How do you teach a computer to “feel” how a lithium ion sticks to a π-system?

Classical simulations often miss one of the most subtle but powerful interactions in battery materials: cation–π interactions — the short-range attraction between a lithium ion and the π-electron cloud of a conjugated polymer.

For π-conjugated organosulfur polymers used in Li/S batteries, this interaction changes everything: how lithium moves, where it prefers to sit, and how charges flow through the cathode.
But popular classical force fields (like OPLS-AA) simply cannot capture it.

So in this project, we built a bottom-up force field from first principles, teaching the simulation to “see” cation–π physics correctly.

The outcome is a corrected OPLS-AA force field (OPLS-AA/corr.) that accurately reproduces cation–π interactions and can be used in realistic polymer-electrolyte simulations for Li/S batteries.

This work combines DFT, force-field parameter optimization, PMF reconstruction, solvent thermodynamics, and ion–polymer interaction physics, opening the door to more predictive simulations of π-conjugated polymer cathodes.

Optimizing cation–π force fields for molecular dynamics studies of competitive solvation in conjugated organosulfur polymers for lithium–sulfur batteries

D. Gayen, Y. Schütze, S. Groh, J. Dzubiella

Physical Chemistry Chemical Physics (2025)

(Link) (PDF)

What happens when you drop a spaghetti-like polymer into different liquids?

If we had a microscope that could watch every atom in motion --- in real time --- what surprising shapes and behaviors would we discover?

In this project, we built such a “virtual microscope.” Using large-scale molecular dynamics simulations with a force field we specifically optimized, we followed a single conjugated polymer chain as it interacted with different battery solvents. What we found was unexpectedly beautiful: depending on how you mix the solvents, the polymer can collapse, or swll --- like spaghetti that suddenly expands in hot water.

This work combines atomistic modeling, force-field development, polymer physics, and electrolyte chemistry --- and opens the door to simulating full polymer networks and charge-transport pathways in next-generation Li/S batteries.

Solvation structure of conjugated organosulfur polymers for lithium-sulfur battery cathodes

D. Gayen, Y. Schütze, S. Groh, J. Dzubiella

ACS Applied Polymer Materials (2023)

(Link) (PDF)

How does a polymer decide whether to form a messy pile or a perfect crystal?

If we could zoom in far enough to see every monomer arrange itself --- could we watch order emerge from chaos?

In this project, we built a multiscale “virtual laboratory” to observe exactly that. Using molecular dynamics simulations, we let multiple conjugated polymer chains self-assemble and asked a simple question: Does the way you connect the monomers (the regiochemistry) change how the polymer crystallizes --- and how fast charges move through it?

The answer was striking. When the chains are connected in a highly ordered head-to-tail pattern, they spontaneously fold into a beautiful, planar, crystalline phase. This crystal is not just visually symmetric --- it also provides a high-mobility pathway for charges to move through the material.

To verify the prediction, we turned to experiments:
X-ray diffraction confirmed the same crystalline phase that our simulations revealed.

By combining MD simulations, crystal-structure prediction, and charge-transport modeling, this work uncovers how microscopic chain order shapes macroscopic electronic performance in organosulfur polymer cathodes --- key for stable, high-energy Li/S batteries.

How regiochemistry influences aggregation behaviour and charge transport in conjugated organosulfur polymer cathodes for lithium-sulfur batteries

Y. Schütze, D. Gayen, K. Palczynski, R.O. Silva, Y. Lu, M. Tovar, P. Partovi-Azar, A. Bande, J. Dzubiella

ACS Nano (2023)

(Link) (PDF)

Sulfur Containing Polymers: Synthesis and Applications

D. Gayen, Y. Schütze, S. Groh, J. Dzubiella

Science China Chemistry (2025) (Under review)