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Integration of solvothermal reaction products into complex thin-layer architectures is frequently achieved by combinations of layer transfer and subtractive lithography, whereas direct additive substrate patterning with solvothermal reaction products has remained challenging. We report reactive additive capillary stamping under solvothermal conditions as a parallel contact-lithographic access to patterns of solvothermal reaction products in thin-layer configurations. To this end, corresponding precursor inks are infiltrated into mechanically robust mesoporous aerogel stamps derived from double-network hydrogels. The stamp is then brought into contact with a substrate to be patterned under solvothermal reaction conditions inside an autoclave. The precursor ink forms liquid bridges between the topographic surface pattern of the stamp and the substrate. Evaporation-driven enrichment of the precursors in these liquid bridges, along with their liquid-bridge-guided conversion into the solvothermal reaction products, yields large-area submicron patterns of the solvothermal reaction products replicating the stamp topography. For example, we prepared thin hybrid films, which contained ordered monolayers of superparamagnetic submicron nickel ferrite dots prepared by solvothermal capillary stamping surrounded by nickel electrodeposited in a second orthogonal substrate functionalization step. The submicron nickel ferrite dots acted as a magnetic hardener, halving the remanence of the ferromagnetic nickel layer. In this way, thin-layer electromechanical systems, transformers, and positioning systems may be customized.

The non-equilibrium dynamics of linear and star-shaped

Semicrystalline polymers are solids that are supposed to flow only above their melting temperature. By using confinement within nanoscopic cylindrical pores, we show that a semicrystalline polymer can flow at temperatures below the melting point with a viscosity intermediate to the melt and crystal states. During this process, the capillary force is strong and drags the polymer chains in the pores without melting the crystal. The unexpected enhancement in flow, while preserving the polymer crystallites, is of importance in the design of polymer processing conditions applicable at low temperatures, e.g., cold drawn polymers such as polytetrafluoroethylene, self-healing, and in nanoconfined donor/acceptor polymers used in organic electronics.

Materials 15(1), 46 (2022). doi:10.3390/ma15010046, Here, we present the (element-specific) magnetic properties and cation ordering for ultrathin Co-rich cobalt ferrite films. Two Co-rich Co$_x$Fe$_{3−x}$O$_4$ films with different stoichiometry (x=1.1 and x=1.4) have been formed by reactive solid phase epitaxy due to post-deposition annealing from epitaxial CoO/Fe$_3$O$_4$ bilayers deposited before on Nb-doped SrTiO$_3$(001). The electronic structure, stoichiometry and homogeneity of the cation distribution of the resulting cobalt ferrite films were verified by angle-resolved hard X-ray photoelectron spectroscopy. From X-ray magnetic circular dichroism measurements, the occupancies of the different sublattices were determined using charge-transfer multiplet calculations. For both ferrite films, a partially inverse spinel structure is found with increased amount of Co$^{3+}$ cations in the low-spin state on octahedral sites for the Co$_{1.4}$Fe$_{1.6}$O$_4$ film. These findings concur with the results obtained by superconducting quantum interference device measurements. Further, the latter measurements revealed the presence of an additional soft magnetic phase probably due to cobalt ferrite islands emerging from the surface, as suggested by atomic force microscope measurements., Published by MDPI, Basel

Hybrids of nitrate-based molten salts (KNO3, NaNO3, and Solar Salt) and anodic aluminum oxide (AAO) with various pore sizes (between 25 and 380 nm) were designed for concentrated solar power (CSP) plants to achieve low melting point ([removed]1 W m-1K-1). AAO pore surfaces were passivated with octadecyl phosphonic acid (ODPA), and the results were compared with as-anodized AAO. The change in phase transition temperatures and melting temperatures of salts was investigated as a function of pore diameter. Melting temperatures decreased for all salts inside AAO with different pore sizes while the highest melting temperature decrease (ΔT = 173 ± 2 °C) was observed for KNO3filled in AAO with a pore diameter of 380 nm. Another nanoconfinement effect was observed in the crystal phases of the salts. The ferroelectric phase of KNO3(γ-phase) formed at room temperature for KNO3/AAO hybrids with pore size larger than 35 nm. Thermal conductivity values of molten salt (MS)/AAO hybrids were obtained by thermal property analysis (TPS) at room temperature and above melting temperatures of the salts. The highest increase in thermal conductivity was observed as 73% for KNO3/AAO-35 nm. For NaNO3/AAO-380 nm hybrids, the thermal conductivity coefficient was 1.224 ± 0.019 at room temperature. To determine the capacity and efficiency of MS/AAO hybrids during the heat transfer process, the energy storage density per unit volume (J m-3) was calculated. The highest energy storage capacity was calculated as 2390 MJ m-3for KNO3/AAO with a pore diameter of 400 nm. This value is approximately five times higher than that of bulk salt.

