SELF-ASSEMBLING FLUIDS

Cooke IR, Deserno M. Solvent-free model for self-assembling fluid bilayer membranes stabilization of the fluid phase based on broad attractive tail potentials. J. Chem. Phys. 2005 123 224710. 

We divide our review by material there are important current advances in all three subflelds of homopolymers, multicomponent polymer fluids, and self-assembled fluids. 

Cooke, I. R., and Desemo, M. 2005. Solvent-free model for self-assembling fluid bilayer membranes Stabilization of the fluid phase based on broad attractive tail potentials. J. Chem. Phys. 123 224710. de Gennes, P. G. 1980. Conformations of polymers attached to an interface. Macromolecules 13 1069. Espanol, R, and Warren, P. 1995. Statistical mechanics of dissipative particle dynamics. Europhys. Lett. 30 ... 

We note that analogous condensation effects can take place in a liquid - for example, surface-induced phase transitions in self-assembly fluids (85, 86) - and it has also been speculated that the mechanism of the hydrophobic interaction involves a similar spinodal decomposition where vapour films on the hydrophobic surfaces grow and fuse (87). 

Laradji, M. and Kumar, P.B.S. (2005) Domain growth, budding, and fission in phase-separating self-assembled fluid bilayers. Journal of Chemical Physics,... 

Crystallization is an important separation proeess that purifies fluids by forming solids. Crystallization is also a partiele formation proeess by whieh moleeules in solution or vapour are transformed into a solid phase of regular lattiee strueture, whieh is refleeted on the external faees. Crystallization may be further deseribed as a self-assembly moleeular building proeess. Crystallo-graphie and moleeular faetors are thus very important in affeeting the shape (habit), purity and strueture of erystals, as eonsidered in detail by, for example, Mullin (2001) and Myerson (1999). In this ehapter the internal erystal strueture and external partiele eharaeteristies of size and shape are eonsidered, whieh are important indieators of produet quality and ean affeet downstream proeessing, sueh as solid-liquid separation markedly. Larger partieles separate out from fluids more quiekly than fines and are less prone to dust formation whilst smaller partieles dissolve more rapidly. 

The above results show that the structure of the system with the molecules self-assembled into the internal films is determined by their correlation functions. In contrast to simple fluids, the four-point correlation functions are as important as the two-point correlation functions for the description of the structure in this case. The oil or water domain size is related to the period of oscillations A of the two-point functions. The connectivity of the oil and water domains, related to the sign of K, is determined by the way four moleeules at distanees eomparable to their sizes are eorrelated. For > 0 surfactant molecules are correlated in such a way that preferred orientations... 

The presence of the C15 saturated chain displayed an efficient gelling ability in a wide range of organic solvents, water, and protic solvent mixtures (1 1), whereas the unsaturated derivatives (mixture of four molecules) formed fibrous nanostructures as opposed to stronger gels. The diene and triene components of the cardanyl glycosides in their fully hydrated state formed fluid nanostructures at room temperature and could not self-assemble to form gels. 

Tanahashi, M. and Matsuda, T. (1997) Surface functional group dependence on apatite formation on self-assembled monolayers in a simulated body fluid. Journal of Biomedical Materials Research, 34, 305-315. 

Sun, B. Sirringhaus, H. 2006. Surface tension and fluid flow driven self-assembly of ordered ZnO nanorod films for high-performance field effect transistors. /. Am. Chem. Soc. 128 16231-16237. 

This situation changed dramatically in 1996 with the discovery of strong electro-optic (EO) activity in smectics composed of bent-core, bowshaped, or banana-shaped achiral molecules.4 Since then, the banana-phases exhibited by such compounds have been shown to possess a rich supermolecular stereochemistry, with examples of both macroscopic racemates and conglomerates represented. Indeed, the chiral banana phases formed from achiral or racemic compounds represent the first known bulk fluid conglomerates, identified 150 years after the discovery of their organic crystalline counterparts by Pasteur. A brief introduction to LCs as supermolecular self-assemblies, and in particular SmC ferroelectric and SmCA antiferroelectric LCs, followed by a snapshot of the rapidly evolving banana-phase stereochemistry story, is presented here. 

The fluid mosaic model conveniently describes how the constituent molecules are ordered, and it correctly describes, in first order, some of the membrane s properties. However, it does not give explicit insight into why the biological membrane has a particular structure, and how this depends on the properties of the constituent molecules and the physicochemical conditions surrounding it. For this reason, only qualitative and no quantitative use can be made of this model as it pertains to permeation properties, for example. It is instructive to review the physicochemical principles that are responsible for typical membrane characteristics. In such a survey, it is necessary to discuss simplified cases of self-assembly first, before the complexity of the biological system may be understood. The focus of this quest for principles will therefore be more on the level of the molecular nature of the membrane, rather than viewing a... 

A detailed justification of the surfactant parameter approach is still the subject of theoretical investigations, and we will return to several issues below. We mention that the surfactant parameter approach is consistent with the fluid mosaic model of Singer and Nicolson. It tells us that the self-assembly of amphiphiles is driven by the strong segregation of water and hydrocarbon chains, and that packing effects dominate the self-assembly process. 

An important aspect of the methods described in the preceding section is that Lx and Ly can be time dependent. As we will show in this section, this flexibility allows the simulation cell to fluctuate independently along different spatial dimensions during the simulation. This capability is useful in simulations of systems such as self-assembled monolayers under shear. However, care must be taken when allowing for this additional flexibility because, for some systems, e.g., simple fluids under shear, there is no particular reason why Lx and Ly should be chosen to be independent of one another. In this... 

It was mentioned that ordinary surfactants (soaps, etc.), when dissolved in water, form self-assembly micellar structures. Phospholipids are molecules like surfactants they also have a hydrophilic head and generally have two hydrophobic alkyl chains. These molecules are the main components of cell membranes. Lung fluid also consists mainly of lipids of this kind. In fact, usually, cell membrane are made up of two layers of phospholipids, with the tails turned inward, in an attempt to avoid water. The external membrane of a cell contains all the organelles and the cytoplasm. 

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