Non-aqueous microgel particles: synthesis, properties and applications

Bonham, Jessica; Faers, Malcolm A.; Duijneveldt, Jeroen S. van

doi:10.1039/c4sm01834f

Cited by 60 publications

(64 citation statements)

References 73 publications

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“…For all microgel batches, an aliquot of product was set aside before drying the particles, in order to obtain DLS sizes of the particles in water. For a more detailed description of the different microgel synthesis routes, see Bonham et al [2]. …”

Section: Methodsmentioning

confidence: 99%

“…The choice of both the monomer and solvent governs the χ parameter, as does the temperature. To what extent particles do swell in good solvents is determined by the molar mass between cross-links, as shown by the Flory-Rehner theory [2]. Here, we demonstrate that, in addition to these properties of the bulk gel, the nature of the particle surface also needs to be considered, and the initiator used during particle synthesis can influence whether the microgel particles will disperse in a given solvent [3].…”

Section: Introductionmentioning

confidence: 92%

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The role of initiator on the dispersibility of polystyrene microgels in non-aqueous solvents

et al. 2017

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Non-aqueous microgel particles are commonly synthesised in water, dried, and then redispersed in non-aqueous solvents. An important factor to consider when synthesising such particles is the initiator, which can determine how well the particles disperse in solvents. Polystyrene microgel particles were made with three different initiators. When a neutral, oil soluble initiator (azobisisobutyronitrile) was used the particles dispersed in toluene as well as cyclohexane and decalin. In contrast, anionic, water-soluble initiators (potassium persulfate or azobis(4-cyanovaleric acid)) created particles that only redispersed in toluene and not the other two solvents. Of the three considered, toluene is the best solvent for polystyrene and also has the highest polarizability, making it most effective at redispersing particles with polar or ionisable functional groups. Zeta potential and conductivity measurements, however, did not detect a direct relationship between particle charging and redispersibility. Oil soluble initiators result in “inside out” polymerisation where the initiator groups are buried inside the growing particle, whereas water-soluble initiators result in “outside in” polymerisation, with the polar initiator groups residing on the particle surface. By tailoring the ratio between water and oil soluble initiators, it may be possible to synthesise microgel particles with uniform or designed charge profiles from the core to the surface.Electronic supplementary materialThe online version of this article (doi:10.1007/s00396-017-4023-y) contains supplementary material, which is available to authorized users.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 92%

The role of initiator on the dispersibility of polystyrene microgels in non-aqueous solvents

et al. 2017

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“…There are two main interconnected features that make microgels so interesting: their softness and their responsiveness. Microgels are soft due to the compressibility of the solvated hydrogel network, while their responsiveness comes from changes in the polymer solubility and swelling as a function of the environmental conditions 1,2 . The paradigmatic example is the case of poly(N-isopropylacrylamide)(PNiPAm) microgels, showing a strong temperature-dependent swelling behavior and a volume-phase-transition temperature around 32 • C; the particles are highly swollen and compressible below this temperature, while the polymer chains become more hydrophobic and partially collapse above it, causing particle shrinkage 3 .…”

Section: Introductionmentioning

confidence: 99%

Isostructural solid–solid phase transition in monolayers of soft core–shell particles at fluid interfaces: structure and mechanics

et al. 2016

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We have studied the complete two-dimensional phase diagram of a core-shell microgel-laden fluid interface by synchronizing its compression with the deposition of the interfacial monolayer. Applying a new protocol, different positions on the substrate correspond to different values of the monolayer surface pressure and specific area. Analyzing the microstructure of the deposited monolayers, we discovered an isostructural solid-solid phase transition between two crystalline phases with the same hexagonal symmetry, but with two different lattice constants. The two phases corresponded to shell-shell and core-core inter-particle contacts, respectively; with increasing surface pressure the former mechanically failed enabling the particle cores to come into contact. In the phase-transition region, clusters of particles in core-core contacts nucleate, melting the surrounding shell-shell crystal, until the whole monolayer moves into the second phase. We furthermore measured the interfacial rheology of the monolayers as a function of the surface pressure using an interfacial microdisk rheometer. The interfaces always show a strong elastic response, with a dip in the shear elastic modulus in correspondence with the melting of the shell-shell phase, followed by a steep increase upon the formation of a percolating network of the core-core contacts. These results demonstrate that the core-shell nature of the particles leads to a rich mechanical and structural behavior that can be externally tuned by compressing the interface, indicating new routes for applications, e.g. in surface patterning or emulsion stabilization.

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“…Microgel particles (MG) are crosslinked macromolecules of colloidal size that swell or shrink to varying extents in solvents depending on the constituent chemistry, crosslinked density, and external stimuli such as temperature or pH. 16,17 This allows the thermodynamic and physical property state to be controlled in situ through the imposition of external conditions. The MG have found use in medical applications as potential cartilage replacement 18 and as friction and antiwear modifiers.…”

Section: Introductionmentioning

confidence: 99%

Spatially dependent diffusion coefficient as a model for pH sensitive microgel particles in microchannels

2016

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Solute transport and intermixing in microfluidic devices is strongly dependent on diffusional processes. Brownian Dynamics simulations of pressure-driven flow of model microgel particles in microchannels have been carried out to explore these processes and the factors that influence them. The effects of a pH-field that induces a spatial dependence of particle size and consequently the self-diffusion coefficient and system thermodynamic state were focused on. Simulations were carried out in 1D to represent some of the cross flow dependencies, and in 2D and 3D to include the effects of flow and particle concentration, with typical stripe-like diffusion coefficient spatial variations. In 1D, the mean square displacement and particle displacement probability distribution function agreed well with an analytically solvable model consisting of infinitely repulsive walls and a discontinuous pHprofile in the middle of the channel. Skew category Brownian motion and nonGaussian dynamics were observed, which follows from correlations of step lengths in the system, and can be considered to be an example of so-called "diffusing diffusivity." In Poiseuille flow simulations, the particles accumulated in regions of larger diffusivity and the largest particle concentration throughput was found when this region was in the middle of the channel. The trends in the calculated cross-channel diffusional behavior were found to be very similar in 2D and 3D. Published by AIP Publishing. [http://dx

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Non-aqueous microgel particles: synthesis, properties and applications

Cited by 60 publications

References 73 publications

The role of initiator on the dispersibility of polystyrene microgels in non-aqueous solvents

The role of initiator on the dispersibility of polystyrene microgels in non-aqueous solvents

Isostructural solid–solid phase transition in monolayers of soft core–shell particles at fluid interfaces: structure and mechanics

Spatially dependent diffusion coefficient as a model for pH sensitive microgel particles in microchannels

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