The phase state and molecular dynamics of 1-dodecanol are studied in the bulk and under nanometer confinement within self-ordered nanoporous alumina templates. A rotator phase in the bulk is absent under confinement. A nematic liquid crystalline phase is formed instead in pores with diameters from 400 down to 25 nm. Results are based on the changes in temperature-dependence of dielectric permittivity and X-ray diffraction. The phase diagram under confinement is explored, and the limits of the nematic-to-isotropic and crystalline-to-nematic phase transitions are identified. The phase diagram allows for a direct transition from the liquid to the low-temperature crystalline phase in pores with a diameter below 20 nm. Furthermore, we report on the dielectric fingerprint of the rotator phase and the molecular dynamics in bulk 1-dodecanol.

Rapid pattering of honeycomb nonlinear optical, 2D-photonic crystals on ITO is demonstrated via parallel capillary stamping of lithium niobate. Mediated interaction between the photonic crystal and gold nanoparticles by infrared light is validated using SHG.

The contribution of water to gecko and gecko-inspired adhesion remains a debate. Here, by investigating the adhesion performances of gecko-inspired nanopillar arrays in humid environments, the func...

The imbibition dynamics of poly(n-butyl methacrylate) (PnBMA) in nanoporous alumina is studied by in situ dielectric spectroscopy at temperatures in the range 30–50 K above the glass temperature. A...

Surface modification of porous glass beads by ethanol-based 3-mercaptopropyltrimethoxysilane (MPTMS) grafting solutions is directly evidenced by nitrogen adsorption, elemental analysis, thermogravimetry, infrared and 29Si CP MAS NMR spectroscopy. Furthermore, the energetic characterization of the surface is essential to understand comprehensively the physico-chemical interactions between the pristine and MPTMS-modified surface and its gas/liquid-phase environment. In this study, inverse gas chromatography (IGC) is used to characterize the surface properties of porous glass (PG). By means of IGC at infinite dilution (IGC-ID), the dispersive component of the surface energy ( γ s d ), the enthalpy and entropy of adsorption of C6-C10 hydrocarbon probes were determined at temperatures between 30 and 120 °C. The specific component of the surface energy ( γ s s p ) at the temperature of 120 °C has been obtained via the Van Oss theory and a least-squares procedure evaluating the IGC data of 8 polar probe molecules collectively. After surface silylation, the total surface energy ( γ s t ) decreased from 402 to 255 mJ/m² indicating both a reduced wettability and an increased hydrophobicity of the MPTMS-modified PG. Moreover, the acidity/basicity parameters according to the Van Oss and the Gutmann approach indicated that the acidity of the PG surface decreases by MPTMS grafting. Using n-octane and isopropanol probes, IGC at finite concentration (IGC-FC) was applied to obtain their adsorption isotherms and subsequently the BET specific surface areas. In addition, the surface heterogeneity of the studied PGs was also computed. The energy distribution functions of adsorption sites were monomodal (peak maximum at about 22 kJ/mol) for the n-octane probe, while isopropanol revealed a bimodal distribution function (maxima at about 18 and 25 kJ/mol) on both pristine and MPTMS-modified PG. Furthermore, the proportion of high energy sites (apparently assigned to Si OH groups) has been reduced by surface modification from 65% to only 35% despite a high surface coverage of ˜10 MPTMS species/nm2. These findings are in agreement with the results of 29Si CP MAS NMR measurements and are supported by DFT calculations on the adsorption of isopropanol and n-octane on the surface of a silica cluster model.

