This work presents a new method for the synthesis of antifouling polymer brushes using surface-initiated photoinduced electron transfer-reversible addition–fragmentation chain-transfer polymerization with eosin Y and triethanolamine as catalysts. This method proceeds in an aqueous environment under atmospheric conditions without any prior degassing and without the use of heavy metal catalysts. The versatility of the method is shown by using three chemically different monomers: oligo­(ethylene glycol) methacrylate, N-(2-hydroxypropyl)­methacrylamide, and carboxybetaine methacrylamide. In addition, the light-triggered nature of the polymerization allows the creation of complex three-dimensional structures. The composition and topological structuring of the brushes are confirmed by X-ray photoelectron spectroscopy and atomic force microscopy. The kinetics of the polymerizations are followed by measuring the layer thickness with ellipsometry. The polymer brushes demonstrate excellent antifouling properties when exposed to single-protein solutions and complex biological matrices such as diluted bovine serum. This method thus presents a new simple approach for the manufacturing of antifouling coatings for biomedical and biotechnological applications.

that perform certain biological functions, such as specific cell adsorption or interaction with a specific protein or analyte. [3] As part of a device, bioactive surfaces are commonly required to perform in complex biological media such as blood, saliva, or urine. [1,[4][5][6] These fluids typically contain numerous types of proteins and cells that may interfere with the performance of the bioactive surface by nonspecific adsorption. Such nonspecific adsorption by proteins and cells from biological media on a surface is called fouling. [7,8] Thus, the practical application of bioactive surfaces requires antifouling layers capable of preventing protein and cell fouling from complex biological media. [9,10] Antifouling coatings can be generated by immobilizing self-assembled monolayers (SAMs) or "grafted-to" or "graftedfrom" polymer coatings on a surface. [6,[11][12][13][14] SAMs are broadly applied to introduce different functionalities to the surfaces. [15,16] Notably, oligo(ethylene glycol)-terminated [4] and zwitterionic SAMs [17] can resist or decrease fouling from single-protein solutions and cell cultures. "Grafted-to" polymers based on ethylene glycol oxide, oxazoline, [18] N-(2-hydroxypropyl) methacrylamide (HPMA), [12] and zwitterionic moieties [19] have shown good resistance toward single-protein solutions and moderate-to-good resistance toward more complex biological media. The "grafted-from" approach, in which polymer chains are grown from a surface, allows the Surface-initiated photoinduced electron-transfer-reversible addition-fragmentation chain transfer (SI-PET-RAFT) is, for the first time, used for the creation of antifouling polymer brushes on gold surfaces based on three monomers: oligo(ethylene glycol) methyl ether methacrylate (MeOEGMA), N-(2-hydroxypropyl) methacrylamide (HPMA), and carboxybetaine methacrylamide (CBMA). These coatings are subsequently characterized by X-ray photoelectron spectroscopy (XPS) and ellipsometry. The living nature of this polymerization allows for the creation of random and diblock copolymer brushes, which are based on HPMA (superb antifouling) and CBMA (good antifouling and functionalizable via activated ester chemistry). The polymer brushes demonstrate good antifouling properties against undiluted human serum, as monitored by quartz crystal microbalance with dissipation (QCM-D) and surface plasmon resonance (SPR) spectroscopy in real time. The amount of immobilization of bioactive moieties, here an antibody immobilized using N-succinimidyl ester-1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (NHS-EDC) coupling, in the diblock and random copolymer brushes is monitored by SPR, and is analyzed with respect to the brush structure, and is shown to be superior in the diblock copolymer brush. This approach represents a scalable, robust, mild, oxygen-tolerant, and heavy-metal-free route toward the production of antifouling and functional copolymer brushes (on gold surfaces) that open up applications in biosensing and tissue engineering.

A new Ir catalysed approach for the selective cleavage of the Cα–Cβ bond in lignin β-O-4 units, allowing access to novel and tuneable monomeric product mixtures.

the system. The ability to control polymer solubility is of great interest in, for example, drug delivery, [4] tissue engineering, [5] or membrane technology. [6] Commonly employed thermoresponsive polymers are those that exhibit a lower critical solution temperature (LCST). [7][8][9] Such polymers are soluble at temperatures below that critical temperature, whereas they are insoluble at temperatures exceeding the LCST. [10] This change in solubility is accompanied by a conformational transformation, with a coilto-globule transition from soluble to insoluble polymers. [11] For thermoresponsive polymers endgrafted to a surface, specifically polymer brushes, this conformational change manifests itself by chains that point away from the surface when soluble, whereas insoluble chains collapse and minimize interaction with solvent molecules (Figure 1A). [12,13] This behavior results in addressable surface wettability and adhesive properties, which open the door to smart applications in cell-culture substrates, [14] temperature-dependent chromatography, [15] on-off membranes, [16] and microfluidic systems. [17] Typically, in order to obtain sufficiently high grafting densities and brush thicknesses, such polymer brushes are synthesized by surface-initiated polymerization techniques. [18] Commonly employed controlled surface-initiated polymerization procedures involve surface-initiated atom transfer radical polymerization (SI-ATRP) and surface-initiated radical additionfragmentation chain transfer (SI-RAFT) polymerization. [18,19]

This work presents a novel route for creating metalfree antiviral coatings based on polymer brushes synthesized by surface-initiated photoinduced electron transfer-reversible addition−fragmentation chain transfer (SI-PET-RAFT) polymerization, applying eosin Y as a photocatalyst, water as a solvent, and visible light as a driving force. The polymer brushes were synthesized using N- [3-(decyldimethyl)-aminopropyl] methacrylamide bromide and carboxybetaine methacrylamide monomers. The chemical composition, thickness, roughness, and wettability of the resulting polymer brush coatings were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), water contact angle measurements, and ellipsometry. The antiviral properties of coatings were investigated by exposure to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and avian influenza viruses, with further measurement of residual viable viral particles. The best performance was obtained with Cu surfaces, with a ca. 20-fold reduction of SARS-Cov-2 and a 50-fold reduction in avian influenza. On the polymer brush-modified surfaces, the number of viable virus particles decreased by about 5−6 times faster for avian flu and about 2−3 times faster for SARS-CoV-2, all compared to unmodified silicon surfaces. Interestingly, no significant differences were obtained between quaternary ammonium brushes and zwitterionic brushes.