Imidazolium Gemini ionic liquids for regulating facilely the swelling and dispersion of montmorillonite in water

The imidazolium Gemini ionic liquids (IL), with alkyl groups ranging from butyl to tetradecyl as tail chains and polyoxyethylene group as linker chain, were synthesized and used as novel efficient modifiers for flexibly controlling the swelling and dispersion of Na-montmorillonite (Na Mt). The correlation between swelling behavior and structure of imidazolium Gemini IL was investigated. Too long or too short tail chains caused greater swelling, obtaining smaller particle size and reductive face-to-face stacking degree of layers. Based on the change of water contact angles, the increased stability of modified Mt in water indicated that the hydrophobicity of the tail chains played an important role in impeding the entry of water molecules into the interlayer. Zeta potential, Fourier transform infrared spectra and X-ray photoelectron spectroscopy validated the cation exchange between imidazolium Gemini IL and Na ⁺, and confirmed the adsorption site. The molecular arrangement and intercalation were determined through adsorption behavior, interlayer space of Mt and simulation of molecular size. The imidazolium Gemini IL covered the Mt layers in monolayer, finally taking lateral (short tail chains) or paraffin (long tail chains) arrangement. The investigation will provide useful guidance for modifying Mt to obtain desirable properties and broadening the practical application of Mt hybrids.