Synthesis And Proprities Of X-type Carboxylate Gemini Surfactants

Because of its high surface activity, low critical micelle concentration（cmc）, and manyother features,Gemini has arisen people widely concern.In this paper, two kinds of Gemini surfactants are prepared by the nucleophilicsubstitution reactions using hexamine octylamine, diethanolamine, succinic anhydride and2,4,6-trichloro^-1,3,5-triazine as starting materials. Their structure were characterized bysingle-crystal X-ray diffraction,¹HNMR, ESI-MS and IR.The surface active of the X-type Carboxylate Gemini Surfactants were studied by surfacetension and steady-state fluorescence methods. Theresult indicates that the target compoundshavegood surface activity: the lowest surface tension （γcmc） of XC6A and XC8A are31.9mN/m and28.8mN/m, and their critical micelle concentrations are2.32×10^-4mol/L and1.41×10^-5mol/L at25℃respectively. As the temperature increases, the cmc value of this twoGeminis increased, while γcmcreduced gradually. The cmc value of XC6A and XC8Ameasured by steady-state fluorescence, were2.36×10^-4mol/L and1.34×10^-5mol/Lrespectively,which are very close to those by surface tension and electrical conductivitymethods.The micellar formation thermodynamic processes of the X-type carboxylate Geminisurfactants isinvestigated by electric conductivity method under different temperatures. Theresults show that, when the temperature rises from25℃to40℃, the β （counter-ion bindingdegree）value of XC6A and XC8A reduced from0.36and0.64to0.29and0.57, respectively.-TΔS_m⁰is smaller than sm-TΔS_m⁰, which indicates that the micelle formation of XCnA inaqueous solution was mainly entropy-driven process.The dynamic surface tension（DST） of X-type carboxylate Gemini surfactants wasmeasured by the maximum bubble pressure method（MBP）, and the dynamic adsorptionmechanism was studied, as well as the effects ofconcentrations and temperature on DST were discussed. The results show that when the surfactant XC6A concentration increases from0.2mmol/L to5.0mmol/L,R_1/2increases from16.43mN·m^-1·s^-1to328.42mN·m^-1·s^-1, whichindicates the increased concentrationcan improve the DST of the solutionsignificantly.Theadsorption process is controlled by diffusion at the first, the middle step of adsorption processis controlled by hybridpower and the adsorption process of the late is controlled by simulantdiffusion. When the temperature rises from25℃to40℃,R_1/2increases from10.90mN·m^-1·s^-1to57.40mN·m^-1·s^-1. The effect of the concentrations of the surfactent on DSTis more significant than that of temperature.The number of micelle aggregation（Nagg） of the X-type carboxylate Gemini surfactantswas measured by a fluorescence quenching method,and the average hydrodynamic radius ofthe micelles was measured by dynamic light scattering method. The results show, whenthenumber of carbon atom of hydrophobic chains of the surfactants increased from6to8, its Naggincreased from19to20correspondently; when the concentrations of the surfactant of XC6Aand XC8A increased from3cmc to20cmc, the hydrodynamic radius of micelles increasedfrom725.1nm and485.1nm to6155nm and3683.5nm, respectively.The solubilizationof the X-type carboxylate Gemini surfactants was measured by UVspectropic method, and the emulsifying power was measured by cylinder method. The resultindicates that the efficiency of solubilization of XC8A to the polycyclic aromatichydrocarbons （pyrene and anthracene） issuperior than XC6A. The emulsification time ofthesurfactant XC6A and XC8A are227s and255s, respectively.