Synthesis And Properties Of Gemini Surfactants

1,3-bis[2-(dodecanoylamino)propyldimethylammonio]-2-hydroxy-propane dichloride (Ⅰ), a cationic Gemini surfactant with amide group, was synthesized in an aqueous micelle medium from the reaction of 2-(dodecanoylamino)propyldimethylamine(Ⅱ)prepared by dimethylpropyldiamine and dodecyl acid, its amine hydrochloride(Ⅲ) and epichlorohydrin(Ⅳ). The yield of the productⅡwas 96%, and the yield of the productⅢwas 96%.The preferred conditions are reaction temperature 80℃, reaction time 6 h and n (Ⅱ)∶n (Ⅲ)∶n (Ⅳ) =1∶1∶1 in 5mL water. The mass fraction ofⅠin total solid is beyond 98%. And the solubilization ofⅡ,Ⅳand their mixtures into the micelles formed byⅠor/andⅢwas investigated. The solubilization power of theⅠmicelle was greater than that of theⅢmicelle; this was the reason for the quarternization carried out in relative shorter time without organic solvent in a micelle medium. The preferred conditions of 1,3-bis[2-(tetradecylamino)propyldimethylammonio]-2-hydroxy-propane dichloride, 1,3-bis [2-( hexadecylamino)propyldimethylammonio]-2-hydroxy-propane dichloride and 1,3-bis [2-(octodecylamino)propyldimethylammonio]-2-hydroxy-propane dichloride were obtained. The mass fractions in total solid are beyond 98%.The structures of these Gemini surfactants were characterized by IR, elemental analysis, mass spectrum and 1HNMR. Surface activity properties of cationic surfactants were measured. The results show that the mass fraction of cationic Gemini surfactant after vacuum evaporation is beyond 98% and Gemini surfactants have the high capacity of surface adsorption and micellization. With the increasing of alkyl chains of these surfactants from 12 to 18, its critical micelle concentration (cmc) declines, and cmc/c20 enhances, and Krafft temperature increases,andΓ∞>0。The results showed that the concentration in the interface phase is higher than that in the bulk phase.Γ∞deceased with the increase of temperature. With the increasing of alkyl chains of these surfactants from 12 to 18, the hydrophobic action increased and micelle is easier to form.