Microgels Adsorbed at Liquid–Liquid Interfaces: A Joint Numerical and Experimental Study

Camerin, Fabrizio; Fernández-Rodríguez, Miguel Ángel; Rovigatti, Lorenzo; Antonopoulou, Maria-Nefeli; Gnan, Nicoletta; Ninarello, Andrea; Isa, Lucio; Zaccarelli, Emanuela

doi:10.1021/acsnano.9b00390

Cited by 111 publications

(228 citation statements)

References 78 publications

(173 reference statements)

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“…However, upon contact with the interface, the lignin particles were deformed and flattened, and formed a 2D surfactant sheet with an extreme aspect ratio ( Figure A; Figure S1, Supporting Information). Different from conventional soft particles whose deformations were limited by particle elasticity due to covalent crosslinking, the lignin particles were completely spread out at the interface in the presence of weak crosslinking, i.e., hydrogen bonding. The driving force of spreading came from the reduction in interfacial energy by maximizing the surfactant covered area and decreasing the unfavorable contacts between oil and water.…”

Section: Resultsmentioning

confidence: 96%

Section: Resultsmentioning

confidence: 99%

“…Recently, the unique properties of soft microgel particles and their function in stabilizing Pickering emulsions have attracted increasing attention . Different from traditional rigid particles (inorganic particles), soft polymer particles preserve the rigid spherical shape in bulk solution but strongly deform, swell, and flatten at an oil/water interface . As opposed to conventional soft particles that are covalently crosslinked, this work created a new “soft particle” that is physically interconnected and prepared from a biomass‐derived material—lignin, which further formed large‐scale surfactant sheets by reassembly and flattening at the interface.…”

Section: Resultsmentioning

confidence: 99%

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A Cast Net Thrown onto an Interface: Wrapping 3D Objects with an Interfacially Jammed Amphiphilic Sheet

Cui

Gao

Bowland

et al. 2020

Adv Materials Inter

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with the encapsulant being either solid elastic films [12][13][14][15][16] or solid-like jammed films of functional particles. [17][18][19][20][21] These films are rigid enough to stabilize nonequilibrium morphologies of the wrapped liquid, thus breaking the limit of equilibrium morphologies and further creating new shapes of wrapped, encapsulated fluids with inimitable functionalities.For traditional liquid-phase technologies, a liquid-like layer of surfactant or particles is usually used for wrapping and stabilizing liquid droplets. [22][23][24] Recent studies show that sufficiently thin elastic sheets offer a novel path to spontaneously wrap liquid droplets using capillary forces, where the elastic energy of curving sheets is balanced by the reduction of interfacial energy. [15,16,25,26] Although negligible at macroscopic scales, capillary forces become dominant and are able to bend the elastic sheets when the bending rigidity of elastic sheets is vanishingly small. [12,15,25] The robust elastic sheets allow the liquid drops to be trapped in nonequilibrium 3D shapes via a process that is usually referred to as capillary origami. [12,16,26] In previous wrapping studies, the final encapsulated 3D geometry was almost solely determined by the initial geometry of the flat thin elastic sheets, which made the process complicated and lacked versatility. The elastic sheets in previous reports were often conventional polymer thin films whose interfacial activities were too weak to manipulate the interfacial tension and participate in morphology evolution. [12,15,16] A large-scale elastic sheet [27] with a significant interfacial activity is desired to manipulate the interface that can adapt to various nonequilibrium shapes by external influence-a stimulant for evolved morphologies at the interface.Here, we report in situ formation of a large-scale surfactant sheet with strong interfacial activities by interfacial jamming of poorly soluble amphiphilic lignin macromolecules in particulate form at an oil/water interface. The amphiphilic nature of the surfactant sheet enables wrapping of either water or oil droplets, while its rigidity allows it to hold the liquid phases in various nonequilibrium morphologies. The surfactant sheet is physically networked by reversible hydrogen bonding and π-π interaction, which endows it with transforming and self-healing ability. The strong interfacial activity of the surfactant sheet results in an interfacial instability, which drives evolution of interfacial morphology and novel wrapped microstructures.Wrapping a 3D object with a 2D sheet is not uncommon, but the wrapping behavior becomes complex and interesting when the sheet is bestowed with strong interfacial activities. Amphiphilic lignin macromolecules, isolated from biomass, form a scalable thin surfactant sheet at an oil/water interface through the interfacial jamming process. The process marks three distinct stages of interfacial behavior: a) diffusive assembly, b) viscous assembly with retarded mobility, and c) flexible yet irre...

