On the Environmental and Electrical Bias Stability of Radical Polymer Conductors in the Solid State

Radical polymers are emerging as a promising class of electronically active macromolecules for solid-state organic electronic applications due to their synthetic flexibility and scalability; however, the electrical and chemical stability of radical polymer thin films has yet to be established. Here, it is demonstrated that the model radical polymer, poly(2,2,6,6-tetramethylpiperidinyloxy methacrylate) (PTMA), shows excellent solid-state electrochemical stability when exposed to both bias stressing and varying amounts of moisture in the environment. Specifically, PTMA thin films show consistent performance when continuously swept across a variety of voltage ranges. Furthermore, PTMA remains stable when exposed to a constantly applied bias for 20 h. These two key results demonstrate the stability of the open-shell repeat unit and the reversibility of the chemical oxidation-reduction (redox) reaction that facilitates charge transport. Additionally, PTMA thin films that are exposed to a range of relative humidity values for 2 h retained consistent electronic performance before and after humidity exposure. This highlights that exposure to water vapor does not decrease the robustness associated with the nitroxide radical. These results establish the stoutness associated with radical polymers and highlight the potential for radical polymers to be implemented in a number of advanced organic electronic technologies.