Homogeneous catalysts (“mediators”) are useful for tuning selectivity in organic electrosynthesis. However, they can have a negative impact on the overall mass and energy balance if used only once or recycled inefficiently. In a previous work, we introduced the polymediator concept, in which soluble redox‐active polymers catalyze the electrochemical reaction, allowing for recovery by dialysis or pressure‐driven membrane filtration. Using anodic alcohol oxidation as a test case, it was shown that TEMPO‐modified polymethacrylates (TPMA) can serve as efficient and reusable mediators. In the present study, the properties of a TPMA sample with well‐defined molecular weight distribution were studied using cyclic voltammetry and compared to low‐molecular TEMPO species. The non‐catalytic profiles of TPMA are shaped by diffusive and adsorptive processes, whereby the latter only become pronounced at low mediator concentrations and high scan rates. Electrocatalytic studies suggest that under the applied conditions, TPMA‐catalyzed alcohol oxidation is a predominantly homogeneous process. The homogeneous kinetics are determined rather by the mediator potential than by steric influences of the polymer backbone.

Hydrogels have become an increasingly interesting topic in numerous fields of application. In addition to their use as immobilization matrixes in (bio)catalysis, they are widely used in the medical sector, e.g., in drug delivery systems, contact lenses, biosensors, electrodes, and tissue engineering. Cartilage tissue engineering hydrogels from natural origins, such as collagen, hyaluronic acid, and gelatin, are widely known for their good biocompatibility. However, they often lack stability, reproducibility, and mechanical strength. Synthetic hydrogels, on the other hand, can have the advantage of tunable swelling and mechanical properties, as well as good reproducibility and lower costs. In this study, we investigated the swelling and mechanical properties of synthetic polyelectrolyte hydrogels. The resulting characteristics such as swelling degree, stiffness, stress, as well as stress-relaxation and cyclic loading behavior, were compared to a commercially available biomaterial, the ChondroFiller® liquid, which is already used to treat articular cartilage lesions. Worth mentioning are the observed good reproducibility and high mechanical strength of the synthetic hydrogels. We managed to synthesize hydrogels with a wide range of compressive moduli from 2.5 ± 0.1 to 1708.7 ± 67.7 kPa, which addresses the span of human articular cartilage.

Invited for this month's cover picture is the group of Robert Francke at the Leibniz Institute for Catalysis (LIKAT Rostock). The cover picture illustrates the anodic oxidation of 4‐methoxybenzyl alcohol catalyzed by TEMPO‐modified polymethacrylate, one of the model reactions that was used to study the catalytic behavior of the polymediator. Two transformations are shown, one proceeding at the electrode surface (left) and one in solution (right), indicating that the electrocatalytic process comprises both homogeneous and heterogeneous contributions. Read the full text of the Article at 10.1002/celc.202100768.

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