Adsorption onto Functionalized Surfaces

Similar methods to the formation of hydrophobic self-assembled monolayers (SAMs), as described in the previous section, were used with chemical modification to prepare surfaces with different functionality, such as alkenes or hydro-xylated surfaces. This approach was used by Thirtle et al. [67], where the adsorption of a series on nonionic surfactants from C12E5 to C16E6 onto surfaces 

An alternative approach to producing a differently functional surface is to use spin coating techniques. This was done by Turner et al. [68], who spun cast layers of polystyrene onto a silica surface. They investigated the nature of the surface and of SDS adsorbed to that surface by neutron reflectivity and IR-ATR. A thin layer of polystyrene, 275 A, was established. The subsequent SDS adsorption was consistent with a monolayer 15 A thick and an adsorbed amount similar to that observed at the air-solution interface. Measurements above the cmc of SDS showed clearly the effects on the adsorption pattern of dodecanol impurities in the SDS. 

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The existence of multiple peaks for molecular desorption has been attributed to lateral interactions among adsorbed species 62-64). As discussed previously, adsorption onto the surface lattice may occur preferentially in next nearest neighbor sites to form p(2 x 2) structures. Even at low coverages, attractive forces may cause adatoms to occupy next nearest neighbor positions, so that clusters of adsorbate form which have local twofold periodicity 65) with respect to the surface. Such effects are entirely consistent with the perturbations of the surface electronic wave functions due to adsorption 66-68) which show that these binding sites represent the... 

Few comprehensive classification schemes for CCP exist. The American Society for Testing and Materials (ASTM 1994) classifies two catgories of fly ash (Class F and Class C) based upon chemical and physical properties of the fly ash (the total amount of Si + A1 + Fe, sulphate, loss on ignition). This classification system was developed for the use of fly ash as an admixture in concrete. More recently, new classification schemes have been developed that place emphasis on textural descriptions, the form of carbon (or char ), and the surface properties of fly ash (Hower Mastalerz 2001). These new classification schemes for fly ash may be the result of growing concern over mercury emissions from coal-fired boilers. Studies have shown that mercury adsorption onto the surface of fly ash particles is a function of both the total carbon content and the gas temperature at the point of fly ash collection (Hower et al. 2000). 

The usual way of representing polymer adsorption onto clay surfaces is to plot an isotherm showing the amount of polymer adsorbed in grams per gram of clay as a function of the equilibrium concentration of polymer in units of g cm 3. We have to be careful in comparing our results with standard isotherms because we are measuring the total amount of PEO inside the clay. This absorbed mass is not necessarily adsorbed onto the clay surfaces, but may be located in the interlayer solution. To reflect this difference, we have used the unusual nomenclature absorption isotherm rather than the usual adsorption isotherm in the presentation of the data. 

Chibowski, S., Effect of functional groups of polyacrylamide and polyacryhc acid on their adsorption onto TiOj surface, J. Colloid Interf. Sci., 140, 444, 1990. 

Forte, G., Grassi, A., and Marietta, G., Molecular modeling of oligopeptide adsorption onto functionalized quartz surfaces, J. Phys. Chem. B, 111, 11237, 2007. 

The function of emulsifier in the emulsion polymerization process may be summarized as follows [45] (1) the insolubilized part of the monomer is dispersed and stabilized within the water phase in the form of fine droplets, (2) a part of monomer is taken into the micel structure by solubilization, (3) the forming latex particles are protected from the coagulation by the adsorption of monomer onto the surface of the particles, (4) the emulsifier makes it easier the solubilize the oligomeric chains within the micelles, (5) the emulsifier catalyzes the initiation reaction, and (6) it may act as a transfer agent or retarder leading to chemical binding of emulsifier molecules to the polymer. 

The key features of soot are its chemical inertness, its physical and chemical adsorption properties, and its light absorption. The large surface area coupled with the presence of various organic functional groups allow the adsorption of many different materials onto the surfaces of the particles. This type of sorption occurs both in the aerosol phase and in the aqueous phase once particles are captured by cloud droplets. As a result, complex chemical processes occur on the surface of soot particles, and otherwise volatile species may be scavenged by the soot particles. 

Most elastomers require reinforcing fillers to function effectively, and NMR has been used to characterize the structures of such composites as well. Examples are the adsorption of chains onto filler surfaces [275], the immobilization of these chains into "bound rubber" [276], and the imaging of the filler itself [277]. 

For homopolyelectrolyte, we first studied the ellipsometric measurement of the adsorption of sodium poly(acrylate) onto a platinum plate as a function of added sodium bromide concentration (5). We measured the effect of electrolyte on the thickness of the adsorbed layer and the adsorbances of the polyelectrolyte. It was assumed that the Donnan equilibrium existed between the adsorbed layer and the bulk phase. The thickness was larger and the adsorbance of the polyelectrolyte was lower for the lower salt concentration. However, the data on the molecular weight dependence of both the adsorbance and the thickness of the adsorbed polyelectrolyte have been lacking compared with the studies of adsorption of nonionic polymers onto metal surfaces (6-9). 

The flocculation rate dependency on the fractional surface coverage 0 in Equation (1) has been qualitatively confirmed (13, 14), although the maximum rate appears to occur for a surface coverage of less than 50%. The adsorption rate is also a function of 0, and it has been shown (15) for adsorption onto a smooth solid surface that the rate is proportional to the fraction of polymer-free surface area, 1-0. This approach has not... 

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