules. The diffusion process is found to be non‐Fickian. By using the dual‐mode sorption model, the Fickian‐controlled part and the relaxation‐controlled part of diffusion were separated. Further, the positron results seem to indicate the existence of water clusters in the sorbed lens material. The tolerance or stability of the soft lens material to UV radiation seems to be satisfactory as revealed by positron results. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1355–1366, 2004 |
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Bibliography: | University of Mysore ArticleID:APP20131 istex:46FF8C41079153F5BBE73B13BAB21D6B6E074318 ark:/67375/WNG-1NPKLTJT-S |
ISSN: | 0021-8995 1097-4628 |
DOI: | 10.1002/app.20131 |