title: Temperature-induced microstructural changes in ionic liquid-based microemulsions.
abstract: In the present contribution, results concerning the effect of temperature on the nonionic surfactant Triton X-100 based 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4)-in-cyclohexane and bmimBF4-in-toluene ionic liquid (IL) reverse microemulsions are reported. Dynamic light scattering (DLS) along with freeze-fracture transmission electron microscopy (FF-TEM) measurements revealed that the sizes of single microemulsion droplets increased with increasing temperature. However, a decreased temperature led to the appearance of droplet clusters, which have also been observed previously when the single microemulsion droplets were swollen by added bmimBF4 to a certain extent (Gao, Y. A.; Vogit, A.; Hilfert, L.; Sundmacher, K. ChemPhysChem, 2008, 9, 1603-1609). Compared to traditional aqueous microemulsions, IL microemulsions revealed relatively high temperature-independence. The droplet-shaped microstructure was always kept in a large range of temperature. The temperature-independence is ascribed to the temperature-insensitive electrostatic attraction between the solubilized bmimBF4 and Triton X-100, which was considered to be the driving force for solubilizing bmimBF4 into the cores of Triton X-100 aggregates. Two-dimensional rotating frame nuclear Overhauser effect (NOE) experiments (ROESY) further confirmed the microstructural change with temperature.
authors.affiliation: Key Laboratory of Colloid and Interface Chemistry, Shandong University, Ministry of Education, Jinan 250100, China.
authors.forename: Yanan
authors.initials: Y
authors.lastname: Gao
authors.forename: Na
authors.initials: N
authors.lastname: Li
authors.forename: Liane
authors.initials: L
authors.lastname: Hilfert
authors.forename: Shaohua
authors.initials: S
authors.lastname: Zhang
authors.forename: Liqiang
authors.initials: L
authors.lastname: Zheng
authors.forename: Li
authors.initials: L
authors.lastname: Yu