Abstract:

Two imidazole-based surface active ionic liquids (C_nmimBr) were synthesized, and their aggregation behavior at the air/water interface was studied via an oscillating bubble method. The effects of the C_nmimBr concentration, inorganic salts (NaBr and CaBr₂), and temperature on the aggregation behavior were investigated. The results of the adsorption dynamics showed that the adsorption-controlled process dominated, but the relaxation process was not purely mono-exponential. The addition of inorganic salt or increase in temperature improved the surface activity of the C_nmimBr and lowered the dynamic surface tension. The dilational rheological results revealed that the dilational modulus, elastic modules, and viscous modules increased with increasing oscillating frequencies, and the modulus reached a maximum value with increasing C_nmimBr concentration. Increasing the temperature or adding inorganic salts (NaBr or CaBr₂) decreased the dilational modulus. The elastic modulus was dominant for the C_nmimBr layer, and the elastic modulus of C₁₄mimBr was larger than that of C₁₂mimBr.

Key words: Adsorption dynamics, Dilational modulus, Air/water interface, Imidazole-based surface active ionic liquid