Microgels and fractal structures at interfaces and surfaces

Vilgis, Thomas A.; Stapper, Michael

doi:10.1007/s100510050226

Cited by 9 publications

(8 citation statements)

References 19 publications

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“…Second, aer arrival at the heptane-water interface, the microgels deformed and spread at the interface, and this dynamic spreading process was mainly dominated by the microgels' deformability. 21,59,60 It is worthy pointing out that all of our measurements were carried out at a microgel concentration of 5 Â 10 À3 g mL À1 . We have shown that at this concentration and at a temperature of 317 K, diffusion has limited inuence on the microgels adsorption behaviours to the heptane-water interface.…”

Section: Resultsmentioning

confidence: 99%

Poly(N-isopropylacrylamide) microgels at the oil–water interface: temperature effect

Richtering

Ngai

2014

Soft Matter

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Understanding the interfacial properties of soft poly(N-isopropylacrylamide) (PNIPAM) microgels covering an oil-water interface is essential for engineering stimuli-responsive emulsions stabilized by soft microgel particles. This study presents a systematic study on the interfacial properties of the PNIPAM-microgel-laden heptane-water interface as a function of temperature. We measured the interfacial tensions as well as dilatational rheology properties of the microgel-laden heptane-water interface using a pendant drop tensiometer. From fresh droplet experiments, the anomalous interfacial tension minima of the microgels covered oil-water interface were observed around the volume phase transition temperature (VPTT) of the PNIPAM microgels. Such interfacial tension minima are observable regardless of the microgel aggregates. Both dynamic and static parameters contributed to the observed interfacial tension minima around VPTT. The PNIPAM microgel deformability dynamically dominated the microgel spreading at the heptane-water interface in the early states, while PNIPAM microgel packing and interactions dominated the final static equilibrium states. Combining the interfacial tension and the dilatational rheology properties, we propose that the microgels would approach three distinctive states at temperatures below, around, and above VPTT at the heptane-water interface. Single droplet experiments further demonstrate that there exists an irreversible transition among these three states. The results of this study deepen our understanding of soft, porous, and deformable microgels' behaviors at the oil-water interface and have important implications for engineering microgels as stimuli-responsive emulsion stabilizers.

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Section: Resultsmentioning

confidence: 99%

Poly(N-isopropylacrylamide) microgels at the oil–water interface: temperature effect

Richtering

Ngai

2014

Soft Matter

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“…When the above formula for the microgel extension equations (8,10) are extrapolated to R a deformation of order one is recovered ensuring a smooth crossover to the macroscopic regime. The exponent 1/ν − 1 2/3 reflects the non-linear elasticity of the chains.…”

Section: Two-dimensional Spreading: a Polymer Ring On A Thick Fibermentioning

confidence: 99%

“…When adsorption proceeds from a solution [4], a concentration profile develops that extends over one bulk correlation length. In first attempts one of us has constructed a scaling approach for adsorption of branched structures [8]. Provided that D is smaller than the bulk correlation length, the reduction in surface tension a e-mail: johner@ics.u-strasbg.fr with respect to pure solvent is dominated by this proximal layer and ∆γ ∼ −k B T /D 2 .…”

Section: Introductionmentioning

confidence: 99%

Gels at interfaces

Joanny

Johner

Vilgis

2001

The European Physical Journal E

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We discuss the adsorption of polymer gels on flat surfaces. Even in cases of complete wetting where the spreading power S is positive and where an equivalent liquid would spread, the elastic stresses due to the gel deformation upon adsorption oppose the spreading. The competition between elasticity characterized by the bulk shear modulus G and capillarity characterized by the spreading power S defines a typical length scale = S/G for the deformation in the gel. For loose gels can be of the order of 1 µm. Macroscopic gels larger than deform only at their edges over a region of size . Microscopic gels smaller than show a finite deformation despite the elastic stresses. The elastic stresses limit the spreading of the polymer, but solvent can be sucked out of a swollen gel by wetting the surface. The thin solvent film can extend rather far from the gel edge and carry solvent. We calculate the kinetics of the solvent film formation and of the solvent transfer from a more swollen gel to a less swollen gel.

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“…Increased distortion from spherical increases the interfacial area occupied by the microgel and thus might be expected to increase the desorption energy, by analogy with classic Pickering particles. Thus, more deformable particles might be expected to adsorb more easily and be better stabilizers and this seems to be supported by several experimental Ngai, 2018b, Kwok andNgai, 2018a); (Destribats et al, 2011), (Matsui et al, 2017), (Schmitt and Ravaine, 2013) and modelling studies (Mourran et al, 2016), (Style et al, 2015), (Vilgis and Stapper, 1998). On the other hand, this seems to be contradicted by other findings, i.e., more deformable particles adsorbed less efficiently and are worse stabilizers (Destribats et al, 2014a), (Keal et al, 2017), (Koh and Saunders, 2005).…”

Section: Deformation Of Microgels On Adsorptionmentioning

confidence: 88%

Microgels at fluid-fluid interfaces for food and drinks

Murray

2019

Advances in Colloid and Interface Science

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Various aspects of microgel adsorption at fluid-fluid interfaces of relevance to emulsion and foam stabilization have been reviewed. The emphasis is on the wider non-food literature, with a view to highlighting how this understanding can be applied to food-based systems. The various different types of microgel, their methods of formation and their fundamental behavioral traits at interfaces are covered. The latter includes the aspects of microgel deformation and packing at interfaces, their deformability, size, swelling and de-swelling and how this affect their surface activity and stabilizing properties. Experimental and theoretical methods for measuring and modelling their behaviour are surveyed, including interactions between microgels themselves at interfaces but also other surface active species. It is concluded that challenges still remain in translating all the possibilities synthetic microgels offer to microgels based on food-grade materials only, but Nature's rich tool box of biopolymers and biosurfactants suggests this field still opens up important new avenues of food microstructure development and control.

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Microgels and fractal structures at interfaces and surfaces

Cited by 9 publications

References 19 publications

Poly(N-isopropylacrylamide) microgels at the oil–water interface: temperature effect

Poly(N-isopropylacrylamide) microgels at the oil–water interface: temperature effect

Gels at interfaces

Microgels at fluid-fluid interfaces for food and drinks

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