General Strategies for Nanoparticle Dispersion

Mackay, Michael E.; Tuteja, Anish; Duxbury, Phillip M.; Hawker, Craig J.; Horn, Brooke A. Van; Guan, Zhibin; Chen, Guanghui; Krishnan, R. S.

doi:10.1126/science.1122225

Cited by 892 publications

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References 30 publications

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“…It has been recently proposed that a thermodynamically stable dispersion of nanoparticles without agglomeration or phase separation should be achieved when the radius of gyration, R g , of the polymer host is larger than the radius of the nanoparticles. 60 Hooper and Schweizer 16 suggested that R g is not the key variable, but rather the ratio of particle diameter to monomer (D/d) is crucial magnitude taking dense polymer-particle mixtures as a model system. This size ratio is relevant for the magnitude of particle-particle attraction.…”

Section: Resultsmentioning

confidence: 99%

Optical Properties of Composites of PMMA and Surface-Modified Zincite Nanoparticles

et al. 2007

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Composites that show visible light transmittance, UV absorption, and moderately high refractive index, based on poly(methyl methacrylate) (PMMA) and zinc oxide (zincite, ZnO) nanoparticles, were prepared in two steps. First, surface-modified ZnO nanoparticles with 22 nm average diameter were nucleated by controlled precipitation via acid-catalyzed esterification of zinc acetate dihydrate with pentan-1-ol. The surface of growing crystalline particles was modified with tert-butylphosphonic acid (tBuPO 3 H 2 ) in situ by monolayer coverage. Particle size and graft density of -PO 3 H 2 on the particle surface were controlled by the amount of surfactant applied to the reaction solution. Second, the surface-modified particles were incorporated into PMMA by in-situ bulk polymerization. Free radical polymerization was carried out in the presence of these particles using AIBN as initiator. Volume fraction (φ) of the particles was varied from 0.10 to 7.76% (0.5 to 30 wt %). Although the particles are homogeneously dispersed in monomer, segregation of the individual particles upon polymerization was observed. Optical constants of the films ca. 2.0 µm including absorption and scattering efficiencies, indices of refraction, and dispersion constants were determined. The absorption coefficient at 350 nm increases linearly with ZnO, obeying Beer's law at low particle contents. However, it levels off toward a value of about 5000 cm -1 and shows a negative deviation at high concentrations because of aggregation of the individual particles. Waveguide propagation loss coefficients of the composite films were examined by prism coupling. A steep increase of the loss coefficient was found with a slope of 52 dB cm -1 vol % -1 as the volume fraction of the particle increases. The refractive index of the composites depends linearly on volume fraction of ZnO and varies from 1.487 to 1.507 (φ ) 7.76%) at 633 nm. The dispersion of refractive index was found to be consistent with Cauchy's formula. IntroductionThe development of polymer-based composites which exhibit various optical functionalities such as high/low refractive index, tailored absorption/emission properties, or strong optical nonlinearities attracts great interest because of the potential optoelectronic applications. 1,2 More specifically, it was pointed out that such composite materials could be applied as transparent substrate or flexible functional layers of optoelectronic devices which require high transparency in the visible range of the optical spectrum. 3 Replacing the conventional substrates made up of inorganic glasses by polymer-based materials could provide a number of advantages, as the polymer composites have milder processing conditions and better impact resistance, can be made flexible, and the optical parameters can be tailored. These composites are typically obtained by the incorporation of functional inorganic particles into a transparent polymer matrix. 3 While the polymeric component provides processability, flexibility, and transparency, the inorg...

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Section: Resultsmentioning

confidence: 99%

Optical Properties of Composites of PMMA and Surface-Modified Zincite Nanoparticles

et al. 2007

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“…On the basis of our results, we show the effect of confinement on dispersibility, D, of nanoparticles as a function of size asymmetry f and fraction of inclusion f p , which would alter the reported bulk phase behaviour 4,9,11,13,15 . As a consequence of the enhanced dispersion, we observe a reduction in T g of such blends as compared with that in the bulk at comparable nanoparticle volume fractions.…”

