Hydrophobic surface property

Highly dealuminated Y zeolite, commercially labeled as DAY (dealuminated Y), with an FAU framework type is an excellent adsorbent for the removal of organic compounds in wastewaters, as a consequence of the hydrophobic surface properties of this zeolite, owing to the low concentration of A1 (see Section 2.5.1). As an example of adsorption in a zeolite, in Figure 6.9, the N2 adsorption isotherm at 77 K of the DAY zeolite, DAY-20 F (Si/Al = 20), provided by Degussa AG, Dusseldorf, Germany, is shown. The N2 adsorption isotherms were measured with an Accelerated Surface Area and Porosimetry System (Autosorb-1) from Quantachrome, Boynton Beach, FL, USA [21] which is a volumetric automatic equipment similar to that reported in Figure 6.8. 

The source of the silica can be either the treating reagent (14) or the zeolite sample itself through rearrangement of silica from another part of the framework or from a silica impurity within the sample. (Note that in the chromic salt case, chromia rather than silica is claimed to be inserted in the structure.) Because of the dealumination and the silica insertion, the treated samples are usually found to have a higher framework silicon to aluminum ratio and a higher thermal stability than the untreated materials. Furthermore, hydrophobic surface properties usually result from substantial dealumination (7). 

Essential is that the membrane is preferentially wetted by the continuous phase if the aim is to make an oil-in-water emulsion, the membrane should have hydrophilic surface properties if one aims to produce a water-in-oil emulsion, the membrane should have hydrophobic surface properties. Thus, XME can be used not only to make oil-in-water emulsions, but also water-in-oil emulsions. 

The second set of descriptors describes hydrophobic surface properties of a molecule. As with the first set, the second set contains similar partial hydrophobic and partial hydrophilic surface area descriptors (PPHS-%and PNHS-%, respectively), differences in partial surface area descriptors (FPHS-% and FNHS-%), as well as total surface area weighted descriptors (WPHS-x and WNHS-%). In addition, two descriptors assessing the most hydrophobic atom and the most hydrophilic atom on the overall lipophilicity are also described (RPH and RNH). The atom-based fractional log P contributions used for calculations are those of Wildman and Crippen [37] and... 

Due to its predominantly hydrophobic surface properties, activated carbon preferentially adsorbs organic substances and other non-polar compounds from gas and liquid phases. Activated alumina, silica gel and molecular sieves will adsorb water preferentially from a gas-phase mixture of water vapor and an organic contaminant. In Europe cylindri-cally-shaped activated carbon pellets with a diameter of 3 or 4 mm are used for solvent recovery, because they assure a low pressure drop across the adsorber system. Physical and... 

Hegemann [36] reviewed plasma polymerization processes as a means to achieve hydrophobic surface properties of textiles, discussing the possibilities of using hydrocarbon, organosilicon, fluorocarbon process gases. A typical example of this process design based on the use of a fluorocarbon is described by Zhang et al. [37]. It should be mentioned here that in contrast to a photo-chemical process as is dis-... 

Functionalized polysiloxanes have been investigated as elastomers for this purpose [23, 24], Polysiloxanes, widely known as silicone, are of particular interest due to their extremely low glass transition temperatures and flexibility, their hydrophobic surface properties, good thermal stability and excellent flame retardant [25]. 

Epoxy group functionalized polyphenylsilsesquioxane oligomers were used for modification of phenol-formaldehyde oligomer (novolac resin -SF-0112) for increasing their flexibility, their hydrophobic surface properties, thermal stability and flame-retardant properties. Novolac resin - SF-0112 contains a little amount of free phenols (0.9%) compared with other phenol-formaldehyde oligomers. 

The major objective of this work was to investigate the effect of biomolecules such as proteins and enzymes under stress conditions on GUV formation. First, the preparative behavior of GUV was observed in the presence of proteins, polymers and salts. Second, the surface properties of vesicles and proteins at various conditions were evaluated by using the aqueous two-phase partitioning method [18]. Then the effect of stressed proteins against GUV formation was discussed in relation to the hydrophobic surface properties of vesicles and proteins. 

Sangermano, M., Bongiovanni, R., Longhin, M., et al. Hybrid organic/inorganic UV-cured acrylic films with hydrophobic surface properties. Macromol. Mater. Eng. 294, 525-531 (2009)... 

In earlier work, Vaswani et al. [40] verified the effectiveness of plasma deposition of polymerized fluorocarbon films on paper and regenerated cellulose surfaces for the purpose of enhancing barrier properties as well as achieving hydrophobic surface properties. The monomers used for the plasma polymerization process were pentafiuoroethane (CF3CHF2) and octafiuorocyclobutane (C4F8). Although the deposited polymerized films allowed water vapor diffusion, the deposited films were hydrophobic and therefore remained unwetted by water contact. Contact angle studies confirmed that a small fluorocarbon film thickness at 70 nm was only needed to completely envelop the paperboard surface and its near-surface fibers. Aside from this hydrophobic surface characteristic, it was also confirmed that plasma deposited films imparted improved barrier to lipophilic materials. 

As we mentioned in Section 10.4.1, Mn(Salen) immobilized in a hydrophobic nanopore affords much higher activity and even enantioselectivity than that in a hydrophilic nanopore in the asymmetric epoxidation of olefins [80]. This is due to the increased diffusion rate of the hydrophobic substrate into the nanopore with hydrophobic surface properties. Thus, the surface modification of the nanoreactor, depending on the polarity of the reactants and products, may be an efficient method for increasing the activity of the immobilized molecular catalysts. 

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