The surface composition and properties of the copolymer miniemulsions containing fluorinated acrylate(FA) were investigated by X-ray photoelectron spectroscopy(XPS) and contact angle measurements.The surface energy of these copolymers was calculated by the harmonic equation from the static contact angles.The surfaces of the copolymers are very hydrophobic even with a low content of FA due to the surface enrichment of FA segments.The surface energy of copolymers decreases drastically with the increase of FA content and can reach 11.6 mN/m when the concentration of FA in copolymerization increases to 17.54%.The element composition and surface segregation of the fluorinated component as a function of depth of fluorocopolymer thick films were investigated by angle-dependent XPS.The content of fluorine on the surface of copolymers was higher than the calculated value according to the feeds.Our analyses demonstrate that the side groups containing fluorine tend to enrich on the copolymer-air interface.The surface segregation is enhanced when the samples are annealed,which results in further decrease of surface energy.
Aim To study unitary-core osmotic pump tablet for delivering water-insoluble drug for 24 hours. Methods Unitary-core osmotic pump tablet was prepared using nifedipine as the model drug. The effects of various core formulation variables on drug release were studied. Results Polyethylene oxide and potassium chloride have comparable positive effects on drug release, whereas, nifedipine has markedly negative effect on drug release. Conclusion Unitary-core osmotic pump tablet is very easy in preparation and it can deliver water-insoluble drug in substantially constant rate for 24 hours.
