Solubility surface pressure

If the spreading is into a limited surface area, as in a laboratory experiment, the film front rather quickly reaches the boundaries of the trough. The film pressure at this stage is low, and the now essentially uniform film more slowly increases in v to the final equilibrium value. The rate of this second-stage process is mainly determined by the rate of release of material from the source, for example a crystal, and the surface concentration F [46]. Franses and co-workers [47] found that the rate of dissolution of hexadecanol particles sprinkled at the water surface controlled the increase in surface pressure here the slight solubility of hexadecanol in the bulk plays a role. 

Therefore, the following method was suggested and realized (the scheme is shown in Fig. 17). A 1.5 M solution of KCl or NaCl (the effect of preventing BR solubility of these salts is practically the same) was used as a subphase. A platinum electrode was placed in the subphase. A flat metal electrode, with an area of about 70% of the open barriered area, was placed about 1.5-2 mm above the subphase surface. A positive potential of +50 -60 V was applied to this electrode with respect to the platinum one. Then BR solution was injected with a syringe into the water subphase in dark conditions. The system was left in the same conditions for electric field-induced self-assembly of the membrane fragments for 1 hour. After this, the monolayer was compressed to 25 mN/m surface pressure and transferred onto the substrate (porous membrane). The residual salt was washed with water. The water was removed with a nitrogen jet. 

We also noticed that the molecular area decreases gradually when the surface pressure is held at a certain value. Two possible explanations for this are (1) there may be some leakage of protein molecules from the surface into the subphase, since the protein is water soluble (2) protein denaturation may be taking place at the air-water interface. 

The classic studies of Saunders( 17) demonstrated that in the presence of excess surfactant methyl cellulose (MC) would desorb from monodispersed polystyrene latices. MC is one of the most surface active water-soluble polymers (W-SPs) and it will readily dominate the surface pressure 7T (7T = cre - cr t where cr is the surface tension of water and is the surface tension of the aqueous polymer solution) of the aqueous solution. For example, hydroxyethyl cellulose (HEC) lowers the surface tension of water much less than MC or HPMC, and when the combination of HEC and MC or HPMC in water is studied, there is no notable influence of HEC on the surface pressure (Figure 2). 

The differences in time-dependent adsorption behavior between 99% PVAC at 25° and 50°C demonstrate the influence of intra- and intermolecular hydrogen bonding in the adsorption process. The limiting surface pressure of the hydrophobic water-soluble polymer appears to be 33 mN/m, approximately 7 mN/m below that of commonly used surfactants. The rate of attainment of equilibrium surface pressure values is faster if there is uniformity of the hydrophobic segments among the repeating units of the macromolecule. 

Surface pressure vs surface area isotherms have been investigated for stable Langmuir-films formed from soluble (Bombyx mori) silk [1],... 

Schulman (51) on Li, Na, and K stearates. The NH4OH and LiOH curves are similar in shape to the HC1 curve. The CsOH, RbOH, KOH, and NaOH curves are highly expanded, with lower collapse pressures. The NaOH curve seems to exhibit unusually pronounced solubility effects at low surface areas. At areas greater than 50 sq. A. per molecule, the surface pressures for the soaps are still substantial (greater than 5 dynes per cm.), while they fall to near zero for the unionized fatty acid. 

The principal requirements for an ideal gaseous film are that the constituent molecules must be of negligible size with no lateral adhesion between them. Such a film would obey an ideal two-dimensional gas equation, ttA kT, i.e. the it-A curve would be a rectangular hyperbola. This ideal state of affairs is, of course, unrealisable but is approximated to by a number of insoluble films, especially at high areas and low surface pressures. Monolayers of soluble material are normally gaseous. If a surfactant solution is sufficiently dilute to allow solute-solute interactions at the surface to be neglected, the lowering of surface tension will be approximately linear with concentration - i.e. 

It should be pointed out at this juncture that strict thermodynamics treatment of the film-covered surfaces is not possible [18]. The reason is difficulty in delineation of the system. The interface, typically of the order of a 1 -2 nm thick monolayer, contains a certain amount of bound water, which is in dynamic equilibrium with the bulk water in the subphase. In a strict thermodynamic treatment, such an interface must be accounted as an open system in equilibrium with the subphase components, principally water. On the other hand, a useful conceptual framework is to regard the interface as a 2-dimensional (2D) object such as a 2D gas or 2D solution [ 19,20]. Thus, the surface pressure 77 is treated as either a 2D gas pressure or a 2D osmotic pressure. With such a perspective, an analog of either p- V isotherm of a gas or the osmotic pressure-concentration isotherm, 77-c, of a solution is adopted. It is commonly referred to as the surface pressure-area isotherm, 77-A, where A is defined as an average area per molecule on the interface, under the provision that all molecules reside in the interface without desorption into the subphase or vaporization into the air. A more direct analog of 77- c of a bulk solution is 77 - r where r is the mass per unit area, hence is the reciprocal of A, the area per unit mass. The nature of the collapsed state depends on the solubility of the surfactant. For truly insoluble films, the film collapses by forming multilayers in the upper phase. A broad illustrative sketch of a 77-r plot is given in Fig. 1. 

