Structure of Nanoparticles Embedded in Micellar Polycrystals

Tamborini, Elisa; Ghofraniha, Neda; Oberdisse, Julian; Cipelletti, Luca; Ramos, Laurence

doi:10.1021/la301369z

Cited by 25 publications

(34 citation statements)

References 44 publications

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“…The effect of the polystyrene NPs on the sample structure, partial accumulation in the GBs and influence on the microstructure, is similar to that of the silica NPs [23]. Moreover, experiments on dilute suspensions of polymer and polystyrene NPs indicate an adsorption of the central block of the polymer to the surface of the NPs [43] with an amount of adsorbed polymer per unit area of NPs comparable to the one evaluated for silica NPs (1 mg/m 2 ) [29]. Despite these similarities, the impact of polystyrene NPs on the sample dissipation is strikingly different to that on silica NPs.…”

Section: Discussionsupporting

confidence: 56%

“…We interpret this peak as the signature of the packing of the NPs in the grain boundaries. The position of this peak does not vary significantly with φ orṪ , indicating a nearly constant average distance between NPs in the GBs [29]. By contrast, its amplitude changes.…”

Section: Correlation With Structural Datamentioning

confidence: 88%

“…Conversely, at room temperature the affinity of PPO for water is poor, and F108 self-assembles into micelles of diameter 2a = 22 nm that arrange on a face-centered cubic lattice (lattice parameter 32 nm) [29,32]. A small amount of nanoparticles (NPs) is added to the F108/water mixture.…”

Section: Experimental Samplesmentioning

confidence: 99%

“…Samples without NPs are prepared with pure D 2 O in order to maximize the contrast between the copolymer and the solvent. Samples with NPs are prepared using 39/61 H 2 O/D 2 O w/w to contrast-match the NPs or 85/15 H 2 O/D 2 O w/w to contrast-match the copolymer, as detailed previously [29]. We have checked that changing the solvents does not modify the sample structure [29].…”

Section: Experimental Samplesmentioning

confidence: 99%

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Viscoelasticity of colloidal polycrystals doped with impurities

et al. 2015

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We investigate how the microstructure of a colloidal polycrystal influences its linear viscoelasticity. We use thermosensitive copolymer micelles that arrange in water in a cubic crystalline lattice, yielding a colloidal polycrystal. The polycrystal is doped with a small amount of nanoparticles, of size comparable to that of the micelles, which behave as impurities and thus partially segregate in the grain boundaries. We show that the shear elastic modulus only depends on the packing of the micelles and does not vary neither with the presence of nanoparticles nor with the crystal microstructure. By contrast, we find that the loss modulus is strongly affected by the presence of nanoparticles. A comparison between rheology data and small-angle neutron scattering data suggests that the loss modulus is dictated by the total amount of nanoparticles in the grain boundaries, which in turn depends on the sample microstructure.

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Section: Discussionsupporting

confidence: 56%

Section: Correlation With Structural Datamentioning

confidence: 88%

Section: Experimental Samplesmentioning

confidence: 99%

Section: Experimental Samplesmentioning

confidence: 99%

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Viscoelasticity of colloidal polycrystals doped with impurities

et al. 2015

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“…The system [27,28] comprises water-based thermosensitive block-copolymers (Pluronics F108) forming micelles arranged on a face-centered cubic lattice (lattice parameter d c = 32 nm), to which a small amount of nanoparticles (NPs) of diameter 2a ≈ d c is added. The NPs act as impurities, segregated in the GBs upon crystallization.…”

