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Polymers: Molecular Weight Distribution

Polymers: Molecular Weight Distribution

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Updated: Dec 17, 2025

Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level

Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level

Published on: September 26, 2016

Nanoparticle diffusion in polymer melts: Molecular dynamics simulations and mode-coupling theory.

Hristina Popova¹, Sergei A Egorov², Andrey Milchev¹

¹Institute of Physical Chemistry, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria.

The Journal of Chemical Physics

|June 24, 2020

Summary

Nanoparticle diffusion in polymer melts deviates from Stokes-Einstein predictions for small nanoparticles. Mode-Coupling Theory (MCT) was improved using Molecular Dynamics (MD) simulations to accurately model this behavior.

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Last Updated: Dec 17, 2025

Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level

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Analyzing Melts and Fluids from Ab Initio Molecular Dynamics Simulations with the UMD Package

Analyzing Melts and Fluids from Ab Initio Molecular Dynamics Simulations with the UMD Package

Published on: September 17, 2021

Area of Science:

Materials Science
Polymer Physics
Computational Chemistry

Background:

Nanoparticle diffusion in polymer melts is crucial for material properties.
Existing models like Stokes-Einstein (SE) and Mode-Coupling Theory (MCT) have limitations.
Discrepancies exist between simulation and theoretical predictions for nanoparticle diffusion coefficients.

Purpose of the Study:

To investigate nanoparticle diffusion in polymer melts using Molecular Dynamics (MD) simulations and Mode-Coupling Theory (MCT).
To refine MCT by incorporating MD-derived data to improve accuracy.
To understand the role of friction in nanoparticle transport.

Main Methods:

Performed Molecular Dynamics (MD) simulations to obtain structural and dynamical data.
Applied Mode-Coupling Theory (MCT) with MD data as input.
Developed an improved MCT approach by splitting microscopic friction into binary and collective terms.

Main Results:

Stokes-Einstein relation (D~1/R) holds for large nanoparticles (R > R_g).
For smaller nanoparticles (R < R_g), diffusion coefficients exceed SE predictions.
Improved MCT, using MD data, accurately predicts a 1/R^2 scaling for nanoparticle diffusion in the non-hydrodynamic regime, with friction dominated by short-time dynamics.

Conclusions:

The binary short-time friction term is dominant in nanoparticle diffusion within polymer melts.
Neglecting this term in MCT leads to significant overestimation of diffusion coefficients.
The revised MCT approach provides accurate predictions consistent with MD simulations for nanoparticle transport.