Clusters in a mixture of an “amphiphilic” ionic liquid and a nonionic liquid: Theoretical study

Mapping the Extra Solvent Power of Ionic Liquids for Monomers, Polymers, and Dry/Wet Globular Single-Chain Polymer Nanoparticles

Ionic liquids (ILs) have shown advantages in organic synthesis and catalysis, energy storage and conversion, and a variety of pharmaceutical applications. Understanding the miscibility behavior of IL/monomer, IL/polymer, and IL/polymer nanoparticle mixtures is critical for the use of ILs as green solvents in polymerization processes as well as to rationalize recent observations concerning the superior solubility of some proteins in ILs when compared to standard solvents. In this work, the most relevant results obtained in terms of extended three-component Flory-Huggins theory concerning the extra solvent power (ESP) of ILs when compared to traditional nonionic solvents for monomeric solutes (Case I), linear polymers (Case II), dry (i.e., without IL inside) globular single-chain polymer nanoparticles (SCNPs) (Case III), and wet (i.e., with IL inside) globular SCNPs (Case IV) are presented. Moreover, useful ESP maps are drawn for the first time for IL mixtures corresponding to Cases I, II, III, and IV at a constant temperature and pressure. Finally, a potential pathway to improve the miscibility of nonionic polymers in ILs is proposed.

Theory of Phase Separation and Polarization for Pure Ionic Liquids

Room temperature ionic liquids are attractive to numerous applications and particularly, to renewable energy devices. As solvent free electrolytes, they demonstrate a paramount connection between the material morphology and Coulombic interactions: the electrode/RTIL interface is believed to be a product of both polarization and spatiotemporal bulk properties. Yet, theoretical studies have dealt almost exclusively with independent models of morphology and electrokinetics. Introduction of a distinct Cahn-Hilliard-Poisson type mean-field framework for pure molten salts (i.e., in the absence of any neutral component), allows a systematic coupling between morphological evolution and the electrokinetic phenomena, such as transient currents. Specifically, linear analysis shows that spatially periodic patterns form via a finite wavenumber instability and numerical simulations demonstrate that while labyrinthine type patterns develop in the bulk, lamellar structures are favored near charged surfaces. The results demonstrate a qualitative phenomenology that is observed empirically and thus, provide a physically consistent methodology to incorporate phase separation properties into an electrochemical framework.