Synthesis And Aggregation Behavior Of Sulfonate Trimeric Surfactants

Dimeric（Gemini）surfactants are synthesized by chemical bonding of two single-chain surfactant molecules at or near the head group by a linking group.Because of its stronger hydrophobic effect has higher surface activity than traditional single-chain surfactants and has a wide range of applications in materials,petroleum,and daily chemicals.At present,scientists are more in-depth exploration of dimeric surfactants,but there are few studies on the synthesis and performance of surfactants with higher polymerization degrees.In this paper,we successfully synthesized a sulfonate type three with a dendritic structure using tribromoneopentanol,long alkyl chain amine and 1,3-propane sultone as reactants.The molecular structure of sulfonate trimeric surfactants 3CnTriS（n=12,14,16）was confirmed with modern instruments such as nuclear magnetic resonance and elemental analysis.The results showed that the structure of the synthesis product was consistent with the structure of the target product.The surface properties and aggregation behavior were studied by Wilhelmy method,conductivity method,steady-state fluorescent probe method,dynamic light scattering method,critical stacking parameter method and transmission electron microscopy method.The CMC values of 3CnTriS（n=12,14,16）are 0.0997mmol·L^-1、0.0166 mmol·L^-1、0.00495 mmol·L^-1at 25°C,respectively,which decreases by 1-2 order of magnitude than those of analogousmonomeric surfactants（for instance,SLS）.These results are in keeping with that of the steady-state fluorescent probe method and conductivity method.BothΔG_mic^o andΔH_mic^o of 3C_nTri S are negative,indicating that the micellization process of3C_nTri S is spontaneous and exothermic.The results of dynamic light scattering and TEM show that 3C₁₂Tri S can form micelles with a diameter of about 2-6 nm in a pyrene-water mixed solution,while 3C₁₄Tri S and 3C₁₆Tri S can form vesicle with a diameter of about60-120 nm.The foam performance and emulsification performance of 3C_nTri S were studied by the oscillation method and the water separation time method.The results showed that their foam performance and emulsification performance were good,which were superior to the traditional single-chain surfactant SLS.