Computer Simulation Studies of PEO/Layer Silicate Nanocomposites

Hackett, E.; Manias, Evangelos; Giannelis, E.P.

doi:10.1021/cm990676x

Cited by 212 publications

(200 citation statements)

References 28 publications

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“…13,14 On the structure, the current opinion is that PEO arranges in the interlayer gallery in an amorphous bilayer parallel to the confining clay platelets, with Li ϩ cations located in the immediate vicinity of the solid surfaces. This structural description is supported by experimental findings 7 and also by simulations 12,13 but contradicts the traditional viewpoint of extended crystalline PEO chain conformations with the Li cations located in the centers of the films [e.g., ref. 5 (Fig.…”

Section: Introductionmentioning

confidence: 77%

“…2 Because these systems self-assemble in highly ordered intercalated structures, it is easy to prepare samples with macroscopic quantities of severely confined polymers so that conventional analytical techniques such as solid-state NMR, dielectric spectroscopy, and X-ray and neutron diffraction studies can be successfully applied. [2][3][4][5][6][7][8][9][10][11] Such experimental investigations combined with simulation studies [12][13][14][15][16][17] unveil a striking picture for the physics of polymers in severe confinements between solid surfaces.…”

Section: Introductionmentioning

confidence: 98%

“…For the system in focus here, that is, 1-nmthick poly(ethylene oxide) (PEO)/Li ϩ films confined between montmorillonite (MMT) clay platelets, [3][4][5][6][7][8] a complete understanding of the segmental relaxations, chain dynamics, and the structural arrangement of the polymer layers still remains largely elusive despite numerous experimental and simulations studies. [2][3][4][5][6][7][8][12][13][14] Despite the severe confinement the system dynamics, Li ϩ and PEO segmental, are very rich, characterized by a coexistence of ultraslow and ultrafast dynamics across all temperatures examined, 6,8,13,14 with the temperature affecting only the relative population of fast-slow species. 13,14 On the structure, the current opinion is that PEO arranges in the interlayer gallery in an amorphous bilayer parallel to the confining clay platelets, with Li ϩ cations located in the immediate vicinity of the solid surfaces.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Simulation insights on the structure of nanoscopically confined poly(ethylene oxide)

Kuppa

Menakanit

Krishnamoorti

et al. 2003

J Polym Sci B Polym Phys

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ABSTRACT:We employ atomistic computer modeling to investigate the structure and morphology of poly(ethylene oxide) (PEO) chains confined in 1-nm slit pores defined by montmorillonite silicate layers. Molecular dynamics computer simulations reveal the Li ϩ cations to be located in the immediate vicinity of the silicate surfaces and PEO to adopt highly amorphous conformations in a liquidlike bilayer across the slit pores. Despite the orienting influence of the parallel stacked silicate walls, PEO shows no indication of crystallinity or periodic ordering; in fact, for all temperatures simulated, it is less ordered than the most disordered bulk PEO system. These amorphous PEO film configurations are attributed to the combination of severe spatial confinement and the strong coordination of ether oxygens with the alkali cations present in the interlayer gallery. These conclusions challenge the picture traditionally proposed for intercalated PEO, but they agree with a plethora of experimental observations. Indicatively, the simulation predictions are confirmed by wide-angle neutron scattering and differential scanning calorimetry experiments on PEO/montmorillonite intercalates.

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Section: Introductionmentioning

confidence: 77%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Simulation insights on the structure of nanoscopically confined poly(ethylene oxide)

Kuppa

Menakanit

Krishnamoorti

et al. 2003

J Polym Sci B Polym Phys

Self Cite

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“…Although models with atomistic descriptions of both nanoparticles and chains have been developed for nanocomposites, [4][5][6][7][8] their application is often limited to systems with one nanoparticle, and they can only provide information on local polymer structures (length scales <4 nm) over short times of the order of ns. In order to describe largerscale properties such as nanoparticle dispersion and transport, a NOHMs model with solid-sphere nanoparticles and atomistic polymers was recently proposed that is suitable for simulating systems consisting of hundreds of nanoparticles.…”

