Temperature dependant self-assembly of surfactant Brij 76 in room temperature ionic liquid

Room temperature ionic liquids (RTILs) are non-flammable, non-volatile and thermally stable solvents and as much as very promising replacements for the traditional volatile organic solvent. Surfactants in RTILs can significantly increase the solubility of many solutes and modify the properties of RTILs as solvents. We reported here self-assembly processes of polyoxyethylene 10 stearyl ether (Brij 76) in RTIL 1-butyl-3-methyl-imidazolium tetrafluoroborate (BmimBF₄). Under 30°C, Brij 76 self-assemblied as nanofibers and a gel formed; as temperature increased until 85°C, the mixture were a clear solution; at about 90°C, Brij 76 self-assemblied as vesicles; at an even higher temperature of 110°C, a clouding phenomena observed. Based on the FT-IR, DSC, NMR and polarized optical microscopy (POM) results, a possible mechanism of self-assembly of Brij 76 in BmimBF₄ at varied temperature via the electrostatic interaction was proposed.