Chain Conformation in Polymer Nanocomposites with Uniformly Dispersed Nanoparticles

Large-scale Molecular Dynamics simulations are used to study the internal relaxations of chains in nanoparticle (NP)/polymer composites. We examine the Rouse modes of the chains, a quantity that is closest in spirit to the self-intermediate scattering function, typically determined in an (incoherent) inelastic neutron scattering experiment. Our simulations show that for weakly interacting mixtures of NPs and polymers, the effective monomeric relaxation rates are faster than in a neat melt when the NPs are smaller than the entanglement mesh size. In this case, the NPs serve to reduce both the monomeric friction and the entanglements in the polymer melt, as in the case of a polymer-solvent system. However, for NPs larger than half the entanglement mesh size, effective monomer relaxation is essentially unaffected for low NP concentrations. Even in this case, we observe a strong reduction in chain entanglements for larger NP loadings. Thus, the role of NPs is to always reduce the number of entanglements, with this effect only becoming pronounced for small NPs or for high concentrations of large NPs. Our studies of the relaxation of single chains resonate with recent neutron spin echo (NSE) experiments, which deduce a similar entanglement dilution effect.

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“…However, the important conclusion here is that chain conformations are essentially unaffected by the NPs at all length scales. 17, 42 …”

Section: Resultsmentioning

confidence: 99%

Rouse mode analysis of chain relaxation in polymer nanocomposites

et al. 2015

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“…Driven by the need to develop functionally superior materials, significant effort has been directed towards the understanding of structure and thermodynamics of polymer blends [1][2][3][4][5] and polymernanoparticle mixtures/blends [6][7][8][9][10][11] . Fundamentally, the delicate balance of enthalpic and entropic driving forces, arising from the interplay of polymer and particle chemistry, polymer molecular weight, architecture, particle size, and the blend composition dictates the phase transition from mixed (dispersed) to demixed (aggregated) states.…”

Section: Introductionmentioning

confidence: 99%

Wetting–Dewetting and Dispersion–Aggregation Transitions Are Distinct for Polymer Grafted Nanoparticles in Chemically Dissimilar Polymer Matrix

et al. 2015

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Simulations and experiments are conducted on mixtures containing polymer grafted nanoparticles in a chemically distinct polymer matrix, where the graft and matrix polymers exhibit attractive enthalpic interactions at low temperatures that become progressively repulsive as temperature is increased. Both coarse-grained molecular dynamics simulations, and X-ray scattering and neutron scattering experiments with deuterated polystyrene (dPS) grafted silica and poly(vinyl methyl ether) PVME matrix show that the sharp phase transition from (mixed) dispersed to (demixed) aggregated morphologies due to the increasingly repulsive effective interactions between the blend components is distinct from the continuous wetting-dewetting transition. Strikingly, this is unlike the extensively studied chemically identical graft-matrix composites, where the two transitions have been considered to be synonymous, and is also unlike the free (ungrafted) blends of the same graft and matrix homopolymers, where the wetting-dewetting is a sharp transition coinciding with the macrophase separation.

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“…Indeed, the spectroscopy of high spin states in Ti isotopes suggests that these orbitals are practically degenerate [8]. With increasing neutron number in the vicinity of N = 40 a * Electronic address: p.sarriguren@csic.es new island of inversion is predicted and deformation sets in [9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

β -decay properties of neutron-rich Ca, Ti, and Cr isotopes

2018

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β-decay properties of neutron-rich Ca, Ti, and Cr isotopes are studied within a deformed protonneutron quasiparticle random-phase approximation. The underlying mean field is described selfconsistently from deformed Skyrme Hartree-Fock calculations with pairing correlations. Residual spin-isospin interactions in the particle-hole and particle-particle channels are also included in the formalism. The energy distributions of the Gamow-Teller strength, the β-decay feedings, the β-decay half-lives, and the β-delayed neutron emission probabilities are discussed and compared with other theoretical results, as well as with the available experimental information. The evolution of these nuclear β-decay properties is investigated in isotopic chains in a search for structural changes. A reliable estimate of the β-decay properties in this mass region is a valuable information for evaluating decay rates in astrophysical scenarios.

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Chain Conformation in Polymer Nanocomposites with Uniformly Dispersed Nanoparticles

Cited by 82 publications

References 28 publications

Rouse mode analysis of chain relaxation in polymer nanocomposites

Rouse mode analysis of chain relaxation in polymer nanocomposites

Wetting–Dewetting and Dispersion–Aggregation Transitions Are Distinct for Polymer Grafted Nanoparticles in Chemically Dissimilar Polymer Matrix

β -decay properties of neutron-rich Ca, Ti, and Cr isotopes

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