Simulations of polymer brushes with charged end monomers under external electric fields

Using Langevin dynamics simulations, the response of neutral polymer brushes with charged terminal monomers to external electric fields has been investigated. The external electric field is equivalent to the field generated by the opposite surface charges on two parallel electrodes. The effects of charge valence of terminal monomers on the structure of double layers and overall charge balance near the two electrodes were examined. Using the charge density distributions obtained from simulations, the total electric field normal to the electrodes was calculated by numerically solving the Poisson equation. Under external electric fields, the total electric field across the two electrodes is highly non-uniform and in certain regions within the brush, the total electric field nearly vanishes. The probability distribution of electric force acting on one charged terminal monomer was obtained from simulations and how it affects the probability density distribution of terminal monomers was analyzed. The response of polymer brushes with charged terminal monomers to a strongly stretching external electric field was compared with that of uniformly charged polymer brushes.