Hydrophobic vs. hydrophilic

SW Kim, JR Cardinal, S Wisniewski, GM Zenter. Solute permeation through hydrogel membranes, hydrophilic vs. hydrophobic solutes. ACS Symp Ser 127 347-359, 1980. 

The choice of solid carriers spans a wide spectrum (Table 1) from materials most suitable for research purposes (sintered glass beads, laterite stone deposited on a gramophone disk) to industrial materials (pumice, activated carbon, etc.). Key properties that affect the performance of the carrier are porosity (from impervious to controlled-size pores), composition (from ceramics to activated carbon), and hydrophilic behavior. It is difficult to perform a direct comparison of different carriers. Colonization and biofilm growth depend strongly on the nature of bacteria and on their intrinsic propensity to adhere on hydrophilic vs. hydrophobic surfaces. 

Interfacial Attraction of Functional Polymers Hydrophilic vs. Hydrophobic... 

The array of PPy dots (diameter 80-180 nm) was patterned in a parallel fashion using block copolymer micelle as a soft template [256]. The Langmuir-Blodgett (LB) film composed of PS-fi-poly(2-vinylpyridine) was deposited onto the solid substrate, and the ahgned PPy dots could be formed through the chemical oxidation polymerization of pyrrole in the presence of the block copolymer micelle template. The chemical differentiation (hydrophilic vs. hydrophobic) between the core and the corona in block copolymer micelle led to spatially-limited PPy growth. 

The magnitude of T, also depends on several factors. For example, any intrinsic modification to the composition of the polymer chain as a result of changing the sequence or distribution of the different domains, or extrinsic factors such as salt additions, that modifies the tendency of water molecules to take part in hydrophilic vs. hydrophobic hydration will alter the clathrate structure and modify the T,. This effect is a result of both the mean polarity of the polymer chain and the molecular architecture and distribution of the different amino acid domains in the ELRs [27]. Tt can also be affected by the polymer concentration and by other factors, such as changes in pH or the oxidation state of a side chain or functional group, the... 

Activated Carbon (AC) is frequently used as a support in heterogeneous catalysis. It is attractive due to inertness of carbon in acidic and basic environments, and because precious metals, such as platinum, can easily be reclaimed by combustion of the carbon. AC is generally prodnced from naturally occiming caibon sources, such as nutshells, wood or peat. By pyrolysis in the absence of air or treatment with steam a carbon snpport of a high specific surface area is obtained. However, with AC it is difficult to produce bodies of a desired size distribution that are mechanically strong and thus attrition resistant. Also the pore structure and the surface characteristics (hydrophilic vs. hydrophobic) are difficult to control. 

Fig. 13 Stress-slip velocity variations for a microgel paste sheared along hydrophilic closed circles) and hydrophobic surfaces open circles). The dashed arrow denotes the yield stress, (7y = 34 Pa. The solid arrows denote the stress below which the paste adheres to the surface as = 0.7 Pa and 5.8 Pa for the hydrophilic and hydrophobic surface, respectively. The solid lines represent the quadratic (Vs and linear (Vs a) fits to the data for the hydrophobic and hydrophilic surfaces respectively...

The mean values max. deviation of the open cell rest potentials were -19 135 and +45 20 mV (vs. SCE) for the hydrophilic and hydrophobic electrodes, respectively. The electrode potential has in several studies been shown to influence protein adsorption (cf. ref. 5). Therefore the range of the rest potential of the hydrophilic surfaces in the present study, from -154 to +116 mV vs. SCE could be large enough to influence the adsorption of the two proteins used. These variations in rest potential, however, had no correlation with the spreading of the ellipsometric date and the change in potential. 

Figure 20 shows the plot of the surface tension vs. the logarithm of the concentration (or-lg c-isotherms) of sodium alkanesulfonates C,0-C15 at 45°C. In accordance with the general behavior of surfactants, the interfacial activity increases with growing chain length. The critical micelle concentration (cM) is shifted to lower concentration values. The typical surface tension at cM is between 38 and 33 mN/m. The ammonium alkanesulfonates show similar behavior, though their solubility is much better. The impact of the counterions is twofold First, a more polarizable counterion lowers the cM value (Fig. 21), while the aggregation number of the micelles rises. Second, polarizable and hydrophobic counterions, such as n-propyl- or isopropylammonium and n-butylammonium ions, enhance the interfacial activity as well (Fig. 22). Hydrophilic counterions such as 2-hydroxyethylammonium have the opposite effect. Table 14 summarizes some data for the dodecane 1-sulfonates.

Factors which influence properties chain length, branching vs. linear, nature of the monomer, density, interchain bonds, hydrophobic and hydrophilic interactions. 

Some of the compounds described in this chapter were studied for specific physical properties. Surface tension measurements with solutions of 9-16 in 0.01 M hydrochloric acid demonstrated that these zwitterionic X5Si-silicates are highly efficient surfactants.21 These compounds contain a polar (zwitterionic) hydrophilic moiety and a long lipophilic z-alkyl group. Increase of the n-alkyl chain length (9-15) was found to result in an increase of surface activity. The equilibrium surface tension vs concentration isotherms for 9 and 16 were analyzed quantitatively and the surface thermodynamics of these surfactants interpreted on the molecular level. Furthermore, preliminary studies demonstrated that aqueous solutions of 9-16 lead to a hydrophobizing of glass surfaces.21... 

The plots of log k vs. log P w and the plots of log k (v) vs. log k (z) were studied for seven cephalosporins. A linear relationship was obtained in micellar solution and in microemulsion solution (Tables 3 and 4). The results obtained indicate that the capacity factor determined by EKC could be used both as parameter to characterize the partition behavior of drugs in ME and MC and as hydrophobic parameter instead of log Pow. k appears to be an evident parameter, and it shows a better diversification than P w. In the 1-octanol/water system, we did not found high values of the partition coefficients. In contrast, the ME systems used provide a better characterization of the drugs according to their hydrophilic/lipophilic properties. 

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