Design, Synthesis And Application Of Gemini Ester Quaternary Ammonium Salt Surfactants

Gemini ester quaternary ammonium surfactant containing two hydrophilic groups and two hydrophobic groups per molecule,i.e.,two classical monomeric surfactant molecules covalently bonded together.Gemini quaternary ammonium surfactants with ester groups are known as"green surfactants"because of their relatively high surface activity,excellent biodegradability,etc.Stemming from their unique molecular structures,i.e.,two hydrophilic groups and two hydrophobic groups per molecule,gemini ester quaternary ammonium surfactants usually have better surface activity than traditional single-chain surfactants,they can be employed to efficiently tune the surface properties of a variety of materials.Because of their technical advantages,gemini ester cationic surfactants have been widely used in textile processing,leather manufacturing,petroleum processing and other industries.In this thesis,a new type of gemini quaternary ammonium salt with ester groups,N¹,N¹,N⁴,N⁴-tetramethyl-N¹,N⁴-bis?2-?hexadecanoyloxy?ethyl?butane-1,4-diammonium bromide?TBDB?,was designed and synthesized.The third step in its synthesis process was optimized due to its important role.In addition,several surface properties of TBDB aqueous solutions,its fabric softening and corrosion inhibition behaviors were explored.The main contents are as follows:1.TBDB was synthesized in a three-step reaction from natural palmitic acid,N,N-dimethylethanolamine,1,4-dibromobutane.The single factor analysis was used to optimize the effects of four synthetic conditions on the quaternization reaction:reaction temperature,solvent volume,mole ratio of raw materials,and reaction time.The structures of the target product TBDB was confirmed by means of infrared spectroscopy,nuclear magnetic resonance proton spectroscopy,and mass spectrometry.The physical and chemical properties of TBDB were characterized systematically.From the experimental results,the optimal reaction conditions for the quaternization reaction are that the molar ratio of the intermediate dimethylaminoethanol palmitate?DAP?to 1,4-dibromobutane is 2.05:1,and the solvent volume?per molar DAP?is 0.3 L/mol,the reaction temperature is 100?,and the reaction time is 6 h.Under these conditions,the conversion rate of DAP in the quaternization reaction reached about94.6%.The critical micelle concentration of TBDB aqueous solution is 3.09×10^-5mol·L^-1at25?,and the corresponding surface tension is 38.4 mN/m.TBDB shows good thermal stability and foam stability,as well as excellent benzene solubilization capacity.The solubilization capacity to benzene is around 3.91×10⁴ mL/mol,much higher than that of the traditional single-chain surfactant cetyltrimethylammonium bromide CTAB?1.87×10⁴ mL/mol?.Compared with dodecyltrimethylammonium bromide DTAB,TBDB has better emulsification capacity.Its emulsification capacities for different oil phases is in order of:turpentine>liquid paraffin>carbon tetrachloride>kerosene>benzene.2.Fabric softener emulsions with TBDB were prepared with a non-ionic surfactant as the emulsifier.The particle size and stability of the emulsion were used as main evaluation indicators to optimize the preparation process of the fabric softener emulsion.The bending rigidity,rewetting performance and other properties of the fabric treated by softeners with different surfactants were systematically evaluated.The morphologies of fabric fibers treated with and without TBDB softener emulsion were measured by SEM.The experimental results show that the optimized compound emulsifier ratio betweenTween-20:Tween-60 is 1:3,the emulsifier content is 70%?owf?,the preparation temperature is 70?,and the time is 2.5 h.Under above conditions,the particle size of the fabric finishing emulsion is?23.69 nm.The fabric treated by TBDB emulsion has good rewettability,anti-yellowing ability and thermal stability.The TBDB emulsion can be used as a high-efficiency fabric softener because TBDB molecule can be quickly adsorbed onto the surface of the fiber through physical interactions to fill the cracks in fabric structure.3.The corrosion inhibition behaviors of TBDB and its composite corrosion inhibition systems on carbon steel in acid media were investigated by the weight loss method and electrochemical methods.The morphologies of the surface of carbon steel before and after the use of the TBDB corrosion inhibitor were measured by using SEM/EDS,AFM and other surfaces analysis technologies.The quantum chemical method was used to calculate related quantization parameters,and the interaction between TBDB and the carbon steel.The mechanism of the corrosion inhibition of the TBDB molecules was also discussed.The experimental results show that:TBDB has good adsorption and corrosion inhibition performance on Q235 carbon steel in 1.0 M HCl solution.TBDB shows better corrosion inhibition performance than several regular corrosion inhibitors tested here.The addition of sodium salicylate?SS?or NaI can further improve the corrosion inhibition effects of TBDB,showing a synergistic effect between the surfactant and salts in the system.The adsorptions of the inhibitor molecules in the TBDB,TBDB/SS,and TBDB/NaI systems on the surface of Q235carbon steel all follow the Langmuir adsorption isotherm.Results from SEM,AFM,static contact angles and other surface measurements show that:TBDB?addition of SS or NaI?can be adsorbed onto the surface of carbon steel through chemical interactions to form a protective film,which can block the attack of acidic medium and effectively inhibit the metal surface from acid corrosion.Quantum chemical calculation results show that TBDB molecules form covalent bonds with Fe atoms on the surface of the Q235 carbon steel,so as to form a dense hydrophobic protective film on the carbon steel surface,which effectively protects the carbon steel from the attack by acidic medium.