Apostolos Vagias

A promising antibacterial strategy relies on surfaces that combine contact-killing activity with controlled release, enabling rapid response and long-term reusability. Herein, we report such kill-and-release antibacterial surfaces based on lamellar-organized amphiphilic diblock copolymer thin films. Amphiphilic diblock copolymers comprising a hydrophobic, hydrolyzable poly(tetrahydropyranyl methacrylate) (PTHPMA) block and a hydrophilic poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) block are synthesized via group transfer polymerization and subsequently quaternized with propyl iodide to convert the DMAEMA units into cationic, biocidal quaternary ammonium groups (PQDMAEMA). Upon solvent annealing, the PQDMAEMA-b-PTHPMA thin films self-assemble into lamellae oriented parallel to the substrate, with the biocidal PQDMAEMA block forming the outermost surface layer. Mild hydrolysis converts the hydrophobic THPMA units into hydrophilic methacrylic acid moieties, rendering the copolymer water-soluble and enabling its layer-by-layer removal, renewing the active antibacterial surface. Structural ordering of the diblock copolymers is confirmed by optical and atomic force microscopy, X-ray reflectivity, and grazing incidence small-angle X-ray scattering. The film's self-polishing behavior in water is monitored by ellipsometry for 300 days. The annealed films exhibit effective and durable antibacterial activity, achieving ∼2-log reduction against both Gram-positive and Gram-negative bacteria, both annealed and after 30 days of immersion in pH 7.4 water, demonstrating sustained long-term antimicrobial performance.

By means of Grazing Incidence Small Angle Neutron Scattering under hydrostatic pressure (HP - GISANS) and neutron reflectometry at the solid-liquid interface, we compare effects of pressure and temperature on two model homopolymer mixed brush systems in thin (< 100 nm) film geometry: a weakly incompatible (poly(methylmethacrylate) / poly(2-(dimethylamino)ethyl methacrylate)) (PMMA / PDMAEMA) and strongly incompatible ((poly((2,2,3,3,4,4,5,5-octafluoro)pentyl methacrylate))/ poly(2-(dimethylamino)ethyl methacrylate) ) (POFPMA/PDMAEMA) one. A dual responsive, temperature and pressure-sensitive, polymer (PDMAEMA) in both systems allows to explore the role of mixing incompatibilities between tethered macromolecules with solvent and also pressure on the morphological changes in the PDMAEMA-containing nanostructures. Our findings indicate distinct pressure-dependent response in both lateral (HP-GISANS) and transversal (specular NR) nanostructure depending on the chemical composition. Specular ToF-NR results suggest that temperature effects are found to be counteracted by pressure and also that presumably mixing non-idealities and residual unoccupied volume within the investigated mixed brushes are polymer-compatibility dependent as evidenced by enhanced D2O retention within the brush by the strongly incompatible POFPMA/PDMAEMA mixed brush. GISANS analysis indicates the presence of uncorrelated cylindrical hydrophobic nanostructures within a PDMAEMA-based swollen matrix. Moreover, off-specular scattering (OSS) analysis demonstrates that the spacing between hydrophobic domains and the associated surface coverage exhibits changes with pressure only for the strongly incompatible POFPMA/PDMAEMA mixed brush. Our HP - GISANS and off-specular scattering results suggest that the length scale of phase separation on the sample surface along the beam direction can strongly depend on the compositional variation in the mixed brushes.

This work investigates the growth mechanisms and optimization of optical properties in block copolymer (BCP)‐templated MAPbBr ₃ perovskite nanocrystals (PeNCs). Neutron scattering, transmission electron microscopy, and in situ optical spectroscopy studies combined with confinement‐model‐based size estimation of the nanocrystals during the perovskite formation revealed a complex multispecies growth behavior of BCP‐templated PeNCs, which was significantly influenced and could be controlled by systematically varying the stoichiometry between polystyrene‐b‐poly(2‐vinylpyridine) (PS‐b‐P2VP) and PbBr ₂ in the precursor, and the manner of adding the A‐cation either as a dispersion in a polymer solution or dissolved in methanol. The combination of optimized precursor stoichiometry and methanol‐based A‐cation addition yielded narrow emission linewidths of 83 meV and photoluminescence quantum yields of up to 87%. These findings provide new mechanistic insights and practical levers for improving BCP‐templated perovskite nanocrystals, paving the way for their application in future optoelectronic devices.

This work investigates the growth mechanisms and optical property optimization of block copolymer (BCP)templated MAPbBr3 perovskite nanocrystals (PeNCs). Neutron scattering, transmission electron microscopy and in situ optical spectroscopy studies combined with confinement-model-based size estimation of the nanocrystals during the perovskite formation revealed a complex multi-species growth behavior of BCP-templated PeNCs, which was significantly influenced and could be controlled by systematically varying the stoichiometry between polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) and PbBr2 in the precursor, and the manner of adding the A-cation from either as a dispersion in a polymer solution or dissolved in methanol. The combination of optimized precursor stoichiometry and methanol-based A-cation addition yielded narrow emission linewidths down to 83meV and PLQYs up to 87%. These findings provide new mechanistic insights and practical levers for improving BCP-templated perovskite nanocrystals, paving the way for their application in future optoelectronic devices.

Grazing-incidence small-angle neutron scattering (GISANS) under pressure (HP-GISANS) at the solid (Si)–liquid (D₂O) interface is demonstrated for the pressure-induced lateral morphological characterization of the nanostructure in thin (T = 45°C for two pressures, P = 1 bar and P = 800 bar. Our GISANS results reveal nanostructural rearrangements with increasing P, underlining P-induced effects in tethered polymer brush layers swollen with bulk solvent.

The humidity influence on the electronic and ionic resistance properties of thin post-treated poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films is investigated. In particular, the resistance of these PEDOT:PSS films post-treated with three different concentrations (0, 0.05, and 0.35 M) of ethyl-3-methylimidazolium dicyanamide (EMIM DCA) is measured while being exposed to a defined humidity protocol. A resistance increase upon elevated humidity is observed for the 0 M reference sample, while the EMIM DCA post-treated samples demonstrate a reverse behavior. Simultaneously performed in situ grazing-incidence small-angle X-ray scattering (GISAXS) measurements evidence changes in the film morphology upon varying the humidity, namely, an increase in the PEDOT domain distances. This leads to a detriment in the interdomain hole transport, which causes a rise in the resistance, as observed for the 0 M reference sample. Finally, electrochemical impedance spectroscopy (EIS) measurements at different humidities reveal additional contributions of ionic charge carriers in the EMIM DCA post-treated PEDOT:PSS films. Therefrom, a model is proposed, which describes the hole and cation transport in different post-treated PEDOT:PSS films dependent on the ambient humidity.

Time‐of‐flight neutron reflectometry (ToF‐NR) performed under different relative humidity conditions demonstrates that polymer brushes constituted by hydrophilic, cyclic macromolecules exhibit a more compact conformation with lower roughness as compared to linear brush analogues, due to the absence of dangling chain ends extending at the polymer–vapor interface. In addition, cyclic brushes feature a larger swelling ratio and an increased solvent uptake with respect to their linear counterparts as a consequence of the increased interchain steric repulsions. It is proposed that differences in swelling ratios between linear and cyclic brushes come from differences in osmotic pressure experienced by each brush topology. These differences stem from entropic constraints. The findings suggest that to correlate the equilibrium swelling ratios at different relative humidity for different topologies a new form of the Flory‐like expression for equilibrium thicknesses of grafted brushes is needed.