Hydrophobic/hydrophilic separation

Figure 13. A few microstructural parameters for Nafion and sulfonated poly(arylene ether ketone)s,i as a function of the solvent (water and/or methanol) volume fraction Xy. (a) the internal hydrophobic/hydrophilic interface, and (b) the average hydrophobic/hydrophilic separation and the diameter of the solvated hydrophilic channels (pores).

FIGURE 27.19 Schematic representation of the microstructures of Nation and a sulfonated polyetherketone illustrating the less-pronounced hydrophobic/hydrophilic separation of the latter compared to the former. (Reprinted from Kreuer, K.D., J. Memb. Sci., 185, 29, 2001. With permission from Elsevier.)... 

Is there anything similar in the physics of biopolymers, any general laws that are not affected by the random choices There certainly are They control the formation of knots in DNA (see Section 2.6), the hydrophobic-hydrophilic separation of a globular protein (Section 5.7), and many other properties most of these laws may still be unknown. 

The smaller hydrophobic/hydrophilic separation and the lesser flexibility of the polymer backbone of SPEEK produce narrow proton channels and a highly branched structure, which baffles the transfer of methanol. 

Figure 1. Schematic representation of the microstructures of the NAFION and S-PEEK illustrating a comparison in terms of hydrophobic/hydrophilic separation. Reprinted from [4] with permission from Elsevier.

Fig. 11.15 Left-. A schematic representation of the fully hydrated morphology of a PFSA ionomer (e.g., Nafion) under the assumptions of a cubic lattice model which fitted data from small angle X-ray scattering (SAXS) experiments. Right. SAXS spectra of hydrated Nafion and a hydrated sulfonated polyetherketone. The characteristic hydrophobic/hydrophilic separation lengths are obtained from the position of the ionomer peaks while the internal hydrophobic/hydrophilic interfaces are obtained from the intensities in the Porod regime. First reported in Ref. [66]...

FIG. 3.11 Scheme for the comparison between hydrophobic/hydrophilic separation regions in the microstructures of Nation and sPEEK. (Reprinted with permission from Elsevier (2001). Copyright 2001 Elsevier [178].)... 

Figure 15-25 shows a combination device containing coalescers and both hydrophobic and hydrophilic separating membranes. Coalescers... 

Drug Release from PHEMA-l-PIB Networks. Amphiphilic networks due to their distinct microphase separated hydrophobic-hydrophilic domain structure posses potential for biomedical applications. Similar microphase separated materials such as poly(HEMA- -styrene-6-HEMA), poly(HEMA-6-dimethylsiloxane- -HEMA), and poly(HEMA-6-butadiene- -HEMA) triblock copolymers have demonstrated better antithromogenic properties to any of the respective homopolymers (5-S). Amphiphilic networks are speculated to demonstrate better biocompatibility than either PIB or PHEMA because of their hydrophilic-hydrophobic microdomain structure. These unique structures may also be useful as swellable drug delivery matrices for both hydrophilic and lipophilic drugs due to their amphiphilic nature. Preliminary experiments with theophylline as a model for a water soluble drug were conducted to determine the release characteristics of the system. Experiments with lipophilic drugs are the subject of ongoing research. 

The ProteinChip System from Ciphergen Biosystems uses patented SELDI (Surface-Enhanced Laser Desorption/Ionization) ProteinChip technology to rapidly perform the separation, detection, and analysis of proteins at the femtomole level directly from biological samples. ProteinChip Systems use ProteinChip Arrays which contain chemically (cationic, anionic, hydrophobic, hydrophilic, etc.) or biochemically (antibody, receptor, DNA, etc.) treated surfaces for specific interaction with proteins of interest. Selected washes create on-chip, high-resolution protein maps. This protein mass profile, or reten-tate map of the proteins bound to each of the ProteinChip Array surfaces, is quantitatively detected in minutes by the ProteinChip Reader. 

