Modification And Properties Of Fatty Alcohol Block Polyethers

Extended surfactants are a new class of surfactants that introduce oxypropylene（PO）group（PO）or oxypropylene-oxyethylene block groups（PO-EO）between the hydrophilic and hydrophobic groups of traditional surfactants,and are widely studied because of their excellent surface（interface）properties and high solubilization performance.Two extended surfactants,namely sodium aliphatic alcohol polyoxypropylene-polyoxyethylene sulfate（hereinafter referred to as PESO）and sodium aliphatic alcohol polyoxypropylene-polyoxyethylene propyl sulfonate（hereinafter referred to as PES）,were prepared by sulfating and sulfonating a fatty alcohol block polyether,i.e.a fatty alcohol polyoxypropylene-polyoxyethylene ether(C₂₆P₆E₇).The process parameters for the synthesis of the target products PESO and PES were optimized by single-factor experiments and response surface analysis experiments.The two-phase titration method was used to determine the contents of the active substances in the products as 96.49%and 90.23%,respectively.The structures of the target products PESO and PES were characterized by FT-IR and 1H-NMR,and the results showed that the molecular structures of PESO and PES were as expected.The surface tensions of PESO and PES at different temperatures and concentrations were measured by the drop volume method to study the changes of surface properties such as critical micelle concentration（CMC）,corresponding surface tension(γ_CMC),maximum surface adsorption capacity(Γ_max),minimum molecule sectional area(A_min)and surface tension reduction efficiency(p C₂₀)during the formation of micelles of PESO and PES and changes in thermodynamic parameters such as Gibbs free energy change（ΔG）,enthalpy change（ΔH）,entropy change（ΔS）and comparison with commonly used surfactants sodium dodecyl polyoxyethylene ether sulphate（AES）,sodium dodecyl sulfate（SDS）and sodium dodecyl benzene sulphonate（SDBS）.The results showed that the CMC of PESO and PES were 0.0186and 0.0126 mmol/L,respectively,and theγ_CMC were 31.80 and 33.88 m N/m.Compared with AES,SDS and SDBS,PESO and PES had lower CMC,γ_CMC,Γ_max and higher A_min and p C₂₀,indicating that the introduction of the PO group lengthens the hydrophobic chain length of PESO and PES,increasing the contact area with both air and water phases,making it easier to form micelles with higher surface activity.The process of micelle formation by PESO and PES was mainly entropy driven by the study of thermodynamic parameters.The low temperature solubility,heat resistance hydrolysis,electrolyte resistance,emulsification,foam,dispersion and solubilization of PESO and PES were measured by turbidity method,turbidimetric method,water splitting time method,Ross-Miles method and dispersion index method,and compared with common surfactants.The experimental results showed that PESO and PES had significant advantages over AES,SDS and SDBS in emulsification and defoaming of kerosene and dispersing of calcium soap particles,and were comparable to them in low temperature dissolution,electrolyte resistance and solubilization.