The roles of betaine-ester analogues of 1-N-alkyl-3-N′-methyl imidazolium salts: as amphotropic ionic liquid crystals and organogelators

Abstract

Betaine-ester analogues of 1-N-alkyl-3-N′-methyl imidazolium salts exhibiting both thermotropic and lyotropic liquid crystal behaviors are reported. Two typical compounds, structurally determined by single crystal X-ray diffraction exhibit an interdigitated bilayer packing. These compounds are gelators, which form gels in a variety of organic solvents such as chloroform, methanol, ethanol, tetrahydrofuran, while also exhibiting a lamellar mesophase. Results from IR and variable-temperature ¹H NMR spectroscopy studies show that a trace amount of water (0.3–0.5% by volume) in CHCl₃ plays a crucial role for developing the H-bonded network during gel formation. Ag-NPs (∼5–10 nm size) obtained from lyotropic LC solution and LC gel exhibit different morphologies ranging from spherical to truncated triangular plates.