Design of Mixed Electron- and Ion-Conducting Radical Polymer-Based Blends

Abstract

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.

Charge transport and antiferromagnetic ordering in nitroxide radical crystals

“…Stable organic radicals have been used extensively in electronic, [1][2][3][4][5][6][7][8][9] electrochemical, [10][11][12][13][14][15][16][17][18][19] and magnetic field-responsive applications [20][21][22][23][24][25][26][27][28][29] because radical-based polymers and small molecules are proven electronic and ionic conductors. [30][31][32][33][34][35] Additionally, stable radical molecules have intriguing magnetic properties because the unpaired electrons of the radical sites interact with applied magnetic fields, and intermolecular spin-spin interactions inside these open-shell materials can result in magnetic effects.…”

Graphene-Enhanced Ion Transport in Dual-Conducting Composite Films of Polyacetylene and an Imidazolium Iodide Ionic Liquid

“…The electronic and ionic conductance could be varied by changing the relative amounts of the electron- and ion-conducting nanoparticles in the binary blends. Akkiraju et al studied a radical polymer (instead of a conjugated polymer) to obtain mixed electron and ion conductivity. They blended a radical polymer, poly­(4-glycidyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl) (PTEO), with poly­(poly­(ethylene oxide) methyl ether methacrylate).…”

Electronic and Magnetic Properties of a Three-Arm Nonconjugated Open-Shell Macromolecule

“…Since their initial discovery, the development of organic electronic molecules has led to materials with impressive optoelectronic, thermoelectric, and bioelectronic performance. − Moreover, the ability to tune the properties of electronic polymers using straightforward organic chemistry design strategies has allowed for the refinement of both their mechanical properties and their end-use device performance in a ready manner. − As such, the polymer electronics community has made impressive strides in applications ranging from energy conversion and storage systems to materials that are used in health monitoring devices. − In most of these applications, π-conjugated polymers have been implemented as their molecular architecture can facilitate charge delocalization (i.e., through conjugation) and relatively ordered packing (i.e., in driving crystallization of the macromolecules), which typically improves charge transport across macroscopic distances. , However, these conjugated polymers have not shown as much success in magnetic-field-dependent applications relative to electronic applications due to the singlet ground state of their electronic configurations and their diamagnetic nature. − As a result, researchers have transitioned to molecules containing stable open-shell entities to push this important area forward. , That is, these open-shell molecules contain robust spin sites and offer more promise for magnetic field-dependent applications. In fact, several classes of molecules containing one or more radicals have been reported. − One material group, polyradicals, has shown strong magnetic properties due to the large number of open-shell sites within a single repeat unit. , This architecture facilitates interactions between the unpaired electrons, resulting in strong antiferromagnetic or ferromagnetic behavior.…”

“…Since their initial discovery, the development of organic electronic molecules has led to materials with impressive optoelectronic, thermoelectric, and bioelectronic performance. 1 − 6 Moreover, the ability to tune the properties of electronic polymers using straightforward organic chemistry design strategies has allowed for the refinement of both their mechanical properties and their end-use device performance in a ready manner. 7 − 10 As such, the polymer electronics community has made impressive strides in applications ranging from energy conversion and storage systems to materials that are used in health monitoring devices.…”