Kinetic arrest and glass-glass transition in short-ranged attractive colloids

Abstract

A thermally reversible repulsive hard-sphere to sticky-sphere transition was studied in a model colloidal system over a wide volume fraction range. The static microstructure was obtained from high resolution small angle x-ray scattering, the colloid dynamics was probed by dynamic x-ray and light scattering, and supplementary mechanical properties were derived from bulk rheology. At low concentration, the system shows features of gas-liquid type phase separation. The bulk phase separation is presumably interrupted by a gelation transition at the intermediate volume fraction range. At high volume fractions, fluid-attractive glass and repulsive glass-attractive glass transitions are observed. It is shown that the volume fraction of the particles can be reliably deduced from the absolute scattered intensity. The static structure factor is modeled in terms of an attractive square-well potential, using the leading order series expansion of Percus-Yevick approximation. The ensemble-averaged intermediate scattering function shows different levels of frozen components in the attractive and repulsive glassy states. The observed static and dynamic behavior are consistent with the predictions of a mode-coupling theory and numerical simulations for a square-well attractive system.

Absence of equilibrium cluster phase in concentrated lysozyme solutions

“…In addition, S M (q) displays a peak at small angles, and the position of the peak q m is related to the average distance between the neighboring particles, d Ϸ 2 /q m . In contrast, when particles attract each other, they could form clusters or aggregates, which are manifested by an increase of S M (0), being proportional to the mean cluster mass and number density (17). For a nonaggregating system, q m increases with c and the low angle peak in S M (q) moves to higher q values.…”

Development of an ultra-small-angle X-ray scattering instrument for probing the microstructure and the dynamics of soft matter

“…The incident intensity is recorded by measuring the scattering from a thin mica window which separates the vacuum in the incident section and sample stage. Sztucki et al, 2006). The structure and dynamics of these shortranged attractive colloids is a topic of contemporary interest (Dawson et al, 2001;Sciortino & Tartaglia, 2005).…”

“…PðqÞ is the polydisperse form factor describing the spherical shape of the particles. The interparticle interaction is described by the structure factor, SðqÞ, for a square-well system calculated using the leading order series expansion of the Percus-Yevick approximation (Dawson et al, 2001;Narayanan et al, 2006;Sztucki et al, 2006). S c ðqÞ describes the structure factor of the colloidal clusters Sztucki et al, 2006).…”

“…As a result, USAXS is used to study multi-level structural features in nano-materials, microstructure and interactions in soft matter etc. (Long et al, 1991;Beaucage, Kammler, Mueller et al, 2004;Narayanan et al, 2006;Sztucki et al, 2006). However, for probing micron scale structural information in crystalline and semicrystalline systems, a high-resolution pinhole SAXS camera with a two-dimensional detector has certain advantages (Yagi & Inoue, 2003;Petukhov et al, 2006).…”

Interaction of Human Serum Albumin and Silica at the air-water interface

“…No further changes occur over a three hour period. The fringe structure shows a polydispersity of about 20% and a mean particle radius of 41 Å calculated from fitting the data of Figure 5 with a Sztuki model (11). This radius and the manufacturer's weight fraction give a consistent particle number of approx.…”