Insight into the Permeation Barrier of Glued Langmuir-Blodgett Bilayers

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• 作者：Donald H. McCullough ; III ; Ruslan Grygorash ; James T. Hsu ; Steven L. Regen
• 刊名：Journal of the American Chemical Society
• 出版年：2007
• 出版时间：July 11, 2007
• 年：2007
• 卷：129
• 期：27
• 页码：8663 - 8667
• 全文大小：86K
• 年卷期：v.129,no.27(July 11, 2007)
• ISSN：1520-5126

文摘

Permeation measurements have been made for He, CO₂, and N₂ across single Langmuir-Blodgett (LB) bilayers derived from 1,2,4,5-tetrakis[(N-(undecanoamidoethyl)-N,N-dimethyl ammonium)methyl]benzene tetrabromide (2) and 1,2,4,5-tetrakis[(N-(perfluoroundecanoamidoethyl)-N,N-dimethyl ammonium)methyl]benzene tetrabromide (3) in the absence and in the presence of entrapped poly(acrylicacid) (PAA). In the absence of PAA, single LB bilayers of 3 show a higher permeance for He and N₂ buta lower permeation rate of CO₂, as compared with analogous LB bilayers made from 2. The relatively lowpermeation rate of CO₂ for the former has been attributed to reduced associative interactions with thefluorocarbon-rich bilayer. The same behavior has also been observed for LB bilayers containing PAA, formedunder conditions that yield glued bilayers of 2 and 3 having similar diffusional pathways, as judged byHe/N₂ selectivities. These results, together with the fact that glued bilayers of 2 (having a thinner PAAlayer as compared with those made from 3) exhibit lower He and N₂ permeances, provide compellingevidence that the main barrier for gas transport is the combination of surfactant plus PAA and not simplya thin PAA layer that is encased within the surfactant bilayer.