Hydrophobic/hydrophilic ratio

The most straightforward morphologies (i.e. spheres, cylinders and bilayers) are obtained by the combination of parameters given in Table 7.3. From this table it is evident that an increasing hydrophobic/hydrophilic ratio results in a change in aggregate morphology from spherical to rod-like micelles to vesicles. 

The wide range of hydrophobe / hydrophile ratios in the cubic phase region is also Afficult to reconcile wiA a bilayer model, and in fact has never bwn observed to Ais extent in any bilayer cubic phase, but it is reaAly explained by Ae progression depicted in Hgure 4 ... 

Figures Temperature-triggered self-assembly of an ELP diblock copolymer to form multivalent spherical micelles. Appropriate selection of the size and hydrophobic/hydrophilic ratio results in self-assembly at or near 40 °C. This permits multivalent display of a targeting motif (green triangle) and sequestering of a drug or imaging agent (lightning bolt) within the core of the micelles. Reproduced with permission from Dreher, M. R. Simnick, A. J. Fischer, K. etal. J. Am. Chem. Soc. 2008, 130, 687-694. ...

Oxygen permeability, WVP and carbon dioxide permeabihty are of special interest in packaging applications, especially food packaging where exposure of the product to some of these gases may lead to deterioration in quahty. Several factors influence permeability of plastics films, such as integrity of the film, ciystahine-to-amorphous ratio, mobility of polymeric chains, hydrophobic-hydrophilic ratio, and the presence of plasticizer or other additives (Souza et al., 2009). 

However, transfer of the monolayers to solid substrates was inefficient because of the small size of the hydrophilic anchor, which imparted a hydrophobic/hydrophilic imbalance. Accordingly, increasing the size of the hydrophilic anchor facilitated the formation of stable Langmuir films that could be transferred to sohd substrates with a transfer ratio of 1 (Nierengarten et al. 2001). Bayer s research group reported a related approach in which the fullerene was modified with carboxylate-terminated dendrons and alkyl chains (Maierhofer et al. 2000). This amphiphilic fullerene derivative formed stable monolayers that could be compressed and expanded without hysteresis (Fig. 11.46d Maierhofer et al. 2000). 

Surfactants having an appropriate hydrophobic/hydrophilic balance (sodium bis(-2-ethylhexyl)sufosuccinate, or AOT, for example) undergo concentration-dependent self association in apolar solvents to form reversed or inverted micelles (Fig. 33) [256-262]. Reversed micelles are capable of solubilizing a large number of water molecules (AOT reversed micelles in hexane are able to take up 60 water molecules per surfactant molecule, for example). Reversed-micelle-entrapped water pools are unique they differ significantly from bulk water. At relatively small water-to-surfactant ratios (w = 8-10, where w = [H20]/[Surfactant]), all of the water molecules are strongly bound to the surfactant headgroups. Substrate solubilization in the restricted water pools of reversed micelles results in altered dissociation constants [256, 257, 263-265], reactivities [256, 258, 266], and reaction products [267]. 

Table 7.5. presents the results on foam stability depending on the hydrophile-hydrophobe surfactant ratio and kerosene concentration for transparent solutions. It should be noted that the direct measurement of the capillary pressure in the foam with a capillary... 

The area per surfactant molecule at the hydrophobic-hydrophilic interface -the head-group area - is prescribed by the temperature, water content, steric effects and ionic concentration for ionic surfactants. Assume for now that the area per each surfactant "block" making up the assembly is set a priori. This assumption implies that the surface to volume ratio of the mixture (assumed to be homogeneous) is set by the concentration of the surfactant. So the interfacial topology is predetermined by this global constraint, the surface to volume ratio. 

Experimental results (12) showed a transition to a lamellar liquid crystal for 14 added water molecules. Our calculations (to be reported at a later occasion) showed no discontinuity or any other indication of instability of the soap/acid water complex for the subsequent water molecules added in excess of 14. It appears reasonable to assume that the isotropic liquid/liquid crystal transition does not depend on the energy levels of the polar group interactions. The phase transition probably depends on the hydrophobic/hydrophilic volume ratio and estimations according to Israelachvili/Ninham (15) approach may offer a better potential for an understanding. 

Functional properties of some enzymatically modified and EPM-treated products of milk proteins [136] were determined as follows. An enzymatically prehydrolyzed commercial milk protein concentrate (SR) without further hydrolysis, and casein hydrolyzed by alcalase, a-chymotrypsin, and papain, respectively, were used as substrates in the EPM reaction. The concentration of the hydrolysates was 20% w/ v in the EPM reactions. A methionine methyl ester hydrochloride/ substrate ratio of 1 5 was used for incorporating this amino acid. After incubation, the products with methionine incorporation were simultaneously dialyzed for 2 days through a cellophane membrane against distilled water. The nondialyzable fractions and the EPM products without amino acid enrichment were freeze-dried. Covalent methionine incorporation in the EPM products with amino acid enrichment was verified by exopeptidase hydrolysis of the protein chains. The functional properties of the different EPM products are summarized in Table 1. An important functional property of proteins and/or peptide mixtures is their emulsifying behavior. This is highly influenced by the molecular structure, the position and ratio of hydrophobic-hydrophilic amino acids. Emulsion activity was found to be low (34.0) for casein, and the values determined for enzyme hydrolyzed and modified products were in general even lower. The papain hydrolysate, sample H3, showed here a different behavior as well this was the one of the sample series that had the highest EAI value (43.0). The emulsion stability of the enzymatically modified products displayed tendencies quite opposite to the values of emul-... 

The successful design of MIC-type phases is not limited to any one synthetic approach. Subsequently, a multitude of chemistries can be employed for synthesizing MIC-type phases. Phase selectivity is dependent upon the ratio, distribution, and geometric structure of hydrophobic/hydrophilic/ ionic sites on the stationary phase. The ability to both control and vary this... 

Xu,Z.T. Kiang, Y.H. Lee, S. Lobkovsky. E.B. Emmott, N. Hydrophilic-to-hydrophobic volume ratios as structural determinant in small-length scale amphiphilic crystalline systems Silver salts of phenylacetylene nitriles with pendant oligo(ethylene oxide) chains. J. Am. Chem. Soc. 2000. 122. 8376-8391. 

S. Gogolewski, Biocompatible, biodegradable polym-ethane materials with controlled hydrophobic to hydrophilic ratio, EP Patent App. 20, PCT/CH2004/000471, WO/2006/010278. 

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