The dynamics of unentangled cis-1,4-polyisoprene confined within self-ordered nanoporous alumina (AAO) is studied as a function of molecular weight (5000–300 g/mol) and pore size (400–25 nm) with dielectric spectroscopy. The main effects are the pronounced broadening of both segmental and chain modes with decreasing AAO pore diameter. This suggests that the global chain relaxation is retarded on confinement. Remarkably, the distribution of relaxation times is broadened even within pores with size 50 times the unperturbed chain dimensions. The glass temperature is unaffected by confinement. These results are discussed in terms of confinement and adsorption effects. Confinement effects are negligible for the studied molecular weights. Chain adsorption, on the other hand, involves time and length scales distinctly different from the bulk that can account for the experimental findings.

The eutectic mixture of liquid crystals E7 is studied in confinement by means of thermal and dielectric measurements. The uniform 1-D confinement provided by self-ordered nanoporous alumina leads to a decrease in the nematic to isotropic transition temperature due to interaction with the pore surface, e.g. surface anchoring. The prevalence of certain dynamic modes of relaxation is found to depend on the surface properties of the confining pores. The dynamics (i.e., relaxation times) were found to accelerate with increasing confinement, resulting in a decreasing glass temperature, independent of surface treatment. From the pre- and meta-transitional dependence of the dielectric permittivity on temperature we are able to deduce a weakening effect of confinement on the nematic to isotropic (N/I) transition which allows the determination of a critical pore diameter (in the range from 11 nm to 23 nm) below which the transition becomes continuous. Comparison of the N/I transition of E7 to those of its constituent liquid crystals reveals a significantly weaker transition occurring over a widened temperature range. This suggest the importance of concentration fluctuations in rounding first order phase transitions that are triggered by the different length scales and ranges of nematic stability in E7. The results have an impact beyond the present case and for several soft materials (e.g. oligomers used as OLEDs, polymers, colloids) as it demonstrates the importance of concentration fluctuations in addition to thermal fluctuation on the strength of phase transitions.

The exploration of promising renewable energy sources for the future is likely the most significant challenge for humanity. Hydrogen is considered to play a major role in the urgently required reorganization of our current energy sector. Water can be split into hydrogen and oxygen and therefore presents an in principle inexhaustible and environmentally friendly hydrogen source. However, electrochemical approaches for the cleavage of H2O remain challenging, especially considering that the experimentally required potential at which oxygen evolves is substantially higher than the theoretically required potential. This results in significant overpotentials (η) on the anode side, which limits the widespread applicability of this technique. Here, we have applied a two-step activation procedure of a Co-containing steel, which led to a significant reduction of η for the oxygen evolution reaction (OER) down to almost zero. The enhanced electrochemical behavior comes as a result of Li-ion doping, which leads to Li ...

The dual nature of Janus particles confers fascinating properties such as a response to multiple stimuli. In this communication, we systematically study the sensitivity to a uniform external magnetic field of isolated Janus rod-shaped and spherical particles in water confined to two dimensions. The Janus asymmetry of the particles is given by magnetic [Co(0.28 nm)/Pd(0.90 nm)]

Summary Thin polymer coatings covering on porous substrates are a common composite structure required in numerous applications, including membrane separation, and there is a strong need to push the coating thicknesses down to the nanometer scale to maximize the performances. However, producing such ultrathin polymer coatings in a facile and efficient way remains a big challenge. Here, uniform ultrathin polymer covering films (UPCFs) are realized by a facile and general approach based on rapid solvent evaporation. By fast evaporating dilute polymer solutions spread on the surface of porous substrates, we obtain ultrathin coatings (down to ∼30 nm) exclusively on the top surface of porous substrates, forming UPCFs with a block copolymer of polystyrene-block-poly(2-vinyl pyridine) at room temperature or a homopolymer of poly(vinyl alcohol) (PVA) at elevated temperatures. Upon selective swelling of the block copolymer and crosslinking of PVA, we obtain highly permeable membranes delivering ∼2–10 times higher permeance in ultrafiltration and pervaporation than state-of-the-art membranes with comparable selectivities. We have invented a very convenient but highly efficient process for the direct preparation of defective-free ultrathin coatings on porous substrates, which is extremely desired in different fields in addition to membrane separation., Graphical Abstract, Public summary • Fast solvent evaporation is developed to produce UPCFs on porous substrates • Selective swelling to cavitate block copolymers to form interconnected mesopores • UPCFs enable the preparation of highly permeable membranes

