Chi-Long Lee

Effects of polymer structure on the gas permeability of silicone membranes

Abstract The effect of organic substituents and polymer backbone structure on the oxygen and nitrogen permeability of the following silicone polymers was investigated: Series A, (MeRSiO)x, where R is alkyl, aryl, or CH2CH2CF3; Series B, (Me2SiCnH2nSiMe2O)x, where n=2, 6 and 8; Series C, (Me2SiC6H4SiMe2O)x. It was found that as the size of the alkyl group in Series A was increased, the permeability decreased markedly, whereas the O2-N2 selectively remained more or less constant. Aryl substituents in Series A and p-silarylene linkages in Series C caused a significant decrease in permeability but an increase in the selectivity. Incorporation of organosilyl pendant groups onto organic polymers causes pronounced increases in permeability but decreases in selectivity. The cost for the oxygen enrichment of air using these silicone membranes was analyzed using computer modelling. A quantitative permeability-selectivity-cost relationship has been established.

Kinetics and Thermodynamics of Drug Permeation Through Silicone Elastomers iv. Effect of Polymer Backbone Structure

AbstractThe effect of silicone polymer backbone structure on the permeability of progesterone and testosterone through silicone membranes was investigated in the capsule-type drug delivery system at 25, 37 and 50°C, respectively. Three types of polymer were studied: (I) (Me2SiCH2)x, (II) (Me2Sl-CH4-SiMe2O)x, and (III) [Me2Si(CH2)n SiMe2O] x, where n=2, 6 and 8.Permeabilities of progesterone in these polymers were found to decrease in the following order: Polymer (III) < Polymer (I) < Polymer (II). The same order was also observed for the permeabilities of testosterone, but their values were one order of magnitude lower than those of progesterone. Incorporation of the phenylene group in the polymer backbone in Polymer (II) caused a significant decrease in the diffusion coefficient but an increase in the solubility coefficient. The net effect is a 50% decrease in the permeability with respect to (Me2 SiO)x. This effect was found to be less pronounced with alkylene group in Polymer (III).The activation energ...

Kinetics and Thermodynamics of Drug Permeation Through Silicone Elastomers III. Effect of Alkyl Substituent (R) in (MeRSiO) Polymer

AbstractThe effect of silicone polymer structure on the permeability of drug through silicone membranes was investigated in the capsule-type drug delivery system. The permeability, diffusivity and solubility of progesterone and testosterone through polymethylalkylsiloxane membranes, (MeCn H2n+1 SiO)x, where n = 1, 2, 3, 6 and 8, were determined at 25, 37 and 50°C respectively.As the size of the alkyl substituent was increased from methyl to octyl, the diffusivity decreased, whereas the solubility increased. As a result, the permeability of progesterone decreased initially but increased gradually thereafter, going from (Me2SiO)x to (MeOctSiO)x, in this series of polymer. The same results were obtained with testosterone; however, permeabilities of testosterone were found to be one order of magnitude lower than those of progesterone. This was attributed to the lower solubilities of testosterone in (MeRSiO)x polymers when compared to those for progesterone. The activation energies of permeation for progestero...