Dispersion and Diffusion Mechanism of Nanofillers with Different Geometries in Bottlebrush Polymers: Insights from Molecular Dynamics Simulation

Qu, Jiajun; Chen, Qionghai; Huang, Wanhui; Zhang, Liqun; Liu, Jun

doi:10.1021/acs.jpcb.2c04389

Cited by 9 publications

(7 citation statements)

References 60 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Like Zografos et al 38 and Lopez et al, 27 for densely grafted bottlebrushes we identify a star-like to bottlebrush-like transition with power law exponents for the flow curves progressively decreasing and converging to a Zimm scaling of ∼−0.33 with increasing N BB , 58 even if in our case the total molecular weight is constant instead of progressively increasing N BB at fixed side chain length. We attribute the shear thinning behavior to the orientation of the individual bonds rather than the backbone relaxation, in line with the computational findings of Qu et al 59 This idea would also be in line with the recent findings that a monomeric friction coefficient in Brownian dynamics simulations of Fraenkel chains is necessary to correctly capture experimental viscosity data for unentangled linear polymers under flow. 60−62 Yet, this might be caused by the high shear rates accessible to our simulations, close to the inverse of the bond relaxation times τ b , while different architectural effects might play a more important role at lower shear rates that we could not access.…”

Section: ■ Methodssupporting

confidence: 90%

Shear Thinning from Bond Orientation in Model Unentangled Bottlebrush Polymer Melts

Gürel,

Giuntoli

2023

Macromolecules

View full text Add to dashboard Cite

The rheology of molecular brushes remains challenging to control due to the multiple length scales and relaxation processes involved and the lack of direct observation of molecular conformation during flow. We use molecular dynamics simulations to determine the shear thinning of unentangled bottlebrush polymers with varying architecture, from linear chains to combs, to densely grafted bottlebrushes, to star-like and star polymers. We find shear thinning exponents in line with theoretical and experimental results and characterize the shape and orientation of bottlebrushes in steady-state flow. Many shape parameters derived from the gyration tensor show molecular alignment with the flow for all systems. Yet, the orientation of individual bonds is what most strongly correlates with the architecture-dependent shear-thinning exponents. In densely grafted bottlebrushes, the packing of side chains prevents alignment with the flow, causing a reduction in shear thinning. The molecular insight from our simulations is useful to tune the architecture of bottlebrushes to control their rheology.

show abstract

Section: ■ Methodssupporting

confidence: 90%

Shear Thinning from Bond Orientation in Model Unentangled Bottlebrush Polymer Melts

Gürel,

Giuntoli

2023

Macromolecules

View full text Add to dashboard Cite

show abstract

Section: Models and Methodsmentioning

confidence: 99%

“…In order to investigate the behavior of individual monomers, we compute MSD curves for several representative simulation systems. The diffusion coefficient ( D ) is determined, and the average distance a monomer diffuses in time τ is estimated as , where D is calculated using the equation: , . Finally, we compare the diffusion distance of individual monomers within time τ in the selected system with 0.02 times the box sizes, and we present results in Table S2.…”

Section: Models and Methodsmentioning

confidence: 99%

Insights into Uniaxial Tension and Relaxation of Nanorod-Filled Polymer Vitrimer Nanocomposites: A Molecular Dynamics Simulation

et al. 2023

Self Cite

View full text Add to dashboard Cite

The mechanical properties of polymer nanocomposites (PNCs) depend sensitively on the structure (e.g., orientation, dispersion, and so on) of the incorporated nanofillers. Many studies have shown that the alignment of anisotropic nanofillers can improve the mechanical properties of PNCs. However, achieving this alignment typically requires complex preparation processes. To address this challenge, researchers have introduced dynamic covalent bonds to form reversible cross-linked polymer systems, which would lead to unique properties, such as self-healing, recyclability, and reprocessibility. In addition, inspired by the above ideas, we introduce nanorods as fillers into a linear vitrimer system to form nanorod vitrimer composites (NVCs). In NVCs, we can easily manipulate the alignment of the nanorods due to bond exchange reactions (BERs) in the vitrimer matrices. By using coarse-grained molecular dynamics (CGMD) simulations, we systematically investigate the factors affecting the nanorod orientation in NVCs. We find that the main factor affecting the nanorod orientation is the network rearrangement caused by BERs. Specifically, the BER potential barrier (ΔE sw) directly determines the probability of BERs’ occurrence. At the same time, the increase of the interfacial interaction between polymer chains and nanorods (εnp) confines the motion of the active beads, which slows down the rate of BERs. Additionally, the impact of temperature (T) and aspect ratio (ld) on the orientation of nanorods during uniaxial stretching or stress relaxation are also discussed. Finally, by combining uniaxial stretching and stress relaxation processes, we elucidate the orientation retention mechanism of NVCs and demonstrate the mechanical property enhancement phenomenon of the pre-oriented NVC systems. This work provides a simple strategy for manipulating the nanorod alignment in vitrimer matrices and uncovers guidelines for designing new functional polymer vitrimer nanocomposites at the molecular level.

show abstract

“…11 Chen et al investigated the diffusion mechanism of nanofillers with different geometries by the use of molecular dynamics. 12 Kawada et al used machine learning approaches to accelerate their simulations and used it to investigated water diffusion in a variety of different polymers. 13 In the field of fuel cells molecular dynamics is used to describe transport mechanisms in exchange membranes.…”

Section: Introductionmentioning

confidence: 99%

Calculating diffusion coefficients from molecular dynamics simulations for modelling foam processes of polypropylene: Investigating different process conditions and blowing agents

Melzer,

Breuer,

Dahlmann

et al. 2024

Journal of Cellular Plastics

View full text Add to dashboard Cite

The choice of blowing agent is very important in foaming processes. In an earlier work the use of molecular dynamics simulations for the estimation of the diffusion coefficients of different blowing agents was discussed at elevated temperatures above the melting point. Therein it was shown that these simulations can give valuable information on blowing agent diffusion in polypropylene. The aim of the recent work is to expand this discussion to the simulation of different influences like pressure, blowing agent mixtures and blowing agents with higher molecular weight at temperatures above the melting point of PP. First a pressure range applied on the combined system of polymer and blowing agent, reasonable for the foam processing is discussed and their influence on the diffusion coefficients for CO2 in polypropylene is evaluated via MD simulations. The next step is the investigation of the influence of mixing a blowing agent with a co-blowing agent. The last part is the presentation of diffusion coefficients for different organic solvents, namely 2-propanol, acetone, ethyl acetate and butyl acetate which could be used as potential co-blowing agents. For both, the change in pressure and the mixing of blowing agents for the systems in question only small influences on the diffusion coefficients was discovered. The results of the diffusion coefficients for the different organic solvents are compared to each other and with former results, considered different molecular structure, size and polarities and are found to be reasonable.

show abstract

Dispersion and Diffusion Mechanism of Nanofillers with Different Geometries in Bottlebrush Polymers: Insights from Molecular Dynamics Simulation

Cited by 9 publications

References 60 publications

Shear Thinning from Bond Orientation in Model Unentangled Bottlebrush Polymer Melts

Shear Thinning from Bond Orientation in Model Unentangled Bottlebrush Polymer Melts

Insights into Uniaxial Tension and Relaxation of Nanorod-Filled Polymer Vitrimer Nanocomposites: A Molecular Dynamics Simulation

Calculating diffusion coefficients from molecular dynamics simulations for modelling foam processes of polypropylene: Investigating different process conditions and blowing agents

Contact Info

Product

Resources

About