Electroresponsive Weak Polyelectrolyte Brushes

Abstract

We explored the effect of an applied electric field on the molecular conformation of two weak polyelectrolytes grafted on gold electrodes─poly(acrylic acid) and the weak polybase poly(2-(dimethylamino)ethyl methacrylate)─by combining a quartz crystal microbalance with an electrochemical setup. Our results indicate that different mechanisms influence the response of weak polyelectrolytes to an externally applied potential difference, including electrochemical modification of the local pH by oxygen reduction and the electrostatic interaction between the metallic electrode and the charged monomers and ions in solution. Our results evidence that fine control of polymer conformation can be readily obtained at low applied potentials, opening pathways for precise, localized control of surface properties. However, these applications require considering the history-dependent behavior of polyelectrolyte brushes, hysteresis in the response, and the influence of electrochemical reactions driven by potential changes.