Computer simulations of micellar systems

Abstract

LINTRODUCTIONMicelles, which represent nanosized aggregates formed from amphiphilic molecules in solutions, are, at present, being intensely investigated by different chemical and physical methods. Surfactants, block copolymers, and biomolecules are typical amphiphilic compounds. These compounds are distinguished by the presence of spatially separated polar and nonpolar moieties in their molecule, which differently interact with solvent molecules and predetermine the ability of the compounds to aggregate in solutions. Aggregates formed in solutions are characterized by diverse shapes and sizes, while their solutions are distin guished by various phase states, which, first of all, depend on the nature of a solvent, the concentration of an amphiphilic substance, and the structure of its mol ecules. So called normal and reverse micelles are formed in polar and nonpolar solvents, respectively. Researchers studying micellar solutions have to solve the following main problems:-determination of the shape and average size of micelles and the size distribution of aggregates; -description of the molecular structure of aggre gates and surrounded solutions;-estimation of the characteristics of the interac tion of aggregates with each other and with a sol vent;-investigation of the influence of different addi tives (first of all, salts) present in solvents on micelles;-revealing mechanisms that predetermine the aggregation processes and their kinetics;-determination of the domains of different phase states; and -studying the behavior of micelles in surface lay ers, including solution-solid interfaces.All of the above listed problems and a large number of other questions are solved using diverse experimen tal and theoretical methods, including the methods of molecular simulations. The latter are increasingly being employed to supplement both real experiments and theoretical approaches, especially those used to determine the molecular structure of aggregates and mechanisms of their formation. In these cases, the suppleness of the simulation methods and the possibil ity of visualization of studied objects sometimes make these methods indispensable instruments for describ ing micellar systems. However, it should be noted that, at present, computer simulations are characterized by constraints on the sizes of examined systems (several nanometers) and the times of their observation (sev eral nanoseconds), which are partly overcome by sim plifying the description of the molecular structure of studied compounds. This review is devoted to studies of micellar systems performed by the methods of molecular simulations since 2000 up to the present. This work does not pre tend to absolute completeness; however, in the opin ion of the author, it reflects the main results of using computer methods for solving the above formulated problems. Works devoted to simulations of micellar systems were first carried out using lattice models more than 20 years ago [1]. Then, using a similarly simplified description devoid of the constraints inher ent in...

Parameterization of a mesoscopic model for the self-assembly of linear sodium alkyl sulfates

“…21,22 Major advances have been made at several levels of computer simulation for surfactant solutions. It has been proved that molecular dynamics (MD) simulation can yield information on the free energy of micelle formation, 23 the structure of a single micelle, [24][25][26][27][28] and so on.…”

Assessing the transferability of common top-down and bottom-up coarse-grained molecular models for molecular mixtures

“…This is vital in many areas of biochemical modelling, including prediction of membrane structure and stability [25][26][27] and protein/nucleic acid interactions. 28 Structure prediction also underpins many important areas of soft matter chemistry, such as micelle formation 29,30 and the formation of the microphase-separated structures seen in lyotropic liquid crystal 18,[31][32][33] and block copolymer phase diagrams. [34][35][36] An accurate representation of free energy changes (as a function of temperature and/or concentration) underpins the prediction of thermotropic liquid crystal phase diagrams, 37,38 liquid-liquid miscibility and the phase boundaries in many industrially important soft matter systems formed from polymers and/or surfactants.…”

Volumetric Properties of Sodium Decylsulfate Solutions at the Micelles Shape Transformations Region

“…Главное направление теоретических исследо-ваний молекулярных наноразмерных структур, в том числе и мицелл в растворах ПАВ, в последние десятилетия ассоциируется с молекулярной механикой [1,2]. Для мицеллярных систем актуальной остается и структурно-термоди-намическое моделирование, особенно на базе экспериментальных исследований [3].…”