The preparation of monoliths with polyNIPAAm chains grafted to the internal pore surface was discussed previously. The extended solvated polyNIPAAm-chains that are present below the lower critical solution temperature of this particular polymer are more hydrophilic, while the collapsed chains that prevail above the lower critical solution temperature are more hydrophobic. In contrast to isothermal separations in which the surface polarity remains constant throughout the run [ 136], HIC separation of proteins can be achieved at constant salt concentrations (isocratically) while utilizing the hydrophobic-hydrophilic... 

Robertson and Yeager used Py and Ru(bpy)3 probes for the purpose of locating the locations of Cs+ and 1 ions in the nanophase-separated morphology. It is known that these probes take residence in the intermediate polarity hydrophobic—hydrophilic interfacial regions. The studies concluded that Cs+ ions were located in the aqueous regions, but I ions were in the interfacial regions. 

Because the hydrophilic sulfonic acid groups are covalently bound to the hydrophobic polymer, they aggregate somewhere in the hydrophobic/hydrophilic transition region, with an average separation of 0.8 nm, compared to 1 nm expected for a totally uniform distribution within the material. ... 

This paper has provided the reader with an introduction to a class of polymers that show great potential as reverse osmosis membrane materials — poly(aryl ethers). Resistance to degradation and hydrolysis as well as resistance to stress Induced creep make membranes of these polymers particularly attractive. It has been demonstrated that through sulfonation the hydrophilic/hydrophobic, flux/separation, and structural stability characteristics of these membranes can be altered to suit the specific application. It has been Illustrated that the nature of the counter-ion of the sulfonation plays a role in determining performance characteristics. In the preliminary studies reported here, one particular poly(aryl ether) has been studied — the sulfonated derivative of Blsphenol A - polysulfone. This polymer was selected to serve as a model for the development of experimental techniques as well as to permit the investigation of variables... 

The medium may have a marked effect on the shape of receptor molecules itself. Shape modifications could strongly influence their substrate binding properties, for instance in the case of amphiphilic cyclophane receptors subjected to hydrophobic-hydrophilic factors in aqueous solution. Such medium effects in action are visualized by the solid state structures of two different forms of the water-soluble hexasodium salt of the macrobicyclic cyclophane 66, which could be crystallized in two very different shapes an inflated cage structure 71 building up cylinders disposed in a hexagonal array and a flattened structure 72 stacked in molecular layers separated by aqueous layers in a lamellar arrangement [4.73]. These two... 

We have examined two types of organized media that effectively control the charge separation and back reactions of the intermediate photoproducts. These include, (a) charged colloids i.e. SiC>2 and ZrC>2 colloids that introduce electrostatic interactions between the photoproducts and interface (7-10), and (b) water-in-oil microemulsions that provide aqueous-oil two phase systems capable of controlling the reactions by proper design of the hydrophobic-hydrophilic balance of the photoproducts ( 6). 

Figure 2. Charge separation and stabilization of photoproducts in organized environments a) Application of the electrostatic interactions with charged Si02 colloids, b) Use of hydrophobic-hydrophilic interactions in water-in-oil microemulsions.

Chung et al. (1998) studied the micellar solutions of terminally modiLed PIPAAms, such as PIPAAm-Ci8H35 and PIPAAm-PST. These show nearly the same lower critical solution temperature (LCST) as that of pure PIPAAm. The LCST is the temperature above which the polymer solution phase separates (Heskins and Guillet, 1968) and is related to how the hydrophobic-hydrophilic balance ofthe polymer changes. In contrast, randomly modiLed PIPAAm [P(lf MAiSE)]... 

Fig. 8a, b. Control of photoinduced ET reactions in organized microenvironments a) application of charged interfaces to effect charge separation and retard recombination processes by means of electrostatic interactions b) application of water-oil two phase systems in charge separation and stabilization of photoproducts against back reactions by means of hydrophobic-hydrophilic interactions... 

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