Microgels at droplet interfaces of water-in-oil emulsions—challenges and progress

Stock, Sebastian; Klitzing, Regine von

doi:10.1016/j.cocis.2021.101561

Cited by 35 publications

(26 citation statements)

References 101 publications

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“…Nano- and microgels based on poly- N -isopropylacrylamide (pNIPAM) have a high interfacial activity 14 and at the same time maintain their thermo-responsiveness once adsorbed to air- 15 – 17 , liquid- 18 – 21 , or solid interfaces 22 – 25 . They can be used to prepare smart emulsions 18 , 19 , 26 – 28 that can be broken on demand as a function of external stimuli such as temperature and pH 18 , 19 , 29 – 32 .…”

Section: Introductionmentioning

confidence: 99%

In-situ study of the impact of temperature and architecture on the interfacial structure of microgels

et al. 2022

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The structural characterization of microgels at interfaces is fundamental to understand both their 2D phase behavior and their role as stabilizers that enable emulsions to be broken on demand. However, this characterization is usually limited by available experimental techniques, which do not allow a direct investigation at interfaces. To overcome this difficulty, here we employ neutron reflectometry, which allows us to probe the structure and responsiveness of the microgels in-situ at the air-water interface. We investigate two types of microgels with different cross-link density, thus having different softness and deformability, both below and above their volume phase transition temperature, by combining experiments with computer simulations of in silico synthesized microgels. We find that temperature only affects the portion of microgels in water, while the strongest effect of the microgels softness is observed in their ability to protrude into the air. In particular, standard microgels have an apparent contact angle of few degrees, while ultra-low cross-linked microgels form a flat polymeric layer with zero contact angle. Altogether, this study provides an in-depth microscopic description of how different microgel architectures affect their arrangements at interfaces, and will be the foundation for a better understanding of their phase behavior and assembly.

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Section: Introductionmentioning

confidence: 99%

In-situ study of the impact of temperature and architecture on the interfacial structure of microgels

et al. 2022

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“…15,16 Very recently, Stock et al summarized the development and stabilization mechanism of microgels at the oil-water interface in water-in-oil (W/O) emulsions. 17 Whereas very few studies have focused on the preparation of W/O emulsions using inherently hydrophilic microgels as the sole emulsier, because the requirement of oil with high polarity strongly limits their applications. 18,19 Normally, the intermediate wettability of particles and an external supply of energy (such as homogenization or ultrasonication) are necessary to facilitate particle adsorption at the uid-uid interface, consequently yielding a signicant increase in the surface coverage of particles and resulting in better emulsion stability.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Non-covalent reconfigurable microgel colloidosomes with a well-defined bilayer shell

et al. 2022

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“…In other applications, MGs may act as drug or catalyst delivery vehicles to the interface [ 16 ], and ultimately their responsivity can enable emulsion breakage on demand [ 24 ]. However, a drawback of their application is that most of the common MGs fall under the aforementioned category of hydrophilic particles and are not able to stabilize w/o emulsions on their own [ 15 , 25 ]. A solution to still ensure the formation of w/o emulsions is to deploy a second stabilizing agent.…”

Section: Introductionmentioning

confidence: 99%

Maximum Incorporation of Soft Microgel at Interfaces of Water in Oil Emulsion Droplets Stabilized by Solid Silica Spheres

et al. 2022

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The incorporation of soft hydrophilic particles at the interface of water in non-polar oil emulsion droplets is crucial for several applications. However, the stabilization of water in non-polar oil emulsions with hydrophilic soft material alone is, besides certain exceptions, not possible. In our previous works, we showed that stabilizing the emulsions with well-characterized spherical hydrophobic silica nanospheres (SNs) and soft equally charged microgel particles (MGs) is a robust strategy to stabilize w/o emulsions while still incorporating a large amount of MGs at the interface. In the present study, we address the question of what the maximum amount of MGs at the interface in these kinds of emulsion droplets can be. By using well-characterized mono-disperse SNs, we are able to calculate the fraction of interface covered by the SNs and complementary that of the present MG. We found that it is not possible to decrease the SN coverage below 56% irrespective of MG softness and SN size. The findings elucidate new perspectives to the broader topic of soft/solid stabilized emulsions.

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Microgels at droplet interfaces of water-in-oil emulsions—challenges and progress

Cited by 35 publications

References 101 publications

In-situ study of the impact of temperature and architecture on the interfacial structure of microgels

In-situ study of the impact of temperature and architecture on the interfacial structure of microgels

Non-covalent reconfigurable microgel colloidosomes with a well-defined bilayer shell

Maximum Incorporation of Soft Microgel at Interfaces of Water in Oil Emulsion Droplets Stabilized by Solid Silica Spheres

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