Structure and Dynamics of Polymer Nanocomposites Involving Chain-Grafted Spherical Nanoparticles

Green, Peter; Oh, Hyunjoon; Akcora, Pinar; Kumar, Sanat K.

doi:10.1007/978-1-4614-0727-0_13

Cited by 11 publications

(15 citation statements)

References 83 publications

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“…We believe that these results are a direct manifestation of the macrophase separation/NPs aggregation caused by the effective dislike between the PEO matrix chains and the NPs surface (only relevant for systems where h dry < 0) coupled to the immiscibility between the brush and the matrix chains as we increase P / N at a fixed σ. These results are consistent with several other studies, which have shown that σ is an essential factor that affects the PNCs dispersion state. ,,− …”

Section: Results and Discussionsupporting

confidence: 93%

“…These results are consistent with several other studies which have shown that σ is an essential factor which affects the PNC dispersion state. 13,39,[47][48][49][50] Returning now to the large σ data, we note that there are only two states: well-dispersed or aggregated NPs. This is thought to be a reflection of the matrix "autophobically" dewetting 6 the brush for large P/N.…”

Section: 2the Dispersion State Of Peo-g-sio 2 Nps In the Peo Matrixmentioning

confidence: 82%

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Direct Relationship between Dispersion and Crystallization Behavior in Poly(ethylene oxide)/Poly(ethylene glycol)-g-Silica Nanocomposites

Wen

Liu

et al. 2021

Macromolecules

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The inclusion of polymer-grafted nanoparticles (PGNPs) can impart various functional properties to polymer nanocomposites (PNCs). For semicrystalline polymers, we can control the spatial dispersion of PGNPs and presumably use it to modulate the nucleation rate of the polymer. In this work, the correlation between the dispersion quality of poly(ethylene glycol) (PEG) grafted silica (PEG-g-SiO 2 ) nanoparticles and the crystallization ability of poly(ethylene oxide) (PEO) nanocomposites is systematically investigated by varying the grafting density (σ, chains/nm 2 ) and the value of P/N (P: molecular weight of matrix chains, N: molecular weight of grafted chains). The variation of PEG-g-SiO 2 dispersion state was studied by morphological characterization and small-angle X-ray scattering (SAXS). It was found that, in contrast to the unmodified SiO 2 and poly(methyl methacrylate) grafted silica (PMMA-g-SiO 2 ), PEG-g-SiO 2 (high σ and low P/N) can increase the nucleation rate of PEO even under conditions where they are well dispersed in the PEO matrix.Evidently, the nature of the graft, i.e., amorphous PMMA vs. crystallizable PEO, has profound consequences in this context, a novel result that has not been anticipated based on previous work. NP aggregation occurs at higher P/N values and limits the effectiveness of the grafted PEG on the crystallization ability of PEO nanocomposites.Based on differential scanning calorimetry (DSC) and polarized light optical microscopy (PLOM) characterization, we deduced that the increased nucleation density at high σ and low P/N has a strong impact on accelerating the overall crystallization of PEO nanocomposites.

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Section: Results and Discussionsupporting

confidence: 93%

Section: 2the Dispersion State Of Peo-g-sio 2 Nps In the Peo Matrixmentioning

confidence: 82%

Direct Relationship between Dispersion and Crystallization Behavior in Poly(ethylene oxide)/Poly(ethylene glycol)-g-Silica Nanocomposites

Wen

Liu

et al. 2021

Macromolecules

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“…Also, it was difficult to differentiate the effect of entanglement, the number of arms, and shape. Polymer grafted nanoparticles in the melt have been investigated, − in which they had a core of 10 nm or larger and squeezable long grafted chains as a shell. In these grafted nanoparticles, the core volume fractions were less than 20% of the overall volume.…”

