Different Types of Self-Assembled Structures

At low concentration of amphiphiles micelles are usually formed. Micelles typically contain some 20-100 monomeric molecules. In most cases they are spherical, but sometimes they adopt a rod-like shape. In the latter case, they contain more monomers. The radius of the sphere or the cylindrical, more or less worm-like, rod is comparable to the length of the apolar parts of the amphiphilic molecule, which is usually in the range of a few nanometers. Spherical micelles are extensively studied and well understood. 

FIGURE 11.5 Typical phase diagram for a solution of amphiphilic molecules. 

Hydration water and counterions Incorporated between the head groups (volume fraction 0.8) 

FIGURE 11.6 Associative structures formed in systems containing high concentrations 

The insights obtained from studying micellar systems appear to be useful as well for understanding more complex self-assembled structures. 

---

Hager, M., Olsson, U. and Holmberg, K. (2004) A nucleophilic substitution reaction performed in different types of self-assembly structures. Langmuir, 20, 6107-6115. 

Microemulsions, isotropic liquid mixtures of oU, water, and surfactant, frequently in combination with a cosurfactant, were stable. In the binary systems (water/ surfactant or oil/surfactant), different types of self-assembled structures can be formed, providing excellent templating systems to synthesize monodispersed nanocrystals with controllable size and morphology [28]. Recently, imidazolium-based ILs had been explored and used as solvents of the iimer phase, or continuous... 

We have a specific interest in the self-assembled structures formed by poly(ferrocenylsilane) block copolymers, such as poly(ferrocenyldimethylsilane-Z -dimethyl-siloxane) (PFS-PDMS) and (ferrocenyldimethylsilane-Z>-isoprene) (PFS-PI). The PFS block contains an iron atom in the main chain repeat unit. These polymers are particularly promising for novel applications, since they can be used as charge-transport materials and, by pyrolysis, as precursors to ferromagnetic ceramics [4-6], Moreover, they can by synthesized with a very narrow molar mass distribution, with excellent control over chain length and composition [7], An important feature of PFS is that the polymers bearing two methyl groups on the silane unit are crystalline, whereas polymers with two different substituents on each silane (methyl, ethyl methyl, phenyl) are atactic and remain amorphous. This feature of the polymer composition has a strong influence on the type of self assembled structures that these poly-... 

This section briefly discusses the use of self-assembly in the designed synthesis of coordination compounds having higher structures. The different types of self-assembly are reviewed, along with factors which influence them. Certain well-known synthetic strategies are also described. 

Recent studies by Lin and co-workers [63] have shown that not only the fatty acid composition influences the kind and ratio of carbonyls formed during heating of lipids, but also the structure of the reaction medium. The type of self-assembly stmcture had a significant influence on reaction yields. Egg phosphatidylcholin, which forms a lamellar phase together with water, generated significantly more 41 than phosphatidylethanolamine which adopts a different nanostructure, namely a reversed hexagonal structure. 

Different other attractive way to modify the active electrode of amperometric sensors, besides deposition of polymers or electropolymerization, is formation of self-assembled structures, e.g., self-assembled monolayers (SAM) on solid supports 88 89 or bilayer lipid membranes (BLM) on various types of support.90 Both types of theses structures can either induce selectivity of sensor to particular analytes and... 

In most cases the different constituent blocks are incompatible, giving rise to intramolecular phase separation, but the chemical connectivity restricts the special dimension of phase segregation to the nanoscale. As a result, at sufficiently high molecular weight, monodisperse block copolymers form a rich variety of self-assembled structures or an array of periodic nanostructures with a periodicity of 10-100 nm, commonly referred to as microphase-separated structures. By changing the relative composition, the compatibility between the component polymers, and the architecture of the copolymer molecules, the size and type of nanostructures can be precisely controlled [1-6]. 

---