Structures and Interfacial Properties of Alkylbenzenesulfonate Gemini Surfactants

Three dialkyldibenzenedisulfonate gemini surfactants with different structures 10-4-10,12-4-12 and 10-6-10(10,12 and 4,6 are referred to as the carbon numbers of the hydrophobic chain and those of the spacer respectively) were synthesized through five-step process,including Friedel-Crafts acylation,Grignard reaction,Pd-catalyzed hydrogenation,sulfonation and neutralization.Their structures were identified by 1HNMR and ESI-MS.The interfacial tension between anionic sulfonate gemini surfactant solution and heptane was measured by spinning drop method.It was found that CMC's of gemini surfactants were two orders of magnitude lower than those of the corresponding monomeric surfactants,and the CMC increased with the increase of carbon numbers of the hydrophobic chains or the spacer.A(min)(the minimum area per surfactant molecule) of 10-4-10,12-4-12 and 10-6-10 are 0.23,0.35 and 0.97 nm2 respectively,their Γ(max)(the maximum surface excess concentration) are 7.37×10(-10),4.65×10(-10) and 1.72×10(-10) mol/cm2 respectively,and their γ(CMC)(the interfacial tension at CMC) are 3.60,3.06 and 1.89 mN/m respectively.