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“…Recent studies, however, have also shown that dispersion and thermomechanical properties could be controlled using multicomponent grafted polymer chains 16 . On the other hand, very little is known or understood about the nature of dispersion of nanoparticles in thin polymer films [5][6][7]9,10,12 . This is a bit surprising since, a vast amount of research has been devoted to understanding of structure and properties of thin polymer films, especially those related to the perturbation of chain conformation [17][18][19][20][21] and glass transition due to confinement [5][6][7][8]11,[22][23][24][25] .…”

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confidence: 99%

“…Extensive research has, therefore, been devoted to understand the morphological and dynamical phase diagram of such blends and the consequent role it plays in determining the physical properties of these materials [5][6][7][8][9][10][11][12][13] . On the basis of these studies, various strategies are therefore being devised to enhance the dispersibilty of various functional nanoparticles in PNCs [5][6][7][8][9][10][11][12][13][14][15] . It is believed 4,8,11,13 that a wetting nanoparticle-polymer interface is required for homogeneous nanoparticle dispersion in bulk PNCs.…”

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Confinement enhances dispersion in nanoparticle–polymer blend films

et al. 2014

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Polymer nanocomposites constitute an important class of materials whose properties depend on the state of dispersion of the nanoparticles in the polymer matrix. Here we report the first observations of confinement-induced enhancement of dispersion in nanoparticle-polymer blend films. Systematic variation in the dispersion of nanoparticles with confinement for various compositions and matrix polymer chain dimensions has been observed. For fixed composition, strong reduction in glass transition temperature, T g , is observed with decreasing blend-film thickness. The enhanced dispersion occurs without altering the polymer-particle interactions and seems to be driven by enhanced matrix-chain orientation propensity and a tendency to minimize the density gradients within the matrix. This implies the existence of two different mechanisms in polymer nanocomposites, which determines their state of dispersion and glass transition.

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“…This has led to much excitement about the possible applications of these nanoparticles in many materials science applications. [1][2][3][4][5][6][7] Though the quantitative understanding of the mechanisms behind these property improvements is still developing, it is well accepted that the surface area of NP in contact with the polymer matrix plays a pivotal role. 2 Moreover, the amount of NP surface area in contact with polymers depends on NP dispersion, and thus the problem of ensuring a stable NP dispersion has been a preoccupation with these materials.…”

Section: Introductionmentioning

confidence: 99%

Model for reversible nanoparticle assembly in a polymer matrix

Rahedi

Douglas

Starr

2008

The Journal of Chemical Physics

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The clustering of nanoparticles ͑NPs͒ in solutions and polymer melts depends sensitively on the strength and directionality of the NP interactions involved, as well as the molecular geometry and interactions of the dispersing fluids. Since clustering can strongly influence the properties of polymer-NP materials, we aim to better elucidate the mechanism of reversible self-assembly of highly symmetric NPs into clusters under equilibrium conditions. Our results are based on molecular dynamics simulations of icosahedral NP with a long-ranged interaction intended to mimic the polymer-mediated interactions of a polymer-melt matrix. To distinguish effects of polymer-mediated interactions from bare NP interactions, we compare the NP assembly in our coarse-grained model to the case where the NP interactions are purely short ranged. For the "control" case of NPs with short-ranged interactions and no polymer matrix, we find that the particles exhibit ordinary phase separation. By incorporating physically plausible long-ranged interactions, we suppress phase separation and qualitatively reproduce the thermally reversible cluster formation found previously in computations for NPs with short-ranged interactions in an explicit polymer-melt matrix. We further characterize the assembly process by evaluating the cluster properties and the location of the self-assembly transition. Our findings are consistent with a theoretical model for equilibrium clustering when the particle association is subject to a constraint. In particular, the density dependence of the average cluster mass exhibits a linear concentration dependence, in contrast to the square root dependence found in freely associating systems. The coarse-grained model we use to simulate NP in a polymer matrix shares many features of potentials used to model colloidal systems. The model should be practically valuable for exploring factors that control the dispersion of NP in polymer matrices where explicit simulation of the polymer matrix is too time consuming.

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General Strategies for Nanoparticle Dispersion

Cited by 892 publications

References 30 publications

Optical Properties of Composites of PMMA and Surface-Modified Zincite Nanoparticles

Optical Properties of Composites of PMMA and Surface-Modified Zincite Nanoparticles

Confinement enhances dispersion in nanoparticle–polymer blend films

Model for reversible nanoparticle assembly in a polymer matrix

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