Study On The Mechanism Of Aggregation Transition In Quaternary Ammonium Gemini Surfactant/Additives Mixtures

Surfactants are widely used in various aspects of industrial products,due to its excellent properties.From its initial use as a detergent,it has since extended to applications in medicine,lubricants,emulsifiers,corrosion inhibitors,cosmetics,and even crude oil harvesting.Because of its special hydrophilicity and lipophilicity,it is particularly concerned in the field of colloidal and interface chemistry in recent years,and its depth of research into the mechanism of action.In this thesis,cationic surfactants were mixed with different additives to form a stable and homogeneous mixed system.The interaction between additives and surfactant molecules was used to construct a stable micellar system that can be controlled by environmental conditions.The steady-state and dynamic rheological techniques,conductivity measurement,and micro-thermal measurement techniques were applied to determine the state of molecular aggregation and the structural transformation in the micellar system solution.The relevant kinetic and thermodynamic parameters were obtained with nuclear magnetic,cryogenic electron microscopy,UV,fluorescence,crystal diffraction and other technical means,from the molecular level to explore the mechanism of the aggregation of surfactant molecules in the mixed system of the state and the law,and reveal the aggregation mechanism during the process of molecular interaction mechanism.It provides experimental data for the mechanism of surfactant molecule self-assembly,and is of great significance to its application in life production.This thesis is supported by the National Natural Science Foundation of China(No.21073081 and No.21473084),and the specific work is as follows:I.Effect of the addition salt and storage time on the micelle formation of gemini cationic surfactant solutionThe critical micelle concentration of series Gemini surfactants n-3(OH)-n(2Cl)was measured by conductivity method at different temperatures.The effects of temperature and chain length on the critical micelle concentration were also discussed.Select the surfactant 12-3(OH)-12(2Cl),by rheological properties of aqueous mixture of 12-3(OH)-12(2Cl)and different add salt(Na Sal,Na Cl)were studied by the rheological measurement.Combined with cryo-EEM and X-ray analysis,the effect of salt addition and storage time on the aggregation structure of the mixed system was investigated.As a result of comprehensive experiments,the mechanism of the conversion of the aggregation structure of micellar solution is mainly due to the formation of intermolecular hydrogen bonds in the mixed solution.II.Study on rheological behavior and temperature response mechanism of gemini cationic surfactant/hydroxy naphthalate sodium mixed solutionThe viscoelastic characteristics of the worm-like micelles formed in the different mixed solutions of 14-3(OH)-14(2Cl)and sodium 1-hydroxynaphthalene-2-carboxylate(1SHNC)and sodium 2-hydroxynaphthalene-3-carboxylate(2SHNC)were researched by steady and dynamic shear rheological measurements.Combined with cryo-TEM to observe the structure of aggregates in the mixed solutions,and the transformation mechanism was studied.The results have shown that the zero shear viscosity increases rapidly as the salt concentration increases above a certain concentration and decreases after reaching a maximum value in the mixed solution.The reason for the increase and decrease of the viscosity of the solution was analyzed according to the molecular structure of salt.Different mixed solutions were selected before and after the maximum value,and the influence of temperature on the viscoelasticity of the system was examined.The results show that the zero-shear viscosity of the mixed solution before the maximum decreases linearly with temperature,and satisfied the Arrhenius law.The subsequent mixed system has a temperature sensitive response with the maximum viscosity.This is mainly related to the hydrogen bonds formed in 14-3(OH)-14(2Cl)molecules and the low solubility of SHNC at low temperatures.The results of rheological measureme nts were further confirmed by cryogenic electron microscopy.III.Study the mechanism of additives affecting the rheological properties of gemini cationic surfactant solutionVarious additives,including inorganic salts(Na Cl)and organics,have been studied by various techniques such as steady-state and dynamic shear rheology,cryo-TEM and 1H NMR.Effect of salt(benzoate homologue)on worm-like micelle formation in gemini cationic surfactant 14-3(OH)-14(2Cl)solution.The results indicated that the growth of micelles depends strongly on the concentration,properties and chemical structure of the additive employed at the fixed concentration of 14-3(OH)-14(2Cl).The influence of inorganic salt is much weaker than that of organic salts.For the three organic salts examined,it is found that the strength of their interactions with 14-3(OH)-14(2Cl)is arranged in the order of sodium m-hydroxybezoate>sodium salicylate>sodium p-hydroxybenzoate.In these interactions,the relative position of the hydroxyl groups on the aromatic ring and the type of hydrogen bonding formed between 14-3(OH)-14(2Cl)and the counterions play the most critical roles.