Switching of strong polyelectrolyte brushes induced by changes in the electrode potential

Electrochemically responsive polymer brushes that can undergo a transition between a swollen and collapsed state in response to an electrical potential hold considerable promise for incorporation into "smart devices". Despite their significant advantages, this type of switching trigger has received only minor attention. Our study demonstrates that the hexacyanoferrate redox pair induces rapid conformational changes in permanently positively charged polymer brushes due to changes in the electrode potential. These films were prepared by quaternizing poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes grafted onto gold and silicon substrates using a robust, reproducible grafting-to approach. Insights into the electrochemically induced complexation behavior of strong polyelectrolyte brushes are gained by combining the results of static spectroscopic in situ ellipsometry measurements and dynamic measurements using an electrochemical quartz crystal microbalance with dissipation monitoring (EQCM-D). This knowledge is applied to determine the optimal hexacyanoferrate concentration for the switching of such brushes under an electric potential. Our findings reveal that the switching under optimized conditions occurs within the millisecond range, showcasing the potential of this underrepresented switching trigger.