Removing hazardous particulate and macromolecular contaminants as well as viruses with sizes from a few nm up to the 100-nm-range from water and air is crucial for ensuring sufficient sanitation and hygiene for a growing world population. To this end, high-performance separation membranes are needed that combine high permeance, high selectivity and sufficient mechanical stability under operating conditions. However, design features of separation membranes enhancing permeance reduce selectivity and vice versa. Membrane configurations combining high permeance and high selectivity suffer in turn from a lack of mechanical robustness. These problems may be tackled by using block copolymers (BCPs) as a material platform for the design of separation membranes. BCPs are macromolecules that consist of two or more chemically distinct block segments, which undergo microphase separation yielding a wealth of ordered nanoscopic domain structures. Various methods allow the transformation of these nanoscopic domain structures into customized nanopore systems with pore sizes in the sub-100-nm range and with narrow pore size distributions. This tutorial review summarizes design strategies for nanoporous state-of-the-art BCP separation membranes, their preparation, their device integration and their use for water purification.

We report an optimized two-step thermopolymerization process carried out in contact with micropatterned molds that yields porous phenolic resin dual-use stamps with topographically micropatterned contact surfaces. With these stamps, two different parallel additive substrate manufacturing methods can be executed: capillary stamping and decal transfer microlithography. Under moderate contact pressures, the porous phenolic resin stamps are used for nondestructive ink transfer to substrates by capillary stamping. Continuous ink supply through the pore systems to the contact surfaces of the porous phenolic resin stamps enables multiple successive stamp-substrate contacts for lithographic ink deposition under ambient conditions. No deterioration of the quality of the deposited pattern occurs, and no interruptions for ink replenishment are required. Under a high contact pressure, porous phenolic resin stamps are used for decal transfer printing. In this way, the tips of the stamps' contact elements are lithographically transferred to counterpart substrates. The granular nature of the phenolic resin facilitates the rupture of the contact elements upon stamp retraction. The deposited phenolic resin micropatterns characterized by abundance of exposed hydroxyl groups are used as generic anchoring sites for further application-specific functionalizations. As an example, we deposited phenolic resin micropatterns on quartz crystal microbalance resonators and further functionalized them with polyethylenimine for preconcentration sensing of humidity and gaseous formic acid. We envision that also preconcentration coatings for other sensing methods, such as attenuated total reflection infrared spectroscopy and surface plasmon resonance spectroscopy, are accessible by this functionalization algorithm.

The shape of objects has a strong influence on their dynamics. Here, we present comparative studies of two different motile objects, spherical Ag/AgCl Janus particles and polystyrene Janus nanorods, that move due to an ionic self-diffusiophoretic propulsion mechanism when exposed to blue light. In this paper, we propose a method to fabricate Janus rodlike particles with high aspect ratios and hemispherical tip shapes. The inherent asymmetry due to the ratio between capped and uncapped parts of the particles as well as the shape anistropy of Janus nanorods enables imaging and quantification of rotational dynamics. The dynamics of microswimmers are compared in terms of velocities and diffusion coefficients. We observe that despite a small amount of the Ag/AgCl reagent on the surface of rodlike objects, these new Janus micromotors reveal high motility in pure water. While the velocities of spherical particles reach 4.2 μm/s, the single rodlike swimmers reach 1.1 μm/s, and clusters reach 1.6 μm/s. The effect of suppressed rotational diffusion is discussed as one of the reasons for the increased velocities. These Janus micro- and nanomotors hold the promise for application in light-controlled propulsion transport.

Highly dense, ordered arrays of a titania (TiO2) nanomaterial with a bowl-shape morphology are generated by using poly(styrene-block-ethylene oxide) (PS-b-PEO) block copolymers as templates combined with a sol-gel process. Porous organic-inorganic hybrid films with titania nanodomains incorporated in the PEO domains can be produced by one step spin-coating. By manipulating the relative composition of the precursor ingredients, a simple protocol to fabricate hexagonally packed arrays of nanobowls is defined. Addition of a second inorganic precursor into the common solution leads to arrays of composite Au-TiO2 nanobowls. Such organic-inorganic hybrids and pure titania nanostructures with controlled shape and size exhibit unique photophysical properties.