The interaction of soluble cations with the phospholipid phosphate groups has been investigated on a mixture of DPPC and 1,2-dipalmitoyl-sn-glycero-3-phosphoserine DPPS as a function of surface pressure and Ca2+ ion presence [51], The presence of Ca2+ in the subphase induce an acyl chain ordering at all surface pressures in both components of the binary mixture that was not observed in the case of pure DPPC alone. Unlike the bulk phase mixture of... 

Schofield and Bideal1 have mapped the relation between F and A for the longer chain, yet still appreciably soluble, fatty acids from 6 to 12 carbons long, using Frumkin s measurements of the surface tension of their solutions.8 Their results are shown in the upper six curves of Fig. 29, the product FA being plotted as ordinates and the surface pressure F as abscissae. For comparison, the results for the acids from 12-15 carbon atoms, determined by spreading the acid and measuring the surface... 

Data on emulsion film formation from insoluble surfactant monolayer are rather poor. It is known, however, that such films can be obtained when a bubble is blown at the surface of insoluble monolayers on an aqueous substrate [391,392]. Richter, Platikanov and Kretzschmar [393] have developed a technique for formation of black foam films which involves blowing a bubble at the interface of controlled monolayer (see Chapter 2). Experiments performed with monolayers from DL-Py-dipalmitoyl-lecithin on 510 3 mol dm 3 NaCl aqueous solution at 22°C gave two important results. Firstly, it was established that foam films, including black films, with a sufficiently long lifetime, formed only when the monolayer of lecithin molecules had penetrated into the bubble surface as well, i.e. there are monolayers at both film surfaces on the contrary a monolayer, however dense, formed only at one of the film surfaces could not stabilize it alone and the film ruptured at the instant of its formation. Secondly, relatively stable black films formed at rather high surface pressures of the monolayer at area less than 53A2 per molecule, i.e. the monolayer should be close-packed, which corresponds to the situation in black films stabilized with soluble surfactants. 

The chemical component of CMP slurry creates porous unstable oxides or soluble surface complexes. The slurries are designed to have additives that initiate the above reactions. The mechanical component of the process removes the above-formed films by abrasion. In most planarization systems the mechanical component is the rate-limiting step. As soon as the formed porous film is removed, a new one is formed and planarization proceeds. Therefore, the removal rate is directly proportional to the applied pressure. To achieve practical copper removal rates, pressures greater than 3 psi are often required. These pressures should not create delamination, material deformation, or cracking on dense or relatively dense dielectrics used in silicon microfabrication on conventional dielectrics. However, the introduction of porous ultra-low-fc (low dielectric constant) materials will require a low downpressure (< 1 psi) polishing to maintain the structural integrity of the device [7-9]. It is expected that dielectrics with k value less than 2.4 will require a planarization process of 1 psi downpressure or less when they are introduced to production. It is expected that this process requirement will become even more important for the 45-nm technology node [10]. 

Poly(y-w-decyl-L-glutamate). Monolayers of this polymer were spread from solution in chloroform in which it is freely soluble. The surface pressure-area isotherm (Figure 1) has several notable features. In contrast to most polymers previously studied, there is very little tail at low pressures, and there is an almost linear rise to the commencement of the plateau just below 30 A /residue. There is very little indication of hysteresis, shown by a small hump at the beginning of the plateau with certain other polymers, and the plateau extends almost completely level down to 12.5 A. The pressure then rises, and final collapse occurs at a pressure well below that of most other polymers. 

The steady adsorption of dissolved organic material onto a rising bubble, with the resulting increase in surface pressure, should progressively force the more water soluble and less surface-active species out of the bubble surface (35). Thus, for a given sized bubble, the proportion of various species varies with bubble age. This is refiected in the com-... 

Sai/ts (theory of), double, 118 mixtures of, 259 solubility surface, 120 transformation point, 152 Saponihcation, 54 Saturation, of solution, 63 Solubility, and pressure, 200 curve, 216, 2, 240 of isomoiphous salts, 264 surface of, 120, 131 Solution, concentration of, 204, 216 freesing-point lowering, 203 saturation, 63, 196, 216 soUd, 156, 263, 301 supersaturated, 86 unsaturated, 217 vapor tension of, 204 Specific heat, of gs, 30-33 Surfusion, 164, 185... 

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