Simple Amphiphiles

The term simple amphiphile describes the principle of molecular constitution of compounds which will be discussed in this section. The simplest molecular architecture of an amphiphile consists of a hydrophilic group connected to a lipophilic substructure as shown in Fig. 4. 

the layer distance in such meso-phases is not twice the molecular length but 

For the arrangement of molecules within the layers the usual notation is used in the SmA phase the molecules have no two-dimensional order within their layers, in the SmB phase the molecules within their layers are set in a hexagonal arrangement, characteristically in the SmC the molecules are tilted with respect to the layer normal but possess no other degree of order. An interesting fact is that the smectic phases of such amphiphiles are not miscible with the me-sophases of the same type of nonamphiphil-ic smectic mesogens. 

The general phase behavior of mono-tailed amphiphiles is shown in Fig. 6. Starting at a certain chain length of the lipophilic part of the molecule, a thermotropic smectic phase 

Lyotropically, several arrangements of their supramolecular aggregates (formations of layered, columnar and cubic phases) are observed for the simple amphiphilic type of molecules. 

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From Simple Amphiphiles to Protocell Models Volume Editor Walde, P. 

It is found that, even a monolayer of lipid (on water), when compressed can undergo various states. In the following text, the various states of monomolecular films will be described as measured from the surface pressure, n, versus area, A, isotherms, in the case of simple amphiphile molecules. On the other hand, the Il-A isotherms of biopolymers will be described separately since these have a different nature. 

In the case of simple amphiphiles (fatty acids, fatty alcohols, lecithins, etc.), in several cases, transition phenomena have been observed between the gaseous and coherent states of films, which show a very striking resemblance to the condensation of vapors to liquids in three-dimensional systems. The liquid films shows various states in the case of some amphiphiles, as shown in Figure 4.6 (schematic). In fact, if the II versus A data deviate from the ideal equation, then the following interactions may be expected in the film ... 

The analogy between three- and two-dimensional phase diagrams can be carried much further. Monomolecular amphiphilic films show ordered phases similar to three-dimensional systems [579], The phases of an amphiphilic monolayer can be detected most conveniently in pressure-area (7r-versus-OA) isotherms. These may look different for different substances. The behavior of simple amphiphilic molecules, like long-chain alcohols, amines, or acids, was extensively investigated (reviews Refs. [580,581]). In monolayers so-called mesophases can occur. In a mesophase the tail groups are ordered over relatively large areas, while the order in the hydrophilic head groups is only over a much smaller distances. 

The colloids and simple amphiphiles have been extensively studied in this respect for more than 150 years. Only in the last 20 to 30 years have we reached some understanding on the behavior of super-amphiphilic block copolymer systems. In the above-mentioned systems though, it is still clear that as soon as supramolecular interactions are involved, there are still no definitive rules predicting the resulting structures. 

The concentration at which micelles first form is the - critical micellization concentration or c.m.c.. Initially the micelles formed by SDS and other simple amphiphiles are roughly spherical in shape with a reasonably well-defined number of molecules associating ( 50... 

The surface film acts as a two-dimensional analogue to normal matter in that it may exist in different physical states, which in some ways resemble solids, liquids and gases. In this section we shall consider the three different states of monolayers of simple amphiphiles, referred to as solid or condensed, expanded, and gaseous monolayers (see Fig. 6.7). 

Concluding remarks Other simple amphiphilic peptides... 

Lee CK, Huang HW, Lin IJB (2000) Simple amphiphilic liquid crystcilline N-eilkylimidazolium Stilts. A new solvent system providing a partitilly ordered environment. Chem Commun 1911-1912... 

Formally, one could compare the structure with two simple amphiphiles (see Fig. 4) which are linked at the ends of their lipophilic parts. The principal structure of... 

Since bolaamphiphilic molecules form hydrogen bond networks at both of their molecular ends the stability of their mesophase is remarkably increased compared to simple amphiphiles of half the length. 

All the multiols shown in Fig. 23 are liquid crystalline except the tetrol 23 with its bis-l,3-diol headgroups [81]. Apparently, this situation causes a high melting point (103 °C [81]) suppressing the occurrence of a mesophase. The same effect was discussed in subsection 2.1 Simple Amphiphiles of this chapter, for example, for members of a... 

For simple amphiphilic compounds, the association is of low co-operativity in non-polar solvents and leads typically only to smaller and polydisperse aggregates. An illustration is given in Figure 19.16. However, introduction of even quite small amounts of water can induce a co-operative self-assembly leading to reverse micelles. 

Self-assembly is used to organize molecules into amazing and complex structures. Small molecular weight molecules can be assembled into structures of varying degrees from dimers and trimers all the way up to and including supramolecular polymers. Simple amphiphiles form micelles and vesicles. Dendrimers, DNA-based materials, peptides, and peptides amphiphiles have been assembled into nanostructured fibrals reminiscent of the extracellular matrix. Obviously, we cannot cover here even a fraction of the creative and functional assembled systems reported. In this section, we highlight selected symmetrical self-assembled systems to illustrate how different... 

Highly diastereo- and enantioselective aldol reactions between aromatic aldehydes and cyclohexanone performed in water were developed by Tao et al. by using a novel simple amphiphilic proline-derived organoeatalyst bearing a... 

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