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In this chapter we discuss the basics of the phase behaviour of hard spheres plus depletants. Phase transitions are the result of physical properties of a collection of particles depending on many-body interactions. In Chap. 2 we focused on two-body interactions. As we shall see, depletion effects are commonly not pair-wise additive. Therefore, the prediction of phase transitions of particles with...
So far we have considered the phase behaviour of colloidal spheres plus depletants. In Chap. 3 we considered the simplest type of depletant, the penetrable hard sphere. We then extended this treatment in Chap. 4 to ideal and excluded volume polymers and in Chap. 5 we considered small colloidal spheres (including micelles) and colloidal rods as depletants. In this chapter we consider the phase...
In this chapter we consider the depletion interaction between two flat plates and between two spherical colloidal particles for different depletants (polymers, small colloidal spheres, rods and plates). First of all we focus on the depletion interaction due to a somewhat hypothetical model depletant, the penetrable hard sphere (phs), to mimic a (ideal) polymer molecule.
When a dispersion containing spherical colloids is mixed with a polymer solution two kinds of instabilities can occur: bridging flocculation (1) caused by adsorbing polymer or unmixing driven by the depletion force (2). The type of instability encountered depends on whether the polymers adsorb onto the colloidal surfaces. Polymer adsorption occurs when the contact between the colloid surface and the...
Apart from such similarities, there are also distinct differences between atoms and colloidal particles. In contrast to pair interactions between atoms, interactions between colloidal particles can be tuned by choosing particle type, temperature, solvent, by supplementing additives such as electrolytes, polymers or colloidal particles, or by modifying the particle surface. Since the 1970s it gradually...
Recently we have shown how to tune length- and timescales in demixed colloid-polymer dispersions in such a way that thermal capillary waves at the free interface between demixed fluid phases can be studied directly by means of laser scanning confocal microscopy [Aarts, Schmidt and Lekkerkerker, Science 304, 847 (2004)]. Here, we focus on several static properties of the interface. We show...
In the previous chapter we considered the effect of added non-adsorbing polymers on the phase behaviour of suspensions of spherical colloids. The depletion effect is also operational in mixtures of large and small (hard) spheres, where two big spheres in a sea of small spheres are brought together. As the big spheres get close, the smaller spheres can no longer enter the gap between the big ones....
We have studied the effect of additions of both anionic and cationic spherical silica colloids of different sizes on the rheology of dispersions of a well-characterised montmorillonite clay, SWy-2. The systems have been studied above and below the critical hydrodynamic overlap concentration, c*, of the clay. For dispersions at c < c* on replacement of ∼10 % w/w of the clay content by silica, it...
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