The Synthesis Of Quaternary Ammonium Salt-Type Tetraameric Surfactants And Their Properties

Oligomeric surfactants,also known as a new generation of surfactants,can help people realize the idea of regulating ordered aggregates at the molecular level and achieve a conceptual breakthrough in molecular structure.At present,scholars at home and abroad have conducted in-depth explorations on synthesis methods and physicochemical properties of dimeric or Gemini surfactants.However,due to the difficulties in synthesis and product purification etc,there are few reports on trimerization,tetramerization,and oligomeric polymerization degrees surfactants.In this paper,a series of quaternary ammonium salt-type tetrameric surfactants with ester groups and flexible alkyl chains（4C_nester Q）are synthesized,and the pentaerythritol is the linking group.Modern instruments such as FT-IR,¹H NMR and elemental analysis characterize the structure of the synthetic products,and the results show that their molecular structures are consistent with theoretical structures.The surface activities of the products were measured by the Wilhelmy method.The CMC values of 4C_nester Q（12,14,16）are 0.3801,0.0436,0.00776 mmol·L^-1 at25°C,respectively,which decreases by 1-2 order of magnitude than those of analogous monomeric surfactants（for instance,DTAB）.These values are in accordance with those from surface tension and steady-state fluorescent probe method measurements.In addition,the values ofΔG^o_mic are all negative,indicating that the processes of micellization are spontaneous.The values ofΔH^o_mic are lower than those of-TΔS⁰_mic,showing that the micellization processes of these surfactant molecules are entropy-driven.DLS results show that 4C₁₂ester Q molecules only form larger aggregates in the pyrene-water mixed solution,while 4C₁₄tra Q and 4C₁₆tra Q have two kinds of aggregates:micelles and vesicles.The water separation time method shows that4C_ntetra Q has good emulsification properties,and the shaking method shows that4C_ntetra Q has excellent foam properties,and their emulsification and foam properties are better than DTAB.The corrosion inhibition performance of 4C₁₂ester Q on N80 steel in 1 mol/L hydrochloric acid solution was investigated by the weight loss method.The results showed that the corrosion inhibition rate reached 85.58%when its concentration was 7×10^-4 mol/L;it was found by electrochemical method.The anti-corrosion behavior of 4C₁₂ester Q on N80 steel is a mixed corrosion inhibitor,and the adsorption behavior on the surface of the steel sheet conforms to the Langmuir adsorption model.