Surface-induced wetting layer

The pseudo-Casimir force in a heterophase system wiU be illustrated with the example of a thin nematogenic film with order-inducing wetting layers on both confining surfaces discussed before. The resulting fluctuation force can be interpreted in terms of two contributions (i) the interaction between the substrates and the phase boundaries and (ii) the interaction between the two phase boundaries. 

Fig. 12. Schematic variation of the order parameter profile /(z) of a symmetric (f=l/2) diblock copolymer melt as a function of the distance z from a wall situated at z=0. It is assumed that the wall attracts preferentially species A. Case (a) refers to the case % %v where non-linear effects are still negligible, correlation length and wavelength X are then of the same order of magnitude, and it is also assumed that the surface "field" Hj is so weak that at the surface it only induces an order parameter 0.2 n if mb is the order parameter amplitude that appears for %=%t at the first-order transition in the bulk. Case (b) refers to a case where % is only slightly smaller than %t, such that an ordered "wetting layer" of thickness 1 [Eq. (76)] much larger than the interfacial thickness which is of the same order as [Eq. (74)] is stabilized by the wall, while the bulk is still disordered. The envelope (denoted as m(z) in the figure) of the order parameter profile is then essentially identical to an interfacial profile between the coexisting ordered phase at T=Tt for (zl). The quantitative form of this profile [234] is shown in Fig. 13. From Binder [6]...

The formation of structured thin films (both phase morphology and surface topography) is typically the result of the phase-separation processes, which are, in turn, strongly influenced by the presence of an interface. Therefore, these processes may lead to surface-oriented phase separation [27] among others, or the formation of a wetting layer [61], or, in the case of a partial wetting, the presence of a surface field that can induce the breakup of a surface layer [62,63], In this section, we will detail the main factors involved in the phase-separation phenomena. 

In this chapter, we will review the consequences of solid deformation in the kinetics of the spreading of a liquid on a soft material, in both wetting and dewetting modes. The influence of solid deformation induced by the liquid surface tension will be shown in the case of a liquid drop placed on a soft elastomeric substrate and in the case of an unstable liquid layer dewetting on a soft rubber. The impact of solid deformation on the kinetics of the wetting or dewetting of a liquid will be analyzed theoretically and illustrated by a few concrete examples. The consequences of solid deformation in capillary flow will be also analyzed. 

Zeta potential and SPR measurements are sensitive tools to follow changes in surface properties induced by polyelectrolyte adsorption in the wet state. The results obtained by these two methods for PMBQ layer on glass and glass coated with gold were in good agreement, con-... 

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