Keywords: Ionic liquids, biobased ionic liquids, biopolymers, added values biocompounds
Ionic liquids (ILs, organic salts that melt below 100 °C) have attracted considerable interest inside the broad scientific community in the last fifteen years; the combination of their unique physico-chemical properties, their tunability and the extremely high structural versatility (the evaluated number of possible ILs is more compatible with Astrophysics that with Chemistry!) have determined an incredible growth in the interest in these compounds for the more disparate technological applications. Interestingly, while ILs were growing in popularity, mythology flourished about both positive and negative attributes that each ‘IL’ is supposed to possess. Most of the paper on ILs, including recent reports, generally describe these liquid media as ‘environmentally-benign solvents” in the first sentences, with the properties of non-volatility, thermal stability and non-flammability claimed in this regard. This despite it has been shown/proved that commonly used ILs have very low but not null vapour pressures (they can be distilled under appropriate conditions), that a large group of ILs is combustible and some commercially available ionic compounds are decidedly non-green. On the other hand, several ILs are truly thermally stable and some can be classified as non-toxic, indeed several are approved for food grade use. Thus, an excessive confidence or an unnecessary diffidence can lead to inappropriate and even dangerous uses of ILs, as well as to a lack of use, although appropriate. These opposite behaviours arise essentially from the unjustified attribution of features which have been observed for selected classes of ILs, to all ionic liquids. Actually, due to the generic nature of the definition of ILs as low-melting salts, the properties of ILs vary extensively and probably the most attractive feature of ILs is just the fact that the extremely high variability of ions can give rise to salts with uncommon properties and behaviours.
Here, some common myths and established facts will be critically revised in light of our experience in the field, of course taking into account also the vast literature on the different topics.
Ionic liquids are undeniably interesting compounds with a wide range of potential applications and with a unique ability to be designed to meet a specific set of requirements. These features cannot be stifled by false myths and distorted truths.
Cinzia Chiappe received Laurea (cum laude) and PhD degrees from the University of Pisa, Italy, in 1985 and 1989, respectively. After a two years period at the Regional Agency for Environmental Protection, she moved to the Department of Bioorganic Chemistry (University of Pisa) as a researcher. Since 2002 she is Full Professor of Organic Chemistry at the University of Pisa.
Her primary research interests focus on the ionic liquids (ILs) chemistry and their application. Using the tools of physico-organic chemistry her research group is dedicated to obtain information on ILs and their physico-chemical and biological properties, often correlating experimental results with theoretical calculations. In this field, she has developed several projects that using these “designer solvents” as novel media, catalysts or additives have allowed developing new and more sustainable chemical processes affording a lot of new compounds and materials.