Cost-affordable phenolic membranes having gradient nanostructures can be facilely synthesized from resol oligomers in the presence of ZnCl2 and poloxamers. The gradient nanostructures are formed by stacking phenolic nanoparticles with gradually enlarged diameters as the distance from the upper surface increases. The use of poloxamers for creating gelation surroundings is of great significance for controlling the nucleation and growth of phenolic nanoparticles, which in turn dictates the performance of the phenolic membranes thus-produced. Hence, a study of the effects of poloxamers species on the preparation of the phenolic membranes is highly demanded since such robust membranes have much potential to be scale up for mass production. Herein, the poloxamer Pluronic F127 (EO106-PO70-EO106; EO = ethyleneoxide, PO = propyleneoxide) was introduced in the membrane-forming formulations. As opposed to P123 (EO20-PO70-EO20) that we used previously, F127 possessing extended PEO chains can delay the gelation during membrane formation. Hence, the phenolic nucleates are able to grow for longer durations, leading to the generation of more distinct gradient nanostructures in the phenolic membranes. Enhanced permeance can then be realized with F127-derived phenolic membranes. We also demonstrate that L31 (EO1-PO22-EO1) with merely single terminal EO units at the ends of the PPO block could be used to prepare gradient phenolic membranes. This work is not only much helpful to deeply understand the design of the structural gradient in phenolic membranes, but capable of sheding light on the development of such intriguing structures for water purification.

Classical microcontact printing and polymer pen lithography (PPL) involve ink transfer to substrates using solid elastomeric stamps. Ink depletion thus limits the number of successive stamping steps without reinking. Porous stamps developed to overcome this limitation are used only for manual proof‐of‐principle experiments. Here, porous composite stamps for scanner‐based capillary stamping (SCS) that can be mounted on automated printing devices designed for PPL are developed. Porous SCS composite stamps consist of a rigid controlled porous silica glass (CPG) layer and a porous polymeric stamping layer. The latter can be topographically structured with contact elements by replication molding. The mechanical stabilization by the CPG layer ensures that the contact elements are coplanar. SCS allows automated, continuous, high‐throughput patterning enabled by ink supply through the porous SCS composite stamps. Even after more than 800 consecutive stamp–substrate contacts without reinking (the porous SCS composite stamps themselves are used as ink reservoirs), ink microdroplets are deposited without deterioration of the pattern quality. However, SCS also allows supply of additional ink during ongoing stamping operations through the pore systems of the porous SCS composite stamps. SCS can easily be adapted for multi‐ink patterning and may pave the way for further upscaling of contact lithography.

Classical contact lithography involves patterning of surfaces by embossing or by transfer of ink. We report direct lithographic transfer of parts of sacrificial stamps onto counterpart surfaces. Using sacrificial stamps consisting of the block copolymer polystyrene-block-poly(2-pyridine) (PS-b-P2VP), we deposited arrays of nanostructured submicron PS-b-P2VP dots with heights of about 100 nm onto silicon wafers and glass slides. The sacrificial PS-b-P2VP stamps were topographically patterned with truncated-pyramidal contact elements and penetrated by spongy-continuous nanopore systems. The spongy nature of the sacrificial PS-b-P2VP stamps supported formation of adhesive contact to the counterpart surfaces and the rupture of the contact elements during stamp retraction. The submicron PS-b-P2VP dots generated by sacrificial stamping can be further functionalized, examples include loading submicron PS-b-P2VP dots with dyes and attachment of gold nanoparticles to their outer surfaces. The arrays of submicron PS-b-P2VP dots can be integrated into setups for advanced optical microscopy, total internal reflection fluorescence microscopy or Raman microscopy. Arrays of nanostructured submicron block copolymer dots may represent a preconcentration platform for locally resolved sensing and locally resolved monitoring of cellular interactions or might be used as microreactor arrays in lab-on-chip configurations., ACS Applied Nano Materials 2018

