Investigation of the properties of nanographene in polymer nanocomposites through molecular simulations: dynamics and anisotropic Brownian motion

Rissanou, Anastassia N.; Bačová, Petra; Harmandaris, Vagelis

doi:10.1039/c9cp02074h

Cited by 14 publications

(7 citation statements)

References 57 publications

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“…However, the SE equation is applicable when L > R g , implying that the NRs can feel the macroscopic viscosity completely. It is well known that for particles of anisotropic shape, different diffusion coefficients in the directions parallel to their major axis and perpendicular to it are predicted. − We further investigate the anisotropic dynamics of NRs by calculating the diffusion coefficients along the rod axis ( D ∥ ) and the diffusion coefficients perpendicular to the rod axis ( D ⊥ ). Both D ∥ and D ⊥ decrease with increasing L and D (Figure S5) as NRs experience more drag from the surrounding polymers.…”

Section: Resultsmentioning

confidence: 99%

Dispersion and Diffusion Mechanism of Nanofillers with Different Geometries in Bottlebrush Polymers: Insights from Molecular Dynamics Simulation

Chen

Huang

et al. 2022

J. Phys. Chem. B

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The dispersion and diffusion mechanism of nanofillers in polymer nanocomposites (PNCs) are crucial for understanding the properties of PNCs, which is of great significance for the design of novel materials. Herein, we investigate the dispersion and diffusion behavior of two geometries of nanofillers, namely, spherical nanoparticles (SNPs) and nanorods (NRs), in bottlebrush polymers by utilizing coarse-grained molecular dynamics simulations. With the increase of the interaction strength between the nanofiller and polymer (εnp), both the SNPs and NRs experience a typical “aggregated phase–dispersed phase–bridged phase” state transition in the bottlebrush polymer matrix. We evaluate the validity of the Stokes–Einstein (SE) equation for predicting the diffusion coefficient of nanofillers in bottlebrush polymers. The results demonstrate that the SE predictions are slightly larger than the simulated values for small SNP sizes because the local viscosity that is felt by small SNPs in the densely grafted bottlebrush polymer does not differ much from the macroscopic viscosity. The relative size of the length of the NRs (L) and the radius of gyration (R g) of the bottlebrush polymer play a key role in the diffusion of NRs. In addition, we characterize the anisotropic diffusion of NRs to analyze their translational and rotational diffusion. The motion of NRs in the direction perpendicular to the end-to-end vector is more hindered, indicating that there is a strong coupling between the rotation of NRs and the motion of the polymer. The NR motion shows stronger anisotropic diffusion at short time scales because of the steric effects generated by side chains of the bottlebrush polymer. In general, our results provide a fundamental understanding of the dispersion of nanofillers and the microscopic mechanism of nanofiller diffusion in bottlebrush polymers.

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Section: Resultsmentioning

confidence: 99%

Dispersion and Diffusion Mechanism of Nanofillers with Different Geometries in Bottlebrush Polymers: Insights from Molecular Dynamics Simulation

Chen

Huang

et al. 2022

J. Phys. Chem. B

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“…Significant insight into the dynamic properties of polymer nanocomposites has also been obtained from molecular simulations which seem to indicate that important dynamic heterogeneities emerge in polymer nanocomposites for nanoparticles of different types and for various host polymer matrices. − Atomistic-level simulations have found extensive use in the study of such systems due to the detailed and precise representation of the chemical structure of the system. − A good example is the early molecular dynamics (MD) study of Barbier et al of PEG oligomers filled with small spherical silica nanoparticles, where all components of the nanocomposite were represented in full atomistic detail. According to their work, the strong adsorption of PEG chains on the silica nanoparticles leads to the formation of a tight adsorbed layer, whose density and local dynamics are significantly altered compared to the bulk.…”

