Entropy interfacial

S 7, sa Interfacial entropy in Gibbs convention(JK-1) and interfacial entropy per unit area (JK-1m-2), respectively T Temperature (K)... 

Linearity of y(T) then suggests that the slope is Just the excess Interfacial entropy... 

To obtain any thermodynamic information of such systems it is useful to consider the effect of temperature on the interfacial tension. The aUcane-water interfacial tension data have been analyzed (Eigure 3.10). These data show that the interfacial tension is lower for Cg (50.7 mN/m) than for the other higher chain length alkanes. The slopes (interfacial entropy -djIdT) are all almost the same, 0.09 mN/m per CH2 group. This means that water dominates the temperature effect, or that the surface entropy of the interfacial tension is determined predominantly by the water molecules. Eurther, as described earlier, the variation of surface tension of alkanes varies with chain length. This characteristic is not present in interfacial tension data however, it is worth noting that the slopes in the interfacial tension data are lower than those of both pure alkanes and water. The molecular description must be analyzed. 

As we know (dy/dT). = -(3Ss/dA)T>n., from Equation (213), the temperature variation of surface tension can be related to the differential surface excess entropy, and since the left-hand side of the equation is almost always negative, there is an increase in the interfacial entropy with the increase in surface area. For a constant unit area of As = 1 m2, if we want to compare the surface excess entropy of a one-component pure liquid, with the entropy of its bulk liquid, we have to use Equation (219), SsdTs + dy + -TfdJuf =0... 

Entropy Effects. Interfacial orientation such as suggested for the fatty acids, alcohols, and amines (and which would be present with certain other series of compoimds also) should lead to a negative contribution to the interfacial entropy, asi The interfacial tension will be greater than in the absence of the orientation, since... 

Water-in-oil dispersions are far less stable than their aqueous counterparts. This is a consequence of the low dielectric constant of organic compoimds which renders electrostatic stabilization ineffective [7]. Steric repulsive forces are therefore required to counterbalance the van der Waals attractive forces which are significant i kT) in non-aqueous dispersions [8]. This can be achieved by using block copolymers as stabilizers to prevent flocculation, or nonionic emulsifier blends which maximize the interfacial entropy of mixing by forming a condensed surfactant layer [9] (see Chapter 3). 

Values of thermodynamic properties of the L/G interfaces for a variety of compounds are listed in Table 5.1. Over a rather wide temperature range, say, at least some tens of degree Celsius (or Kelvin), dy/dT is essentially constant. The values in Table 5.1 clearly indicate that the interfacial entropy largely, and often dominantly, contributes to the interfacial tension. 

The maximum heat exchange between the n-decane and its environment What is the relation between the interfacial tension and changes in the enthalpy and entropy due to expanding an interface at constant temperature and pressure Derive the relation between the differential interfacial entropy and the temperatnre dependence of the interfacial tension. 

Statistical Thermodynamics of Adsorbates. First, from a thermodynamic or statistical mechanical point of view, the internal energy and entropy of a molecule should be different in the adsorbed state from that in the gaseous state. This is quite apart from the energy of the adsorption bond itself or the entropy associated with confining a molecule to the interfacial region. It is clear, for example, that the adsorbed molecule may lose part or all of its freedom to rotate. 

The temperature coefficient of the potential of zero charge has often been suggested to indicate the orientation of solvent molecules at the met-al/solution interface. However, this view is based only on the response of a simple two-state model for the interfacial solvent, and on neglecting any contribution from the electronic entropy.76,77 This is in fact not the case. The temperature coefficient of 0in many instances is negative and of the... 

The entropy of formation of the interface was calculated from the temperature coefficient of the interfacial tension.304 The entropy of formation has been found to increase with the nature of the electrolyte in the same sequence as the single cation entropy in DMSO.108, 09,329 The entropy of formation showed a maximum at negative charges. The difference in AS between the maximum and the value at ff=ocan be taken as a measure of the specific ordering of the solvent at the electrode/solution interface. Data 108,109304314 have shown that A(AS) decreases in the sequence NMF > DMSO > DMF > H90 > PC > MeOH. 

The restricted access principle is based on the concept of diffusion-based exclusion of matrix components and allows peptides, which are able to access the internal surface of the particle, to interact with a functionalized surface (Figure 9.2). The diffusion barrier can be accomplished in two ways (i) the porous adsorbent particles have a topochemically different surface functionalization between the outer particle surface and the internal surface. The diffusion barrier is then determined by an entropy controlled size exclusion mechanism of the particle depending on the pore size of adsorbent (Pinkerton, 1991) and (ii) the diffusion barrier is accomplished by a dense hydrophilic polymer layer with a given network size over the essentially functionalized surface. In other words, the diffusion barrier is moved as a layer to the interfacial... 

In the NVT ensemble one cannot compute the chemical potential or entropy of the system two properties which are of critical importance for interfacial systems. The choice of an ensemble also determines the sampling algorithm used to generate molecular configurations from random moves of the molecules. 

A nonpolar neutral species in a polar medium such as water experiences interfacial tension. Solvophobic theory is a general statement of hydrophobic theory, which has been developed to explain the tendency of neutral organic species to flee the water phase. It has been reported that the solution of nonelectrolytes in water is attended by a net decrease in entropy [65,158]. This has been attributed to an increased structuring of water molecules in the vicinity of the solute. The process may be conceptually rationalized by considering that a solute must occupy space in a cohesive medium. The solute must create a cavity in the water milieu and then occupy that cavity [19,65,158]. The very high cohesive density of water creates considerable interfacial tension in the... 

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