Water interaction with functional groups

Since the Me-O-Si bonds are relatively stable, and because the Si-O-Si bonds are highly hydrophobic, the interphase polymer-silane-substrate has become highly resistant to moisture, or in other words, to corrosive attack. The functional group X can be selected from a wide range of available molecules, so that it interacts with functional groups in the polymer. In this way, an extremely stable interface can be obtained that is completely covalently bonded and resistant to water. Such silane technology has been very successful... 

Fig. 7. Besides direct interactions between functional groups of the biopolymer molecule itself there are also various kinds of interactions with water molecules. These hydrophilic and hydrophobic interactions are essential for stabilizing the native conformation of biopolymers. In the last few years some progress was made in elucidating the hydration of these molecules.

Structure, Size, and Orientation of the Adsorbed Organic Molecule. In general, hydrocarbon chains, whether linear or branched, are expected to interact relatively weakly, both with water molecules and with the electrode material. Aliphatic molecules with functional groups (e.g., diols, sugars, or thiourea) may interact strongly with water molecules via H bonds and this interaction affects... 

As had been predicted prior to the determination of the X-ray structure, the proteinase assembles its catalytic machinery using a C2 symmetric homodimer (as opposed to a monomer in renin). The symmetrical nature of the enzyme suggested that C2 symmetric inhibitors might be effective. The X-ray structure also revealed the presence of an ordered water molecule bound to two of the carbonyl groups of the inhibitor. Displacement of such a water molecule with an inhibitor should, theoretically, lead to greatly enhanced activity. This theory was exploited with a class of cyclic inhibitors that mimicked the interactions of the water molecule with functionality within the inhibitor leading to highly potent and compact inhibitors, e.g., XM-323 (see Scheme 9) (15). 

Water molecules are very weakly adsorbed on the surface of hydrophobic activated carbons [356], Nevertheless, when humidity is high water was found to interfere with adsorption of organic compounds. Although, some of them are able to replace preadsorbed water [75], these quasistable conditions affect the kinetics of the process and feasibility of adsorptive separation/removal [357]. The process is even more complex when the surface of carbon is decorated with functional groups. They provide the hydrogen bonding sites, which are the primary adsorption centers [358]. Then water- water interactions lead to the formation of clusters and condensation of water in micropores at much lower humidity than that at which it happens on a fully hydrophobic carbon surface. Due to the importance of this problem in industrial and military applications numerous reviews were published describing the effects of surface chemisby on the adsorption of water [356, 359]. 

It is assumed in all models that the mineral s surface has amphoteric properties and active centres neutral as well as positively or negatively charged. The standard state is viewed as interaction of infinitely diluted solution with a neutral surface. All models are based on the concept of coordination interaction between functional groups of minerals and cations, ligands, and OH in the water solution. At that, all processes are... 

Biocomposites are very fascinating materials since they offer characteristics of two or more different materials, in order to have very specific features that would be practically impossible to obtain by every single material of biocomposite. Chitin is an abundant biopolymer obtained from shrimp, insects and some vegetal species. This material is capable to remove some contaminants like fluoride from water. Nevertheless, in order to improve the mechanical characteristics of chitin, in order to be applied in water treatment in real conditions, it must be supported. Polyurethane is a very versatile polymer due to its chemical structure. During its synthesis, interactions between functional groups take place in order to create the urethane group. The synthesis of biocomposite must bear in mind that interaction between compounds is essential to create a mechanical and chemical resistant material. FTIR with ATR analysis was carried out to characterize a biocomposite based on chitin and polyurethane, demonstrating that interaction between them occurs. 

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