Arylazopyrazoles are an emerging class of photoswitches with redshifted switching wavelength, high photostationary states, long thermalh alf-lives and facile synthetic access. Understanding pathways for as imple modulation of the thermalh alf-lives,w hile keepingo ther parameters of interest constant,i sa ni mportanta spectf or out-of-equilibrium systems design anda pplications. Here, it is demonstrated that the thermalh alf-life of aw ater-solubleP EG-tethered arylazo-bis(o-methylated)pyrazole (AAP) can be tuned by more than five orderso fm agnitude using simple pH adjustment, which is beyond the tunability of azobenzenes. The mechanism of thermalr elaxation is investigated by thorough spec-troscopic analyses and density functional theory (DFT) calculations.F inally,t he concepts of at unable half-life are transferred from the molecular scale to the materials cale. Based on the photochromic characteristics of E-a nd Z-AAP,t ransient information storage is showcased in form of light-written patterns inside films cast from different pH, which in turn leads to different times of storage. With respect to prospective precisely tunable materials and time-programmed outof-equilibrium systems, an externally tunable half-life is likely advantageous over changing the entire system by the replacementoft he photoswitch.

Responsive materials, such as switchable hydrogels, have been largely engineered for maximum changes between two states. In contrast, adaptive systems target distinct functional plateaus between these maxima. Here, we demonstrate how the photostationary state (PSS) of an E/Z‐arylazopyrazole photoswitch can be tuned by the incident wavelength across a wide color spectrum, and how this behavior can be exploited to engineer the photo‐dynamic mechanical properties of hydrogels based on multivalent photoswitchable interactions. We show that these hydrogels adapt to the wavelength‐dependent PSS and the number of arylazopyrazole units by programmable relationships. Hence, our material design enables the facile adjustment of the mechanical properties without laborious synthetic efforts. The concept goes beyond the classical switching from state A to B, and demonstrates pathways for a truly wavelength‐gated adaptation of hydrogel properties potentially useful to engineer cell fate or in soft robotics.

The use of DNA as a building block in synthetic polymer hydrogels promises high levels of programmability regarding sol/gel temperatures, tunable bond lifetimes, biocompatibility, and interaction with biological components (e.g., enzymes, cells, and growth factors). However, scalability and quantitative structure−property relationships for large-scale materials are still challenging to achieve. Building on our recently introduced and scalable one-pot liquid-phase oligonucleotide synthesis of DNA onto star-shaped poly(ethylene glycol) (PEG), we here report hydrogels based on starPEG-DNA conjugates together with divalent DNA linkers of tunable duplex hybridization length. By systematically varying parameters such as the duplex melting temperature, salinity, and building block concentrations, we establish the mechanical phase space of such hydrogels. We elucidate tunable mechanical properties ranging from a few Pa to the kPa regime and discuss time scales of self-healing and bond exchange, as well as tunable sol/gel transition temperatures. These comprehensive investigations shed some light on the future design principles for DNA hydrogel materials based on scalable building blocks, that allow for the formation of quasi-ideal networks due to their starshaped and flexible building block topologies. Such materials can be useful in the field of biomedicine and cell culture.

Here, this study reports a novel single‐step preparation of graphene functionalized by redox‐active nitroxyl radicals, a promising electrode material, without the requirement of graphite oxidation. Key feature of this concept is the Diels‐Alder [4+2] cycloaddition of dispersed graphene (DG), which has been obtained by shear‐induced solution exfoliation of graphite and functionalized maleimides as dienophiles. The redox‐active organic radical 2,2,6,6,‐tetramethylpiperdinyl‐1‐oxyl (TEMPO) is covalently attached by cycloaddition of DG with either N‐(1‐oxyl‐2,2,6,6,‐tetramethyl‐4‐piperidinyl)‐maleimide (TEMPO‐MI), or N‐(2,2,6,6‐tetramethyl‐piperidinyl)‐maleimide (TEMP‐MI), and subsequent oxidation. Successful product formation could be confirmed by high field Electron Paramagnetic Resonance (EPR) spectroscopy. Temperature‐dependent reaction monitoring by time‐resolved EPR in conjunction with Raman spectroscopy and elemental analysis results in an optimum cycloaddition temperature of 130 °C, at which 2.2 wt% TEMPO‐MI has been incorporated. However, owing to the limited thermal stability of TEMPO‐MI at temperatures above 100 °C, as again verified by EPR spectroscopy, the route via TEMP‐MI and subsequent oxidation is favored. Cyclovoltammetric evaluation of TEMPO‐functionalized graphene shows a reversible redox potential of +0.65 V as measured against Ag/AgCl, similar to that of TEMPO in solution. Hence, organic radical functionalized graphene derived by cycloaddition shows great potential for an easy production of electrodes that aim toward applications in organic energy storage devices.

Responsive Materialien, wie z. B. schaltbare Hydrogele, wurden in den meisten Fällen dahingehend entworfen, eine maximale Änderung zwischen zwei Zuständen zu generieren. Im Gegensatz dazu zielen adaptive Systeme auf unterschiedliche funktionelle Plateaus zwischen diesen Maxima ab. In diesem Forschungsartikel zeigen wir daher, wie der photostationäre Zustand (PSS) eines E/Z‐Arylazopyrazol‐Photoschalters mit Hilfe der eingestrahlten Wellenlänge über ein breites Farbspektrum eingestellt werden kann, um die photodynamischen Eigenschaften von Hydrogelen auf der Grundlage von multivalenten, photoschaltbaren Wechselwirkungen zu beeinflussen. Wir präsentieren, dass sich diese Hydrogele an den wellenlängenabhängigen PSS und an die Anzahl der Arylazopyrazol‐Einheiten durch programmierbare Beziehungen anpassen. Unser Materialdesign ermöglicht daher die einfache Einstellung der mechanischen Eigenschaften ohne eine zeitaufwändige Synthese. Das Konzept geht über das klassische Schalten zwischen Zustand A und B hinaus und zeigt Wege für eine wellenlängenabhängige Adaption der Hydrogeleigenschaften auf, die für Weiterentwicklungen in der Zellkultivierung oder in der Soft‐Robotik nützlich sein werden.