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

Abstract

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.;

Hairy nanoparticle assemblies as one-component functional polymer nanocomposites: opportunities and challenges

“…However, attempts at coarsegraining the MD models to develop effective interaction potentials at lower temperatures and shorter chain lengths have met with limited success. [33] Chremos and Panagiotopoulos [34] then use this MD model to investigate the structural transitions of these materials as a function of grafting density, core size, and temperature, and demonstrate that the HNPs can form glasses, isotropic aggregates, anisotropic aggregates, and star fluids [Figs. 2(c) and 2 (d)].…”

Microscopic Dynamics and Topology of Polymer Rings Immersed in a Host Matrix of Longer Linear Polymers: Results from a Detailed Molecular Dynamics Simulation Study and Comparison with Experimental Data

“…In all MD simulations, we used the modified TrAPPE united-atom (UA) force-field introduced by Fischer et al [42,43], which has been thoroughly validated through extensive comparisons of its predictions for several material properties (density, mean square radius-of-gyration, self-diffusion coefficient, dynamic structure factor, etc.) of low and high molecular weight linear and ring PEO melts with published simulation [44] or experimental [45,46,47,48,49,50,51,52] data and/or the predictions of other force fields reported in the literature [53]. The simulations were executed with the GROMACS [54] simulation software in the isothermal–isobaric (NPT) statistical ensemble by applying the Nosé–Hoover thermostat [55,56] coupled with the Parrinello–Rahman [57] barostat to keep the temperature T and the pressure P fixed at the desired values ( T = 413 K and P = 1 atm).…”

Coarse-grain molecular dynamics simulations of nanoparticle-polymer melt: Dispersion vs. agglomeration

“…Numerous molecular simulation studies have been done using coarse-grain models, derived from fully atomistic simulations. [13][14][15][16][17] These model systems have been quite successful in explaining many experimental observations. [18][19][20][21][22][23][24][25][26] In a) Author to whom correspondence should be addressed.…”