OXYGEN-TRANSPORT THROUGH METHACRYLATE-BASED HYDROGELS WITH POTENTIAL BIOLOGICAL CAPABILITY

The permeability to oxygen of hydrogels prepared from copolymers of 2- hydroxymethyl methacrylate and p-methacryloxyl-oxyacetanilide have bee n studied by using an oxygen electrode in combination with a permeomet er. The transmissibility Dk/L and the permeability Dk (where D, k and L are, respectively, the diffusion coefficient, the Henry constant and the thickness of the hydrogel) are measured by a combination of stead y state and transitory state measurements. Both transport coefficients increase with the water content, which in turn depends on the copolym er composition. The values of these quantities tend toward a limiting value for water-saturated hydrogels. The ratio of the characteristic v olume for diffusion of the oxygen molecule to the free volume of water per mole water is found to be in the vicinity of 0.10, and this value increases slightly as the fraction of the hydrophilic comonomer in th e hydrogel increases. A detailed comparison of the biogels studied wit h six commercial contact lenses has also been performed. (C) 1996 Else vier Science Limited.