Section: Introduction and Theoretical Backgroundmentioning

confidence: 99%

Dynamics of Shape-Persistent Giant Molecules: Zimm-like Melt, Elastic Plateau, and Cooperative Glass-like

et al. 2017

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Giant molecules are a new class of soft matter having three-dimensional (3D) shapes and composed of chemically linked rigid molecular nanoparticles. Structurally, a 3D cluster of molecular nanoparticles can be one giant molecule or a few giant molecules associated together via specific interactions. The dynamics of clusters that are smaller than a critical diameter (∼5 nm) presents a power law relaxation exponent of 0.7 at the high frequency region corresponding to segmental dynamics. Such scaling is similar to the result of the Zimm model although those clusters are neither chain-like nor in solution. Clusters that are larger than this critical diameter and formed by the association of giant molecules exhibit an elastic plateau due to caging of individual giant molecules. We hypothesize that clusters of such a large size cannot move as a whole, even above the glass transition temperature of the sample. They thus are “cooperative glass-like”. A structural cluster of giant molecules could be abstracted as a dynamical cluster consisting of unlinked but cooperatively mobile beads. As derived in the random first-order transition theory, the cluster loses its mobility and reaches the glassy state when the diameter of the cluster is 6 times larger than the bead diameter. In our cases, we estimate that the critical diameter for these clusters is also approximately 6 times the bead diameter based on the glassy shear modulus of giant molecules. Thus, shape-persistent giant molecules may serve as a bridge between polymers and colloids and a platform to mimic cooperative rearrangements.

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“…The incorporation of nanoparticles (NPs) into polymer can drastically alter the properties of the host polymer. 1,2 The nanoscopic size of NPs allows for high particle number densities to be achieved at small particle loadings <10 wt %, enabling a large fraction of the polymer to be in direct contact with the surface of the particles. 2,3 The NPs are often grafted with polymer chains to introduce steric (entropic) repulsion between the NPs and prevent their aggregation due to attractive van der Waals and depletion forces.…”

Section: ■ Introductionmentioning

confidence: 99%

Viscoelastic Properties of Polymer-Grafted Nanoparticle Composites from Molecular Dynamics Simulations

Hattemer

Arya

2015

Macromolecules

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To provide insights into how polymer-grafted nanoparticles (NPs) enhance the viscoelastic properties of polymers, we have computed the frequency-dependent storage and loss modulus of coarse-grained models of polymer nanocomposites by means of molecular dynamics simulations. Nanocomposites containing NPs grafted with chains similar to those comprising the host polymer matrix exhibit considerably higher moduli than nanocomposites containing bare NPs across the entire frequency range investigated. This effect is shown to arise from the additional distortion of the shear field in the polymer matrix resulting from the grafted chains and from the slower relaxation time of the grafted chains compared to the matrix chains when the former are at least half as long as the latter. Increasing the attraction between the grafted and matrix chains results in further enhancement in the two moduli, but only at frequencies slower than those corresponding to the longest relaxation time of the chains. This effect is shown to arise from a dramatic slowdown in the relaxation dynamics of both the matrix and grafted chains. In addition, the nanocomposite moduli are found to increase with decreasing NP size and increasing NP loading, grafted chain length, and grafting density with varying frequency dependence. These parametric effects are also explained in terms of shear distortion effects and chain relaxation times. Based on these results, a phenomenological model is proposed to estimate the storage and loss modulus of such nanocomposites as a function of the Rouse relaxation times of the grafted and matrix chains and the volume fractions of the NPs, grafted chains, and matrix chains. The model captures the observed dependence of the moduli with the examined parameters of the grafted NPs and yields moduli predictions that agree quantitatively with those computed from the simulations at low frequencies.

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Structure and Dynamics of Polymer Nanocomposites Involving Chain-Grafted Spherical Nanoparticles

Cited by 11 publications

References 83 publications

Direct Relationship between Dispersion and Crystallization Behavior in Poly(ethylene oxide)/Poly(ethylene glycol)-g-Silica Nanocomposites

Direct Relationship between Dispersion and Crystallization Behavior in Poly(ethylene oxide)/Poly(ethylene glycol)-g-Silica Nanocomposites

Dynamics of Shape-Persistent Giant Molecules: Zimm-like Melt, Elastic Plateau, and Cooperative Glass-like

Viscoelastic Properties of Polymer-Grafted Nanoparticle Composites from Molecular Dynamics Simulations

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