Conversion of Micelles to Vesicles and Thin Films

The symmetrical bolaamphiphile 7 with two bipyridinium head groups, a long connecting diester chain and four bromide counterions dissolves in water. 

Other conversion methods depend on the disruption of micelles containing water-insoluble compounds. For example, lipids e.g. lecithins can be reasonably well cosolubilized in micelles of sodium cholate or SDS. Dialysis slowly removes monomeric detergent molecules which dissociate away from the micelle resulting in a more concentrated lipid. Time and temperature controlled dialysis of the micelles finally yields monolamellar vesicles of uniform radii.  

A somewhat different micelle-disruption method was used to prepare thin reactive films on electrode surfaces. For this purpose, micelles containing ferrocenyl surfactant 9 and a dissolved dye, e.g. phthalocyanine or quinone, were electrolyzed. The ferrocenyl micelles broke up into monomers whenever the iron atoms were oxidized electrochemically. The dissolved dyes then precipitated as transparent nanometre films onto the electrode surface.  

Dispersed dyes precipitate as mono- and multilayers on the electrode s surface.  

As a general result, we conclude that micelle and vesicle formation cannot be explained by cone or cylinder shapes of the monomeric amphiphiles. The key criterion for the curvature of molecular assemblies lies in the saturation solubility or cmc of the amphiphile. A cmc above 10 M usually means appreciable dissociation leading to small aggregation numbers of micelles. A cmc below 10 M means large planar bilayers or, upon their disruption, vesicles. 

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