“Layer-by-layer” deposits of coordination polymers show a rich morphology spectrum and display unusual structural transformations as a function of the deposition cycle number.

To overcome one of the disadvantages of most coordination polymers and metal-organic frameworks (MOFs) being insulators, conjugated coordination polymers are inves-tigated regarding their electrical conductivity. Rhodium paddle-wheel units containing coordination polymers are synthesized as bulk. They are deposited on functionalized gold substrates via a layer-by-layer approach using a self-built dip-coater. For the detailed characterization of topography and conductivity, atomic force microscopy (AFM) is used. The exchange of the equatorial coordinated acetates with acetamides leads to a change from insulating to semiconducting behavior. A temperature dependence of the current, more precisely, an increase of current with increasing temperature, is observable. The determined activation energy is between 0.3 and 0.5 eV. Bulk-limitation of charge transport is observed, and related hopping mechanisms are discussed. Conductive AFM allows us to characterize conductive coordination polymers and MOFs for a later potential usage in sensor devices.

Though amphiphiles are ubiquitously used for altering interfaces, interfacial reorganization processes are in many cases obscure. For example, adsorption of micelles to liquid-liquid interfaces is often accompanied by rapid reorganizations toward monolayers. Then, the involved time scales are too short to be followed accurately. A block copolymer system, which comprises poly(ethylene oxide)(110)-b-poly{[2-(methacryloyloxy)ethyl]diisopropylmethylammonium chloride}(170) (i.e., PEO110-b-qPDPAEMA(170) with quaternized poly(diisopropylaminoethyl methacrylate)) is presented. Its reorganization kinetics at the water/n-decane interface is slowed down by electrostatic interactions with ferricyanide ([Fe(CN)(6)](3-)). This deceleration allows an observation of the restructuring of the adsorbed micelles not only by tracing the interfacial pressure, but also by analyzing the interfacial rheology and structure with help of atomic force microscopy. The observed micellar flattening and subsequent merging toward a physically interconnected monolayer lead to a viscoelastic interface well detectable by interfacial shear rheology (ISR). Furthermore, the "gelled" interface is redox-active, enabling a return to purely viscous interfaces and hence a manipulation of the rheological properties by redox reactions. Additionally, interfacial Prussian blue formation stiffens the interface. Such manipulation and in-depth knowledge of the rheology of complex interfaces can be beneficial for the development of emulsion formulations in industry or medicine, where colloidal stability or adapted permeability is crucial.

Variable interfacial tension could be desirable for many applications. Beyond classical stimuli like temperature, we introduce an electrochemical approach employing polymers. Hence, aqueous solutions of the nonionic-cationic block copolymer poly(ethylene oxide)114-b-poly{[2-(methacryloyloxy)ethyl]diisopropylmethylammonium chloride}171 (i.e., PEO114-b-PDPAEMA171 with a quaternized poly(diisopropylaminoethyl methacrylate) block) were investigated by emerging drop measurements and dynamic light scattering, analyzing the PEO114-b-qPDPAEMA171 impact on the interfacial tension between water and n-decane and its micellar formation in the aqueous bulk phase. Potassium hexacyanoferrates (HCFs) were used as electroactive complexants for the charged block, which convert the bishydrophilic copolymer into amphiphilic species. Interestingly, ferricyanides ([Fe(CN)6]3-) act as stronger complexants than ferrocyanides ([Fe(CN)6]4-), leading to an insoluble qPDPAEMA block in the presence of ferricyanides. Hence, bulk micellization was demonstrated by light scattering. Due to their addressability, in situ redox experiments were performed to trace the interfacial tension under electrochemical control, directly utilizing a drop shape analyzer. Here, the open-circuit potential (OCP) was changed by electrolysis to vary the ratio between ferricyanides and ferrocyanides in the aqueous solution. While a chemical oxidation/reduction is feasible, also an electrochemical oxidation leads to a significant change in the interfacial tension properties. In contrast, a corresponding electrochemical reduction showed only a slight response after converting ferricyanides to ferrocyanides. Atomic force microscopy (AFM) images of the liquid/liquid interface transferred to a solid substrate showed particles that are in accordance with the diameter from light scattering experiments of the bulk phase. In conclusion, the present results could be an important step toward economic switching of interfaces suitable, e.g., for emulsion breakage.