Close Packing of Nitroxide Radicals in Stable Organic Radical Polymeric Materials

Abstract

The relationship between the polymer network and electronic transport properties for stable radical polymeric materials has come under investigation owing to their potential application in electronic devices. For the radical polymer poly(2,2,6,6-tetramethylpiperidine-4-yl-1-oxyl methacrylate), it is unclear whether the radical packing is optimal for charge transport partially because the relationship between radical packing and molecular structure is not well-understood. Using the paramagnetic nitroxide radical as a probe of the polymer and synthetic techniques to control the radical concentration on the methyl methacrylate backbone, we investigate the dependence of radical concentration on molecular structure. The electron paramagnetic resonance data indicate that radicals in the PTMA assume a closest approach distance to each other when more than 60% of the backbone is populated with radical pendant groups. Below 60% coverage, the polymer rearranges to accommodate larger radical-radical spacing. These findings are consistent with theoretical calculations and help explain some experimentally determined electron-transport properties.

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

“…Therefore, electrolyte‐supported radical polymer systems have extremely useful transport properties, as the liquid‐based electrolytes provide ample mobility to the radical polymer pendant groups. On the other hand, only recently was it established that these types of reactions can also occur in a rather rapid manner in solid‐state organic electronic applications . Specifically, the model radical polymer, poly(2,2,6,6‐tetramethylpiperidinyloxy methacrylate) (PTMA), is an extraordinarily transparent material and can be easily synthesized in large batches .…”

Controlling open‐shell loading in norbornene‐based radical polymers modulates the solid‐state charge transport exponentially

“…A high degree of spin‐exchange results in broadening of the three prominent nitroxide peaks, which, in the case of PTNB, converge to form a single Lorentzian curve (as seen in Supporting Information Fig. S5) …”

Transport and thermoelectric properties of magnetic organic chains

“…. A variety of molecules and polymers with radicals/polyradicals are known in organic chemistry and were intensively studied due to their high spin states resulting from intramolecular ferromagnetic exchange coupling between unpaired electrons . For example, trinitroxide was synthesized and the magnetic measurements were performed up to room temperature .…”

“…Low‐dimensional purely organic systems with ferromagnetic ordering appear to be attractive for spintronics applications . High spin states of molecules and polymers result from ferromagnetic exchange coupling between unpaired electrons .…”