Interface acid-base interactions

Polymer Surfaces and Interfaces Acid-Base Interactions and Adhesion in Polymer-Metal Systems... 

Polymer Surfaces and Interfaces Acid-Base Interactions and Adhesion in Polymer-Metal Systems Irina A. Starostina, DSc, Oleg V. Stoyanov, DSc, and Rustam Ya. Deberdeev, DSc... 

Characterization and interfacial properties of solid surfaces, solid-fluid interfaces, acid-base interactions, and colloidal dispersions... 

The comparison of I —> N and N —> I may also be explained by the buffered pH in the diffusion layer and leads to an interesting comparison between a process under kinetic control versus one under thermodynamic control. Because the bulk solution in process N —> I favors formation of the ionized species, a much larger quantity of drug could be dissolved in the N —> I solvent if the dissolution process were allowed to reach equilibrium. However, the dissolution rate will be controlled by the solubility in the diffusion layer accordingly, faster dissolution of the salt in the buffered diffusion layer (process I—>N) would be expected. In comparing N—>1 and N —> N, or I —> N and I —> I, the pH of the diffusion layer is identical in each set, and the differences in dissolution rate must be explained either by the size of the diffusion layer or by the concentration gradient of drug between the diffusion and the bulk solution. It is probably safe to assume that a diffusion layer at a different pH than that of the bulk solution is thinner than a diffusion layer at the same pH because of the acid-base interaction at the interface. In addition, when the bulk solution is at a different pH than that of the diffusion layer, the bulk solution will act as a sink and Cg can be eliminated from Eqs. (1), (3), and (4). Both a decrease in the h and Cg terms in Eqs. (1), (3), and (4) favor faster dissolution in processes N —> I and I —> N as opposed to N —> N and I —> I, respectively. 

In addition to adsorbing at mineral-oil interfaces, asphaltene molecules also adsorb at oil-water interfaces. Strong intermolecular dipole-dipole, hydrogen bonding, electron donor-acceptor and acid-base interactions cause the surface-adsorbed asphaltene molecules to form rigid skins" at oil-water interfaces (41 43). When water droplets are dispersed in an oil which contains asphaltene molecules, molecularly thick, viscous asphaltene films form around the water droplets, inhibit the drainage of intervening oil and sterically stabilize the water-inoil emulsion. 

X ray photoelectron spectroscopy (XPS) is powerful in identifying species present at the surface/interface and atoms or functional groups involved in acid-base interactions [116]. Since XPS measures the kinetic energy of photoelectrons emitted from the core levels of surface atoms upon X ray irradiation of the uppermost atomic layers, it can be used to characterize surface acid sites, in combination with base probe molecules adsorption. 

Acid-base reactions across the interface. This subject was well covered by a symposium on Acid-Base Interactions Relevance to Adhesion Science and Technology in honor of Professor F. M. Fowkes on his 75th birthday. Most of these papers have been published in Vol. 4, No. 4, No. 5 and No. 8 (1990) and Vol. 5, No. 1 (1991) of the Journal of Adhesion Science and Technology. 

Cain SR (1991) Quantum-mechanical approach to understanding acid-base interactions at metal-polymer interfaces Jensen. In Mittal KL, Anderson HR (eds) Acid-Base-Interactions. VSP Utrecht, p 47... 

A study of the interaction of Lewis acids and bases (or electron acceptors and donors) in surface dynamics has led to new insight into interactions with various solid surfaces [26,64,99,100,104,110,130-142], as well as interactions at interfaces between two different substances. It is noted that the acid-base interactions of Lewis, including the orientational properties of charge transfer forces of Mulliken [143], occur between specific (or polar) groups in substances. These interactions are quite dependent on the Stockmayer degree of polarity, <5, [126] as measured by dipole moment in Eq. (58). Furthermore, it can be found that a concept of acids attract bases may be substituted... 

Extending work done previously (1 - 2), the purpose of this paper is to examine how these characteristics could be determined using inverse gas chromatography (IGC) and to what extent these acid/base interactions are relevant to the description of the fibre-matrix interface. 

In contrast, as shown in Figures 8 and 9, there is a very good correlation between the interfacial shear strength X (average or maximum) and the specific interaction parameter A, expressing the acid/base interactions exchanged at the interface. 

Single fiber tests were used to evaluate the fiber-matrix adhesion. Acid/base interactions do play a role in this adhesion but are not exclusively responsible for improvements at the interface. Treatment with a siloxane coupling agent was proven to be effective in lowering the dispersive component of the carbon fibers and altering their acid/base properties, producing poorer adhesion. 

The orientation of PMMA chains on the surface of alumina was found to be affected by acid-base interactions. Due to these interactions, the trans conformation was more common at the interface than the gauche conformation which was prevalent in bulk." ... 

The above description stresses either chemical reactions in these combinations or physical interactions between components. In reality there is still additional effect which may induce changes to structure and thus properties. It is a commonly known effect of fillers on the nucleation of polymers. It can be perceived that filler does not affect nucleation of both polymers with the same intensity. In addition, the availability of polymers at the interface with fillers depends on various parameters such as viscosity, acid/base interaction, etc. If these two are included in the number of combinations, there is a theoretical abundance of possible combinations and thus... 

Recently, much attention is being placed on fibres-reinforced/polymer systems as subjects of study. It was caused by increasing emphasis on high performance reinforced polymer composites. The concept of acid/base interactions across the fibre/polymer interface was noted particularly and the relevance of acid/base theories to the behaviour of po-... 

Dispersive and specific interactions are considered to contribute independently to the adsorption of probe molecules at the adsorbent surface. It was presented that the adhesion of the fibre-matrix interface depends clearly on the measured strength of acid/base interactions of both fibre and polymer-matrix. Fowkes [2,3] indicated also that the surface of fillers can be chemically modified to enhance acid-base interaction and increase adsorption. 

James, R.O. and Healy, T.W., Adsorption of hydrolyzable metal ions at the oxide-water interface, 1. Co(II) adsorption on Si02 and TiOj as model systems, J. Colloid Interface Sci., 40, 42, 1972. Backman, J., Eklund, T, and Rosenhohn, J.B., Acid-base characterization of porous sihca particles, in Acid-Base Interactions, Vol. 2, K.L. Mittal, Ed., VSP BV, Zeist, 2000, 465. 

In the field of snrface science and interfaces, it is well known that acid-base interactions play an important role for a large nnmber of phenomena, snch as adhesion on polymers, polishing, etc. The oxide surfaces in an aqneons solntion become charged due to amphoteric dissociation of surface M-OFl groups. The Brpnsted acidity or basicity of an oxide surface can be characterized by the point-of-zero charge (pzc), which corresponds to the pFI value required to achieve zero net surface charge. 

The difference between these two models could be due to the acid-base interactions established between OH grafts and PMMA chains during evaporation of the solvent (spin-coating) PMMA blocks will be attracted to the OH grafts and thus will be more flattened on the functionalized gold interface, while the PCL chains implied in the crystalline phase are less mobile and are not able to establish such interactions. 

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