| Research Abstract |
This study is concerned with the preparation and adsorbability of cationic LB films of monocationic alkylammonium salts, dicationic alkylammonium salt and alkylamine.
At first, the film-forming properties of the cationic monolayers on the aqueous subphase were examined for a series of monocationic alkylammonium salts [Stearyltrimethylammonium chloride (SAC), docosyltrimethylammonium chloride (DAC), Distearyldimethylammonium (DSAC), Tristearylmethylammonium chloride (TSAC)], dicationic alkylammonium salt (XSAC) and primary octadecylamine (ODA). Owing to the strong hydrophilic property of the ammonium group, the monolayers of SAC and DAC having a long-chain tended to dissolve into the subphase, while DSAC, TSAC and XSAC having two or three stearyl chains formed the stable monolayers. On the other hand, ODA formed the stable monolayer on the subphase above pH 10.1. Theπ-A isotherm showed that the monolayers of TSAC, XSAC and ODA interacted strongly with MO and NO in the aqueous subphase.
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e LB films of TSAC, XSAC and ODA were fabricated with preserving the cationic property, and subsequently the adsorption characteristics of these LB films, being different in their valency as well as ionic property, were investigated. It was found that the cationic LB films showed high adsorbability for the negatively-charged dye ions such as NO and MO.The adsorption behavior was influenced by the packing of the hydrocarbon chain in the LB film and the pH value of aqueous dye solutions. Nevertheless, the adsorption of dyes occurred almost stoichiometrically by the ionic interaction. These facts imply that the cationic LB film would adsorb the other negatively-charged adsorbates, e. g., functionalized molecules, dispersed particle, etc. Moreover, distinction in the adsorbing state was obviously obscrved for MO and NO in the cationic LB films, i. e., MO took the edge-on configuration with respect to the film surface, while NO exhibited the lie-flat configuration typically in the XSAC LB film. This is probably due to the differerece in the molecular structure between MO and NO, and therefore, capability of incorpolation of dye molecules in the film with desired orientation was suggested by designing the molecular structure of adsorbate.
Information on the molecular arrangement obtained in tits study is expected to be helpful for understanding the adsorption behavior of various adsorbates on the cationic LB Glms. This study is also considered to contribute to the appearance of new functionality of the functional adsorbates in the LB matrix. as be exemplified by photoinduced isomerization, polymerization and so on. Less
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