Multi-responsive ionic liquid emulsions stabilized by microgels

Monteillet, Hélène; Workamp, Marcel; Li, Xiaohua; Schuur, Boelo; Kleijn, J. Mieke; Leermakers, F.A.M.; Sprakel, Joris

doi:10.1039/c4cc04990j

Cited by 35 publications

(34 citation statements)

References 48 publications

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“…They can thus be used to stabilize emulsions. [6][7][8][9][10][11][12][13] Microgels composed of poly(N-isopropylacrylamide) possess special properties (e.g. softness, deformability and stimuli-sensitivity towards external parameters) that differentiate the respective emulsions from the ones stabilized with solid particles.…”

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confidence: 99%

New Insight into Microgel-Stabilized Emulsions Using Transmission X-ray Microscopy: Nonuniform Deformation and Arrangement of Microgels at Liquid Interfaces

2014

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Microgel-covered interfaces, e.g., in emulsions, have attracted much interest lately. Different imaging techniques have been used to image these interfaces, either flat or curved, to investigate their properties and appearance. Techniques such as cryogenic scanning electron microscopy (cryo-SEM) and confocal microscopy have provided valuable insight into microgel-covered systems but still have some disadvantages such as part of the microgels being trapped in vitrified liquid or the need for fluorescent markers. Some of these disadvantages can be overcome by using transmission X-ray microscopy (TXM), which has the advantage of allowing the investigation of adsorbed and free microgels simultaneously. We used TXM to acquire tomographic image series of microgel-covered droplets and calculated 3D reconstructions from these image stacks. As a result, we could show that microgels deform anisotropically and penetrate the oil droplets in the hydrated state. Additionally, 3D reconstruction gives an idea of the arrangement of microgels adsorbed to oil droplets and reveals that droplet stabilization is possible without full coverage of the interface with polymer segments.

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confidence: 99%

New Insight into Microgel-Stabilized Emulsions Using Transmission X-ray Microscopy: Nonuniform Deformation and Arrangement of Microgels at Liquid Interfaces

2014

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“…These form easily [6,10,11], and can be tuned in situ, for instance by altering solvent properties, such as temperature and pH [12][13][14][15][16][17]. This has been demonstrated with emulsions created with poly(Nisopropylacrylamide) (pNIPAM) particles.…”

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confidence: 99%

Adsorption of soft particles at fluid interfaces

2015

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Soft particles can be better emulsifiers than hard particles because they stretch at fluid interfaces. This deformation can increase adsorption energies by orders of magnitude relative to rigid particles. The deformation of a particle at an interface is governed by a competition of bulk elasticity and surface tension. When particles are partially wet by the two liquids, deformation is localized within a material-dependent distance L from the contact line. At the contact line, the particle morphology is given by a balance of surface tensions. When the particle radius R L, the particle adopts a lenticular shape identical to that of an adsorbed fluid droplet. Particle deformations can be elastic or plastic, depending on the relative values of the Young modulus, E, and yield stress, σp. When surface tensions favour complete spreading of the particles at the interface, plastic deformation can lead to unusual fried-egg morphologies. When deformable particles have surface properties that are very similar to one liquid phase, adsorption can be extremely sensitive to small changes of their affinity for the other liquid phase. These findings have implications for the adsorption of microgel particles at fluid interfaces and the performance of stimuli-responsive Pickering emulsions.Emulsions are vital in many fields, including foods, cosmetics, pharmaceuticals, and oil recovery [1][2][3][4]. Emulsions are typically stabilised by molecular surfactants, but they can also be stabilised with microparticles [5,6]. The resulting Pickering emulsions have many benefits over regular emulsions. In particular, they are highly stable and avoid the use of potentially harmful or irritating surfactants [5].A recent development is the use of soft colloidal particles (typically microgels) to make Pickering emulsions [6][7][8][9]. These form easily [6,10,11], and can be tuned in situ, for instance by altering solvent properties, such as temperature and pH [12][13][14][15][16][17]. This has been demonstrated with emulsions created with poly(Nisopropylacrylamide) (pNIPAM) particles. Since pNI-PAM undergoes a reversible swelling/shrinking transition at a temperature close to body temperature, they have potential for stimuli-responsive release of encapsulated active ingrediants for drug delivery [6].A key difference between soft and hard particles as Pickering emulsifiers is that soft particles stretch as they adsorb [8,18]. For example, microgel particles can have a much larger diameter at the interface than they do in the bulk. The extent of stretching depends on the crosslinking ratio of the hydrogel [18,23,24]. Figure 1 shows a side view of a p(NIPAM) microgel at a water/n-decane interface using cryo-SEM after freeze-fracture [25]. While these soft particles have a spherical shape in solution, they are strongly deformed at the interface. The central region of the particle remains somewhat spherical, especially the part exposed to the bulk water phase. However, the particles are pulled strongly outward at the contact line, and a thin film of ...

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“…Thermo‐, pH‐, and magnetic‐field‐responsive microgels based on poly(ethylene glycol) were developed by Chen et al Therein, magnetic attapulgite/Fe 3 O 4 nanoparticles were introduced into the dual‐responsive microgel network by in situ polymerization 176. Sprakel and co‐workers reported magnetic‐field‐, pH‐, and temperature‐responsive microgel particles, which were shown to efficiently stabilize oil–water interfaces 177…”

Section: Multi‐stimuli‐responsive Particlesmentioning

confidence: 99%

Multi-Stimuli-Responsive Polymer Materials: Particles, Films, and Bulk Gels

Cao

Wang

2016

The Chemical Record

172

109

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Stimuli-responsive polymers have received tremendous attention from scientists and engineers for several decades due to the wide applications of these smart materials in biotechnology and nanotechnology. Driven by the complex functions of living systems, multi-stimuli-responsive polymer materials have been designed and developed in recent years. Compared with conventional single- or dual-stimuli-based polymer materials, multi-stimuli-responsive polymer materials would be more intriguing since more functions and finer modulations can be achieved through more parameters. This critical review highlights the recent advances in this area and focuses on three types of multi-stimuli-responsive polymer materials, namely, multi-stimuli-responsive particles (micelles, micro/nanogels, vesicles, and hybrid particles), multi-stimuli-responsive films (polymer brushes, layer-by-layer polymer films, and porous membranes), and multi-stimuli-responsive bulk gels (hydrogels, organogels, and metallogels) from recent publications. Various stimuli, such as light, temperature, pH, reduction/oxidation, enzymes, ions, glucose, ultrasound, magnetic fields, mechanical stress, solvent, voltage, and electrochemistry, have been combined to switch the functions of polymers. The polymer design, preparation, and function of multi-stimuli-responsive particles, films, and bulk gels are comprehensively discussed here.

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Multi-responsive ionic liquid emulsions stabilized by microgels

Cited by 35 publications

References 48 publications

New Insight into Microgel-Stabilized Emulsions Using Transmission X-ray Microscopy: Nonuniform Deformation and Arrangement of Microgels at Liquid Interfaces

New Insight into Microgel-Stabilized Emulsions Using Transmission X-ray Microscopy: Nonuniform Deformation and Arrangement of Microgels at Liquid Interfaces

Adsorption of soft particles at fluid interfaces

Multi-Stimuli-Responsive Polymer Materials: Particles, Films, and Bulk Gels

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