Theoretical Study On The Self-assembly System Of Amphiphilic Molecules And Its Interaction Mechanism With Organic Salts

Surfactant is a kind of special material containing hydrophilic group and hydrophobic group in onemolecule, and it has a high ability to reduce the interfacial tension of liquid.The surfactants are often active near thearea of liquid surface or interface, and usually can self-assemble to different aggregates with its concentration above CMC. Today, there are large amount of research works concerning the exploration of surfactant properties in solution, including characterization of their macroscopic properties, such as CMC, aggregate number, aggregate size, rheological properties, and so on. However, most of these efforts are mainly focused on the study of their macroscopic propertiesexperimentally,less work has been done about the mechanism of the interaction between different surfactant molecules with other addictive such as some coumarins.Therefore, in this work, we use molecular dynamic tools to study some important microstructure and microscopic properties occurredbetweensurfactants and some organic additives. Our work mainly contain three parts. The first one is to study theinfluence of sodium salicylate(NaSal)on the phenomenon of cationic surfactant(R14HTAB) aggregate. The result shows that the organic salt(NaSal) can change the micellar aggregation state. In addtion, the organic salt(NaSal) molecules can penetrate into the micelles of R14 HTAB and screen the electrostatic repulsion among its head groups, leading to the spherical micelles transformed into wormlike when its concentration is below the second micelle concentration. The second part mainly concerned about how the ionic liquid would change the transformation of the hexadecyl sulfobetaine micelles(SB-16).In this part, we confirmed that the ionic liquid anion could penetrate into the micelles deeply,and the volume of spherical micelle increasesbecause of its positive and negative group stretching caused by the electrostatic interaction. The third part of our work is the exploration of the effect of lauryl sodium sulfate anionic surfactant(SDS) on the solubilization of one coumarin molecule(C-343) in a hexadecyl sulfobetaine(SB-16) micelles. The result shows that the SDS molecules could penetrate into the inner part of SB-16 spherical micelles and make the C-343 molecule escape to out space of SB-16 micellessimultaneously.Our investigations on the microscopic interaction mechanism among different surfactant molecules and additives would provide very useful guidance for the future researching works of co-workers on finding out more non-toxic, high efficiency and low cost surfactants used in daily life.