The Research On Synthesis And Surface Properties Of The Ionic Liquid Surfactant

Ionic liquids （ILs） have gained great attention for their promisingrole as alternative media in catalysis, separation, and electrochemicalprocesses due to their unique chemical and physical properties. Thus,knowledge of the aggregation behavior of ILs is a vital part forunderstanding how these compounds participate as components in thepractical applications. ILs composed of1-alkyl-3-methylimidazoliumhave been extensively studied in the field of colloid and interfacescience in recent years. Thereamong, many ILs are amphiphilicsubstances with pronounced hydrophilic and lipophilic molecularfragments that determines their surface activity and the ability toself-organize in the individual state and in solutions. ILs that havesurface activity can be described as ionic liquid surfactants.In this work, the surface properties of ionic liquid surfactants andthe mixed systems of [C₁₄mim]Br with common cationic surfactants inthe absence and presence of sodium bromide have been investigatedby surface tension and conductivity measurements. The main researchcontents and results were as follows:Firstly, we synthesized the ionic liquids [C₈mim]Br,[C₁₂mim]Brand [C₁₄mim]Br, respectively. And studied the surface properties ofionic liquids in the aqueous solution. The experimental datas indicatedthat the surface activity of ionic liquids enhanced with the elongationof chain length.Secondly, the surface properties and mixed micellization behaviorof binary combinations of ionic liquid surfactant, namely,[C₁₄mim]Br with common cationic surfactants viz. DTAB, TTAB, CTAB, and CPBhave been investigated in the aqueous solution. The composition ofmixed micelles and the interaction parameter were evaluated from thecritical micelle concentrations of single and mixed systems usingRubingh’s theory. The mixed systems of surfactants have some uniquesurface properties that the system of single surfactants don’t have dueto the synergism. The CMC values of mixed systems lie between theindividuals and close to the component having lower CMC. In addition,the values of （β|-）are all negative indicating synergism in mixedcationic/cationic systems. TheΓ_maxvalues are always higher in mixedsystems as compared in single system.Thirdly, we studied the surface properties of ionic liquidsurfactant, namely,[C₁₄mim]Br and the mixed systems of [C₁₄mim]Brwith common cationic surfactants viz. TTAB, TPB in the sodiumbromide solution. The CMC and interfacial parameters, such asΓ_max,A_min and Ï€_CMCwere determined from the surface tension data.Thermodynamic parameters, ΔG°_mand ΔG°_adwere also evaluated.These results demonstrated that the CMC values of all the systemsdecreased drastically in presence of salt. Moreover, added electrolyteenhances the spontaneity of micellization and adsorption process. Thevalues ofΓ_maxincreased due to their salting out effect.