New Alkylbenzene Sulfonate Gemini Surfactant Synthesis And Performance

Seven pure dialkyldibenzene disulfonate Gemini surfactants with different structures were synthesized through six-step process, including Friedel-Crafts acyl reaction, Grignard synthesis, Pd-catalyzed hydrogenation, sulfonation reaction and neutralization. Their structures and purity were identified by 1H NMR, IR and MS.The physico-chemical properties such as their surface tensions, krafft temperatures and melting temperatures have been measured. They showed unusual properties. Id, Ie at 25℃and IIb at 50℃showed no cmc and lowered surface tension of water hardly despite their seemingly favorable amphiphilic components. However, the color change of pinacynol chloride solution indicated the formation of micelles of surfactants Id, Ie at 25℃and IIb at 50℃. And the three surfactants showed a sharp cmc and good surface activity with the increment of temperature. Furthermore, for this class of anionic Gemini surfactants, the spacer carbon number had more important effects than the alkyl chain carbon number on their krafft temperatures and melting temperatures.The anionic Gemini surfactant Ie solution exhibited high viscosity at relatively low concentration, even in the absence of any additives, which was only found for some cationic Gemini surfactants previously. The high viscosity was explained by the saturated network micelles. In addition, temperature has a great effect on the solution viscosity. And the variation of viscosity with temperature should be due to the transitions of micelle shapes.The micropolarity in the studied Gemini surfactant micelles sensed by pyrene is relatively high. Because the volume of the hydrophobic pseudophase in small micelles is very small and pyrene partition between this phase and the intermicellar solution.The aggregation number of surfactant Ie is smaller than those of Ib, Ic and Id. It is explained by the formation of premicellar aggregates inhibiting the formation of micelles due to the increasing hydrophobic portion of the Gemini surfactants.Concentration and temperature had great effects on the foam ability and foam stability of the Gemini surfactants.The mixtures of Gemini surfactant Ia and the conventional nonionic surfactant C10E6 showed good synergetic behavior. The micelle aggregation number values of the mixed surfactant system are larger than Ia but lower than C10E6 at all mole ratios. The micropolarity of micelles becomes small gradually with the increment of mole ratio of anionic Gemini surfactant Ia.Interfacial tensions of Gemini surfactants at different oils/water were measured. The interfacial tension at heptane/Gemini surfactant solution decreased with the increment of temperature. In addition, elevating temperature was helpful to reach equilibrium for the dynamic interfacial tension. And the longer the hydrophobic group is, the longer the time needed for dynamic IFT to reach its stable value.