Supramolecular Self‐Assembly of Nanoconfined Ionic Liquids for Fast Anisotropic Ion Transport

Abstract

Materials involving nanoconfinement of ionic liquids (ILs) have been pursued for functionalities and ionic devices. However, their complex synthesis, challenges to achieve long-range order, and laborious tunability limit their practical implementation. Herein, these challenges are addressed by complexing surfactants to ILs, yielding a facile, modular, and scalable approach. Based on structural screening, ionic complexation of di-n-nonylamine to the terminal sulfonic acid of 1-(4-sulfobutyl)-3-methylimidazolium hydrogen sulfate IL is selected as a proof of concept. Spontaneous homeotropic smectic order over micrometers is observed, with alternating ionic and alkyl layers. The 1 nm thick ionic layers involve 2D crystalline internal order up to 150 °C, strongly promoting anisotropic ion transport (σ || /σ ⊥ > 6500), and curiously, still allowing fluidity. High ionic conductivity of 35 mS cm −1 and mesoscopic diffusion coefficient of ≈10 −5 cm 2 s −1 at 150 °C along the ionic layers are observed. Fast anisotropic ion transport by simply complexing two components open doors to functional materials and applications.

Ionic liquid crystals: Synthesis and characterization via NMR, DSC, POM, X-ray diffraction and ionic conductivity of asymmetric viologen bistriflimide salts

“…Even though cubic phases tend to promote particularly high conductivities due to the 3D interconnectivity, lamellar LC phases promoted by rod-like molecules can also assist conductivity by reducing ionic aggregation in electrolytes [86][87][88]. Cherian et al [89] have very recently reported parallel conductivities of 10 - hydrogen sulfate. These values are like those shown here, and are superior to some state-of-theart polymerized ionic liquid electrolytes [90], and comparable to phosphonium or imidazoliumbased ionic liquids (10 -2 S cm -1 , at 30 o C) and to dicationic imidazolium salts forming SmA phases (10 -6 to 10 -4 S cm -1 , near room temperature) [91][92][93].…”

Remarkable Thermal Conductivity Enhancement in Carbon-Based Ionanofluids: Effect of Nanoparticle Morphology

“…ILs that form the continuous phase of INFs have several advantages: wide liquid range, high chemical and thermal stabilities, and very low vapor pressure. Especially important is that ILs have optimal thermophysical properties as a base fluid for heat transfer systems, studied in detail by França et al, Tenney et al, Chernikova et al, and our group. , Moreover, a great diversity of results from a number of possible anion–cation combinations for ILs makes it possible to design a structure with optimal properties, allowing many functionalities for very specific purposes . Thus, the use of ILs as a continuous phase of nanodispersions means that the INFs can be designed to meet any specific application or task requirement .…”

“… 8 , 9 Moreover, a great diversity of results from a number of possible anion–cation combinations for ILs 10 makes it possible to design a structure with optimal properties, allowing many functionalities for very specific purposes. 11 Thus, the use of ILs as a continuous phase of nanodispersions means that the INFs can be designed to meet any specific application or task requirement. 12 Cyano alkylimidazolium ILs such as [EMIM][SCN] seem to be particularly useful because of their low viscosity and acceptable ecotoxicity.…”

Rational ion transport management mediated through membrane structures

“…[ 148 ] Layered ionic liquids with nanoconfined nanochannels were constructed through complexation between surfactants and ionic liquids, showing temperature‐mediated ion transport along the parallel and normal directions. [ 149 ] Recently, 2D nanochannel‐structured membranes with special surface and nanochannel arrangement structures have attracted the attention of researchers. For instance, anti‐T [ 39 ] MXenes showed ion transport in the vertical direction because of the specific surface structure and vertically aligned [ 40 ] structure, exhibiting rapid ion transport owing to the efficient ion transport pathways resulting from the arrangement structure.…”