Interfacial thickness interface

Girault and Schiffrin [4] proposed an alternative model, which questioned the concept of the ion-free inner layer at the ITIES. They suggested that the interfacial region is not molecularly sharp, but consist of a mixed solvent region with a continuous change in the solvent properties [Fig. 1(b)]. Interfacial solvent mixing should lead to the mixed solvation of ions at the ITIES, which influences the surface excess of water [4]. Existence of the mixed solvent layer has been supported by theoretical calculations for the lattice-gas model of the liquid-liquid interface [23], which suggest that the thickness of this layer depends on the miscibility of the two solvents [23]. However, for solvents of experimental interest, the interfacial thickness approaches the sum of solvent radii, which is comparable with the inner-layer thickness in the MVN model. 

Wooster, T.J., Augustin, M.A. (2006). p-Factoglobulin-dextran Maillard conjugates their effect on interfacial thickness and emulsion stability. Journal of Colloid and Interface Science, 303, 564-572. 

Once the free energy of an inhomogeneous system is given, one can calculate by standard methods the properties of the interface—for example, the interfacial tension or the density profile perpendicular the interface [285]. Weiss and Schroer compared the various approximations within square-gradient theory discussed earlier in Section IV.F for studying the interfacial properties for pure DH and FL theory [241, 242], In theories based on local density approximations the interfacial thickness and the interfacial tension were found to differ by up to a factor of four in the various approximations. This contrasts with nonionic fluids, where the density profiles and interfacial... 

Interfaces are not only present in blends, but are also a key feature of structural joints, where it is often necessary to produce interfacial strengths comparable with the cohesive strength of the bulk materials, and of laminates, where a more modest degree of adhesion may suffice [166]. The compatibility between different components can be expressed in terms of the equilibrium interfacial thickness, w, given approximately by ... 

From the results of MD simulations, the non-linear susceptibility, Xs p. can be calculated for each interfacial species of water molecule as a function of distance along the simulation cell (see Figure 2.13) to determine how each species contributes to the SF signal and to the depdi that SF intensity is generated. Although this representation is only a first approximation of the SF probe depth, it is the most relevant measure of interfacial thickness for SF experiments because it indicates the depth to which water molecules are affected by the presence of the interface. To make a direct comparison to experiment, the contribution from each OH oscillator to the total xisp is multiplied by a factor, linear in frequency, that accounts for the IR vibrational response dependency on frequency. For example, an OH vibration at 3400 cm is approximately 12 times stronger in SF intensity than the free OH. 

The molecular-level stmcture of the electrode/electrolyte interface was studied using two- and three- phase systems, including membrane/vapor, membrane/vapor/catalyst and membraneAfapor/ graphite systems. The simulations of a membraneAfapor interface show a region of dehydration near the interface. The interfacial thickness measured from the water density profile was found to decrease in width with increasing humidity. Hydronium ions displayed a preferential orientation at the interface, with the oxygen exposed to the vapor phase. 

Figure 7.20 High-magnification TEM image of the GaN/PSC (5 pm-thick) interface (a), and selected microdiffraction pattern of the interfacial region (b). Arrows in the inset show extra spots arising from the presence of a superlattice-like structure. Reproduced from M. Mynbaeva et al., J. Cryst. Growth, 303, 472-479. Copyright (2007), with permission from Elsevier...

For high molecular weight (M — °o) binary blends, the Helfand and Tagami theory predicts that in binary blends (i) the interfacial thickness, A/ is inversely proportional to the interfacial tension coefficient,v , the product, A/ v being independent of the thermodynamic interaction parameter, X, (ii) the surface free energy is proportional to (iii) the chain-ends of both polymers concentrate at the interface (iv) any low molecular... 

The domain size and shape, as well as the interfacial thickness, depend on the following factors (i) magnitude of the repulsive interactions between the A and B blocks, x b (ii) conformation entropy loss necessary to maintain constant segment density (iii) the localization entropy loss that causes the chemical links to be present at the interface and (iv) the composition. These mutually compensating factors (i vs. ii H-iii) depend on molecular weight of each block and the binary interaction parameter [Helfand, 1975 Helfand and Wasserman, 1976,1978,1980 Hashimoto et al, 1980 Inoue et al, 1969 JCrause, 1980 Meir, 1969, 1987 Hashimoto et al, 1993],... 

The interface thickness needs to be corrected using the composition profile. The true interfacial thickness is then determined as A1 = A, = d /1.7. 

Small angle X-ray scattering (SAXS) has been used by many authors to determine the interfacial thickness. An excellent review of this subject can be found in Perrin and Prud homme [1994]. Many methods of calculations can be used. One of these involves an analysis of the deviation from Porod s law, in which the desmearing procedure is avoided. This procedure was applied to blends of PS with PMMA added with a P(S-b-MMA) block copolymer. Upon addition of copolymer the interface thickness changed from A1 = 2 to 6 nm [Perrin and Prud homme, 1994]. 

PS P(S-b-VP) Studied M, effects of di-block copolymer segregation at the interface using the segregation isotherms. A normalized interfacial thickness was found a universal function of that portion of the block copolymer chemical potential due to chain stretching. Dai and Kramer, 1994... 

The chemical reaction at the interface during processing influences the morphology and thus the material properties. During the reaction, block or graft copolymers are formed. These copolymers are expected to reduce the interfacial tension coefficient, and to prevent coalescence of the dispersed particles. Furthermore, the chemical reaction influences the interfacial thickness. It was shown by ellipsometry that as a result of the reactive compatibilization, the interfacial thickness in the ternary system, PA/SMA/ SAN, increased up to Al = 50 nm [Yukioka and Inoue, 1994]. 

Another morphology parameter is the volume fraction of the interface, expressed as a product of S and the interfacial thickness V, = AIS. ... 

Figure 8 shows the time evolution of interfacial thickness for the PS/dPS bilayer as a function of temperature [40]. The of both PS and dPS was fixed at 29k. The interfacial characterization was made by dynamic secondary ion mass spectroscopy (DSIMS). In the case of aimealing at 400, 393, and 380 K (i.e., above the 7 of 376 K), the interfacial thickness proportionally increased to a half power of the annealing time. This is in good accordance with the context of Fickian diffusion. By contrast, a unique interfacial evolution was observed at 370 K (i.e., between 7 and T ). At first, the bilayer interface monotonically thickened with increasing time,... 

However, the creation of interfacial layers has received much attention in recent years and has led to the concept of thick interface or interphase, widely used in adhesion science [27]. Such interphases are formed whatever the nature of both adhesive and substrate, their thickness being between the molecular level (a few angstroms or nanometers) and the microscopic scale (a few micrometers or more). Many physical, physicochemical, and chemical phenomena are responsible for the formation of such interphases, as shown from examples taken from our own recent work [28] ... 

SAXS can be used to study the interfacial region between the two phases. SAXS gives a one-parameter measure of the interfacial thickness if some concentration profile is assumed. In a two-phase system with sharp interfaces, the scattering at high angles will be given by (after background subtraction) ... 

Figure 1 shows the interfacial thickness X, measured by ellipsometry for the blend systems PS/PMMA, PMMA/SAN-5.7 and PMMA/SAN-38.7. The systems containing random copolymers show a relatively thick interface. This is caused by their small polymer-polymer interaction parameter Xab and will be discussed below. The interfacial thickness in the system PS/PMMA increases slightly with temperature. The value at 120 °C was obtained by neutron reflectivity and was taken from ref. 4. 

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