Functional materials engineered to degrade upon triggering are in high demand due their potentially lower impact on the environment as well as their use in sensing and in medical applications. Here, stimuli‐responsive polymers are prepared by decorating a self‐immolative poly(dithiothreitol) backbone with pendant catechol units. The highly functional polymer is fashioned into stimuli‐responsive gels, formed through pH‐dependent catecholato–metal ion cross‐links. The gels degrade in response to specific environmental changes, either by addressing the pH responsive, non‐covalent, catecholato–metal complexes, or by addition of a thiol. The latter stimulus triggers end‐to‐end depolymerization of the entire self‐immolative backbone through end‐cap replacement via thiol–disufide exchanges. Gel degradation is visualized by release of a dye from the supramolecular gel as it itself is converted into smaller molecules.

Creating strong joints between dissimilar materials for high-performance hybrid products places high demands on modern adhesives. Traditionally, adhesion relies on the compatibility between surfaces, often requiring the use of primers and thick bonding layers to achieve stable joints. The coatings of polymer brushes enable the compatibilization of material surfaces through precise control over surface chemistry, facilitating strong adhesion through a nanometer-thin layer. Here, we give a detailed account of our research on adhesion promoted by polymer brushes along with examples from industrial applications. We discuss two fundamentally different adhesive mechanisms of polymer brushes, namely (1) physical bonding via entanglement and (2) chemical bonding. The former mechanism is demonstrated by e.g., the strong bonding between poly(methyl methacrylate) (PMMA) brush coated stainless steel and bulk PMMA, while the latter is shown by e.g., the improved adhesion between silicone and titanium substrates, functionalized by a hydrosilane-modified poly(hydroxyethyl methacrylate) (PHEMA) brush. This review establishes that the clever design of polymer brushes can facilitate strong bonding between metals and various polymer materials or compatibilize fillers or nanoparticles with otherwise incompatible polymeric matrices. To realize the full potential of polymer brush functionalized materials, we discuss the progress in the synthesis of polymer brushes under ambient and scalable industrial conditions, and present recent developments in atom transfer radical polymerization for the large-scale production of brush-modified materials.

Creating interchain cross-links can improve the stability and robustness of polymer brushes. Unfortunately, the synthetic strategies required for this are often tedious and time-consuming, making their scale-up difficult, if not impossible. Herein, we utilize polysulfides to cross-link poly­(glycidyl methacrylate) (PGMA) brushes grafted from stainless steel in a fast and simple step, converting the PGMA brush to a strong nanoscale adhesive layer for bonding stainless steel and ethylene–propylene–diene M-class rubber (EPDM). The polymer brush is cross-linked in aqueous solution, and the polysulfides are made from inexpensive and widely available reagents. The cross-linking introduces 10.9% sulfur in the film according to X-ray photoelectron spectroscopy, and Raman spectroscopy showed bands ascribed to S n (n ≥ 2) species. The polysulfide cross-links may be cleaved using dithiothreitol, resulting in an uncross-linked, thiol-functionalized polymer-brush coating. When used as an adhesive layer for bonding steel and EPDM rubber, the cross-linked polymer film displays higher fracture toughness (comparable to a commercial bonding agent) than the uncross-linked film and gives cohesive failure rather than the adhesive failure seen in the latter case. We anticipate that the industrial scale-up of the procedure using, e.g., dip coating, is straightforward considering that it uses inexpensive chemicals, is oxygen tolerant, takes place in aqueous solution, and can be accomplished within half a minute.

Surface attached catecholato-metal complexes serve as polymer brush initiators with well-defined densities and enable stimuli-responsive degrafting of polymer brushes.

Functional materials engineered to degrade upon triggering are in high demand due their potentially lower impact on the environment as well as their use in sensing and in medical applications.H ere,s timuli-responsive polymers are prepared by decorating as elf-immolative poly(dithiothreitol) backbone with pendant catechol units.T he highly functional polymer is fashioned into stimuli-responsive gels,f ormed through pH-dependent catecholato-metal ion cross-links.T he gels degrade in response to specific environmental changes, either by addressing the pH responsive,non-covalent, catecholato-metal complexes,o rb ya ddition of at hiol. The latter stimulus triggers end-to-end depolymerization of the entire self-immolative backbone through end-cap replacement via thiol-disufide exchanges.G el degradation is visualizedb y release of ad ye from the supramolecular gel as it itself is converted into smaller molecules.