(Invited) Electrically Switchable Surface Properties Using End-Charged Polymers and pH-Responsive Swelling of Polymer Brushes Via Self-Consistent Field Theory

As electroactive or stimuli-responsive materials, polymers offer advantages related to the variety, complexity and control of the molecular structure possible with well-developed modern synthesis methods.  Choice of monomer and sequence allows coupling of response to electric fields or pH to the molecular nanostructure of the polymer chains.  We discuss two such representative materials as modeled using Self-Consistent Field Theory (SCFT). The first is an electroactive polymer brush layer composed of surface-grafted chains with a terminal charge that can fold back in response to an applied field.  We show that by judicious design of the chain sequence as a diblock copolymer with unequal block lengths, the chain folding can create a change in the apparent surface properties due to switching of the exposed block.  The second is a pH-responsive polymer brush that swells as the polymer is increasingly protonated with decreasing pH.  We show that the maximum responsiveness in swelling occurs at a pH that is shifted from the intrinsic pKa of the constituent monomers.