Abstract
The diffusion coefficient of prostaglandin E1 (PGE1) in the pressure sensitive adhesive (PSA) matrices at 37°C were calculated from the release profiles. 2-ethylhexylacrylate and acrylic acid copolymers were used as model PSAs. The viscosity of the PSA, as measured by a shear creep method, increased with increasing acrylic acid contents, average molecular weight of copolymer and contents of crosslinking agent in the PSA. The diffusion coefficient of PGE1 was inversely proportional to the viscosity of the PSA with varying acrylic acid content, whereas it was independent of the viscosity with varying other two factors. To interpret this conflicting results, changes in activation energy on the diffusion of PGE1 were measured. The results suggested that diffusion resistance increased only when increasing the content of acrylic acid.