We report the effect of confinement on the dynamics of three monohydroxy alcohols (1-propanol, 2-ethyl-1-hexanol, and 4-methyl-3-heptanol) differing in their chemical structure and, consequently, in the dielectric strength of the “Debye” process. Density functional theory calculations in bulk 1-propanol identified both linear and ring-like associations composed of up to five repeat units. The simulation results revealed that the ring structures, with a low dipole moment (∼2 D), are energetically preferred over the linear assemblies with a dipole moment of 2.18 D per repeat unit. Under confinement in nanoporous alumina (in templates with pore diameters ranging from 400 to 20 nm), all dynamic processes were found to speed up irrespective of the molecular architecture. The characteristic freezing temperatures of the α and the Debye-like processes followed the pore size dependence: Ta,D=Ta,Dbulk−A/d1/2, where d is the pore diameter. The characteristic “freezing” temperatures for the Debye-like (the slow process for confined 1-propanol is non-Debye) and the α-processes decrease, respectively, by 6.5 and 13 K in confined 1-propanol, by 9.5 and 19 K in confined 2-ethyl-1-hexanol, and by 9 and 23 K in confined 4-methyl-3-heptanol within the same 25 nm pores. In 2-ethyl-1-hexanol, confinement reduced the number of linearly associated repeats from approximately heptamers in the bulk to dimers within 25 pores. In addition, the slower process in bulk 2-ethyl-1-hexanol and 4-methyl-3-heptanol, where the signal is dominated by ring-like supramolecular assemblies, is clearly non-Debye. The results suggest that the effect of confinement is dominant in the latter assemblies.

The crystallization and dynamics of hyperbranched poly(ethylene oxide) (hbPEO), obtained from the direct random copolymerization of EO and glycidol (PEO-co-PG), are studied both in bulk and within nanoporous alumina (AAO). Copolymerization decreases the degree of crystallinity and lowers the crystallization and melting temperatures as compared to linear PEO. The dynamics of capillary imbibition within AAO followed the t1/2 prediction but is slower than predicted by the classical Lucas–Washburn equation. The most prominent effect of confinement is the change in nucleation mechanism—from heterogeneous nucleation in bulk to homogeneous nucleation inside AAO. The homogeneous nucleation temperatures for the hyperbranched PEOs agree with those of linear ones provided that the branch molecular weight is used instead of the total molecular weight. Confinement and interfacial effects further suppress the degree of crystallinity and speed up the segmental dynamics.

Eine aktuelle Studie des Fraunhofer-Instituts sieht im verstärkten Einsatz von Großwärmepumpen einen Schlüssel zur Dekarbonisierung der Fernwärme. Wie dies erfolgreich umgesetzt werden kann, zeigt ein kleines Dorf in den Vorarlberger Alpen, das durch den Einsatz von zwei Großwärmepumpen und mithilfe eines ausgeklügelten Hydraulik-Konzepts seine Einwohner sowie Gäste mit umweltschonender Fernwärme versorgt.

Surface modified silica nanoparticles are well-established composite materials. To improve their embedding and application behavior, surface energy analysis has been performed before and after silanization with mercaptopropyltrimethoxysilane (MPTMS) using inverse gas chromatography technique (IGC). Experiments with two silica materials have been conducted at infinite dilution to determine the dispersive component of the surface energy ( γ s d ) as well as the specific component ( γ s sp ) using the van Oss theory and a least-squares procedure evaluating the IGC data of 8 polar probe molecules collectively (instead of evaluating only the data of a pair of monopolar probes as is often the case in IGC studies). After surface silylation, the total surface energy ( γ s t ) of pyrogenic silica nanoparticles decreased from 225 mJ/m2 to 149 mJ/m2 referring to both a reduced wettability and an increased hydrophobicity of the MPTMS-modified sample. Moreover, the acidity/basicity parameters according to the van Oss and the Gutmann approach indicated that the acidity of the silica surface decreases by MPTMS grafting. In addition, IGC at finite concentration (using isopropanol as probe molecule) was applied to obtain the energetic heterogeneity of the silica surface. The results showed a bimodal energy distribution with maxima at about 18 and 25 kJ/mol and a reduction of the higher energetic sites from 65% to only 35% after MPTMS treatment. Overall, it can be seen that the dominance of specific interactions on silica surfaces is maintained even after extensive silanization. These findings are in agreement with the results of 29Si CP MAS NMR measurements which confirm the assignment of higher energetic sites to silanol groups. For the interpretation of the IGC results, quantum chemical calculations proved the preferred interaction of isopropanol onto silica surfaces via hydrogen bridging.

