Interfacial rheology of model particles at liquid interfaces and its relation to (bicontinuous) Pickering emulsions

Abstract

Interface-dominated materials are commonly encountered in both science and technology, and typical examples include foams and emulsions. Conventionally stabilised by surfactants, emulsions can also be stabilised by micron-sized particles. These so-called Pickering-Ramsden (PR) emulsions have received substantial interest, as they are model arrested systems, rather ubiquitous in industry and promising templates for advanced materials. The mechanical properties of the particle-laden liquid-liquid interface, probed via interfacial rheology, have been shown to play an important role in the formation and stability of PR emulsions. However, the morphological processes which control the formation of emulsions and foams in mixing devices, such as deformation, break-up, and coalescence, are complex and diverse, making it difficult to identify the precise role of the interfacial rheological properties. Interestingly, the role of interfacial rheology in the stability of bicontinuous PR emulsions (bijels) has been virtually unexplored, even though the phase separation process which leads to the formation of these systems is relatively simple and the interfacial deformation processes can be better conceptualised. Hence, the aims of this topical review are twofold. First, we review the existing literature on the interfacial rheology of particle-laden liquid interfaces in rheometrical flows, focussing mainly on model latex suspensions consisting of polystyrene particles carrying sulfate groups, which have been most extensively studied to date. The goal of this part of the review is to identify the generic features of the rheology of such systems. Secondly, we will discuss the relevance of these results to the formation and stability of PR emulsions and bijels.

Building Reconfigurable Devices Using Complex Liquid–Fluid Interfaces

“…This overlooks two key factors: i) in the case of emulsions, particle adsorption may be facilitated by turbulent eddies and ii) there are a number of cases where particles can stabilize emulsions even when they are not surface active . Further comments have also been made elsewhere . Regardless, the results do echo the findings of other studies that, in some instances, particle adsorption does not alter oil–water surface tension …”

“…Intuitively, one expects the reduction in surface energy given by Equation to give rise to a reduction in the macroscopic surface tension of a liquid–fluid interface. The two most widely used tools to study the effect of NP adsorption are pendant drop tensiometry ( Figure a) and the Langmuir trough used in conjunction with a Wilhelmy plate (Figure b) . The effect of adsorption on the liquid–fluid interfacial tension is typically given in terms of a measured interfacial tension, γ′, or a surface pressure, Π, which can be defined by comparison with the surface tension of the liquid–fluid interface with no surface‐active species present, γ clean , such that…”

“…Likewise, the rheology and mechanics of complex interfaces has been discussed extensively in several recent reviews . Thijssen and Vermant recently produced a review dedicated to the rheology of particles at liquid–fluid interfaces with an emphasis on micrometer‐sized particles and bijel formation . Shi and Russell focused specifically on nanomaterial assembly at liquid–liquid interfaces .…”

Yield stress of aerated cement paste

“…We will recall here the main literature results. To get a more complete understanding of this complex issue, one can read the recents reviews from Thijssen and Vermant [33], Maestro [34] and Pitois and Rouyer [35].…”

Colloids at Fluid Interfaces

“…Future developments of the colloidal confinement could enable fabrication of biomimetic and active materials, which could respond to an external perturbation, and even alter their environment. This requires an understanding of the physicochemical bases underlying the behavior of such complex interfaces, which requires a deeper understanding of the physicochemical bases governing the assembly of quasi-2D materials, as well as on the dynamic and equilibrium properties of the assembled systems [3,19,[23][24][25][26][27][28][29][30][31][32][33][34][35][36].…”