The dilational rheology and splashing behavior of ionic liquid-type imidazolium Gemini surfactant solutions: Impact of alkyl chain length

A new series of ionic liquid-type imidazolium Gemini surfactants, 1,10-(Propane-1,3-diyl-2-ol)bis(3-alkyl-1H-imidazol-3-ium) chloride, were synthesized and investigated for their dilational rheology at the air/water interface using the oscillating drop method. The surface properties and splashing behavior of these ionic liquid-type imidazolium Gemini surfactants were studied at different hydrophobic chain lengths, surfactant concentrations and dilational frequencies. With increasing concentration, increasing intermolecular interaction had a positive effect on the dilational modulus, and the increasing surfactant molecular diffusion exchange had a negative effect on the dilational modulus; thus, the surface dilational modulus demonstrated a maximum value. Furthermore, the surface dilational modulus for 1,10-(Propane-1,3-diyl-2-ol) bis (3-tetradecyl-1H-imidazol-3-ium) chloride is higher than that for the other two short-chain ionic liquid-type imidazolium Gemini surfactants, which is due to an increase in the hydrophobic interaction. The results reveal that the bouncing heights of ionic liquid type imidazolium Gemini surfactants on a paraffin liquid surface decrease with increasing alkyl chain length. The splashing behavior of ionic liquid-type imidazolium Gemini surfactants observed on liquid surfaces and the spreading behavior observed on a paraffin surface are closely related to the dilational loss modulus. These findings not only reveal the relationship between dilational rheology and splashing behavior but also provide in-sights for the potential application of ionic liquid-type imidazolium Gemini surfactants in more fields. (C) 2019 Elsevier B.V. All rights reserved.