The effect of oxygen substitution is studied in two homologous compounds of n-cyanobiphenyls with n = 8 in the bulk and under confinement within self-ordered nanoporous alumina (AAO). Oxygen substitution in 8OCB increases the dipole moment and stabilizes the crystalline, smectic, and nematic phases to higher temperatures relative to 8CB. Within their smectic- A (SmA) phase both 8CB and 8OCB behave as weak viscoelastic solids with low shear moduli reflecting the underlying supramolecular defect structure. Dielectric spectroscopy assisted by DFT calculations identified strong dipolar associations within the isotropic phases characterized by a Kirkwood-Fröhlich interaction parameter, g ∼ 0.36. Dielectric spectroscopy further identified a slow process (∼ kHz) of low dielectric strength. The proximity of this process to the rheology time scale suggests as common origin a cooperative relaxation of the defect structure. Confinement alters the phase diagram by stabilizing certain crystalline phases and by reducing the N-I transition temperature in agreement with surface tension effects. However, the N-I transition seems to retain its first order character. Surface treatment with n-decyltrichlorosilane results in destabilization of the SmA phase at the expense of the N phase. This is consistent with a picture of surface anchored LC molecules at the pore walls that stabilize the nematic phase.

Water drops used as reaction compartments are commonly immobilized on hydrophilic areas bordered by hydrophobic areas. For many applications, such as the trapping of non-adherent cells, it is desirable to exploit the inertness and the anti-fouling behavior of hydrophobic surfaces as well as their repulsive behavior towards adsorbates in lab-on-chip configurations. However, the immobilization of water drops on hydrophobic surfaces has remained challenging. We report a nonlithographic approach to arrest water drops on hydrophobically modified macroporous silicon (mSi) with per uorinated surface. Contact line pinning at rings of polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) fibers protruding from the mSi macropores immobilizes water drops when the hydrophobically modified mSi is moved or tilted and prevents dewetting within the PS-b-P2VP fiber rings. Without PS-b-P2VP fiber rings, water drops readily roll off. The PS-b-P2VP fiber rings were prepared by dropping PS-b-P2VP solution onto hydrophobically modified mSi. Selective swelling of the P2VP in the thus-formed circular PS-b-P2VP films with hot ethanol followed by detachment of the latter yielded hydrophobically modified mSi exhibiting annular areas, in which ruptured PS-b-P2VP fibers protruded from the mSi macropores. For example, PS-b-P2VP fiber rings with diameters of 6.5 mm and widths of about 0.2 mm immobilize water drops with a volume of 50 microliters.

The electrodeposition of noble metals using corresponding dissolved metal salts represents an interesting process for the improvement of the electrocatalytic hydrogen evolution reaction (HER) properties of less active substrate materials. The fact that only a small fraction of the dissolved noble metals reaches the substrate represents a serious obstacle to this common procedure. We therefore chose a different path. It was found that the HER activity of Ni42 alloy drastically increased (η=140 mV at j=10 mA cm−2; pH 1) when a platinum counter electrode was used during polarization experiments in acid. This improvement was caused by a platinum transfer from the platinum anode to the steel cathode, a process which occurred simultaneously to the hydrogen evolution. The negligible accumulation of Pt (26 μg) in the electrolyte turns this straight‐forward transfer procedure into a highly cost‐effective, environmentally friendly, and waste reducing approach for the generation of cheap, stable and effective HER electrodes., The use of a platinum counter electrode for the evaluation of non‐Platinum group metal based electrodes can be seen as bad electrochemical practice. Herein, it was done intentionally and this strategy turned out to be a zero‐waste‐approach for the generation of highly active and stable HER electrocatalysts.

We report on the effect of interfacial energy on the glass temperature, Tg, of several amorphous polymers with various glass temperatures and polymer/substrate interactions confined within self-ordered nanoporous alumina (AAO). The polymers studied include poly(phenylmethylsiloxane) (PMPS), poly(vinyl acetate) (PVAc), 1,4-polybutadiene (PB), oligostyrene (PS), and poly(dimethylsiloxane) (PDMS). The segmental dynamics and associated Tg’s are studied by means of dielectric spectroscopy. The interfacial energy for the polymer/substrate interface, γSL, is calculated with Young’s equation whereas the AAO membrane surface energy is obtained by measuring contact angles for several reference liquids. We find that interfacial energy plays a significant role in the segmental dynamics of polymers under confinement within AAO. There is a trend for a decreasing glass temperature relative to the bulk with increasing interfacial energy. PDMS exhibits the highest interfacial energy and the highest reduction in glass temp...

