Correlating the effect of co-monomer content with responsiveness and interfacial activity of soft particles with stability of corresponding smart emulsions

Kwok, M. W.; Ambreen, Jaweria; Ngai, To

doi:10.1016/j.jcis.2019.03.072

Cited by 18 publications

(19 citation statements)

References 47 publications

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“…In contrast, we raise a new question regarding emulsion stability upon environmental changes. Until now, it was generally admitted that microgel deswelling was a simple way to trigger demulsification [2,6,10,14,80]. The present work demonstrates that this link is not systematic.…”

Section: Discussionsupporting

confidence: 58%

“…The intent of this work was to set up a bridge between pNIPAM model microgels, for which fundamental principles of emulsion stabilization have been established [2,3,10,35,36,71,[75][76][77], and the growing chemical diversity of the newly developed ones, either synthetic [37,[78][79][80][81] or biomolecule-based ones [39,40,42,[82][83][84]. A common feature of these particulate emulsifiers is the amphiphilic nature of the polymeric backbone.…”

Section: Discussionmentioning

confidence: 99%

“…This owes to the particle deformability which brings original properties at the interface compared to solid particles [2,3,4]. In particular, the adsorption of microgels at liquid interfaces has led to the stabilization of so-called Pickering emulsions and foams, which can be further destabilized on demand by triggering the volume phase transition of microgels from swollen to collapsed state [5][6][7][8][9][10][11][12][13]. To date, a great knowledge has been collected using poly(N-isopropylacrylamide) as model microgels [3,4,14].…”

Section: Introductionmentioning

confidence: 99%

“…Apart from these model pNIPAM microgels, efforts were carried out to extend the field of applications of such structures. The role of comonomers was explored in pNIPAM chemistry, enlarging the panel of stimuli: various N-alkylacrylamide derivatives to change the VPTT [9], carboxylic acid derivatives to induce pH-responsiveness [10], phenylboronates to introduce glucose-responsiveness [35]. Such studies lead to the conclusion that the main parameter to trigger emulsion stability was the deformability of microgels, which could be tuned by additional physical cross-links brought by the functional groups, whereas electrostatic interactions did not change the stability [36].…”

Section: Introductionmentioning

confidence: 99%

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Pickering emulsions stabilized by thermoresponsive oligo(ethylene glycol)-based microgels: Effect of temperature-sensitivity on emulsion stability

Tatry

Galanopoulo

Waldmann

et al. 2021

Journal of Colloid and Interface Science

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HypothesisThe stability of emulsions stabilized by soft and responsive microgels and their macroscopic properties are governed by the microstructure of microgels, in particular their deformability. However, little is known about the role of the microgel chemistry, though it is expected that polymeric backbone with an amphiphilic structure is a requirement for their adsorption at the oil-water interface. ExperimentsA series of biocompatible, thermoresponsive and amphiphilic poly(oligoethylene glycol)methacrylate (pOEMA) microgels is synthesized, with varying hydrophobic-hydrophilic balance, or equivalent varying volume phase transition temperature (VPTT). Their behavior in the bulk phase and at solid interfaces is compared to their behavior at liquid interfaces, studied on flat and model interfaces by the pendant drop method, and on drops, in microgel-stabilized emulsions. FindingsControlling the composition of microgels by simply changing the number of ethylene oxide groups in the hydrophilic side chain allows a precise tuning of their VPTT in the range of 20 to 60°C. Simultaneously, the swelling ratio and the deformability of the microgels increase by increasing the hydrophilicity, as a result of the polymerization process. Regardless of their hydrophilicity, all the swollen pOEMA microgels adsorb at the liquid interface and stabilize emulsions, whose flocculation state and mechanical stability depends on the microgel deformability. Unexpectedly, most emulsions remain stable upon heating above the VPTT of the microgels. Such feature highlights their extreme robustness, whose origin is discussed. This study opens new opportunities for the use of biocompatible Pickering emulsifiers.

