A representative ESA oligomer model (e.g., C₁₉H₂₂O₅ or C₅₇H₆₂O₁₅) is commonly used for DFT-based parameterization because it better captures polymer connectivity and local chemical environment than small monomeric model compounds

LAMMPS LAMMPS General Discussion
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Is a representative ESA (epoxy styrene acrylate) model compound (C₁₉H₂₂O₅) or oligomeric fragment (e.g., C₅₇H₆₂O₁₅) more appropriate than the PubChem-listed epoxy styrene acrylate (C₁₁H₈O₃) for DFT-based polymer–polymer interaction studies and LAMMPS force-field development of Joncryl® ADR 4368 (molecular weight ≈ 6800 g/mol)?

In my work, Joncryl® ADR 4368 is treated as a random copolymer of styrene, methyl methacrylate, and glycidyl methacrylate, with epoxy functionality responsible for reactions with polyester end groups. Since the exact molecular structure is proprietary, I am using representative ESA models for DFT calculations and subsequent force-field parameterization for LAMMPS.

Specifically, I would like to understand:

  1. Whether a polymerized ESA trimer model (C₁₉H₂₂O₅) is sufficient for deriving partial charges and bonded parameters, or

  2. Whether a larger oligomeric fragment (e.g., C₅₇H₆₂O₁₅) is preferred to better represent the polymer environment, and

  3. Whether modeling epoxy–polyester reactions using a representative ESA trimer interacting with a PLA trimer is considered acceptable practice for DFT-based force-field development, compared to using a single ESA model compound.

I am aiming to ensure that the level of structural simplification used is chemically sound and computationally practical involving polymer–polymer interactions and reactive chain extenders.

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This is probably not the kind of response that you are hoping to get, but please note that even though you are aiming to use LAMMPS in your simulations, what you are asking about are not questions pertinent to LAMMPS but rather about your research and specifically force field parameterization. That is very different from helping people with how to use LAMMPS, and thus your question is off-topic for this forum. I could re-categorize it to the Science Talk category, but I doubt that you will get much help there either. In fact, I doubt that you will find the level of support and assistance you are looking for in any online forum. What you are asking about is something that you need to discuss with domain experts and if you don’t have those available to talk to in person directly, will likely have to find a suitable collaborator and can provide the desired expertise and guidance.

To understand better what you can or cannot get from this forum, I suggest you have a good look at this post: Please Read This First: Guidelines and Suggestions for posting LAMMPS questions