Section: Introductionmentioning

confidence: 99%

Individual Contributions of Adsorbed and Free Chains to Microscopic Dynamics of Unentangled poly(ethylene Glycol)/Silica Nanocomposite Melts and the Important Role of End Groups: Theory and Simulation

et al. 2021

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Molecular dynamics simulations and Rouse theory suitably adapted for polymer chains adsorbed by one or both of their ends are combined to offer a quantitative description of the local structure and microscopic dynamics in attractive polymer nanocomposite melts using a poly(ethylene glycol) (PEG)/silica nanocomposite as a model system. Our work reveals that the adsorbed layer around the silica nanoparticle is far from being characterized as “glassy” or “immobilized” since adsorbed polymer segments in the form of tails and loops on silica exhibit appreciable mobility locally, which helps adsorbed chains to relax at short length scales, albeit rather slowly. The simulations also reveal significant differences in the structural and dynamic properties of the PEG/silica nanocomposite melts studied for different terminal groups (hydroxyl versus methoxy) of the PEG chains, originating from the different ways that polymer chains adsorb on the silica surface: hydroxyl-terminated PEG chains are adsorbed by their ends giving rise to a brush-like structure, whereas methoxy-terminated ones are adsorbed equally probably along their entire contour, thus resulting in better packing of adsorbed segments. Due to the dense interfacial layer that develops in both cases, the diffusive behavior of free chains is also affected (it slows down compared to that in the corresponding pure PEG melt), especially in the nanocomposite where PEG chains are terminated with hydroxyl groups. Direct comparison of simulation and theoretical predictions with previously reported experimental data in the literature for the dynamic structure factor [Glomann et al., Phys. Rev. Lett. 2013, 110, 178001] for the same systems under the same temperature and pressure conditions reveals excellent agreement.

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“…In the case of GP, conformational transitions are present, manifesting a dynamic behavior known also as rippling or wrinkling. − In addition, GO was found to exhibit a higher tendency for curvature compared to GP. , The distribution of functional groups’ charges may lead to such long-lasting curvature effects. ,, …”

Section: Resultsmentioning

confidence: 99%

“…Although the rippling of the diffusing nanosheet 92 may slightly affect the density profiles close to the surface, qualitative information concerning the density fluctuations on the surface can be extracted. In the PAAGP systems, a peak is observed at a distance of almost 5 Å from the GP, which tends to become lower in amplitude and broader as the temperature drops.…”

Section: Resultsmentioning

confidence: 99%

Bound Layer Polymer Behavior on Graphene and Graphene Oxide Nanosheets

et al. 2020

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Molecular dynamics simulations were employed to study the bound layer in polymer/graphene-based nanocomposites. We focused on the dynamic behavior of polar (poly(acrylic acid)) and nonpolar (polystyrene) linear chains, at the interface with graphene-based fillers, bearing different affinities with the polymers and different nanoroughness. Four temperatures were examined with a step of 50 K and the lowest one 100 K above the T g of the corresponding bulk polymers. The dynamic response of the adsorbed layer exhibited an increased departure from that of the bulk, accompanied by a higher degree of dynamical heterogeneity, especially for the oxidized graphene systems. In the case of the nonoxidized analogues, an increased anisotropy of polymer diffusion parallel and perpendicular to the filler’s plane was observed. Dynamics within the adsorbed layer exhibited Arrhenius-like characteristics in all the examined systems, in agreement with recent experimental studies. The combination of the results associated with backbone torsional motion and the chain desorption process revealed a strong dynamic transition near both the examined nanosheets, almost 100 K above the bulk T g. However, in the adjacent-to-the-adsorbed layer, polymer dynamic characteristics approached the bulk behavior. It is therefore implied that, depending on its average size, a polymer chain may experience different dynamic regimes across its length near the interface region.

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Investigation of the properties of nanographene in polymer nanocomposites through molecular simulations: dynamics and anisotropic Brownian motion

Abstract: The dynamical behavior of nanographene sheets dispersed in polymer matrices is investigated through united-atom molecular dynamics simulations.

Cited by 14 publications

References 57 publications

Dispersion and Diffusion Mechanism of Nanofillers with Different Geometries in Bottlebrush Polymers: Insights from Molecular Dynamics Simulation

Dispersion and Diffusion Mechanism of Nanofillers with Different Geometries in Bottlebrush Polymers: Insights from Molecular Dynamics Simulation

Individual Contributions of Adsorbed and Free Chains to Microscopic Dynamics of Unentangled poly(ethylene Glycol)/Silica Nanocomposite Melts and the Important Role of End Groups: Theory and Simulation

Bound Layer Polymer Behavior on Graphene and Graphene Oxide Nanosheets

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