Glassy dynamics in asymmetric binary mixtures of hard spheres

Abstract

The binary hard-sphere mixture is one of the simplest representations of a many-body system with competing time and length scales. This model is relevant to fundamentally understand both the structural and dynamical properties of materials, such as metallic melts, colloids, polymers and bio-based composites. It also allows us to study how different scales influence the physical behavior of a multicomponent glass-forming liquid; a question that still awaits a unified description. In this contribution, we report on distinct dynamical arrest transitions in highly asymmetric binary colloidal mixtures, namely, a single glass of big particles, in which the small species remains ergodic, and a double glass with the simultaneous arrest of both components. When the mixture approaches any glass transition, the relaxation of the collective dynamics of both species becomes coupled. In the single glass domain, spatial modulations occur due to the structure of the large spheres, a feature not observed in the two-glass domain. The relaxation of the self dynamics of small and large particles, in contrast, become decoupled at the boundaries of both transitions; the large species always displays dynamical arrest, whereas the small ones appear arrested only in the double glass. Thus, in order to obtain a complete picture of the distinct glassy states, one needs to take into account the dynamics of both species.

Rheology of colloidal and metallic glass formers

“…In colloidal suspensions and soft-matter systems, most studies focus on the regime of very size-disparate mixtures (see, e.g., Refs. [44][45][46][47][48][49][50][51][52][53][54] for studies of glassy dynamics and Refs. [55][56][57] for the linear and nonlinear rheology).…”

Multiple character of non-monotonic size-dependence for relaxation dynamics in polymer-particle and binary mixtures

“…In recent works [16,21], distinct scenarios are reported for the glass transition in asymmetric binary (colloidal) mixtures. In addition to the possibility of gel formation [16], the larger component can undergo a glass transition while the smaller one remains ergodic.…”

“…Another path is marked by simultaneous loss of ergodicity in both components and is therefore termed as a double glass transition. While the latter is marked by a strong coupling between the dynamics of the two species, the single glass state is ascribed to a decoupling of self-dynamics from collective dynamics at short length scales [16,21].…”

Effect of size disparity on the structure and dynamics of the small component in concentrated binary colloidal mixtures

“…Highly packed states of mixtures are interesting for applications since a large quantity of material occupies a relatively small volume. Glasses of concentrated binary mixtures of hard-sphere like colloids have been also studied recently 11,[17][18][19][20][21][22][23][24] . It has been shown in particular that mixing colloids of sufficiently different size can substantially affect the formation of glasses.…”

“…In the regime of mixed states, complex and anomalous dynamic phenomena have been observed 29,30 , under conditions which are particularly relevant for realistic systems such as cellular 31 or ionic liquids 32 , among others. Due to technical difficulties related with the limited optical resolution of confocal microscopy, or a) Electronic mail: mlaurati@fisica.ugto.mx the complexity of introducing selectivity in scattering techniques, experimental characterization of the structure and dynamics of concentrated binary colloidal mixtures has mainly focused on the study of the large component 23,[25][26][27][28] , with a few exceptions in which, however, only the dynamics of the small particles for specific size ratios or a limited number of compositions were investigated 11,24,29,30 . Here we report a systematic experimental investigation of the microscopic structural organization and the single-particle dynamics of the small component in glassy binary colloidal mixtures with moderate to large size ratios and different compositions.…”