Dynamics of solvent-free grafted nanoparticles

Chremos, Alexandros; Panagiotopoulos, Athanassios Z.; Koch, Donald L.

doi:10.1063/1.3679442

Cited by 51 publications

(67 citation statements)

References 57 publications

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“…[31] When the hairs are extended in the brush regime, but are not so long that the ends are in the semi-dilute regime, the corona is closely correlated with the core, and the HNP system would behave as a soft glass. This model has been confirmed by molecular dynamics simulations [79] and by rheological measurements. [75] Increased fluidity is found in a particular class of HNPsknown as Nanoparticle Ionic Materials (NIMs) where the bonding of the corona to the core is ionic in nature.…”

Section: Dynamics Of Hnps and Hnp Assembliessupporting

confidence: 57%

Hairy nanoparticle assemblies as one-component functional polymer nanocomposites: opportunities and challenges

et al. 2013

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Over the past three decades, the combination of inorganic-nanoparticles and organic-polymers has led to a wide variety of advanced materials, including polymer nanocomposites (PNCs). Recently, synthetic innovations for attaching polymers to nanoparticles to create "hairy nanoparticles" (HNPs) has expanded opportunities in this field. In addition to nanoparticle compatibilization for traditional particle-matrix blending, neat-HNPs afford one-component hybrids, both in composition and properties, which avoids issues of mixing that plague traditional PNCs. Continuous improvements in purity, scalability, and theoretical foundations of structure-performance relationships are critical to achieving design control of neat-HNPs necessary for future applications, ranging from optical, energy, and sensor devices to lubricants, green-bodies, and structures.

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Section: Dynamics Of Hnps and Hnp Assembliessupporting

confidence: 57%

Hairy nanoparticle assemblies as one-component functional polymer nanocomposites: opportunities and challenges

et al. 2013

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“…More recently, binary mixtures of self-suspended grafted nanoparticles (silica particles with covalently bonded small polyethylene glycol chains, in the absence of solvent) were investigated [49].These systems have been proposed as a paradigm of solvent-free colloids [50], [51]. It was found that adding larger particles to a glassy suspension of smaller particles led to its softening, and in the limit of large size disparities, to its complete fluidization.…”

Section: Introductionmentioning

confidence: 99%

Asymmetric soft-hard colloidal mixtures: Osmotic effects, glassy states and rheology

Merola¹,

Parisi²,

Truzzolillo³

et al. 2018

Journal of Rheology

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Whereas mixtures of colloids and non-adsorbing polymers have been studied in great detail in the last two decades, binary colloidal mixtures have not received much attention. Yet, fragmental evidence from asymmetric mixtures of hard spheres indicates a wide-ranging, complex behavior from liquid to crystal to single glass and to double glass, and respective rich rheology. Recently, we addressed the question of softness by investigating a mixture of soft and virtually hard colloidal spheres. We found an unprecedented wealth of states including repulsive single glass (RG), liquid, arrested phase separation (APS) and double glass (DG). This is a consequence of the coupling of softness and osmotic forces due to the hard component. We now report on the rheology of the different states with emphasis on the nonlinear response during start-up of stress at constant rate, its relaxation upon flow cessation, and large amplitude oscillatory shearing. Distinct features are identified, whereas comparison with single-colloid (soft or hard) glasses reveals some phenomenological universalities in yielding, residual stresses and periodic intra-cycle stress response. In brief, the DG exhibits much larger yield and residual stresses as compared to the RG and APS, whereas the yield strain is the same for all states. Two-step yielding is unambiguously evidenced for the APS whereas both yield stress and strain exhibit a weak dependence on Péclet number. Large amplitude oscillatory tests reveal large value of the intrinsic nonlinear parameters, reflecting the role of colloidal interactions. Moreover, RG exhibits intra-cycle stress The following article has been accepted by Journal of Rheology. After it is published, it will be found at http://sor.scitation.org/journal/jor 2 overshoots, a feature that characterizes most of the soft glassy materials formed by interpenetrable particles and that vanishes as hard (nearly impenetrable) colloids are added in the mixtures. These results demonstrate the sensitivity of linear and nonlinear rheology to colloidal state transitions and, more importantly, the power of entropic mixing as a means to tailor the flow properties, hence performance and handling of soft composites.

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“…[1][2][3][4] Experiments and modeling suggest that their self-suspending, solvent-free character is a key determining factor for the structure and dynamics of these systems. 3,[5][6][7][8][9] While progress has been made in theoretical understanding of the simpler versions of these systems, in which chains are covalently graed on the particles giving rise to "Nanoscale Organic Hybrid Materials," there have been relatively few modeling attempts of their ionically graed counterparts -oen referred to as "Nanoparticle Ionic Materials" (NIMs). There are extensive experimental studies of NIMs with diverse core and counterion compositions.…”

Section: Introductionmentioning

confidence: 99%

“…Due to the strong electrostatic forces, ionically graed nanoparticles are also expected to behave differently from neutral systems of graed nanoparticles in free chains. 7,12,13 NIMs share features with charged colloids, 14 and have been characterized as ionic liquids with large, nanoscale ions, 15,16 or as nanoparticles covalently tethered to ionic liquids.…”

Section: Introductionmentioning

confidence: 99%

Diffusivities, viscosities, and conductivities of solvent-free ionically grafted nanoparticles

Hong

Panagiotopoulos

2013

Soft Matter

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A new class of conductive composite materials, solvent-free ionically grafted nanoparticles, were modeled by coarse-grained molecular dynamics methods. The grafted oligomeric counterions were observed to migrate between different cores, contributing to the unique properties of the materials. We investigated the dynamics by analyzing the dependence on temperature and structural parameters of the transport properties (self-diffusion coefficients, viscosities and conductivities) and counterion migration kinetics. Temperature dependence of all properties follows the Arrhenius equation, but chain length and grafting density have distinct effects on different properties. In particular, structural effects on the diffusion coefficients are described by the Rouse model and the theory of nanoparticles diffusing in polymer solutions, viscosities are strongly influenced by clustering of cores, and conductivities are dominated by the motions of oligomeric counterions. We analyzed the migration kinetics of oligomeric counterions in a manner analogous to unimer exchange between micellar aggregates. The counterion migrations follow the "double-core" mechanism and are kinetically controlled by neighboring-core collisions.

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Dynamics of solvent-free grafted nanoparticles

Cited by 51 publications

References 57 publications

Hairy nanoparticle assemblies as one-component functional polymer nanocomposites: opportunities and challenges

Hairy nanoparticle assemblies as one-component functional polymer nanocomposites: opportunities and challenges

Asymmetric soft-hard colloidal mixtures: Osmotic effects, glassy states and rheology

Diffusivities, viscosities, and conductivities of solvent-free ionically grafted nanoparticles

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