Self-assembly of volatile amphiphiles

Abstract

Computer simulations are used to study the aggregation phenomena of volatile amphiphiles in a system displaying liquid/vapor coexistence. These molecular dynamics simulations are based on a simple, yet versatile, model used previously to study oil/water/amphiphile systems: amphiphiles are nothing more than water and oil particles connected together by stiff springs. We observe a highly regulated self-assembly process wherein amphiphiles form bilayers within the liquid phase. The density of amphiphiles in a bilayer varies from a well-defined lower to upper limit as the overall concentration of amphiphiles in the system is changed; we examine how these limits vary for amphiphiles having different hydrophobic chain lengths. The vapor phase plays an important role in this self-assembly process, serving as a reservoir for amphiphiles not included in the bilayers. Finally, we show that bilayer formation can be completely suppressed if the geometry of the amphiphiles is altered, as is predicted by simple packing arguments.