Mesoscopic structures Micelles

Reactions that occur between components in the bulk solution and vesicle-bound components, i.e., reactions occurring across the membrane interface, can be treated mathematically as if they were bimolecular reactions in homogeneous solution. However, kinetic analyses of reactions on the surface of mesoscopic structures are complicated by the finiteness of the reaction space, which may obviate the use of ordinary equations of chemical kinetics that treat the reaction environment as an infinite surface populated with constant average densities of reactant molecules. As was noted above, the kinetics of electron-transfer reactions on the surface of spherical micelles and vesicles is expressed by a sum of exponentials that can be approximated by a single exponential function only at relatively long times [79a, 81], At short times, the kinetics of the oxidative quenching of excited molecules on these surfaces are approximated by the equation [102]... 

Surfactants are popularly known for their detergency properties. Their appeal is based on the observation that while they are dispersible in water, they can remove efficiently oily contaminants from various surfaces, such as apparel, building materials, and appliances. This was found to be due to the capability of surfactants to form mesoscopic structures called micelles, in which surfactant molecules self-organized into spherical, cylindrical, and even lamellar domains. In these domains surfactant molecules arrange themselves like infantry soldiers of a Roman legion in defensive positions, wherein the hydrophilic heads of each molecule are facing the wide... 

Small-angle neutron scattering (SANS) is a unique tool to investigate the structure of mesoscopic molecular systems, e.g. polymeric macromolecules in solution or in the melt or mesoscopic aggregates (micelles, etc.) of small or macro-molecules. The substances involved usually contain a considerable amount of hydrogens, thereby allowing the application of the key technique of SANS, contrast variation. 

Another class of polymers that occupied 165 pages in the book and many years of effort by Meyer and his collaborators is the celluloses. The detailed X-ray crystallography that resolved the local and mesoscopic structure of cellulose and its micelles is presented in detail. His chief collaborators included Herman Mark, J.R. Katz, Michael Polanyi, L. Misch and G. von Susich. A detailed model of the unit cell of native cellulose is given in Fig. 3.13. 

The microheterogenous and nanoheterogenous (mesoscopic) liquid-liquid systems may be concisely called the small systems. They comprise the micro- and nanodomains, described in colloidal chemistry as a variety of structures, e.g., micelles, rods, disks, vesicles, microemulsions, monolayers, and Langmuir Blodgett layers [6,17 19,70]. 

In developing any theoretical method, however, a number of decisions must be made in advance. These include, in addition to a reasonable idea of what specific descriptions and predictions will be sought from the theories or models, a decision on what level of microscopic details will be incorporated into the model. Such a decision is dictated by the current limitations of the theoretical tools (e.g., classical or statistical thermodynamic theories) or computational resources. For example, microscopic models of micellization and solubilization can, in principle, be approached at the molecular level with a detailed structural representation of the various components along with their energetic interactions. Our current understanding of molecular dynamics is sufficiently comprehensive and well established to permit such a detailed approach to the evolution of mesoscopic and macroscopic structures and phenomena in surfactant-oil-water systems. However, the... 

Around the turn of the last century, chemists were reluctant to accept the idea of rubber, starch, and cotton as long, linear chains connected by covalent bonds. A popular alternative was the idea of an associated colloidal structure. As a matter of fact, some small molecules do exhibit such behavior. Soap molecules will associate into complex liquid crystalline structures and are used as the basis for the formation of mesoscopic solids. Other surfactant molecules such as the phospholipids present in the wall of many living cells will form micelles and vesicles. However, the effective molecular weight of such structures varies with concentration and temperature, whereas the molecular weights of true polymers with covalent links do not. 

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