Surface characterization hydrophobicity

The surface of silicon can be hydrophilic or hydrophobic depending on the surface condition. It has been reported that a hydrophilic surface is characterized by OH groups and a hydrophobic surface is covered with Si-H, Si-CH , or Si-F groups. Thus, a hydrogen-terminated surface is hydrophobic whereas an oxide- or hydroxide-covered surface, which tends to be terminated by OH, is, in general, hydrophilic. A surface covered with a substantial amount of carbon bonded to oxygen is hydrophobic. 

Mori, H., Hirao, A., Nakahama, S., Senshu, K. Synthesis and surface characterization of hydrophilic-hydrophobic block copolymers containing poly(2,3-dihydroxypropyl methacrylate). Macromolecules 27, 4093 100 (1994)... 

El Rassy H, Buisson P, BouaU B, Perraid A, Pierre AC (2(X)3) Surface Characterization of Silica aerogels with Different Proportions of Hydrophobic Groups, dried by the CO2 Supercritical Method Langmuir, 19 358-363 Harreld JH, Ebina T, Tsubo N, Stucky G (2(X)2) Manipulation of pore size distributions in silica and ormosil gels dried under ambient pressure crmditions. J Non-Cryst Solids 298 241 251... 

El Rassy, H, Buisson, P, Bouali, B, Perrard, A, Pierre, A C (2003) Surface characterization of silica aerogels with different proportions of hydrophobic groups, dried by the CO2 supercritical method. Langmuir 19(2) ... 

Ratner, B. D., Hoffman, A. S. Surface characterization of hydrophilic-hydrophobic copolymer model systems. I. A preliminary study, in Adhesion and Adsorption of Polymers, Part B (ed.) L. H. Lee, p. 691, New York, Plenum Press 1980... 

Colloidal silica flocculated through hydrophobic bonding between the hydro-phobic spots on silica particles is characterized by the fact that the addition of a watermiscible alcohol such as propanol redisperses the flocculate by wetting the surface. The hydrophobic propyl groups are oriented toward the hydrophobic surface so that the outwardly disposed alcoholic hydroxyls render them hydrophilic. When such silica is recovered and dried the alcohol evaporates leaving a fully hydro-phobic surface. 

Vesicle-mediated hydrophobic photolabeling (VMHL). The extremely hydrophobic photolabel, [ I]3-trifluoromethyl-3-(m-iodophenyl)diazirine, [ I]TID, was introduced by Brunner and Semenza for the study of proteins in biological membranes [13]. By carefully observing certain limitations of the method it is possible to characterize hydrophobic contacts between peptides and lipid vesicles (liposomes), and to distinguish them from the labeling caused by hydrophobic peptide-[ I]TID aggregates in solution and on the vesicle surfaces [14-16]. Hydrophilic peptides or peptide segments that are only adsorbed to the vesicle surface (e.g. by electrostatic interactions) are very weakly labeled. 

Since latex dispersion application properties are related to the surface properties of the latex particles, there is a need for surface characterization of the particles at large. Historically, these types of systems have been applied as model colloids (Hearn et al, 1981) and therefore required well-characterized surfaces but as the sophistication of new coatings increase, the latex particle surfaces become more important from an industrial perspective. In addition to these applications the utilization of latex particles in pharmaceutical and biomedical applications has also contributed to the development of new surface characterization methods. The surface engineering, that is, variations in size, surface charge and surface hydrophobicity, of latex particles as colloidal carriers has been demonstrated to provide opportunities for the site-specific delivery of drugs (Ilium Davis, 1982). Surface... 

Nonionic and ionic surfactant molecules adsorb on solid surface at water-insoluble solid-water interface such as silica gel-water and alumina-water interface through van der Waals, hydrophobic, hydrogen bonding, and polar/ionic interactions at low concentrations of surfactant. Then, at a relatively higher and specific concentration known as critical hemimicelle concentration (CHMC), the adsorption increases dramatically as hemimicelles form on the adsorbent involving forces that characterize hydrophobic, van der Waals, and polar/ionic forces. Hemimicelles are two-dimensional molecular aggregates whose structural and physicochemical behavior have not been studied as extensively as those of normal micelles and, consequently, they are not understood even at a very rudimentary level. 

Kennedy et al. reported [79,80] that the amphiphilic materials consisting of hydrophic polyisobutylene (PIB) and hydrophilic poly(, V-dimethylac-rylamide) showed lower human blood monocyte adhesion than that of PIB and hydrophilic poly(2-hydroxyethyl methacrylate), for which the weight fractions between hydrophobic and hydrophilic components were identical. However, the amounts of various adsorbed proteins onto these samples were similar [79,80]. The relation between protein adsorption and cell adhesion has not yet been elucidated. The surface characterization methods that we employ were contact angle measurements, XPS, and SEM. There must be some structural differences among these samples of PAS that we could not detect using the aforementioned apparatus. Further studies on the surface structure of PAS by TEM and atomic force microscopy (AFM) in dry and wet conditions are now in progress. 

Collectors ndFrothers. Collectors play a critical role ia flotation (41). These are heteropolar organic molecules characterized by a polar functional group that has a high affinity for the desired mineral, and a hydrocarbon group, usually a simple 2—18 carbon atom hydrocarbon chain, that imparts hydrophobicity to the minerals surface after the molecule has adsorbed. Most collectors are weak acids or bases or their salts, and are either ionic or neutral. The mode of iateraction between the functional group and the mineral surface may iavolve a chemical reaction, for example, chemisorption, or a physical iateraction such as electrostatic attraction. 

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