Supramolecular Polymer Brushes Grown by Surface-Initiated Atom Transfer Radical Polymerization from Cucurbit[7]uril-based Non-Covalent Initiators.

Polymer brushes are densely grafted, chain end-tethered assemblies of polymers that can be produced via surface-initiated polymerization. Typically, this is accomplished using initiators or chain transfer agents that are covalently attached to the substrate. This manuscript reports an alternative route towards polymer brushes, which involves the use of non-covalent cucurbit[7]uril-adamantane host-guest interactions to surface-immobilize initiators for atom transfer radical polymerization. These non-covalent initiators can be used for the surface-initiated atom transfer radical polymerization of a variety of water-soluble methacrylate monomers to generate supramolecular polymer brushes with film thicknesses of more than 100 nm. The non-covalent nature of the initiator also allows facile access to patterned polymer brushes, which can be produced in straightforward fashion by drop-casting a solution of the initiator-modified guest molecules onto a substrate that presents the cucurbit[7]uril host.

Mechanoresponsive Micro-and Nanoparticles.

Mechanical stimuli are ubiquitous in the human body. In contrast to biochemical stimuli such as pH, redox, hypoxia or enzymes as well as exogenous stimuli such as magnetic fields, temperature or ultrasound, endogenous biomechanical stimuli have only received relatively limited attention as a means to trigger stimuli-sensitive materials. The aim of this short article is to highlight the potential of endogenous biomechanical stimuli to control the behaviour of biomaterials relevant to, for example, drug delivery or tissue repair and regeneration. This article will first provide an overview of the different biomechanical stimuli present at the cellular and tissue level in the human body. After that, examples from recent work will be presented that illustrate the use of biomechanical stimuli. This article ends with an outlook for future research.

Supramolecular Polymer Brushes.

Polymer brushes are thin polymer films that consist of densely grafted, chain-end tethered polymers. These thin polymer films can be produced either by anchoring presynthesized chain-end functional polymers to the surface of interest ("grafting to"), or by using appropriately modified surfaces to facilitate growth of polymer chains from the substrate ("grafting from"). The vast majority of polymer brushes that have been prepared and studied so far involved chain-end tethered polymer assemblies that are anchored to the surface via covalent bonds. In contrast, the use of noncovalent interactions to prepare chain-end tethered polymer thin films is much less explored. Anchoring or growing polymer chains using noncovalent interactions results in supramolecular polymer brushes. Supramolecular polymer brushes may possess unique chain dynamics as opposed to their covalently tethered counterparts, which could provide avenues to, for example, renewable or (self-)healable surface coatings. This Perspective article provides an overview of the various approaches that have been used so far to prepare supramolecular polymer brushes. After presenting an overview of the various approaches that have been used to prepare supramolecular brushes via the "grafting to" strategy, examples will be presented of strategies that have been successfully applied to produce supramolecular polymer brushes via "grafting from" methods.