The escape of a charged dendrimer from an oppositely charged planar surface

Many of the envisioned applications of dendrimers revolve around placing these molecules at and removing them from charged interfaces. Herein, we provide a prescription for the conditions needed to release a charged dendrimer from an oppositely charged flat substrate. Identifying an effective segment step length that reflects the intramolecular repulsions due to excluded volume and electrostatics, as well as the dendrimer's branching, provides the essential concept leading to an analytical prediction for the boundary between captured and free molecules. We find that this effective step length obeys trends similar to those predicted for linear chains, but is modified by the dendrimer's connectivity. Moreover, the boundary predicted for the capture of linear chains holds for dendrimers once this effective step length is employed. Monte Carlo computer simulations of coarse-grained model dendrimers escaping from charged surfaces validate these findings. The simulations consider generations 2 through 6 with a range of lengths between the branch points, as well as a range of solution ionic strengths and surface charge densities.