Influence of various additives on the physicochemical properties of imidazolium based ionic liquids: a comprehensive review

Abstract

Ionic liquids (ILs) have attracted considerable attention because of their unique properties such as nonflammability, negligible volatility, high ion conductivity, thermal and chemical stability. Self-organization may also influence the potential application of ILs and have consequences in synthesis and purification of bulk ILs and in the solvation properties of the IL. Some authors have focused on these properties of ILs and compiled the results on this topic but nobody has summarized the pertinent data on physicochemical properties of these ILs in the presence of a variety of additives. Therefore, this review is necessary to provide a complete depiction on the interactions between imidazolium based ILs and various additives. In this review, we systematically survey the physicochemical properties of the imidazolium based ILs, highlighting the impact of various additives such as biomolecules, electrolytes, nonelectrolytes, organic solvents, surfactants and drugs on features such as morphology, phase behavior, density, thermostability, polarity (e.g. hydrophilicity, hydrogen bonding capability) micellar, interfacial and electrochemical properties on these ILs. Also, we emphasize various uses of these modified ILs to act as electrolytes or efficient solvents for electrochemistry, extractions, biphasic systems, gas separations, organic synthesis, biomolecular stabilization and activation. Several previous reports based on different characteristics and vast uses of imidazolium based ILs have been summarized in this review article. Here, we have focused on those objectives which will act as suitable candidates to take the field forward. The preceding information will permit us to estimate the effect of surface active property of imidazolium based ILs in separation processes, which makes them more advantageous for a number of technological processes and hence reduces the affect of these ILs on environment.