The effects of polydispersity, additives, impurities, free top layer and of surface roughness on the nucleation are studied for poly(ethylene oxide) located inside self-ordered nanoporous aluminum oxide (AAO). AAO pore diameters ranged from 400 nm to 25 nm. With the exception of a surface layer, none of the above factors is able to induce heterogeneous nucleation under confinement. Homogeneous nucleation remains the sole mechanism in pores having diameters below 65 nm. The internal pore surface roughness is small, which explains the minor effects of AAO surfaces on inducing heterogeneous nucleation especially within the smaller pores. The presence of oligomers shifts the homogeneous nucleation temperature to lower temperatures, reflecting the plasticizing effect of the oligomers on the liquid-to-glass temperature.

Polymer topology matters with respect to the structure, packing, and dynamics of chains. Herein we investigate the impact of polymer architecture on the crystallization under rigid confinement provided by nanoporous alumina. We employ two poly(ethylene oxide) (PEO) star polymers and study the effect of (i) end groups and (ii) molecular weight on polymer crystallization in the bulk and under confinement. Functional end-groups have important consequences on the bulk crystallization process. Bulk end-groups reduce the crystallization/melting temperatures and the corresponding equilibrium melting point. Remaining catalyst in the polymer increases the nucleation density in the bulk. Under confinement, the role of catalyst is to enhance the propensity for heterogeneous nucleation, especially in the larger pores. In the absence of catalyst, homogeneous nucleation prevails as with linear PEOs. Long-range dynamics pertinent to star relaxation are affecting the homogeneous nucleation temperature. The homogeneous nu...

Despite concerns over toxicity, carbon nanotubes have been extensively investigated for potential applications in nanomedicine because of their small size, unique properties, and ability to carry cargo such as small molecules and nucleic acids. Herein, we show that polymer nanotubes can be synthesized quickly and easily from a homopolymer of ethylene glycol dimethacrylate (EGDMA). The nanotubes formed via photo‐initiated polymerization of the highly functional prepolymer, inside an anodized aluminium oxide template, have a regular structure and large internal pore and can be loaded with a fluorescent dye within minutes representing a simple alternative to multi‐walled carbon nanotubes for biomedical applications.

We study changes in the dynamics of polymer chains confined to cylindrical nanochannels within aluminum oxide membranes. Specifically, a proton time-domain NMR technique is used to assess the effect of transient wall contacts on the time-averaged orientational order of poly(butadiene) segments in melts with different molecular weights (MW). Previous work has evidenced that the weakly interacting polymer, residing in ∼100 μm long, 20 and 60 nm wide channels, shows no significant confinement-related changes in the segmental (α) relaxation time and only weak (less than a factor of 2) changes in the micrometer-scale diffusivity. In the relevant temperature range above 340 K, we here use samples with pores oriented at different angles with respect to the main magnetic field to study the macroscopic anisotropy of segmental rotations and the effect of slower motions in regimes III and IV of the tube model up to the milliseconds time scale. We show that the pore walls exert a significant orientation effect on the...

Polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) monoliths containing regular arrays of macropores (diameter ~1.1 microns, depth ~700 nm) at their surfaces are used to pattern substrates by patterning modes going beyond the functionality of classical solid elastomer stamps. In a first exemplary application, the macroporous PS-b-P2VP monoliths are employed as sacrificial templates for the deposition NaCl nanocrystals and topographically patterned iridium films. One NaCl nanocrystal per macropore is formed by evaporation of NaCl solutions filling the macropores followed by iridium coating. Thermal PS-b-P2VP decomposition yields topographically patterned iridium films consisting of ordered arrays of hexagonal cells, each of which contains one NaCl nanocrystal. For the second exemplary application, spongy-continuous mesopore systems are generated in the macroporous PS-b-P2VP monoliths by selective-swelling induced pore generation. Infiltrating the spongy-continuous mesopore systems with ink allows capillary microstamping of continuous ink films with holes at the positions of the macropores onto glass slides compatible with advanced light microscopy. Capillary microstamping can be performed multiple times under ambient conditions without re-inking and without quality deterioration of the stamped patterns. The macroporous PS-b-P2VP monoliths are prepared by double replication of primary macroporous silicon molds via secondary polydimethylsiloxane molds.