CHEMISTRY LETTERS, pp. 1911-1914, 1988. (C) 1988 The Chemical Society of Japan Polymorphism in Bilayer Membranes of Novel Double-Chain Ammonium Amphiphiles1) Nobuo KIMIZUKA, Takahiro TAKASAKI, and Toyoki KUNITAKE* Department of Organic Synthesis, Faculty of Engineering, Kyushu University, Fukuoka 812 New double-chain ammonium amphiphiles which possess the ether linkage in the alkyl tails form bilayer membranes with regular side-chain packing in the crystalline state and display remarkable myelin figures in the liquid crystalline state. Dynamic morphological changes of biomembranes are closely related to fundamental functions of the biological cell such as fusion and fission. As models for these processes, dynamic structural changes of lecithin liposomes2,3) and the formation of myelin figures from lecithin have been studied extensively. 4-7) The lipids used in these studies are limited to a rather narrow class of lecithin and related compounds. In order to elucidate the nature of molecular organization in relation to these dynamic membrane behaviors, it is essential to examine the correlation between the molecular property of bilayer membranes and their dynamic behavior. We and others have shown that a large variety of synthetic amphiphiles produce stable bilayer membranes. Some of the simple double-chain ammonium amphiphiles display versatile morphology changes in motion, 8-9) and helical superstructures are formed from crystalline bilayer membranes of chiral amphiphiles.10-15) These versatilities in chemical structure and aggregate morphology render synthetic bilayers superior to lecithin in studying the structure-morphology relationship. In this communication, we describe the thermal and morphological behavior of novel double-chain ammonium amphiphiles that possess the ether linkage in the hydrophobic tails. These results are compared with those of the corresponding amphiphiles which either lack in the ether linkage as in 2 or possess the oleyl chain as in 3. These amphiphiles are different only in the structure of the hydrophobic tail. The bilayer characteristics of amphiphiles related to 2 were extensively investigated by us 16) and the oleyl unit in 3 is known to enhance the membrane fluidity. ~