Herein, we introduce the wavelength‐orthogonal crosslinking of hydrogel networks using two red‐shifted chromophores, i.e. acrylpyerene (AP, λactivation=410–490 nm) and styrylpyrido[2,3‐b]pyrazine (SPP, λactivation=400–550 nm), able to undergo [2+2] photocycloaddition in the visible‐light regime. The photoreactivity of the SPP moiety is pH‐dependent, whereby an acidic environment inhibits the cycloaddition. By employing a spiropyran‐based photoacid generator with suitable absorption wavelength, we are able to restrict the activation wavelength of the SPP moiety to the green light region (λactivation=520–550 nm), enabling wavelength‐orthogonal activation of the AP group. Our wavelength‐orthogonal photochemical system was successfully applied in the design of hydrogels whose stiffness can be tuned independently by either green or blue light.

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Temperature Programmed Desorption (TPD) spectroscopy was used to determine the binding energies of polycyclic aromatic hydrocarbons CnHm (22 ≤ n ≤ 60) with highly oriented pyrolytic graphite. These energies were then used to estimate the dispersive graphite interlayer cohesion by means of a refined extrapolation method proposed by Björk et al. This yields a cohesion energy of 44.0 ± 3.8 meV per carbon atom. We discuss some limits of the TPD-based approach and contrast our values with previous determinations of the interlayer cohesion energy of graphite.

Waste production associated with the use of non-degradable materials in packaging is a growing cause of environmental concern, with the polyurethane (PU) class being notorious for their lack of degradability....