Ionic Liquids in Bulk and at an Interface

Abstract

In the present chapter, we describe different types of investigation carried out by research groups based at CQE/IST/UTL and ITQB/UNL and their ramifications in terms of surface science. Most of the work is focused on the characterization of ionic liquids (ILs) (both by experimental and theoretical techniques) and on the different types of interaction that they can experience in the bulk or at an interface. Studies in the bulk include the analysis of the aggregation behavior (micelle formation) in aqueous solution of dialkylpyrrolidinium bromide ILs using isothermal titration calorimetry. Other studies involve the exploration of the structural organization of 1-alkyl-3-methylimidazolium chloride ILs in aqueous solution. Studies at the IL-- air interface include surface tension measurements along the 1-alkyl-3-methylimidazolium bistriflimide homologous series over very wide temperature ranges. The results were used to validate other methodologies aimed at the estimation of the (hypothetical) critical and boiling point temperatures of ILs. Finally, the adsorption behavior of ILs at solid surfaces (gold, glass) was studied using different experimental techniques (quartz crystal microbalance with dissipation (QCM-D) and atomic force microscopy (AFM)). The results yielded a fascinating picture of the complex surface behavior of ILs at the solid--liquid interface.