Polymers in Medicine

Polim. Med.
Scopus CiteScore: 3.5 (CiteScore Tracker 3.6)
Index Copernicus (ICV 2023) – 121.14
MEiN – 70
ISSN 0370-0747 (print)
ISSN 2451-2699 (online) 
Periodicity – biannual

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Polymers in Medicine

2016, vol. 46, nr 1, January-June, p. 17–23

doi: 10.17219/pim/62279

Publication type: original article

Language: English

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Creative Commons BY-NC-ND 3.0 Open Access

Investigation of the Degree of Disorder of the Structure of Polymer Soft Contact Lenses Using Positron Annihilation Lifetime Spectroscopy PALS

Jacek Filipecki1,A,E,F, Katarzyna Kotynia2,A,B,C,D, Katarzyna Filipecka1,A,B,C,D

1 Institute of Physics, Faculty of Mathematics and Natural Sciences, Jan Dlugosz University, Częstochowa, Poland

2 Institute of Physics, Faculty of Production Engineering and Materials Technology, Częstochowa University of Technology, Częstochowa, Poland

Abstract

Background. Hydrogel and silicone-hydrogel polymeric materials are widely used in ophthalmology for the manufacture of contact lenses. An important aspect is the investigation of the structure of these materials.
Objectives. This study has been conducted in order to compare the degree of disorder and presence of free volumes in the internal structure of the polymeric soft contact lenses Omafilcon A (hydrogel) and Comfilcon A (silicone-hydrogel). Differences in the occurrence of trapping centers for positrons and free volumes between the types of investigated contact lenses have been demonstrated.
Material and Methods. Two types of polymeric contact lenses were used as materials: Omafilcon A (hydrogel) and Comfilcon A (silicone-hydrogel). The study was performed using positron annihilation lifetime spectroscopy (PALS).
Results. When the results of the measurements has been obtained, a graphical curve has created to describe the relationship of the number of annihilation acts in time. Significant changes were observed between the contact lenses investigated in positron trapping in macropores (based on a two-state model) and the presence of free volumes (based on the Tao-Eldrup model).
Conclusion. The use of the positron annihilation two-state model made it possible to demonstrate that a higher positron trapping rate in macropores occurs in the silicone-hydrogel contact lens. Additionally, calculations using the Tao-Eldrup model show the existence of free volumes in both types of materials. The size and fraction of free volumes is much larger in the silicone-hydrogel contact lens.

Key words

free volumes, polymers, defects, contact lenses, positron annihilations

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