Molecular Modeling of Tethered Polyelectrolytes

Owen Hehmeyer, Princeton University

This series of studies focuses on the computer simulation of charged, tethered polymer systems. Molecular dynamics (MD) simulations were used to study a model system that approximates a flexible polyelectrolyte, such as sodium polystyrene sulfonate, grafted to two apposing walls [1]. The Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) at Sandia was used for this part of the work. The effects of the surface density of the grafted polymer, the chain length, and gap width between walls were examined. Results are compared to surface forces apparatus studies of similar systems.

In the second part of the work, the structure of charged, tethered, lattice polymers was studied using Monte Carlo (MC) and single-chain mean field theory. The density profile of monomers and the brush height were investigated as a function of grafting density and chain length. The MC results are compared to our own and other previous mean-field studies as well as experimental data.

Comparisons of relative efficiencies and limitations of MD and MC are made.

Future work will continue to focus on studies of charged polymer brushes on charged walls, and their interaction with other charged particles. First, we would like to answer more outstanding scientific questions about polymer brushes on charged walls in the absence of additional particles. A longer term goal is examining colloid particles and counterions in the brush system in order to study their interaction (adsorption) with the polymer brush.

[1] Owen Hehmeyer and Mark Stevens, “Molecular Dynamics simulations of grafted polyelectrolytes on two apposing walls,” J. Chem. Phys., 122, Art. No. 134909 (2005).

Abstract Author(s): Owen Hehmeyer, Athanassios Panagiotopoulos, and Mark Stevens