A free volume microprobe study of water sorption in a contact lens polymer

Thimmegowda, M. C. and Sathyanarayana, P. M. and Shariff, G. and Ashalatha, M. B. and Ramani, R. and Ranganathaiah, C. (2002) A free volume microprobe study of water sorption in a contact lens polymer. JOURNAL OF BIOMATERIALS SCIENCE-POLYMER EDITION, 13 (12). pp. 1295-1311.

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Abstract

The kinetics of moisture uptake in a rigid gas-permeable contact lens material, Fluoroperm60, has been investigated. The free volume changes accompanied by the sorption of water were monitored using the position lifetime spectroscopy (PLS) technique. The positron results indicated swelling in the initial stages of sorption and the filling of vacant free volume sites with water in the later stages of sorption. The sorption curve suggests that the diffusion process in this polymer follows the dual-mode sorption model. Using this model, it was possible to separate Fickian-controlled diffusion and relaxation-controlled diffusion. Furthermore, the positron results combined with the sorption results indicated that Fujita's free volume theory does not seem to be valid for the diffusion process in the present sample under study. The variation of the permeability as a function of the free volume suggests that the amount of water in a contact lens is a measure of its permeability.

Item Type: Article
Uncontrolled Keywords: contact lens polymer; free volume; water sorption; positronium lifetime; diffusion; relaxation; permeability
Subjects: Physical Sciences > Physics
Divisions: PG Campuses > Manasagangotri, Mysore > Physics
Depositing User: Users 11 not found.
Date Deposited: 17 Apr 2013 04:18
Last Modified: 14 May 2013 11:42
URI: http://eprints.uni-mysore.ac.in/id/eprint/4374

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