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Section: Resultsmentioning

confidence: 96%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

A Cast Net Thrown onto an Interface: Wrapping 3D Objects with an Interfacially Jammed Amphiphilic Sheet

Cui

Gao

Bowland

et al. 2020

Adv Materials Inter

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“…Indeed, our polymer density profiles correlate very well with the results reported 20 for microgels with fried-egg-like shapes. 28,29,52,57 Even though these simulations correspond to nanogels that are far from the overlap concentration, such deformable objects are intrinsically permeable. This implies that droplet adhesion can be facilitated or inhibited by tunning the invasive capacity of such particles.…”

Section: Solvent Penetration In Deformable Porous Cavitiesmentioning

confidence: 99%

“…1,26,27 The latter, as a mesoscopic simulation approach, allows for a direct mapping to Flory-Huggins lattice models and has been recently employed to understand swelling or deswelling of microgels at suspensions, 28 and their behavior at liquid interfaces. [29][30][31][32][33] The former is rarely used due to its huge computational cost, originating from the longer diffusion times required with respect to the case of fully penetrable DPD particles. Regarding the second element, a critical point in current models is that a regular network (e.g.…”

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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Controlled Adsorption of Cellulose Nanofibrils on Fluid–Fluid Interfaces

Kim

Han

You

et al. 2023

Adv Materials Inter

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applications, such as emulsion stabilization, [1] membrane transduction, [2,3] nanocomposites, [4] drug delivery, [5,6] and the fabrication of advanced materials with micro-and nanostructures. [7][8][9][10] In general, adsorption at the interface is explained by the thermodynamic energy difference ΔE ad = − Aγ ow (1 − |cos θ|), where A is the projection area of the particle in contact with the interface, γ ow is the interfacial tension, and θ is the contact angle. Microparticles and sub-micron particles are bound irreversibly at the interface because of the enormous reduction in interfacial energy (typically thousands to millions [10 3 -10 6 ] times the thermal energy). [16][17][18]20,29] Thus, nearly any particle with a proper size and surface properties, unless they are superhydrophilic or superhydrophobic with nanometer size, is readily adsorbed at the interface in an irreversible manner.However, non-adsorbing particles are frequently observed even with a large binding energy, and in this case, external forces such as mechanical, thermal, and chemical actuation are required for successful particle adsorption. [30][31][32] An example of difficult adsorption is the low interfacial tension of an oil/ water interface. It was consistently found that the lower the interfacial tension at the oil/water interface, the more difficult the adsorption of various particles such as nanocellulose (i.e., cellulose nanocrystal (CNC) [16] and cellulose nanofibrils (CNFs) [18,33,34] ), silica, [17] magnetite, [19] and graphene oxide. [21] A typical explanation for the difficult adsorption at low interfacial tension is the relatively low binding energy. [16][17][18][19]21] However, the binding energy is still several thousand times larger than the thermal energy-even at low interfacial tensions (≈5 mN m −1 ) (Figure 1a). Thus, the relationship between difficult adsorption and substantial adsorption energies is contradictory. Accordingly, conventional thermodynamic theories alone cannot clearly explain the difficult adsorption process. It might be more closely related with the "process" of particle adsorption rather than differences in energy "state".Before a particle adsorbs at an interface, a few intermediate steps occur. Initially, particles are transported to a nearby drop by external shear flow, [37] Brownian motion, [38] or external fields, such as gravity [30] and an electric field. [39] As the gap between the solid and drop surfaces becomes narrower, the fluid in the gap is drained out. [30,40] It is well known that drainage dynamics play a major role in the interfacial adsorption of particles as Adsorption of particles at fluid-fluid interfaces is of great scientific and industrial importance, encompassing a variety of applications, from the stabilization of bubbles and emulsions to the fabrication of sophisticated materials with micro-and nanostructures. The enormous adsorption energy of a particle is believed to be the origin of adsorption, but it cannot fully explain many systems that do not adsorb, even with large ads...

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Microgels Adsorbed at Liquid–Liquid Interfaces: A Joint Numerical and Experimental Study

Cited by 111 publications

References 78 publications

A Cast Net Thrown onto an Interface: Wrapping 3D Objects with an Interfacially Jammed Amphiphilic Sheet

A Cast Net Thrown onto an Interface: Wrapping 3D Objects with an Interfacially Jammed Amphiphilic Sheet

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

Controlled Adsorption of Cellulose Nanofibrils on Fluid–Fluid Interfaces

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