Self-assembly in room temperature ionic liquids

3 Self-assembly in room temperature ionic liquids 

Room temperature ionic liquids (RTILs) are molten salts whose melting points are below room temperature. RTILs are formed when the constituent ions are sterically mismatched, thereby hindering crystal formation [17]. As polar solvents, RTILs have unique applications as tunable and environmentally benign solvents with very low volatility, high fire resistance, excellent chemical and thermal stability and wide liquid temperature range and electrochemical windows [17-19]. Solvent applications of RTILs include, for example, organic synthesis [17,20, 21], separations [22, 23], storage and transportation of hazardous chemicals [24], polymeric electrolytes [25, 26], dissolution of natural products [27] and synthesis of hollow metal oxide microspheres [28]. 

Because of the high polarity of RTILs, self-assembly of amphiphiles in RTILs are quite similar to that observed in aqueous systems. Alkyltrimethylammonium bromides and alkyl pyridinium bromides in the RTIL ethylammonium nitrate (EAN), for example, form micelles just like in water, albeit with critical micelle concentration (CMC) values that are five to ten times larger [4,29]. Liquid crystalline phases are also observed in surfactant-RTIL 

Self-assembly in RTILs is not limited to low molar mass surfactants. For example, He et al. [38 ] have reported about spherical micelles in mixtures of poly( (1,2 -butadiene) -block-ethylene oxide) (PB-PEO) diblock copolymers in the RTIL l-butyl-3-methylimidazolium 

Unlike water, C02 has no dipole moment. Therefore, hydrophilic molecules are practically insoluble even in supercritical C02. Van der Waals forces, arising principally from quadrupolar interactions are weaker even than in hydrocarbons. In principle, addition of surfactants would improve the solubilisation properties of compressed C02 and could also result in self-assembled microstructures. However, most commercially available surfactants are insoluble in supercritical C02 [48]. 

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