Manfred Heuberger

2,2′:6′,2′′-Terpyridine-functionalized redox-responsive hydrogels as a platform for multi responsive amphiphilic polymer membranes

Nanophase-separated amphiphilic polymer co-networks are ideally suited as responsive membranes due to their stable co-continuous structure. Their functionalization with redox-responsive 2,2′:6′,2′′-terpyridine–metal complexes and light-responsive spiropyran derivatives leads to a novel material with tunable optical, redox and permeability properties. The versatility of the system in complexing various metal ions, such as cobalt or iron at different concentrations, results in a perfect monitoring over the degree of crosslinking of the hydrophilic poly(2-hydroxyethyl acrylate) channels. The reversibility of the complexation, the redox state of the metal and the isomerization to the merocyanine form upon UV illumination was evidenced by cyclic voltammetry, UV-Vis and permeability measurements under sequential conditions. Thus, the membrane provides light and redox addressable functionalities due to its adjustable and mechanically stable hydrogel network.

Nanoconfined water can orient and cause long-range dipolar interactions with biomolecules

Surface properties are generally determined by the top most surface layer also defining how molecules adsorb onto it. By exploring effects due to interactions with deeper subsurface layers, however, long-range interaction forces were found to also significantly contribute to molecular adsorption, in which hydration of the subsurface region is the key factor. Water molecules confined to a subsurface amphiphilic gradient are confirmed to cause these long-range dipolar interactions by preferential orientation, thus significantly changing the way how a protein interacts with the surface. These findings imply future exploitation of an additional factor to modulate adsorption processes.

Sensors on Textile Fibres Based on Ag/a-C:H:O Nanocomposite Coatings

In this contribution we present a study of the vacuum deposition process of metal/plasma polymer nanocomposite thin films monitored using plasma diagnostics (optical emission spectroscopy). We investigate the electrical properties of the nanocomposite structures suitable for their application as humidity sensors. Furthermore, the film microstructure is characterized by transmission electron microscopy and electron diffraction analysis. The amount of silver in the nanocomposite is evaluated using inductively coupled plasma optical emission spectrometry and the morphology of the structured system of metal electrodes and nanocomposite films on monofilament textile fibres is visualized using scanning electron microscopy. Ageing of nanocomposite coatings and the influence of an aqueous environment on their internal structure and properties are discussed.

Near-Surface Structure of Plasma Polymer Films Affects Surface Behavior in Water and its Interaction with Proteins

Using low pressure plasma polymerization, nano-scaled oxygen-rich plasma polymer films (CO) were deposited onto pristine silicon wafers as well as on nitrogen-containing plasma polymer (CN) model surfaces. We investigate the influence of the nature of the substrate as well as a potential sub-surface effect emerging from the buried CO/CN interface, just nanometers below the surface. X-ray Photoelectron Spectroscopy and Time-of-Flight Secondary Ion Mass Spectrometry revealed two important phenomena that occurred during the deposition of the terminal CO layer: (1) a strong degree of oxidation, already for 1xa0nm nominal thickness, and (2) a gradual transition in chemical composition between the two layers, clearly indicating that effectively a vertical chemical gradient results, even when a two-step coating process was applied. Such terminal gradient film structures were used to study film stability in aqueous environments. Molecular rearrangements were scrutinized in the top-surface in contact with water and we found that the top-surface chemistry and wetting properties of the oxygen-rich termination layer matched those of thick CO reference coatings. Nevertheless, the adsorption of green fluorescent protein (GFP) was observed to be sensitive to the CO terminal layer thickness. Namely, an enhanced protein adsorption was observed for 1–2xa0nm thick CO layers on CN, whereas a significantly reduced protein adsorption was seen on ≥u20093xa0nm thick CO terminal layers. We conclude that both, surface and sub-surface conditions significantly affect protein adsorption as opposed to the traditional consideration of surface properties alone.