Water‐soluble, and ferrocene‐containing methacrylamide copolymers with different comonomer ratios of the solubility‐promoting comonomer [2‐(methacryloyloxy)‐ethyl]‐trimethylammonium chloride (METAC) are synthesized in order to obtain a novel, temperature‐stable electrolyte for aqueous redox flow batteries. The electrochemical properties of one chosen polymer are studied in detail by cyclic voltammetry and rotating disc electrode (RDE) investigations. Additionally, the diffusion coefficient and the charge transfer rate are obtained from these measurements. The diffusion coefficient from RDE is compared to the value from synthetic boundary experiments at battery concentrations, using an analytical ultracentrifuge, yielding diffusion coefficients of a similar order of magnitude. The polymer is further tested in a redox flow battery setup. While performing charge and discharge experiments against the well‐established bis‐(trimethylammoniumpropyl)‐viologen, the polymer reveals high columbic efficiencies of >99.8% and desirable apparent capacity retention, both at room temperature as well as at 60 °C. Further experiments are conducted to verify the stability of the active compounds under these conditions in both charge states. Lastly, the electrochemical behavior is linked to the characteristics of the polymers concerning absolute values of the molar mass and diffusion coefficients.

The interrelation of experimental rotational and translational hydrodynamic friction data as a basis for the study of macromolecules in solution represents a useful attempt for the verification of hydrodynamic information. Such interrelation originates from the basic development of colloid and macromolecular science and has proven to be a powerful tool for the study of naturally- and synthetically-based, i.e., artificial, macromolecules. In this tutorial review, we introduce this very basic concept with a brief historical background, the governing physical principles, and guidelines for anyone making use of it. This is because very often data to determine such an interrelation are available and it only takes a set of simple equations for it to be established. We exemplify this with data collected over recent years, focused primarily on water-based macromolecular systems and with relevance for pharmaceutical applications. We conclude with future incentives and opportunities for verifying an advanced design and tailored properties of natural/synthetic macromolecular materials in a dispersed or dissolved manner, i.e., in solution. Particular importance for the here outlined concept emanates from the situation that the classical scaling relationships of Kuhn–Mark–Houwink–Sakurada, most frequently applied in macromolecular science, are fulfilled, once the hydrodynamic invariant and/or sedimentation parameter are established. However, the hydrodynamic invariant and sedimentation parameter concept do not require a series of molar masses for their establishment and can help in the verification of a sound estimation of molar mass values of macromolecules.