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Modeling of covalent adaptable networks

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Monica Olvera de la Cruz, Department of Materials Science and Engineering, Northwestern University

05/20/2024

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Context Statement

Goal: To characterize the topological structure, dynamics, and viscoelasticity of covalent adaptable networks.

Bond Exchange

+

Segmental Relaxation

Dynamic covalent crosslinks impart viscoelasticity

Viscoelasticity is impacted by molecular architectures, topological changes, and microscopic dynamics

The rate of dynamic crosslink exchange dictates viscosity

We do continuum modeling and particle-based simulations

Scheutz, G. M. et al. J. Am. Chem. Soc. 141, 16181-16196 (2019)

 

(Kalow group)

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A hybrid molecular dynamics and Monte Carlo simulation

 

bond exchange by Monte Carlo method

 

  • Kremer–Grest bead spring model
  • Polymer chains consist of bonded beads and a fraction of are randomly grafted reactive beads A
  • Cross-linkers have 3 beads (2 end beads are reactive, denoted as B)

 

 

 

 

 

 

 

 

 

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Data

 

 

Xia, J. S. and Olvera de la Cruz, M. submitted

 

higher T

 

 

Podgorski, M. et al.. Adv. Mater. 32 (2020)

Xia, J. S., Kalow, J. A. & Olvera de la Cruz, M. Macromolecules 56, 8080-8093 (2023)

tracer chain

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Limitations and caveats

Sticky Rouse model (SRM)

  • originated for physical associative polymers

Xia, J. S., Kalow, J. A. & Olvera de la Cruz, M. Macromolecules 56, 8080-8093 (2023)

Great agreements at high temperatures for

  • medium and long times
  • low frequencies

Deviations at low temperatures due to

  • cage regime formed by neighbors

Validity of SRM is independent of the associative mechanism

unentangled vitrimers with a low energy barrier

 loop

 bridge

 

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Practical considerations

Xia, J. S. and Olvera de la Cruz, M. submitted

Simulation program:

LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator)

https://www.lammps.org/

Molecular architecture

Continuum models

Material composite

Dynamic covalent chemistry

  • associative or dissociative

Wei, S. et al. Adv. Mater. 2313961 (2024)

Light-induced living CANs

(Campos group)

stress state of dangling chains during recombination