Fluorous protic ionic liquids (FPILs) which consist of a hydrocarbon cation and fluorocarbon anion can possess a complex liquid nanostructure, consisting of segregated polar, hydrocarbon and fluorocarbon domains. FPILs are an interesting series of compounds of relevence to the fields of ionic liquids (Ils), fluorinated amphiphiles and mixed hydrocarbon/fluorocarbon amphiphile systems. Here we show the self-assembly of FPIL ethylammonium perfluorooctanoate (EOAF)-water solutions, which transitions from a low water content L<inf>3</inf> sponge structure in EOAF, to a L<inf>α</inf> lamellar mesophase and then to dispersed lamellar vesicles. The robust lamellar mesophase was present between 10 and 85 wt.% EAOF, and retained up to 91 °C. This phase underwent significant swelling on addition of water. In contrast, the addition of water to the hydrocarbon analogue, ethylammonium octanoate (EAO) swelled the sponge-like liquid nanostructure, with no other lyotropic liquid crystal mesophases observed.
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