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A8 (N): Roberto - Improved dynamics in self-consistent field molecular dynamics simulations of polymers

The aim of this project is to develop a molecular simulation algorithm for chemically realistic polymers and nanocomposites that combines two recently developed methods:
(i) The so-called hybrid particle-field (hPF) method of Milano and coworkers,
(ii) The slip-spring concept as mock-up for entanglements,
which are difficult to capture in the hPF model due to the absence of hard core interactions. The method shall be analyzed in detail and the scientific risks will be carefully evaluated. It will be applied to study the dynamical and rheological properties of polymers and nanocomposites.

Funding for this project has started in July 2018

Combination of Hybrid Particle-Field Molecular Dynamics and SlipSprings for the Efficient Simulation of Coarse-Grained Polymer Models: Static and Dynamic Properties of Polystyrene Melts
Zhenghao Wu, Giuseppe Milano, Florian Müller-Plathe
Journal of Chemical Theory and Computation, (2020);

A quantitative prediction of polymer entangled dynamics based on molecular simulation is a grand challenge in contemporary computational material science. The drastic increase of relaxation time and viscosity in high molecular-weight polymeric fluids essentially limits the usage of classic molecular dynamics simulation. Here, we demonstrate a systematic coarse-graining approach for modeling entangled polymers under the slip-spring particle-field scheme. Specifically, a frequency-controlled slip-spring model, a hybrid particle-field model and a coarse-grained model of polystyrene melts are combined into a hybrid simulation technique. Via a rigorous parameterization strategy to determine the parameters in slip-springs from existing experimental or simulation data, we show that the reptation behavior is clearly observed in multiple characteristics of polymer dynamics: mean-square displacements, diffusion coefficients, reorientational relaxation and Rouse mode analysis, consistent with the predictions of the tube theory. All dynamical properties of the slip-spring particle-field models are in good agreement with classic molecular dynamics models. Our work provides an efficient and practical approach to establish chemical-specific coarse-grained models for predicting polymer entangled dynamics.

Atomistic hybrid particle‐field molecular dynamics combined with slip‐springs: Restoring entangled dynamics to simulations of polymer melts
Zhenghao Wu, Andreas Kalogirou, Antonio De Nicola, Giuseppe Milano, Florian Müller‐Plathe
Journal of Computational Chemistry, (2020);

In hybrid particle‐field (hPF) simulations (J. Chem. Phys., 2009 130, 214106), the entangled dynamics of polymer melts is lost due to chain crossability. Chains cross, because the field‐treatment of the nonbonded interactions makes them effectively soft‐core. We introduce a multi‐chain slip‐spring model (J. Chem. Phys., 2013 138, 104907) into the hPF scheme to mimic the topological constraints of entanglements. The structure of the polymer chains is consistent with that of regular molecular dynamics simulations and is not affected by the introduction of slip‐springs. Although slight deviations are seen at short times, dynamical properties such as mean‐square displacements and reorientational relaxation times are in good agreement with traditional molecular dynamics simulations and theoretical predictions at long times.

Influence of Polymer Bidispersity on the Effective Particle–Particle Interactions in Polymer Nanocomposites
Gianmarco Munaò, Antonio De Nicola, Florian Müller-Plathe, Toshihiro Kawakatsu, Andreas Kalogirou, Giuseppe Milano
Macromolecules, (2019);


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