Interactions between Charged Surfaces and Functionalized Grafted Polymer Layers

The interactions between charged surfaces and grafted polymers with a functional group of opposite charge have been studied using a molecular theory. The ability to control the range and strength of the interactions by changing the polymer chain length, surface coverage, surface charge density, solution ionic strength, and position of the functional group along the chain is demonstrated. When the charge density on the surface is larger than that of the polymer, the minimal free energy is relatively sharp and is found at a separation between the surfaces equal to the polymer layer thickness. For polymer layers that have more charge than the opposite surface, the minimal free energy shows a plateau that can extend for a few nanometers. We show that manipulation of the position of the charged moiety along the polymer chain enables the design of surfaces with optimal attractive interactions of tunable range and strength.