Syntheses, Aggregate Morphologies, and Applications of Membrane-Forming Amphiphiles

Abstract

Bilayer membranes are formed from a large variety of synthetic amphiphiles. The synthetic procedures are mostly common to those for the conventional surfactants. Double-chain amphiphiles produce stable bilayers if the tail length is C10 or longer. The hydrophilic head may be cationic, anionic, nonionic, or zwitterionic. The morphologies of these bilayer aggregates are studied most conveniently by electron microscopy. Fluid bilayers display amazing varieties of morphologies which are often interconvertible. Stable bilayer membranes are also formed from single-chain amphiphiles which possess rigid aromatic segments. The tail length again critically determines the aggregation behavior. Multiple hydrogen bonding is also effective for improving molecular orientation. Some triple-chain amphiphiles exhibit aggregation behavior similar to that of single-chain and double-chain amphiphiles, and produce bilayers. The alkyl tail of the above mentioned amphiphiles can be replaced by a fluoro-carbon chain without affecting the bilayer formation much. Finally, applications of these synthetic molecular membranes are discussed briefly, but their potential applications are extensive.