Aggregates in Ionic Liquids and Applications Thereof

Due to the increasing consciousness of environmental problems, chemical processes were developed with their environmental burden in mind. This results in the past decade, to the definition of Green chemistry encouraging the design of products and processes that reduce or eliminate the use and generation of hazardous substances. Moreover regulation (EC) No 1907/2006 of the European Parliament and of the Council of 18 December 2006 concerning the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH), gives greater responsibility to industry to manage the risks from chemicals and to provide safety information on the substances. REACH Regulation also calls for the progressive substitution of the most dangerous chemicals when suitable alternatives have been identified. Hence, from both societal and legislative point of views, there is a great need to find viable replacements for volatile organic compounds (VOC) used in usual chemical process. Of special interest is the case of solvents. They are used in most areas including synthetic chemistry, analytical chemistry, pharmaceutical production and processing, product purification, extraction and separation technologies, and also in the modification of materials. Due to the hazards of many conventional solvents (e.g. toxicity and flammability), knowledge of alternative, greener solvents is compulsory. The most useful alternatives to traditional solvents are supercritical CO2 (where the gas is compressed until it is nearly as dense as a liquid), ionic liquids and water. Room temperature ionic liquids (RTILs) are of special interest with unique applications as tunable and environmentally benign solvents with negligible vapor pressures, high chemical and thermal stability, high fire resistance and wide liquid temperature range and electrochemical windows. Moreover, owing to their molecular structure associating a cation and an anion, their physicochemical properties can be easily modulated by changing one of the ions. Hence, ionic liquids are now widely used in organic synthesis and chemical separations due to their high solvation ability and their tunable nature. (Dupont et al., 2002; Ranke et al., 2007) Lastly, corresponding to structured polar medium, RTILs can be also exploited to investigate molecular aggregation. Some authors have described in the past few years the ability of ILs to form various aggregates such as micelles,(Patrascu et al., 2006; Gayet et al., 2010b) vesicles,(Kimizuka and Nakashima, 2001; Nakashima and Kimizuka, 2002; Hao et al., 2005; Gayet et al., 2010a) non aqueous microemulsions (Gao et al., 2004; Eastoe et al., 2005; Gayet et al., 2009) or lyotropic phases (Evans et al., 1983; Wang et al., 2004; Araos and Warr, 2005). This gives access to new applications in green chemistry and