Gel transitions in colloidal suspensions

Abstract

Abstract. The idealized mode-coupling theory (MCT) is applied to colloidal systems interacting via short-range attractive interactions of Yukawa form. At low temperatures, MCT predicts a slowing down of the local dynamics and ergodicity-breaking transitions. The non-ergodicity transitions share many features with the colloidal gel transition, and are proposed to be the source of gelation in colloidal systems. Previous calculations of the phase diagram are complemented with additional data for shorter ranges of the attractive interaction, showing that the path of the nonergodicity transition line is then unimpeded by the gas-liquid critical curve at low temperatures. Particular attention is given to the critical non-ergodicity parameters; this is motivated by recent experimental measurements. An asymptotic model is developed, valid for dilute systems of spheres interacting via strong short-range attractions, and is shown to capture all aspects of the low-temperature MCT non-ergodicity transitions.

Gelation in Model Colloid−Polymer Mixtures

“…Here, n is the number density of the colloids, which, in dimensionless form, is φ ) πnσ 3 /6, the colloid volume fraction. To leading order in the concentration of colloids, c(k) is given by a Fourier transform of exp(-u(r)/k B T) -1, 65 which, for small polymer-colloid size ratios ( , 1), takes the form where q ) kσ/b ) q/b and By defining the two parameters b and K in this manner, we observe that eq 5 is identical to an expression we have derived previously 45,46 for the large wavevector asymptotic behavior of c(q) for particles interacting via a hard core plus an attractive Yukawa tail, sometimes referred to as the hard-core attractive Yukawa (HCAY) system, 66 provided use is made of the mean spherical approximation (MSA). For HCAY systems, the interaction potential is given by where the dimensionless parameters K and b determine the strength and range of the attraction, respectively.…”

“…9,10, [45][46][47] Gelation within this framework hinges on short-range, local correlations, while the long-range (or small-q) structure is considerably less important. Whether this indeed is so has yet to be firmly established.…”

Phase equilibria and glass transition in colloidal systems with short-ranged attractive interactions: Application to protein crystallization

“…For very short ranges, in other types of attractive potentials, we have located a glass-glass transition, a transition between two different type of glasses originated either by repulsion or by attraction [10]. For the Yukawa fluid such a phenomenon also appears to be present, although it has not yet been investigated in detail [50,51]. Both the results for the Yukawa potential considered here and those for the square-well fluid that we present next for comparison clearly show that the distinction between the attractive solid and repulsive solid becomes sharper as the range of the potential becomes narrower.…”

“…The mechanical properties of the system have been also studied [11] and they reinforce this interpretation. Earlier studies of the Yukawa potential did not locate this glass-glass phenomenon [19], but it was subsequently realized that the screening parameters which had been studied were not large enough [50], and further calculations seem to give clear indications that both the SW and Yukawa potentials give the same typical behaviour [51], implying that this does not crucially depend either on the potential shape or the approximation used for calculating the structure factor. Thus, it is now believed that this glass-glass scenario, and the attendant dynamical laws, is essentially a universal feature of the very short-ranged attractive potential.…”

Colloidal glasses and gels: The interplay of bonding and caging

“…Nevertheless, it still appears possible to distinguish between the states hitherto known as repulsive and attractive glasses, which we propose to rename ''nonbonded'' and ''bonded' repulsive glasses, respectively. Another unresolved issue in the study of arrest in ''stickyparticle'' systems is how attractive glasses relate to gels (1,11,(17)(18)(19). Traditionally, the term ''gel'' is used in materials science to refer to a system that behaves like a soft solid (i.e., has a finite shear modulus in the low frequency limit) that nevertheless contains a very large amount (say, much more than 50%) of liquid.…”