Molecular Simulation Study On Self-assembly And Viscosity Mechanism Of Organic Salt/Cationic Surfactant System

The surfactant is a substance that can significantly reduce the surface tension of a liquid,has a fixed hydrophilic lipophilic group,and can be oriented in the surface of the solution.In aqueous solution,surfactants can spontaneously form a wide variety of ordered micellar structures,such as:spherical micelles,rod-shaped micelles,worm-like micelles,hexagonal micelles,bilayer micelles,vesicles,etc.Etc.,these ordered micelle structures have different application values and have a very broad application prospect.Spherical micelles and vesicles can be used as drug delivery carriers to deliver drugs to the lesions,which greatly reduce the toxic side effects of the drugs on the normal tissues of the organisms.Hexagonal micelles can be used as templates to prepare molecular sieves,which are widely used in separation and catalysis.In the field of sensors,etc.;when the concentration of worm-like micelles reaches a certain level,the micelles will be entangled and gradually form a network-like structure.It is the formation of such a network structure that makes the micelles have a good viscosity.At present,the viscoelasticity study of the surfactant system is basically based on the experimental method.It is difficult to observe the detailed microscopic process of surfactant self-assembly,and it is impossible to accurately obtain the specific structure and performance between the surfactant assembly.Relationships have had a significant hindrance to the development of high performance surfactants.Based on this,this thesis intends to use the method of coarse-grained molecular dynamics simulation to study the self-assembly process and micro-mechanism of surfactants,to make up for the related deficiencies of experimental observation,and further explore the self-assembly of organic surfactants to cationic surfactants.And the mechanism of influence of shear viscosity.The construction of worm-like micelles generally requires a higher surfactant concentration,which is of lower value in practical applications.Therefore,it is of great practical significance to reduce the concentration of surfactant used in constructing worm-like micelles.In this paper,the effects of different types of aromatic salts（Na Sal,2SHNC）on the self-assembly of cationic surfactant R₁₄HTAB system were studied.Various morphology micelles（spherical micelles,rod micelles,worm-like micelles,branching）were analyzed.The self-assembly process and microstructure characteristics of micelles and vesicles reveal the influence mechanism of organic salts on the self-assembly morphology and viscoelastic properties of surfactants.It is the design and construction of organic salt/cationic surfactant worm-like micelles.And provide some theoretical guidance for the application in engineeringIn this thesis,we have studied the self-assembly of surfactants and the mechanism of viscosity-increasing of surfactants by using coarse-grained molecular dynamics simulation methods,making full use of the advantages of fast calculation and cost saving of molecular dynamics simulation.A method for judging the length of micelles is proposed,which further understands the microscopic mechanism and supplements the shortcomings of experimental research,which provides a new perspective for theoretical research and practical application.