Adhesion is one of the most ubiquitous practical applications at surfaces. With today’s society calling increasingly for more reusable and “green” alternatives, the demand for readily reversible adhesives has triggered many studies into this field, in particular by incorporating molecular photoswitches into composite materials. Responsive polymers can act as reversible adhesives, but their employment brings about synthetic drawbacks and challenges in reproducibility and reusability. Here, our results demonstrate that even a low molecular weight photoswitch can serve as an on-demand adhesive when the intermolecular interactions are sufficiently strong. We show that readily accessible arylazoisoxazoles display a fast photoreversible solid-to-liquid phase transition and perform as excellent photoreversible adhesives, with a remarkable durability over 10 immediate reuse cycles without a loss in adhesive strength or an increase in the unprecedented response time. Furthermore, the versatility of photoreversible adhesion is shown at various surfaces ranging from polymeric materials to metals, demonstrating a wide field of potential application.

From waste to wealth – a self-assembled hydrogel remediates palladium from solution down to sub-ppm levels, and the resulting gel, which has embedded Pd nanoparticles, acts as a green and efficient catalyst for Suzuki–Miyaura cross-coupling reactions.

The preparation of colloidal molecules (CMs), that is, clusters of colloids with a defined aggregation number and configuration, is of continued and significant interest in colloid chemistry and materials science and numerous interactions have been utilized to drive their (self-)assembly. However, only very few reports are available on the assembly of CMs based on host−guest chemistry. In this paper, we investigate the assembly of likecharged silica particles into well-defined, core-satellite AB n -type CMs in water, mediated by host−guest interactions and geometric constraints. Exploiting the inherent dynamics of noncovalent attraction and making use of a soft polymer shell to enhance multivalent host−guest interactions, we successfully synthesized AB 3 , AB 4 , and AB 6 CMs by selecting the appropriate size ratio of satellite to core particles.

Invited for the cover of this issue is the group of Bart Jan Ravoo at Westfälische Wilhelms‐Universität Münster. The image depicts the “universal” post‐modification of silica particles coated with a polythiolactone polymer shell. Read the full text of the article at 10.1002/chem.202100547.

The surface chemistry of colloidal silica has tremendous effects on its properties and applications. Commonly the design of silica particles is based on their de novo synthesis followed by surface functionalization leading to tailormade properties for a specific purpose. Here, the design of robust “precursor” polymer‐decorated silica nano‐ and microparticles is demonstrated, which allows for easy post‐modification by polymer embedded thiolactone chemistry. To obtain this organic‐inorganic hybrid material, silica particles (SiO2P) were functionalized via surface‐initiated atom transfer radical polymerization (SI‐ATRP) with poly(2‐hydroxyethyl acrylate) (PHEA)‐poly(thiolactone acrylamide (PThlAm) co‐polymer brushes. Exploiting the versatility of thiolactone post‐modification, a system was developed that could be used in three exemplary applications: 1) the straightforward molecular post‐functionalization to tune the surface polarity, and therefore the dispersibility in various solvents; 2) the immobilization of metal nanoparticles into the polymer brushes via the in situ formation of free thiols that preserved catalytic activity in a model reaction; 3) the formation of redox‐responsive, permeable polymer capsules by crosslinking the thiolactone moieties with cystamine dihydrochloride (CDH) followed by dissolution of the silica core.