Electric field driven self-assembly of ionic microgels

Nojd, Söfi; Mohanty, Priti S.; Bagheri, Payam; Yethiraj, Anand; Schurtenberger, Peter

doi:10.1039/c3sm51226f

Cited by 46 publications

(50 citation statements)

References 37 publications

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“…Anisotropic stress, rapid quenching, and a small system size have been found to promote martensitic transformations [19]. In colloids, martensitic transitions have been observed in small crystalline clusters [20][21][22] or lattices stretched by external fields [18,[23][24][25]. A solid-solid transition involving an activated nucleation process has recently been experimentally observed at the single-particle level for the first time in colloidal thin-film crystals confined between two glass plates [26].…”

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confidence: 95%

Nonclassical Nucleation in a Solid-Solid Transition of Confined Hard Spheres

Peng

Han

et al. 2015

Phys. Rev. Lett.

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A solid-solid phase transition of colloidal hard spheres confined between two planar hard walls is studied using a combination of molecular dynamics and Monte Carlo simulation. The transition from a solid consisting of five crystalline layers with square symmetry (5□) to a solid consisting of four layers with triangular symmetry (4△) is shown to occur through a nonclassical nucleation mechanism that involves the initial formation of a precritical liquid cluster, within which the cluster of the stable 4△ phase grows. Free-energy calculations show that the transition occurs in one step, crossing a single free-energy barrier, and that the critical nucleus consists of a small 4△ solid cluster wetted by a metastable liquid. In addition, the liquid cluster and the solid cluster are shown to grow at the planar hard walls. We also find that the critical nucleus size increases with supersaturation, which is at odds with classical nucleation theory. The △-solid-like cluster is shown to contain both face-centered-cubic and hexagonal-close-packed ordered particles. The kinetics of phase transitions plays an important role in condensed-matter physics and materials science. In order to gain a better fundamental understanding of how to control self-assembly processes in the fabrication of novel structures, many experimental and simulation studies have been devoted to colloidal systems. Experiments [1-4] and computer simulations [5][6][7] on bulk hard-sphere colloids suggested that the metastable fluid crystallizes and superheated crystals melt via a single-step nucleation process that is well described by classical nucleation theory (CNT) [8]. However, Ostwald's step rule suggests that the kinetic pathway to the most stable state can initially proceed through the nucleation of intermediate, metastable phases [9]. The effect of a nearby metastable state on nucleation and the occurrence of multistep nucleation processes have been studied in the crystallization of a range of systems including colloids [10,11], proteins [12], and patchy particles [13], and in the crystallization of molecular solids from solution [14].In contrast, the kinetic processes of solid-solid phase transitions, which involve complex structural rearrangements [15], have received considerably less attention [16]. Solid-solid transitions usually occur in a martensitic fashion [17,18] involving the concerted, diffusionless motion of the atoms in the unit cell. Anisotropic stress, rapid quenching, and a small system size have been found to promote martensitic transformations [19]. In colloids, martensitic transitions have been observed in small crystalline clusters [20][21][22] or lattices stretched by external fields [18,[23][24][25]. A solid-solid transition involving an activated nucleation process has recently been experimentally observed at the single-particle level for the first time in colloidal thin-film crystals confined between two glass plates [26]. The equilibrium phase diagram of hard spheres confined between two planar hard walls shows an alternati...

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confidence: 95%

Nonclassical Nucleation in a Solid-Solid Transition of Confined Hard Spheres

Peng

Han

et al. 2015

Phys. Rev. Lett.

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“…Compared with crystallization21, melting2223 and glass transitions24, s–s transitions in colloidal systems have been much understudied25262728293031. To drive a s–s transition, the colloidal crystal needs to be tunable.…”

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Diffusive and martensitic nucleation kinetics in solid-solid transitions of colloidal crystals

Peng

Wang

et al. 2017

Nat Commun

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Solid–solid transitions between crystals follow diffusive nucleation, or various diffusionless transitions, but these kinetics are difficult to predict and observe. Here we observed the rich kinetics of transitions from square lattices to triangular lattices in tunable colloidal thin films with single-particle dynamics by video microscopy. Applying a small pressure gradient in defect-free regions or near dislocations markedly transform the diffusive nucleation with an intermediate-stage liquid into a martensitic generation and oscillation of dislocation pairs followed by a diffusive nucleus growth. This transformation is neither purely diffusive nor purely martensitic as conventionally assumed but a combination thereof, and thus presents new challenges to both theory and the empirical criterion of martensitic transformations. We studied how pressure, density, grain boundary, triple junction and interface coherency affect the nucleus growth, shape and kinetic pathways. These novel microscopic kinetics cast new light on control solid–solid transitions and microstructural evolutions in polycrystals.

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“…In contrast, the aggregation behavior of the cationic and anionic microgels was observed in neither acidic nor basic condition (pH = 2 and 12, respectively). It was considered that they did not aggregate at pH 2 or 12 because the zeta potential of cationic or anionic microgel was neutralized and ionic interaction between cationic and anionic microgel was weakened …”

Section: Resultsmentioning

confidence: 99%

“…It was reported that some microgels aggregate voluntarily in solvents . For example, cationic and anionic microgels form aggregates due to the electrostatic interaction in water . Similarly to biomolecules, microgel aggregation has unique properties general gel materials do not have.…”

Section: Introductionmentioning

confidence: 99%

Photo-triggered microgel aggregation using o -nitrobenzaldehyde as aggregating power source

Tamesue

Abe

Mitsumata

et al. 2015

J. Polym. Sci. Part A: Polym. Chem.

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In this work, cationic and anionic microgels which are mainly formed from thermal responsive polymer, poly(Nisopropylacrylamide), are prepared and mixed in water. These microgels interact with each other due to the electrostatic interaction, and aggregate voluntarily. By applying the microgel aggregating system, photo-responsive aggregating system is constructed by using o-nitrobenzaldehyde (NBA), which reacts and releases hydrogen triggered by photo stimuli. The microgel aggregates in an aqueous solution of NBA re-disperse depending on the irradiation time of UV light. In addition, by masking the UV irradiated area, the resultant shapes of microgel aggregates are controlled. The aggregated microgel shows rapid and drastic volume changes in response to heat.

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Electric field driven self-assembly of ionic microgels

Cited by 46 publications

References 37 publications

Nonclassical Nucleation in a Solid-Solid Transition of Confined Hard Spheres

Nonclassical Nucleation in a Solid-Solid Transition of Confined Hard Spheres

Diffusive and martensitic nucleation kinetics in solid-solid transitions of colloidal crystals

Photo-triggered microgel aggregation using o -nitrobenzaldehyde as aggregating power source

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