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

Thimmegowda, M. C. and Sathyanarayana, P. M. and Shariff, Gani 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, 13 (12). pp. 1295-1311. ISSN 1568-5624

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Official URL: https://doi.org/10.1163/15685620260449705

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 positron 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
Subjects: D Physical Science > Physics
Divisions: Department of > Physics
Depositing User: manjula User
Date Deposited: 24 Sep 2019 10:16
Last Modified: 24 Sep 2019 10:16
URI: http://eprints.uni-mysore.ac.in/id/eprint/8470

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