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Li Li, Scott Curtin, Rick Gallagher, Meredith Wiseman, Iris Hilker, Michelle Seitz, Chunxia Sun; Effect of chain length, formulation concentration, hydrophile spacer and linear silicone structure of novel monomer on oxygen permeability of contact lenses. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):6098.
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© ARVO (1962-2015); The Authors (2016-present)
Hydrophilic silicone monomers (SiO Monomer), methacrylate-hydrophile-silicones with Si number 13, 9, 3, were designed to use as ingredients for contact lenses. We investigated the effect of silicone chain length and formulation composition on oxygen permeability (Dk) of cured hydrogel films. In addition, Dk of films were compared with films prepared using commercially available silicone monomers, methacrylate PDMS, TRIS and SIGMA. The influence of presence vs absence of hydrophile spacer and bulky silicone vs. linear PDMS on Dk were studied.
We incorporated novel SiO Monomer 13, 9, 3, methacrylate PDMS, TRIS and SIGMA in formulations with hydrophilic monomer, DMA. The formulations consist of 0.8% crosslinker, 0.2% photoinitiator and various amounts of silicone monomer and DMA (2:1, 3:2, 1:1, 2:3, and 1:2). A modified Mocon MH2/21 was used to measure the oxygen permeability by coulometric method at 34°C.
The Dk results are shown in Table 1.
Our results suggest that Dk increases with increasing amount of silicone which is consistent with general trend observed by the industry. Based on permeability model of Dk, the percolation threshold for connectivity of the silicone phase is estimated to be approximate 20% Si element. It was found that within class of linear PDMS, hydrophile spacer between double bond and silicone chain (methacrylate PDMS vs SiO monomer) and silicone chain length do not appear to have much influence on Dk. In general, Dk from bulky silicone materials are much lower than linear PDMS sources.<br /> <br /> The results give guidance for how to achieve sufficient Dk by controlling three principal material parameters: amount of silicone component present, connectivity of silicone-containing phase, and intrinsic permeability of silicone component.<br /> <br /> © 2014 DSM. All rights reserved.
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