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confidence: 99%

Plasticity of a Colloidal Polycrystal under Cyclic Shear

2014

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We use confocal microscopy and time-resolved light scattering to investigate plasticity in a colloidal polycrystal, following the evolution of the network of grain boundaries as the sample is submitted to thousands of shear deformation cycles. The grain boundary motion is found to be ballistic, with a velocity distribution function exhibiting non-trivial power law tails. The shearinduced dynamics initially slow down, similarly to the aging of the spontaneous dynamics in glassy materials, but eventually reach a steady state. Surprisingly, the cross-over time between the initial aging regime and the steady state decreases with increasing probed length scale, hinting at a hierarchical organization of the grain boundary dynamics. The mechanical properties of amorphous solids are a topic of intense research. Recent works focus on the irreversible (or plastic) rearrangements at the microscopic level [1][2][3][4][5][6][7], resulting from an applied deformation or stress, which are ultimately responsible for the macroscopic mechanical behavior. Research on amorphous solids is also relevant to crystalline materials [8]. On the one hand, simulations and experiments have revealed that particles in the grain boundaries (GBs) separating crystalline grains exhibit glassy dynamics [9,10]. On the other hand, polycrystals may be regarded as an amorphous assembly of crystalline grains separated by GBs. In fact, driven polycrystals display mechanical features similar to those of amorphous solids [11] and GB process has been shown to be at the origin of the plasticity of polycrystals in the limit of small grain sizes [11][12][13][14][15].A large number of numerical works have explored the microscopic dynamics induced in amorphous systems by a continuous shear, finding quite generally diffusive dynamics at the particle level [1][2][3], once the affine component of the displacement is removed, as also confirmed by experiments on sheared colloidal glasses [2,7,16]. By contrast, the effect of a cyclic shear has been less investigated, in spite of its relevance to the fatigue tests commonly adopted in material science. Furthermore, cyclic deformation tests allow one to unambiguously identify irreversible rearrangements (as opposed to the non-affine displacement measured in continuous shear, which may be reversible) and to follow the evolution, or aging, of the dynamics as the sample is kept under an oscillatory deformation.Similarly to the case of continuous shear, the microscopic dynamics in cyclically deformed amorphous solids have been found to be diffusive (or even subdiffusive), in simulations [18,19] as well as in experiments on colloids [2,20] or granular matter [21,22]. Aging effects have been reported for macroscopic quantities, e.g. pressure or compacity [23,24], or for the microscopic dynamics. In the latter case, however, aging has been probed over a few tens of cycles at most [22,25].In this Letter, we report on experiments probing the irreversible rearrangements induced in a colloidal polycrystal by thousands of sh...

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Polyhedral Oligosilsesquioxane (POSS) Nanoparticle Localization in Ordered Structures Formed by Solvated Block Copolymers

Sarkar

Ayandele

Venugopal

et al. 2013

Macro Chemistry & Physics

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The coassembly of polyhedral oligosilsesquioxanes (POSS) of two different surface chemistries is considered, one hydrophilic, poly(ethylene oxide) (PEO), and the other hydrophobic, isobutyl (iB), in cylindrical structures formed by hydrated poly(ethylene oxide)‐poly(propylene oxide)‐poly(ethylene oxide) block copolymer, Pluronic P105 (EO37PO56EO37). Incorporation of PEO‐POSS by replacing an equal mass of water results in an increase in the lattice parameter (d), which is attributed to an increase in the degree of block segregation. In the case of adding PEO‐POSS at a fixed Pluronic P105/water ratio, d ~ φpolymer‐0.7, which suggests that PEO‐POSS particles are located inside the hydrated PEO domains. Incorporation of iB‐POSS in the water‐in‐xylene cylindrical structure causes an order‐to‐order phase transition to a bicontinuous cubic structure, which suggests that iB‐POSS decreases the degree of block segregation by locating at the PEO‐PPO interfacial regions. The nanoparticle versus molecule nature of POSS is discussed by comparing POSS effects to those of 10.6 nm diameter deprotonated silica nanoparticles and of glycerol or glucose.

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Structure of Nanoparticles Embedded in Micellar Polycrystals

Cited by 25 publications

References 44 publications

Viscoelasticity of colloidal polycrystals doped with impurities

Viscoelasticity of colloidal polycrystals doped with impurities

Plasticity of a Colloidal Polycrystal under Cyclic Shear

Polyhedral Oligosilsesquioxane (POSS) Nanoparticle Localization in Ordered Structures Formed by Solvated Block Copolymers

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