The quantification of radical concentration in organic radical polymers: techniques and challenges

The development of new high-tech applications based on organic radical polymers has driven significant and renewed focus on these open shell macromolecules. The versatility in synthetic methods makes them highly accessible materials for a variety of researchers from different backgrounds. Although numerous overviews of the synthesis, structure and properties are available, the determination of radical concentration has been largely overlooked. This primer outlines the methods available and the non-trivial nature of the characterisation process. Although quantitative electron paramagnetic resonance and magnetometry are the gold standard for direct measurement of paramagnetism, there also exists a wide range of highly accessible complimentary methods for indirect measure such as ultraviolet-visible spectroscopy, elemental analysis and infrared spectroscopy. Organic radical polymers are being developed for applications such as energy storage, catalysis and spintronics. Quantification of radical content can be nuanced, with a variety of techniques available for characterisation. This primer provides an overview and discusses the challenges of implementation to macromolecules containing pendant radicals. (Image credit: Theo A. Ellingsen.)This article belongs to the 10th Anniversary Collection of RACI and AAS Award papers.