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Section: Discussionsupporting

confidence: 58%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Pickering emulsions stabilized by thermoresponsive oligo(ethylene glycol)-based microgels: Effect of temperature-sensitivity on emulsion stability

Tatry

Galanopoulo

Waldmann

et al. 2021

Journal of Colloid and Interface Science

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“…Microgels are soft, colloidal particles made of highly swollen cross-linked polymers which can deform upon stress. Prepared with different monomers and comonomers, microgels can be tuned responsive to multistimuli like temperature, pH, light, etc . − The deformability and stimuli-responsiveness of microgels make them very different from rigid particles in properties and interfacial behavior, and unsurprisingly, a good candidate as emulsifiers. Ngai et al first reported the use of poly( N -isopropylacrylamide- co -methacrylic acid) (PNIPAM- co -MAA) microgels as emulsifiers for temperature- and pH-responsive oil-in-water (o/w) emulsions. , Later on, Brugger and Richtering differentiated the emulsifying ability of PNIPAM- co -MAA microgels from that of oligomer byproducts formed during polymerization .…”

Section: Introductionmentioning

confidence: 99%

One-Step Formation of Double Emulsions Stabilized by PNIPAM-based Microgels: The Role of Co-monomer

Zhang

Ngai

2021

Langmuir

Self Cite

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Microgels have been widely used as particulate emulsifiers to stabilize emulsions due to their multiresponsiveness and deformability. Generally, microgels stabilize oil-in-water (o/w) emulsions, whereas occasionally water-in-oil (w/o) emulsions are reported using oils like n-octanol in which microgels can swell. However, the use of microgels to stabilize double emulsions (DEs) remains scarce. In this work, we report a special poly(N-isopropylacrylamide)- (PNIPAM-) based microgel to obtain water-in-oil-in-water (w/o/w) DEs in one step with the introduction of 1-vinylimidazole (VIM) as comonomer and hydroxy silicone oil as the oily phase. By comparison, when methacrylic acid (MAA) is used, an o/w emulsion will be obtained. The same holds true even when we freeze-dry and redisperse the microgels in the oil. Compared with PNIPAM-co-MAA microgel, PNIPAM-co-VIM microgel achieves a lower interfacial tension (IFT) when dispersed in the aqueous phase. This interfacial affinity of PNIPAM-co-VIM is believed to result from acid–base interaction between VIM and hydroxyl groups of the silicone oil, the same interaction used for preparing silica–vinyl polymer composite particles. Increasing the particle concentrations from 0.05% to 0.9% (w/v), we observe the inversion from w/o to o/w/o and w/o/w emulsions. When the oil fraction is changed from 0.1 to 0.9, the emulsion morphology evolves from o/w and w/o/w to w/o emulsions. At last, we examine the emulsifying ability of PNIPAM-co-VIM microgel with other oils and find that w/o/w emulsions are obtained with edible oils as well. Considering the similarity between microgels and biopolymers, the discovery in this work will help in designing food-grade emulsifiers to form edible DEs.

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Advanced Switchable Molecules and Materials for Oil Recovery and Oily Waste Cleanup

Zhu

Yang

et al. 2021

Advanced Science

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Advanced switchable molecules and materials have shown great potential in numerous applications. These novel materials can express different states of physicochemical properties as controlled by a designated stimulus, such that the processing condition can always be maintained in an optimized manner for improved efficiency and sustainability throughout the whole process. Herein, the recent advances in switchable molecules/materials in oil recovery and oily waste cleanup are reviewed. Oil recovery and oily waste cleanup are of critical importance to the industry and environment. Switchable materials can be designed with various types of switchable properties, including i) switchable interfacial activity, ii) switchable viscosity, iii) switchable solvent, and iv) switchable wettability. The materials can then be deployed into the most suitable applications according to the process requirements. An in-depth discussion about the fundamental basis of the design considerations is provided for each type of switchable material, followed by details about their performances and challenges in the applications. Finally, an outlook for the development of next-generation switchable molecules/materials is discussed.

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Correlating the effect of co-monomer content with responsiveness and interfacial activity of soft particles with stability of corresponding smart emulsions

Cited by 18 publications

References 47 publications

Pickering emulsions stabilized by thermoresponsive oligo(ethylene glycol)-based microgels: Effect of temperature-sensitivity on emulsion stability

Pickering emulsions stabilized by thermoresponsive oligo(ethylene glycol)-based microgels: Effect of temperature-sensitivity on emulsion stability

One-Step Formation of Double Emulsions Stabilized by PNIPAM-based Microgels: The Role of Co-monomer

Advanced Switchable Molecules and Materials for Oil Recovery and Oily Waste Cleanup

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