Solvophobic aggregation

It is general considered that the driving force for the self-assembly of amphiphilic molecules is a solvophobic effect, more specific in an aqueous environment, this is referred to as the hydrophobic effect. The type of aggregate morphology formed can be predicted... 

Another unique and specific feature of the interfacial reaction is the formation of aggregate of dye molecules, metal complexes, and other solvophobic molecules. As reported in many interfacial adsorption systems, the saturated interfacial concentration of usual molecules is of the order of 10 10mol/cm2, which can be attained even under an extremely low bulk phase concentration. This means that the liquid-liquid interface is ready to be saturated to form a two-dimensionally condensed state for the adsorbate. In solvent extraction process of metal ions, we used to find formation of some precipitate at the interface, which is called crud. The study of the interfacial aggregate is therefore important to know the real interfacial reaction as met in the industrial solvent extraction where rather concentrated solutes have to be treated. 

Solvophobicity — The effect that a relative unfavorable solvation free energy leads to solute aggregation. See -5- hydrophobic effect. 

When a selective solvent is used to solubilize block copolymers, a reversible assembly may occur in order to minimize energetically unfavorable solvophobic interactions. Micelle formation requires the presence of two opposing forces, i.e., an attractive force between the insoluble blocks which leads to aggregation, and a repulsive force between the soluble blocks which prevents unlimited growth of the micelle into a distinct macroscopic phase. Micelles are stabilized in the solution due to the interaction of the soluble blocks and the solvent [23]. 

Vesicles (Latin vesicula, bladder) are sealed, extremely thin (< 10 nm), often spherical membraneswhich enclose aqueous or other solvent volumes of approximately 10 -10 nm. Aggregation numbers are in the order of 10 -10. The monomers are held together by the same solvophobic effects which produce micelles, and solvation forces together with membrane undulations prevent crystallization. The state of the vesicle membrane is therefore also essentially of a fluid character. Supramolecular ordering within vesicle membranes is negligible. 

Micellar solutions are long-lived because repulsion between the hydrated head groups overcomes the (weak) crystallization tendency of the solvophobic part of the molecule. The micelles themselves do not aggregate as they are too short-lived. Vesicles survive, as far as the monomer crystallization is concerned. 

The research on aggregation of surfactants in nonaqueous, polar solvent systems can be motivated, mainly, with two different arguments. First, are the basic considerations of amphiphile aggregation involving a description of the hydrophobic interaction leading to, for example, micelle and liquid crystal formation. What can be learned from comparing water with other polar solvents Much work has been performed to elucidate those properties of the solvent that are essential in order to obtain a hydrophobic (or solvophobic ) interaction. Comparisons of critical micelle concentrations in different solvents with parameters characterizing the solvent are numerous in the literature [1,2],... 

The LMWGs have in common the property that they self-assemble into fibrous aggregates a process that can be driven by different noncovalent interactions like coulomb interactions, hydrogen bonding, n-n interactions, van der Waals forces, and solvophobic effects. For most of the early examples of LMWGs, the gelation prop-... 

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