In this work, the fundamental design principles of intrinsic self‐healing, polymeric materials with reversible, covalent bonds are described and summarized. The most important properties with regard to the healing ability and potential applications are discussed. A classification of synthetic strategies toward polymers as well as polymer networks and their effect on the properties is given to gain further insight into known design strategies for healable materials. In order to evaluate the advantages and disadvantages of different covalent bonding types, recent examples of intrinsic healable polymers are compared and evaluated. In addition, the unique behavior of vitrimers as a new type of polymer networks is explained. In the end, a short outlook on future work in the field of self‐healing polymers concludes this review.

Hybrid-flow batteries are a suitable storage technology for "green" electricity generated by renewable sources such as wind power and solar energy. Redox-active organic compounds have recently been investigated to improve the traditional metal-and halogen-based technologies. Here we report the utilization of a 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) derivative that is in particular designed for application in semiorganic zinc hybrid-flow batteries. The TEMPO derivative is synthesized and electrochemically characterized via cyclic voltammetry and rotating disc electrode measurements. This derivative features a high solubility in aqueous electrolytes; thus, volumetric capacities above 20 Ah L −1 are achieved. The fabricated hybrid-flow batteries feature over 1100 consecutive charge−discharge cycles at constant capacity retention, and current densities up to 80 mA cm −2 are applied.

Electricity users expect energy on demand. This poses a problem for renewables, such as solar, wind or hydroelectric, as the supply is naturally intermittent. Building scalable and inexpensive energy storage is the answer, and here we describe a new rechargeable battery system that uses salt solutions of organic polymers and a cheap filter membrane.

The combination of 2,2,6,6-tetramethylpiperidinyl-N-oxyl and phenazine yields an organic redox-active material for redox-flow battery applications. This combined molecule (combi-molecule) features a redox voltage of 1.2 V and facilitates the utilization of aqueous electrolytes. It was synthesized from cost-efficient starting materials, electrochemically characterized and applied as charge-storage material in a symmetric aqueous redox-flow battery.

The straightforward synthesis of a urea polymer network is presented. Commercially available monomers are polymerized using light-induced polymerization, resulting in networks crosslinked by hindered urea molecules. These moieties are reversible and, thus, can be converted into the starting compounds (that is, isocyanate and amine) by a simple thermal treatment. This process is monitored using differential scanning calorimetry as well as Raman and infrared spectroscopy. Furthermore, the self-healing ability of these polymer networks is investigated using scratch-healing tests as well as bulk-healing investigations using tensile testing. The resultant materials have a high E-modulus, are able to heal scratches at temperatures above 70°C multiple times and their mechanical properties can be partially regenerated. The underlying healing mechanism is based on the reversible opening of the urea bonds and exchange reactions between two functional groups, which were confirmed from a spectroscopic analysis. In summary, these new materials are a new type of intrinsically healable polymers and provide a first step toward hard and healable polymers.

Within this context, the utilization of renewable energy is gaining increasing interest. One important aspect is the storage of electrical energy. The different applications to store electrical energy range from stationary energy storage (i.e., storage of the electrical energy produced from intrinsically fluctuating sources, e.g., wind parks and photovoltaics) over batteries for electric vehicles and mobile devices (e.g., laptops as well as mobile phones or other smart mobile devices such as smart watches), down to miniature devices for biochips, sensors, as well as "smart packaging" or miniaturized medical devices. Despite being essential in modern life, (some) batteries can look back on a long history-for instance, the lead-acid battery was discovered 150 years ago. Yet, the lead acid battery is still the system of choice for starter batteries in cars until today. Even the beginnings of modern lithium batteries date back to the 1970s. Recently, John B. Goodenough (The

Biology offers a valuable inspiration toward the development of self-healing engineering composites and polymers. In particular, chemical level design principles extracted from proteinaceous biopolymers, especially the mussel byssus, provide inspiration for design of autonomous and intrinsic healing in synthetic polymers. The mussel byssus is an acellular tissue comprised of extremely tough protein-based fibers, produced by mussels to secure attachment on rocky surfaces. Threads exhibit self-healing response following an apparent plastic yield event, recovering initial material properties in a time-dependent fashion. Recent biochemical analysis of the structure–function relationships defining this response reveal a key role of sacrificial cross-links based on metal coordination bonds between Zn2+ ions and histidine amino acid residues. Inspired by this example, many research groups have developed self-healing polymeric materials based on histidine (imidazole)–metal chemistry. In this review, we provide a detailed overview of the current understanding of the self-healing mechanism in byssal threads, and an overview of the current state of the art in histidine- and imidazole-based synthetic polymers.

A conductive polymer (poly(p-phenylenevinylene), PPV) was covalently modified with RuII complexes to develop an all-polymer photocathode as a conceptual alternative to dye-sensitized NiO, which is the current state-of-the-art photocathode in solar fuels research. Photocathodes require efficient light-induced charge-transfer processes and we investigated these processes within our photocathodes using spectroscopic and spectro-electrochemical techniques. Ultrafast hole-injection dynamics in the polymer were investigated by transient absorption spectroscopy and charge transfer at the electrode–electrolyte interface was examined with chopped-light chronoamperometry. Light-induced hole injection from the photosensitizers into the PPV backbone was observed within 10 ps and the resulting charge-separated state (CSS) recombined within ~ 5 ns. This is comparable to CSS lifetimes of conventional NiO-photocathodes. Chopped-light chronoamperometry indicates enhanced charge-transfer at the electrode–electrolyte interface upon sensitization of the PPV with the RuII complexes and p-type behavior of the photocathode. The results presented here show that the polymer backbone behaves like classical molecularly sensitized NiO photocathodes and operates as a hole accepting semiconductor. This in turn demonstrates the feasibility of all-polymer photocathodes for application in solar energy conversion.