Abstract
The mechanism of diffusion of drugs through ethylene-vinyl acetate (EVA) copolymers has been studied. The observed permeability coefficients for the phenols, 4-hexylresorcinol and 3,4-dimethylphenol, increase in a non-linear fashion with increasing vinyl acetate content in the copolymer. Furthermore, their partition coefficients vary in a non-linear manner with increasing vinyl acetate content, while the partition coefficient of a non-phenolic compound, 1-chloro-4-nitrobenzene, increases in a linear manner. Since the diffusion coefficients for the two phenols are shown to be independent of vinyl acetate content, the permeability of phenols in EVA membranes depends almost entirely on the partition coefficient. The non-linear partitioning behavior of the phenolic compounds can be attributed to the formation of vinyl acetate-phenol complexes. The linear increase in partition coefficient for 1-chloro-4-nitrobenzene is attributed to a straightforward solubility enhancement.
Published Version
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