Synthesis of Sterically Stabilized Polystyrene Latex Particles Using Cationic Block Copolymers and Macromonomers and Their Application as Stimulus-Responsive Particulate Emulsifiers for Oil-in-Water Emulsions

Amalvy, Javier Ignacio; Unali, Gianfranco; Li, Y.; Granger-Bevan, and S.; Armes, Steven P.; Binks, Bernard P.; Rodrigues, and J. A.; Whitby, Catherine P.

doi:10.1021/la035921c

Cited by 129 publications

(143 citation statements)

References 42 publications

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“…If the PEGMA chains are located exclusively at the particle surface, an adsorbed amount of PEGMA, in mg m -2 ), can be estimated. calculated to be 2.3 mg m -2 for the linear PTBAEMA latex, which is consistent with values reported by Dupin et al 38 for a PEGMA-stabilized P2VP latex and by Amalvy et al 16 for poly(tertiary amine methacrylate)…”

Section: Latex Preparation and Characterizationsupporting

confidence: 90%

Novel Pickering Emulsifiers Based on pH-Responsive Poly(2-(diethylamino)ethyl methacrylate) Latexes

et al. 2013

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Emulsion copolymerization of 2-(tert-butylamino)ethyl methacrylate in the presence of divinylbenzene (DVB) cross-linker and monomethoxy-capped poly(ethylene glycol) methacrylate (PEGMA) macromonomer at 70 °C afforded sterically-stabilized latexes at approximately 10% solids at pH 9. Dynamic light scattering (DLS) and scanning electron microscopy (SEM) confirmed that relatively narrow size distributions were obtained. SEM confirmed the formation of spherical particles in the absence of any DVB cross-linker using a simple batch protocol, but in the presence of DVB it was necessary to use seeded emulsion polymerization under monomer-starved conditions to prevent the formation of latexes with ill-defined non-spherical morphologies. Lightly cross-linked latexes acquired cationic microgel character upon lowering the solution pH, as expected. Increasing the degree of cross-linking led to a progressively lower effective pK a of the copolymer chains from 8.0 to 7.3, which implies a gradual reduction in their basicity. Poly(tert-butylamino)ethyl methacrylate latex proved to be an effective Pickering emulsifier at pH 10, forming stable oilin-water emulsions when homogenized with either n-dodecane or sunflower oil at 12 000 rpm for 2 min. These Pickering emulsions exhibited pH-responsive behavior: lowering the solution pH to pH 3 resulted in immediate demulsification due to spontaneous desorption of the cationic microgels from the oil/water interface. With subsequent rehomogenization at high pH, four successive demulsification/emulsification pH cycles could be achieved without discernible loss in performance. However, no demulsification occurred on acidification of the fifth cycle.

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Section: Latex Preparation and Characterizationsupporting

confidence: 90%

Novel Pickering Emulsifiers Based on pH-Responsive Poly(2-(diethylamino)ethyl methacrylate) Latexes

et al. 2013

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“…The ability of positively or negatively charged rigid polymer particles to stabilize emulsions or foams has been demonstrated by a number of groups (17)(18)(19)(20)(21)(22). Their results show that rigid particles behave very differently from the soft microgels studied in this paper: pH-sensitive rigid particles are only stable in the aqueous bulk phase at a pH when they are charged.…”

Section: Discussionmentioning

confidence: 84%

“…The stabilization of emulsions through the use of these microgels is at first glance very similar to Pickering emulsions (11)(12)(13)(14), which are solid-stabilized emulsions discovered a century ago (15,16). However, in contrast to solid particles (17)(18)(19)(20)(21)(22), microgels are highly deformable, and the unexpected noncoalescence of the oppositely charged droplets in such systems might be due to the soft and porous structure of microgels at the interface. More interestingly, by changing the pH, the noncoalescence can be switched to coalescence.…”

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confidence: 73%

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Non-coalescence of oppositely charged droplets in pH-sensitive emulsions

