Microgels at fluid-fluid interfaces for food and drinks

Murray, Brent S.

doi:10.1016/j.cis.2019.101990

Cited by 53 publications

(39 citation statements)

References 129 publications

(179 reference statements)

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“…All in all, our study opens the way for the investigation of microgels at the interface as a simple realization of 2D elastic particles. We expect that the evidence reported here will have important consequences on the study of twodimensional elastic objects at the fundamental level [90,91] and for the clever design of composite materials [92][93][94].…”

Section: Discussionmentioning

confidence: 80%

Microgels at Interfaces Behave as 2D Elastic Particles Featuring Reentrant Dynamics

et al. 2020

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Soft colloids are increasingly used as model systems to address fundamental issues such as crystallization and the glass and jamming transitions. Among the available classes of soft colloids, microgels are emerging as the gold standard. Since their great internal complexity makes their theoretical characterization very hard, microgels are commonly modeled, at least in the small-deformation regime, within the simple framework of linear elasticity theory. Here we show that there exist conditions where its range of validity can be greatly extended, providing strong numerical evidence that microgels adsorbed at an interface follow the two-dimensional Hertzian theory, and hence behave like 2D elastic particles, up to very large deformations, in stark contrast to what found in bulk conditions. We are also able to estimate Young's modulus of the individual particles and, by comparing it with its counterpart in bulk conditions, we demonstrate a significant stiffening of the polymer network at the interface. Finally, by analyzing dynamical properties, we predict multiple reentrant phenomena: By a continuous increase of particle density, microgels first arrest and then refluidify due to the high penetrability of their extended coronas. We observe this anomalous behavior in a range of experimentally accessible conditions for small and loosely cross-linked microgels. The present work thus establishes microgels at interfaces as a new model system for fundamental investigations, paving the way for the experimental synthesis and research on unique highdensity liquidlike states. In addition, these results can guide the development of novel assembly and patterning strategies on surfaces and the design of novel materials with desired interfacial behavior.

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Section: Discussionmentioning

confidence: 80%

Microgels at Interfaces Behave as 2D Elastic Particles Featuring Reentrant Dynamics

et al. 2020

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“…Furthermore, the topdown approach may offer some level of control over the microgel particle properties by fine-tuning the macrogel structure, since at least some characteristics of the microgel are expected to be inherited from the initial macrogel, e.g. the internal cross-link density in the microgel (Murray 2019a). Thus specific ''gel recipes'' can be designed in order to produce macrogels with a certain desired microscopic structure: for example, more brittle, highly porous heterogenous gels break down more easily to give microgels with a narrower and smaller size distribution compared to gels which are elastic and homogenous (Saavedra Isusi et al 2019).…”

Section: Complex Formationmentioning

confidence: 99%

“…compressive, tensile or shear) and its magnitude applied during top-down processing also affects how a gel breaks down (Saavedra Isusi et al 2019). Processing may deform and alter the gel network structure, often leading to a more open structure in the microgel particles (Murray 2019a). It has been reported that pectin-based microgels are more easily broken down when conditions favouring extensional forces were employed, for example laminar flow in a rotorstator device, since the tensile strength of the gels was lower than the compressive strength (Saavedra Isusi et al 2019).…”

Section: Complex Formationmentioning

confidence: 99%

“…Altering the synthetic method and conditions of formation allows one to access to a broad range of gel particles with specific morphologies, sizes and microstructures, depending on the desired application. This is reflected by the huge potential impact of microgels in a wide variety of industries, such as food (Murray 2019a), cosmetics (Boularas et al 2018), medicine (Agrawal and Agrawal 2018), and agriculture (Abd El-Rehim 2005).…”

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Advances in the use of microgels as emulsion stabilisers and as a strategy for cellulose functionalisation

2020

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Microgel particles have recently emerged as an alternative route to emulsion stabilisation. Classed as soft colloidal particles, their ability to swell to differing degrees in certain solvents and to rearrange once attached to an interface makes them highly suitable for systems requiring long-term stabilization, such as formulations in the food, agricultural, cosmetic and pharmaceutical industries. Microgels made with biocompatible polymers such as proteins and polysaccharides in particular offer an environmental advantage and currently form a very active area of research. Cellulose, being a natural, biodegradable polymer, is an attractive ingredient for gels and microgels. However, its use as a functional material is often somewhat hindered by its insolubility in water and most other organic solvents. Furthermore, the surface activity of cellulose has proven difficult to harness and therefore its ability to act as an emulsion stabiliser has been almost exclusively applied to oil-in-water (O/W) emulsions, with very few reports on its water in oil (W/O) activity. This review aims to summarise some of the recent progress made in the microgel field including their ability to act as emulsion stabilisers, with a focus on cellulose microgels (CMGs). A brief overview of cellulose processing is also given, describing the dissolution and reprecipitation routes used to functionalise cellulose without covalent modification and the potential for cellulose particles and CMGs to act as O/W and W/O emulsion stabilisers. Graphic abstract

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“…24,25 This however rises the question if due to the solvent penetrability the definition of any contact angle has any sense in such systems. 11,14 Anyhow, it is evident that alternative approaches are required to understand particle conformations at interfaces.…”

Section: Introductionmentioning

confidence: 99%

Deformability and solvent penetration in soft nanoparticles at liquid-liquid interfaces

Arismendi‐Arrieta

Moreno

2020

Journal of Colloid and Interface Science

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Soft nanoparticles hold promise as smart emulsifiers due to their high degree of deformability, permeability and stimuli responsive properties. By means of large-scale simulations we investigate the structural properties of nanogels at liquid-liquid (A-B) interfaces and the miscibility of the liquids inside the nanogels, covering the whole range of interfacial strength from the limit of single-liquid to the case of stiff interfaces. To study the role of the internal architecture and deformability of the nanogel we simulate a realistic disordered and an ideal regular network, for a broad range of cross-linking degrees. Unlike in previous investigations on liquid miscibility, excluded volume interactions are considered for both the monomers and the explicit solvent particles. The nanogel permeability is analysed by using an unbiased grid representation that accounts for the surface fluctuations and adds to the density profiles the exact number of liquid particles inside the nanogel. The better packing efficiency of the regular network leads 1 arXiv:1911.06725v1 [cond-mat.soft] 15 Nov 2019to higher values of the total liquid uptake and the invasive capacity (A-particles in B-side and viceversa) than in the disordered network, though differences vanish in the limit of rigid interfaces. Uptake and invasion are optimized at a cross-linking degree that depends on the interfacial strength, tending to ∼ 15 − 20 for moderate and stiff interfaces. As the interfacial strength increases, the miscibility inside the nanogel is enhanced by a factor of up to 5 with respect to the bare interface, with the disordered networks providing a better mixing than their ideal counterparts. The emerging scenario reported here provides general guidelines for tuning the shape, uptake, invasive, and mixing capacities of nanogels adsorbed at liquid-liquid interfaces.

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Microgels at fluid-fluid interfaces for food and drinks

Cited by 53 publications

References 129 publications

Microgels at Interfaces Behave as 2D Elastic Particles Featuring Reentrant Dynamics

Microgels at Interfaces Behave as 2D Elastic Particles Featuring Reentrant Dynamics

Advances in the use of microgels as emulsion stabilisers and as a strategy for cellulose functionalisation

Deformability and solvent penetration in soft nanoparticles at liquid-liquid interfaces

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