Section: Introductionmentioning

confidence: 99%

Dynamics in coarse-grained models for oligomer-grafted silica nanoparticles

Hong

Chremos

Panagiotopoulos

2012

The Journal of Chemical Physics

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Effect of bidispersity in grafted chain length on grafted chain conformations and potential of mean force between polymer grafted nanoparticles in a homopolymer matrix J. Chem. Phys. 134, 194906 (2011) Coarse-grained models of poly(ethylene oxide) oligomer-grafted nanoparticles are established by matching their structural distribution functions to atomistic simulation data. Coarse-grained force fields for bulk oligomer chains show excellent transferability with respect to chain lengths and temperature, but structure and dynamics of grafted nanoparticle systems exhibit a strong dependence on the core-core interactions. This leads to poor transferability of the core potential to conditions different from the state point at which the potential was optimized. Remarkably, coarse graining of grafted nanoparticles can either accelerate or slowdown the core motions, depending on the length of the grafted chains. This stands in sharp contrast to linear polymer systems, for which coarse graining always accelerates the dynamics. Diffusivity data suggest that the grafting topology is one cause of slower motions of the cores for short-chain oligomer-grafted nanoparticles; an estimation based on transition-state theory shows the coarse-grained core-core potential also has a slowing-down effect on the nanoparticle organic hybrid materials motions; both effects diminish as grafted chains become longer.;

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“…[2][3][4][5] Typical host materials to effect 2D-confinement include cation-containing layered silicates such as montmorillonite, vermiculite, fluoromica or kaolinite. [6][7][8] For strongly adsorbing surfaces, indications of a slow-down of the segmental dynamics have been observed, although different trends have also been noted. 5 For weakly adsorbing surfaces, both positive and negative shifts in Tg and relaxation times have also been reported, yet these results still remain quite controversial and largely open to interpretation.…”

mentioning

confidence: 99%

Macromolecular Structure and Vibrational Dynamics of Confined Poly(ethylene oxide): From Subnanometer 2D-Intercalation into Graphite Oxide to Surface Adsorption onto Graphene Sheets

et al. 2012

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ABSTRACT:In this work, high-resolution inelastic neutron scattering (INS) has been used to provide novel insights into the properties of confined poly(ethylene oxide) (PEO) chains. Two limits have been explored in detail, namely, single-layer 2D-polymer intercalation into graphite oxide (GO) and surface polymer adsorption onto thermally reduced and exfoliated graphite oxide, i.e., graphene (G) sheets. Careful control over the degree of GO oxidation and exfoliation reveals three distinct cases of spatial confinement: i) subnanometer 2D-confinement; ii) frustrated absorption and iii) surface immobilization. Case i) results in drastic changes to PEO conformational (800-1000 cm -1 ) and collective (200-600 cm -1 ) vibrational modes as a consequence of a preferentially planar zig-zag (trans-trans-trans) chain conformation in the confined polymer phase. These changes give rise to peculiar thermodynamic behavior, whereby confined PEO chains are unable to either crystallize or display a calorimetric glass transition. In case ii), GO is thermally reduced resulting in a disordered pseudo-graphitic structure. As a result, we observe minimal PEO absorption owing to a dramatic reduction in the abundance of hydrophilic groups inside the distorted graphitic galleries. In case iii), the INS data unequivocally show that PEO chains adsorb firmly onto the G sheets, with a substantial increase in the population of gauche conformers. Well-defined glass and melting transitions associated with the confined polymer phase are recovered in case iii), albeit at sensibly lower temperatures than those of the bulk.

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Computer Simulation Studies of PEO/Layer Silicate Nanocomposites

Cited by 212 publications

References 28 publications

Simulation insights on the structure of nanoscopically confined poly(ethylene oxide)

Simulation insights on the structure of nanoscopically confined poly(ethylene oxide)

Dynamics in coarse-grained models for oligomer-grafted silica nanoparticles

Macromolecular Structure and Vibrational Dynamics of Confined Poly(ethylene oxide): From Subnanometer 2D-Intercalation into Graphite Oxide to Surface Adsorption onto Graphene Sheets

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