Thickness of adsorption layer

This formula may be useful as a rheological method for determining the thickness of adsorption layer, which is formed as a result of interaction between a dispersion medium and filler, by the results of measuring the t] versus q> dependence. Especially curious phenomena, connected with surface effects, arise when a mixture of fillers of different nature is used according to concentration of an active filler the introduction of the second (inert) filler can either increase or decrease the viscosity of a multicomponent system [35],... 

If the adsorption, T, is expressed in terms of the surface concentration, c(s), and the thickness of adsorption layer, 8, given by eq. (II.2), the Gibbs equation can be written in the following form ... 

Figure 29. The plot of the dependence of the thickness of adsorption layer h on p/po.

When two metal nanoparticles covered by a layer of adsorbed soluble polymer chains approach to a distance less the total thickness of adsorption layers, the polymer layers start to interact (Fig. 1). The interaction brings about steric stabilization and leads, in a majority of cases, to repulsion between the colloidal particles. It was repeatedly attempted to clarify its nature and determine its magnitude. Most frequently the problem is studied in terms of changing the Gibbs s energy when two particles are covered by an adsorbed polymer that are approaching one another from irffinity. 

D is the diffusion coefficient of surfactant 6 is the thickness of diffusion layer at the interface h is the thickness of adsorption layer at T oo... 

Different filled polymer systems with the same kind and same volume content of fillers have different viscosity values because of the different thicknesses of adsorption layer adsorbed on the filler surface. The thicker the adsorption layer, the more stable is the viscosity and the stronger the interfacial interaction. 

Numerous attempts to compare the results of theoretical calculations of the thickness of adsorption layer with experimental data were not satisfactory. The reason for the discrepancies is that assumptions made by theoretical calculations are not valid for real systems. For example, most of the calculations were done for an isolated chain, whereas in real systems we always deal with a great number of adsorbed chains. As a result, the chain conformations do not correspond to what is expected by theory. From the experimental point of view, the adsorption layer may be characterized by three parameters available for experimental determination. These are the adsorption energy (parameter%s), the fraction of bound segments, p, and the thickness of adsorption layer. 

It is evident that when this mechanism is operative, the structure and thickness of adsorption layers are determined by the structure and size of aggregates, and by the ratio between aggregated and isolated macromolecules in the layer. Killmann calculated the thicknesses of adsorption layers of poly(methyl methacrylate) and some other pol3rmers based on comparison of the amount of adsorbed polymer and surface of an adsorbent (adsorption from concentrated solutions (up to 56.0 g/1)). The values found are of the order of 0.7 mcm, which essentially exceeds the thickness of a monolayer. For solutions of isotactic polystyrene and other pol3rmers on disperse powders, the thicknesses were found in the range of 1-8 mcm, which may be explained by adsorption of aggregates. The thick-... 

Thus, investigation of the processes occurring in the filled polymer systems from the thermod3mamics standpoint makes it possible to draw conclusions as to the structure of the polymer in the boundary layer close to the interface. The influence of the filler is not restricted solely to the layers lying in the immediate proximity of the interface. It is substantiated by the data on thickness of adsorption layers, obtained by various methods. The influence of the filler on the structure formation is explained by the so-called relay-race mechanism. The use of thermodynamic methods for the investigation of sorption allows us to assess... 

Equation (4) is widely used for describing the dependence between the thickness of adsorption layer and the molecular mass of the polymer ... 

The typical segment density profile of the AB block copolymer is shown in Fig. 7. The adsorbed segments of A form a relatively compact layer near the surface. The soluble B blocks stretch into the solution and form the brushes [38]. The thickness of adsorption layer depends on the polymerization degree of the chain of the B block copolymer. 

Equations (37)-(40) allow computation of i/ (z) from volume fraction profiles. The calculated density profile of adsorbed polyelectrolyte is qualitatively different on an uncharged polymer. At low ionic strength, the maximum of density appeared as the result of the high electric potential generated by the adsorbed molecules repelling other chains (Fig. 11). The adsorbed amount and the thickness of adsorption layer increase with increasing salt concentration in solution (Fig. 12). 

Equation (78) shows that the thickness of adsorption layer is proportional to the polymerization degree to the power (2CZ — Z + 1)/(Z + 2). 

FIG. 22 Dependence between / and (1) and / and the ratio of the thickness of adsorption layer to the diameter of the blockaded surface area (2) for polystyrene adsorbed on the chromium plate from... 

Investigation of the adsorption of hydrolyzed poly(acrylamide) on the thickness on the polystyrene latex showed [90] that the thickness of adsorption layer increases and the surface area blockaded by macromolecule and the polymer concentration in the adsorption layer decreases when the NaCl concentration in the mixture increases (Table 5). When the concentration of polystyrene latex decreases, the hydrodynamic thickness of the adsorption... 

The adsorption layer compresses under the action of that electrostatic force. The compression force is proportional to the relative decrease of the thickness of adsorption layer... 

The effect of interfacial adsorption can be represented by the dimensionless group [22] S = where do is the thickness of adsorption layer. The 5 is also... 

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