Study On Interactions And Aggregate Behaviors Of The Catanionic Surfactants With Special Molecular Units

The catanionic surfactant mixtures can construct various ordered molecular aggregates.In the research of aggregation structure in the solution,the research scope has been extended to amphiphilic molecules with special molecular units.Studying these special molecular units is helpful to understand the effects of hydrophobic,electrostatic and cation-?interactions on the aggregation behavior of catanionic surfactant systems and provide theoretical basis and predictive guidance for the synthesis and research of new surfactants.Therefore,in this thesis,two kinds of surfactant mixture systems with special molecular units were selected,which are imidazolium-based ionic liquids(ILs)with different carbon chain lengths/sodium dodecyl sulfate(SDS)and catanionic surfactants with benzene ring structure.The cryogenic-transmission electron microscopy(cryo-TEM),dynamic light scattering(DLS),isothermal titration calorimetry(ITC),proton nuclear magnetic resonance spectroscopy(~1H NMR)and ultraviolet-visible spectrophotometer(UV-vis)system were used to study the aggregation structure of these systems and the thermodynamic properties of the aggregate structure transition process.The role of hydrophobic interaction,electrostatic interaction,cation-?interaction were studied by changing the alkyl chain length,molar ratio and adding Na Cl.The relative strength of these effects is to explore the effects of different driving forces on aggregate behavior and system energy.The results show that the aggregation structure of 1-hexyl-3-methylimidazolium chloride([HMIM]Cl)/SDS system has undergone the process from spherical micelles to worm-like micelles to the rod-like vesicles and the spherical vesicle structure with the increase of[HMIM]Cl molar ratio.The transition process is accompanied by the release of the system energy,but the energy release intensity first increases and then decreases.As the proportion of[HMIM]Cl increases,the electrostatic shielding effect of the head region continues to increase,but the hydrophobic activity of the hydrophobic chain is weak,so that when the molar ratio increases to a certain extent,the[HMIM]~+exists in a free form in the aqueous solution.The hydrophobic interaction from the SDS hydrophobic chain first increase and then decrease leads to same trend in the energy release intensity of the system.In 1-octyl-3-methylimidazolium chloride([OMIM]Cl)/SDS system,spherical micelles,low entanglement wormlike micelles high entanglement wormlike micelles and spherical vesicle structures were observed as the increasing of molar ratio of[OMIM]Cl.The mixture system absorbs a large amount of energy during the transition to a highly entangled wormlike micelles,because the asymmetric hydrophobic interaction between the two different lengths of hydrophobic chains results in the opposite direction movement between the hydrophobic chains.Therefore,the system requires a large amount of energy to overcome the gravitational generated by the hydrophobic chains.The aggregation structure transition process of1-dodecyl-3-methylimidazolium chloride([DMIM]Cl)/SDS system is similar to that of[OMIM]Cl/SDS system,but[DMIM]Cl/SDS system is more inclined to form The vesicle structures,the energy release intensity caused by the aggregation structure transformation process is not as strong as that of the[OMIM]Cl/SDS system,because the symmetric hydrophobic interaction of the same length of hydrophobic carbon chains causes the hydrophobic chains of the two to move synchronously.In the system composed of three different carbon chain lengths of imidazolium-based ILs/SDS,the enthalpy curves of SDS titrated into imidazolium-based ILs solution were S-type,and the aggregate structure was vesicle structures.From the enthalpy curve,it was analyzed that the ratio of the number of imidazolium-based ionic liquids to the number of SDS molecules gradually increased with the increase of the alkyl chain length of the imidazolium-based ionic liquids.In this thesis,the second part is to study the SDS/dodecyltrimethylammonium chloride(DTAC),sodium dodecylbenzene sulfonate(SDBS)/DTAC and dodecylbenzyldimethylammonium chloride(DDBAC)/SDS mixture systems.In the SDBS/DTAC system,as the molar ratio of DTAC increases,a transition from spherical micelles to spherical vesicle structures occurs,and this transition process is a dramatic energy release process.The results of ~1H NMR indicate the presence of a cation-?interaction between the benzene ring structure and the quaternary ammonium,which is origin of energy released during the transition of the aggregate structure of the mixture system,and this effect has a greater limitation effect on the movement of the DTAC molecule.In the DDBAC/SDS system,as the molar ratio of DDBAC increases,the compounding system undergoes a transition from spherical micelles to worm-like micelles to spherical vesicle structures.The benzene ring structure of DDBAC has a cation-?effect with its own quaternary ammonium cation,and there is an electrostatic interaction between the headgroup of SDS and the headgroup of DDBAC.The energy minimization between the forces affects the aggregation transition of the mixture system.The effect of electrostatic shielding effect on the enthalpy curve of the complex system at different Na Cl concentrations was studied.The high concentration of Na Cl caused the enthalpy curve of the compound system containing benzene ring structure to move to the left obviously,indicating that the transition of the aggregate structures occurs at a lower molar ratios,and the effect of high concentration of Na Cl on the enthalpy curve of the compound system without benzene ring structure is small,indicating that the cation-?action has a stronger effect of controlling the transformation of the aggregate structure.