Synthesis and surface activity properties of sulfonate Gemini surfactants

Four S-triazine sulfonate Gemini surfactants,Cn-3-Cn(n=6,8,12,14),were synthesized from 1,3-propanediamine and SCT.The SCT had been prepared in our lab.Their critical micelle concentrations(CMC) in the aqueous solutions at 25 ℃ were determined by surface tension method.With the increasing length of the carbon chain,the values of their CMC initially decreased and then reached a minimum 7.23×10-5 mol/L when the carbon number was 14,but increased with the carbon number of 16.The values of CMC of Gemini surfactants C12-3-C12 are about one or two orders of magnitude lower than that of the monomeric surfactant sodium dodecyl sulfate.Results showed that Gemini surfactants have much higher surface activity than traditional ionic surfactants.In addition,with the increasing length of the carbon chain,the values of their γcmc decreased at first and then increased,the minimum value is 35.48 mN/m.