Design Of Mixed Electron- And Ion-Conducting Radical Polymer-Based Blends

Mixed electron- and ion-conducting polymers have received considerable interest over the last few years due to their applicability in a variety of organic electronic devices. To achieve this mixed conduction, researchers tend to rely on copolymerizing or blending two polymers, where one conducts ions and the other conducts electrons. Despite their potential as solid-state charge conductors, radical polymers have received less attention than their conjugated counterparts. This work addresses this unmet opportunity by developing a blended radical polymer poly(4-glycidyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl) (PTEO), poly(poly(ethylene oxide) methyl ether methacrylate) (PPEGMA), and lithium hexafluorophosphate system. PPEGMA, similar to previous publications, had one of the highest polymer-based room-temperature ionic conductivity of 10(-4) S cm(-1). In addition to conducting charges, PTEO had an ionic conductivity of 10(-6) S cm(-1). A blend of the two polymers at equal weight ratios had a room-temperature ionic conductivity of 10(-4) S cm(-1) and an electronic conductivity of 10(-2) S cm(-1) similar to pristine PPEGMA and PTEO thin films, respectively. This similarity resulted from the formation of distinct pathways of ion (i.e., through PPEGMA domains) and electron (i.e., through PTEO domains) conduction due to microscale phase separation between the two polymers with the lithium ions mainly incorporating in the PPEGMA domains. With the addition of lithium salt, the electronic conductivity of the blend increased by 1.7 times. However, at [Li+]/[O] ratios higher than 0.08, the electronic conductivity suffered due to poor film quality. Ultimately, this effort establishes a template for determining mixed conduction in radical polymer-based blends and for developing the next generation of simultaneous conduction devices.