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.