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.