Mobility of Nanoparticles in Semidilute Polyelectrolyte Solutions

Khorasani, Firoozeh Babaye; Poling-Skutvik, Ryan; Krishnamoorti, Ramanan; Conrad, Jacinta C.

doi:10.1021/ma501248u

Cited by 48 publications

(55 citation statements)

References 56 publications

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“…From the long-time slope, we extract the particle diffusivity D and normalize by the diffusivity in pure solvent D 0 to remove explicit size dependence. For large particles, e.g., 2 μm particles in 2.6c* solution, the relative diffusivity agrees with predictions of D SE 21 and does not depend on particle size. By contrast, the relative diffusivity of smaller particles strongly deviates from D SE ( Figure 2).…”

supporting

confidence: 76%

“…We select these particle sizes to span R g and hence probe the crossover to bulk behavior, in contrast to our previous work focusing on a single particle size. 21 Dynamic light scattering measurements confirm that the polymer does not absorb to the surface of the particles. Our solutions are well below the entanglement concentration for polyelectrolyte solutions.…”

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confidence: 85%

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Size-Dependent Dynamics of Nanoparticles in Unentangled Polyelectrolyte Solutions

2015

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The mobility of polystyrene nanoparticles ranging in diameter from 300 nm to 2 μm was measured in dilute and semidilute solutions of partially hydrolyzed polyacrylamide. In this model system, the ratio of particle to polymer size controls the long-time diffusivity of nanoparticles. The particle dynamics transition from subdiffusive on short time scales to Fickian on long time scales, qualitatively similar to predictions for polymer dynamics using a Rouse model. The diffusivities extracted from the long-time Fickian regime, however, are larger than those predicted by the Stokes−Einstein equation and the bulk zero-shear viscosity and moreover do not collapse according to hydrodynamic models. The sizedependent deviations of the long-time particle diffusivities derive instead from the coupling between the dynamics of the particle and the polymer over the length scale of the particle. Although the long-time diffusivities collapse according to predictions, deviations of the short-time scaling exponents and the crossover time between subdiffusive and Fickian dynamics indicate that the particles are only partially coupled to the relaxation modes of the polymer.T ransport of nanoparticles through non-Newtonian media affects applications ranging from targeted drug delivery 1,2 to oil recovery 3,4 to nanocomposite materials. 5,6 In a homogeneous medium of viscosity η, the diffusivity of a particle with radius R NP is given by the Stokes−Einstein (SE) equation D SE = k B T/6πηR NP . As particle size approaches characteristic length scales in the medium, the continuum assumption underlying the SE relation no longer holds, and deviations from SE predictions appear. 7−10 Attempts to explain these deviations in mixtures of polymers and particles have focused on identifying the length scale that controls particle diffusion.In entangled polymer systems, the length scale controlling particle diffusion is the distance between entanglements. The diffusion of nanoparticles smaller than the entanglement mesh is unaffected by entanglement dynamics, but for larger particles diffusion is dictated by polymer reptation until SE behavior is recovered. 11−14 In unentangled systems, however, different physics must control nanoparticle diffusion. Hydrodynamic models treat the polymer solution as a homogeneous medium in which hydrodynamic interactions are screened over the correlation length between polymer chains ξ. 10,15,16 Scaling models describe the particle mobility in terms of the polymer dynamics, 13,17,18 which are set by the characteristic length scales ξ and the polymer radius of gyration R g . Identifying the relevant physics requires model systems that are compatible with a wide range of particle sizes and span the transition from dilute to semidilute regimes in unentangled solutions. In polyelectrolyte solutions, topological entanglements appear at concentrations orders of magnitude above c*, 19,20 enabling investigations of nanoparticle dynamics across a wide and previously inaccessible range of semidilute concentrations in the abs...

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confidence: 76%

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confidence: 85%

Size-Dependent Dynamics of Nanoparticles in Unentangled Polyelectrolyte Solutions

2015

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“…[17, 18] The SAXS sample was treated following a two-step heat treatment. The first annealing step at 870°C for 1 h is the recommended stress-relieving heat treatment for IN625 [19]; the second anneal at 1150°C for 1 h is the homogenization treatment called for by thermodynamic modeling, as described later. More experimental details can be found in the Supplementary Materials.…”

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confidence: 99%

Homogenization kinetics of a nickel-based superalloy produced by powder bed fusion laser sintering

et al. 2017

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Additively manufactured (AM) metal components often exhibit fine dendritic microstructures and elemental segregation due to the initial rapid solidification and subsequent melting and cooling during the build process, which without homogenization would adversely affect materials performance. In this letter, we report in situ observation of the homogenization kinetics of an AM nickel-based superalloy using synchrotron small angle X-ray scattering. The identified kinetic time scale is in good agreement with thermodynamic diffusion simulation predictions using microstructural dimensions acquired by ex situ scanning electron microscopy. These findings could serve as a recipe for predicting, observing, and validating homogenization treatments in AM materials.

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“…The most direct evidence for non‐Gaussian diffusion and for subdiffusion comes from particle tracking studies, in which the actual position

r (t)

is measured directly, with statistical analysis of the recorded trajectory being used to determine

〈 {(x (t + s) - x (t))}^{2} 〉

and

P (Δ r, t)

. Note, for example, results of Khorasani et al, Wang et al, and Guan et al…”

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confidence: 99%

Interpretation of fluorescence correlation spectra of biopolymer solutions

Phillies

2016

Biopolymers

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Fluorescence correlation spectroscopy (FCS) is regularly used to study diffusion in non-dilute "crowded" biopolymer solutions, including the interior of living cells. For fluorophores in dilute solution, the relationship between the FCS spectrum G(t) and the diffusion coefficient D is well-established. However, the dilute-solution relationship between G(t) and D has sometimes been used to interpret FCS spectra of fluorophores in non-dilute solutions. Unfortunately, the relationship used to interpret FCS spectra in dilute solutions relies on an assumption that is not always correct in non-dilute solutions. This paper obtains the correct form for interpreting FCS spectra of non-dilute solutions, writing G(t) in terms of the statistical properties of the fluorophore motions. Approaches for applying this form are discussed.

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Mobility of Nanoparticles in Semidilute Polyelectrolyte Solutions

Cited by 48 publications

References 56 publications

Size-Dependent Dynamics of Nanoparticles in Unentangled Polyelectrolyte Solutions

Size-Dependent Dynamics of Nanoparticles in Unentangled Polyelectrolyte Solutions

Homogenization kinetics of a nickel-based superalloy produced by powder bed fusion laser sintering

Interpretation of fluorescence correlation spectra of biopolymer solutions

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