Liu

Seiffert

Thiele

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

100

102

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Like charges stabilize emulsions, whereas opposite charges break emulsions. This is the fundamental principle for many industrial and practical processes. Using micrometer-sized pH-sensitive polymeric hydrogel particles as emulsion stabilizers, we prepare emulsions that consist of oppositely charged droplets, which do not coalesce. We observe noncoalescence of oppositely charged droplets in bulk emulsification as well as in microfluidic devices, where oppositely charged droplets are forced to collide within channel junctions. The results demonstrate that electrostatic interactions between droplets do not determine their stability and reveal the unique pH-dependent properties of emulsions stabilized by soft microgel particles. The noncoalescence can be switched to coalescence by neutralizing the microgels, and the emulsion can be broken on demand. This unusual feature of the microgel-stabilized emulsions offers fascinating opportunities for future applications of these systems.stimuli-sensitive emulsions | limited coalescence | poly (N-isopropylacrylamide) microgels | Pickering emulsions | lab-on-a-chip E mulsions are multiphase systems, which consist of two immiscible liquids, one dispersed in another in the form of small droplets with submicron to micron sizes. Emulsions are used in food, cosmetics, medicine, coatings, paints, and a large number of other technical applications (1). Due to their large interfacial area, emulsions are thermodynamically unstable and have a tendency to undergo coalescence, a process during which two droplets merge into a bigger one, minimizing the surface energy (2). Certain molecules or materials, such as surfactants or solid particles, can be added to prevent coalescence, making emulsions kinetically stable. These emulsion stabilizers usually provide electrostatic repulsion, steric repulsion, and/or strength to the interfacial layer of the droplets, according to widely accepted theories. For example, when emulsion droplets are covered with an ionic surfactant, they carry like charges; these charges repel each other due to electrostatic interaction, which prevents droplet aggregation or coalescence. By contrast, when oppositely charged droplets are generated in an emulsion, they attract each other and coalescence is hastened; this phenomenon is the key event in processes like electrocoalescence (3, 4).In contrast to this classical behavior, unexpected noncoalescence of two oppositely charged droplets has been reported very recently (5, 6); these investigations show that under the influence of an electric field of sufficient strength, two oppositely charged water droplets recoil after contact rather than coalesce, depending on the curvature and local capillary pressure at the liquid bridge between two adjacent droplets. However, these studies were conducted with drops that were formed temporarily under the influence of an electric field in a continuous phase of air rather than with drops that are dispersed in a liquid. By contrast, stable emulsions, which consist of oppositely charg...

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“…Responsive core-shell nanoparticles have been regularly studied for their potential uses in drug delivery [1][2][3], emulsification and interfacial stabilisation [4][5][6], interfacial transport [7,8] and environmental sensor technologies [9][10][11]. Their properties can also be manipulated to provide functionality when used as building blocks of larger structures such as microcapsules [12] and membranes [13,14].…”

Section: Introductionmentioning

confidence: 99%

Facile synthesis of gold core–polymer shell responsive particles

D’Souza-Mathew¹,

Cayre²,

Hunter³

et al. 2013

Journal of Colloid and Interface Science

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The free adsorption of an end-functionalised weak polybase, poly dimethylaminoethyl methacrylate (pDMAEMA), on the surface of colloidal gold nanoparticles (AuNPs) as a route to produce a responsive core-shell nanoparticle is explored here. Optimal conditions for the physisorption of the polymeric chains onto the colloidal nanoparticles are explored. A dense coverage is facilitated by rapidly mixing the well solvated pH responsive homopolymer, at low pH, into a relatively poor solvent environment, at higher pH, containing a stable dispersion of charge-stabilized gold nanoparticles. The rapid pH change causes the polymer chains to concurrently collapse and adsorb onto the gold nanoparticles. In order to achieve sterically stable, monodisperse and responsive core shell nanoparticles, a crucial factor is the pH difference of the systems prior to their mixing. Once adsorbed, end-functional thiol groups on the adsorbed polymer chains can form more permanent covalent attachments with the core particles. Dynamic light scattering coupled with mobility data of pH titration experiments show that the core-shell particles exhibit a responsive character consistent with the observed potentiometric titration data of the polymer.The same particles demonstrate reversible aggregation when cycled between pH extremes. This is confirmed by shifts in the SPR peak of the corresponding UV-Vis absorption profile. The ease and flexibility of this strategy for core-shell particle production, coupled with the stability and responsiveness of the product, make this a promising colloidal coating mechanism.

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Synthesis of Sterically Stabilized Polystyrene Latex Particles Using Cationic Block Copolymers and Macromonomers and Their Application as Stimulus-Responsive Particulate Emulsifiers for Oil-in-Water Emulsions

Cited by 129 publications

References 42 publications

Novel Pickering Emulsifiers Based on pH-Responsive Poly(2-(diethylamino)ethyl methacrylate) Latexes

Novel Pickering Emulsifiers Based on pH-Responsive Poly(2-(diethylamino)ethyl methacrylate) Latexes

Non-coalescence of oppositely charged droplets in pH-sensitive emulsions

Facile synthesis of gold core–polymer shell responsive particles

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