Loading-Controlled Stiffening in Nanoconfined Ionic Liquids

Abstract

An important strategy for using ionic liquids is to immobilize them by impregnation of supports or incorporation into porous solids to obtain materials called "ionogels". Of considerable importance for applications (electrolyte membranes, supported catalysts, etc.), such confinement results in dramatic changes in the physicochemical properties of the ionic liquid. Here, we report molecular simulations of a silica nanopore that is gradually filled with a typical imidazolium salt ionic liquid to obtain a realistic model of these ionogels. Despite the significant layering and stiffening of the ionic liquid in the vicinity of the silica surface, the pair correlation functions and magnitude of its dynamics clearly evidence liquid-like behavior. An increase in the self-diffusivity and ionic conductivity, associated with a decrease in the characteristic residence times of ions at the silica surface, is observed upon increasing the loading as the ionic liquid fills the nanopore center and tends to recover its bulk properties.

Catalytically Active Membranelike Devices: Ionic Liquid Hybrid Organosilicas Decorated with Palladium Nanoparticles

“…The reduction of the surface area in IL-hybrid organosilicas is usually produced by the filling of the small pores with IL. 37,38 In our case the relative reduction of the surface are as compared to Sg0 support is associated with the distinct size and distributions of pores produced by the IL templates containing different anions.…”

Solid–ionic liquid interfaces: pore filling revisited

“…[40][41][42] For example, a bilayered structure for the first [C 2 mim][NTf 2 ] layer on glass is reported, with the cation in direct substrate contact, and the anion arranged above the cation, which agrees well with molecular dynamics simulations. 40,43 At higher loadings, three-dimensional island growth on top of the first layer is observed. Similar results were obtained in a study combining Atomic Force Microscopy (AFM) and ARXPS investigating 1,2-dimethyl-3-propylimidazolium bis(trifluoromethanesulfonyl)imide on a silicon wafer.…”

Molecular Modeling of Glassy Surfaces

“…As a result, several procedures have been considered in order to build realistic silica surface and porous silica models [57]. For instance, starting from a bulk silica sample obtained through melt quenching by FPMD or classical MD simulation, a single surface [23] or cylindrical [58] and slit [59] pores made up of glassy silica can be obtained by carving out a specific part of the sample (see Fig. 13.4).…”

“…The input of such an approach is the representation of the templating surfactants using simplified potentials to describe the interactions involved in the system. Siperstein et al [63] Glassy Bulk SiO 2 obtained by first principles [23] or classical calculations [17] Cylindrical pore [58] Single surface [24,60] or slit pore [59] MCM-41 [35,39] Fig. 13.4 (color online) (top, left) Typical configuration of bulk silica as obtained from melt quenching technique using first principles [23] and classical calculations [17].…”

“…13.4 (color online) (top, left) Typical configuration of bulk silica as obtained from melt quenching technique using first principles [23] and classical calculations [17]. (top, right) Cylindrical pore of glassy silica obtained by classical simulation (silanol surface density equal to 5.3 OH/nm 2 ) [58]. (top, right) Single silica surface which can be used to build slit pore of silica.…”