Block copolymer surfactant

For example. Ilium et al. demonstrated that if microparticles were coated with surfactant block copolymers (e.g., Pluronic A-B-A polymers, where A is PEG and B is poly (propylene oxide) (PPO)), then the microparticles avoided uptake by the liver and therefore stayed in the blood circulation for long periods... 

Lyotropic liquid crystal phases are formed by amphiphihc molecules (surfactants, block copolymers) in solution, driven by repulsive forces between hydrophobic and hydrophihc parts. In a polar solvent, the hydrophihc parts associate with the solvent, whereas the hydrophobic parts interact to form the interiors of micelles (as in low-molecular smfactants). Micelles can be spherical, rod-like or discotic in shape. The contour of the micelle is determined by the relative sizes of the hydrophihc and hydrophobic groups. MiceUe shapes are influenced by solvent, concentration and temperatme. 

It is well known that block copolymers in a selective solvent (a good solvent for one block but a non-solvent for the other) form a micellar structure through the association of the insoluble segments. In contrast with micelles formed from low molecular weight surfactants, block copolymer micelles dissociate slowly to free polymeric chains. They have a greater capacity for solubilizing aromatic molecules and express lower CMCs. The AB block copolymers are considered useful vehicles for hydrophobic drugs. 

Compared with ionic surfactants, block copolymers have become more and more popular in the synthesis of mesoporous inorganic solids, because of their diverse structural characteristics and rich phase behavior. Different synthesis methodologies have been developed, carefully manipulating reaction parameters such as temperature, pH, ionic strength, reaction time, and solution composition. 

Systems with structure pose problems for continuum models. Examples include surfactants, block copolymers, lipids, and amphiphilic molecules in general. Ad hoc models are used to predict surface packing and phase behavior, but the incorporation... 

Fig. 2 Illustration of two important mechanisms involved in various kinetic processes in micellar systems, (a) Unimer exchange, single surfactant/block copolymer chains are interchanged one by one via the solvent medium, (b) Fusion/fission, where two micelles fuse or are fragmented to...

One particular asset of structured self-assemblies is their ability to create nano- to microsized domains, snch as cavities, that could be exploited for chemical synthesis and catalysis. Many kinds of organized self-assemblies have been proved to act as efficient nanoreactors, and several chapters of this book discnss some of them such as small discrete supramolecular vessels (Chapter Reactivity In Nanoscale Vessels, Supramolecular Reactivity), dendrimers (Chapter Supramolecular Dendrlmer Chemistry, Soft Matter), or protein cages and virus capsids (Chapter Viruses as Self-Assembled Templates, Self-Processes). In this chapter, we focus on larger and softer self-assembled structures such as micelles, vesicles, liquid crystals (LCs), or gels, which are made of surfactants, block copolymers, or amphiphilic peptides. In addition, only the systems that present a high kinetic lability (i.e., dynamic) of their aggregated building blocks are considered more static objects such as most of polymersomes and molecularly imprinted polymers are discussed elsewhere (Chapters Assembly of Block Copolymers and Molecularly Imprinted Polymers, Soft Matter, respectively). Finally, for each of these dynamic systems, we describe their functional properties with respect to their potential for the promotion and catalysis of molecular and biomolecu-lar transformations, polymerization, self-replication, metal colloid formation, and mineralization processes. 

Salt concentration, lyotropic Salt concentration, lyotropic Salt concentration, hydrotropic Alcohol cosurfactant concentration Nonionic polymer concentration Surfactant block copolymer concentration... 

Apart from micelles, surfactants, block copolymers and polar lipids self-assemble to a wide range of liquid crystalline phases and microemulsions [Ij. These systems offer opportunities for increased solubilization of hydrophobic drugs. Similarly, due to their water compartments, some liquid crystalline phases (e.g. cubic) are also interesting delivery systems for proteins, peptides and other biomolecular drugs. Depending on its physicochemical properties, a drug incorporated in such self-assembly systems may localize preferentially in the oil or water compartment(s), or at the interface between these, thereby affecting the structure and stability of the self-assembled system. 

Like surfactants, block copolymers form micelles above a critical concentration. The critical micelle concentration can be located by a variety of techniques [112], the most commonly used being surface tensiometry where the cmc is located as the point at which the surface tension becomes essentially independent of concentration. The primary methods to determine micelle size and shape are light scattering and small-angle X-ray and neutron scattering. The thermodynamic radius (from the thermodynamic volume, which is one eighth... 

Hypeimer CF-6, and Inulin. In general, the abilities of polymeric surfactants to decrease surface and interfacial tension are mnch lower than those of the low-molecular-weight surfactants. Block copolymers exhibit low CMC and lower diffnsion coefficient with respect to classical surfactant. Triblock copolymers are mnch more efficient than the diblock copolymers with the same composition and molecnlar weight [24]. 

HO—PPPPPP—EEEEE—PPPOH Surfactant block copolymer... 

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