POSS–Tetraalkylammonium Salts: A New Class of Ionic Liquids

A series of new polyhedral oligomeric silsesquioxane ionicliquids (POSS-ILs) based on the trimethylpropylammonium dielectric constants, which, conversely, display slight differencesoriginating from the nature of the anions. The longalkyl-chain substituents on the POSS core infer on this seriesof ILs an overall hydrophobic character and solution propertiescomparable to those of classic cationic surfactants, resultingin an effective extractant capability of polyanionsfrom aqueous solutions. Their solution diffusion properties,as investigated by room-temperature dynamic light scattering,solution conductivity, density, and osmometric measurements,do not provide evidence for the occurrence of any hepta(isooctyl)octasilsesquioxane cation and a variety ofanions have been synthesized and characterized. Their thermalbehavior has been ascertained by thermogravimetricand differential thermal analyses and differential scanningcalorimetry; room temperature conductivity, dielectric constants,and dynamic contact angles have been investigatedas well. The obtained data show that the presence of thePOSS moiety is responsible not only for their thermal properties,but also for their low room-temperature conductivity and significant self-assembling processes.