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 degrees C, strongly promoting anisotropic ion transport (sigma(||)/sigma(perpendicular to) > 6500), and curiously, still allowing fluidity. High ionic conductivity of 35 mS cm(-1) and mesoscopic diffusion coefficient of approximate to 10(-5) cm(2) s(-1) at 150 degrees C along the ionic layers are observed. Fast anisotropic ion transport by simply complexing two components open doors to functional materials and applications.
- 2D ionic transport
- Ionic liquid
- supramolecular ionic liquid crystal