Programmierbare transiente Thermogele vermittelt durch eine pH- und Redox-regulierte supramolekulare Polymerisation

Experimental and theoretical evidence for bilayer-by-bilayer surface melting of crystalline ice

On the surface of water ice, a quasi-liquid layer (QLL) has been extensively reported at temperatures below its bulk melting point at 273 K. Approaching the bulk melting temperature from below, the thickness of the QLL is known to increase. To elucidate the precise temperature variation of the QLL, and its nature, we investigate the surface melting of hexagonal ice by combining noncontact, surface-specific vibrational sum frequency generation (SFG) spectroscopy and spectra calculated from molecular dynamics simulations. Using SFG, we probe the outermost water layers of distinct single crystalline ice faces at different temperatures. For the basal face, a stepwise, sudden weakening of the hy…

Molecular scale structure and dynamics at an ionic liquid/electrode interface.

After a century of research, the potential-dependent ion distribution at electrode/electrolyte interfaces is still under debate. In particular for solvent-free electrolytes such as room-temperature ionic liquids, classical theories for the electrical double layer are not applicable. Using a combination of in situ high-energy X-ray reflectivity and impedance spectroscopy measurements, we determined this distribution with sub-molecular resolution. We find oscillatory charge density profiles consisting of alternating anion- and cation-enriched layers at both cathodic and anodic potentials. This structure is shown to arise from the same ion-ion correlations dominating the liquid bulk structure.…

Anisotropic carrier diffusion in single MAPbI(3) grains correlates to their twin domains

Polycrystalline thin films and single crystals of hybrid perovskites – a material group successfully used for photovoltaic and optoelectronic applications – reportedly display heterogeneous charge carrier dynamics often attributed to grain boundaries or crystalline strain. Here, we locally resolved the carrier diffusion in large, isolated methylammonium lead iodide (MAPbI3) grains via spatial- and time-resolved photoluminescence microscopy. We found that the anisotropic carrier dynamics directly correlate with the arrangement of ferroelastic twin domains. Comparing diffusion constants parallel and perpendicular to the domains showed carriers diffuse around 50–60% faster along the parallel d…

Anisotropic Charge Carrier Diffusion Correlated to Ferroelastic Twin Domains in MAPbI3 Perovskite

The Surface of Ice under Equilibrium and Nonequilibrium Conditions

ConspectusThe ice premelt, often called the quasi-liquid layer (QLL), is key for the lubrication of ice, gas uptake by ice, and growth of aerosols. Despite its apparent importance, in-depth understanding of the ice premelt from the microscopic to the macroscopic scale has not been gained. By reviewing data obtained using molecular dynamics (MD) simulations, sum-frequency generation (SFG) spectroscopy, and laser confocal differential interference contrast microscopy (LCM-DIM), we provide a unified view of the experimentally observed variation in quasi-liquid (QL) states. In particular, we disentangle three distinct types of QL states of disordered layers, QL-droplet, and QL-film and discuss…

Both mature KIR+ and immature KIR- NK cells control pediatric acute B-cell precursor leukemia in NOD.Cg-Prkdcscid IL2rgtmWjl/Sz mice.

Therapeutic natural killer (NK)-cell-mediated alloreactivity toward acute myeloid leukemia has largely been attributed to mismatches between killer immunoglobulin-like receptors (KIRs) on NK cells and their ligands, HLA class I molecules, on target cells. While adult acute B-cell precursor leukemia (BCP-ALL) appears to be resistant to NK-cell-mediated lysis, recent data indicate that pediatric BCP-ALL might yet be a target of NK cells. In this study, we demonstrate in a donor-patient-specific NOD.Cg-Prkdc(scid) IL2rg(tmWjl)/Sz (NSG) xenotransplantation model that NK cells mediate considerable alloreactivity toward pediatric BCP-ALL in vivo. Notably, both adoptively transferred mature KIR(+)…

Self-templated synthesis of novel carbon nanoarchitectures for efficient electrocatalysis

AbstractThe cost-efficient large-scale production of novel carbon nanostructure with high performance is still a challenge, restricting their applications in catalysis. Herein, we present a low-cost one-pot and one-step approach for the synthesis of both N-doped graphene (NG) and N-doped carbon nanotubes (NCNTs) from self-templated organic nanoplates. By varying the FeCl3 concentration in the precursor, we can control the formation of graphene or CNTs. To the best of our knowledge, this is the first example for the controllable synthesis of graphene or CNTs by varying the precursors’ compositions. This provides a simple and cost-effective route for the large-scale production of both NG and …

Salt-induced microheterogeneities in binary liquid mixtures

The salt-induced microheterogeneity (MH) formation in binary liquid mixtures is studied by small-angle x-ray scattering (SAXS) and liquid state theory. Previous experiments have shown that this phenomenon occurs for antagonistic salts, whose cations and anions prefer different components of the solvent mixture. However, so far the precise mechanism leading to the characteristic length scale of MHs has remained unclear. Here, it is shown that MHs can be generated by the competition of short-ranged interactions and long-ranged monopole-dipole interactions. The experimental SAXS patterns can be reproduced quantitatively by fitting to the derived correlation functions without assuming any speci…

Redox-Responsive and Thermoresponsive Supramolecular Nanosheet Gels with High Young's Moduli

Supramolecular gels made from 2D building blocks are emerging as one of the novel multifunctional soft materials for various applications. This study reports on a class of supramolecular nanosheet gels formed through a reversible self-assembly process involving both intramolecular folding and intermolecular self-assembly of poly[oligo(ethylene glycol)-co-(phenyl-capped bithiophenes)]. Such hierarchical self-assembled structure allows the gels to switch between sol and gel states under either redox or thermostimulus. Moreover, the gels illustrate high Young's moduli, compared to their controls that are made from the same oligo(ethylene glycol) and phenyl-capped bithiophenes blocks but have h…

Polymerized Ionic Liquids with Polythiophene Backbones: Self-Assembly, Thermal Properties, and Ion Conduction

Single ion conductors, based on polymerized ionic liquids (PILs) with a polythiophene backbone bearing imidazolium salts with butyl, hexyl, octyl, and decyl side groups and six different counterani...

Improving the mesomorphic behaviour of supramolecular liquid crystals by resonance-assisted hydrogen bonding

A systematic structure-property relationship study on hydrogen-bonded liquid crystals was performed, revealing the impact of resonance-assisted hydrogen bonds (RAHBs) on the self-assembling behavior of the supramolecular architecture. The creation of a six-membered intramolecular hydrogen-bonded ring acts as a counterpart to the self-organization between hydrogen bond donators and acceptors and determines thus the suprastructure. Variation of the hydrogen-bonding pattern allowed us to significantly improve the temperature range of the reported liquid crystalline assemblies.

Interfacial premelting of ice in nano composite materials

Physical chemistry, chemical physics 21, 3734 - 3741 (2019). doi:10.1039/C8CP05604H

Bioinspired actuated adhesive patterns of liquid crystalline elastomers.

Gecko-inspired arrays of micropillars made of a liquid crystalline elastomer display thermoswitchable adhesive behavior as a consequence of elongation changes caused by reorientation of the mesogens at the nematic-isotropic (N-I) phase transition.

Naturally occurring polyphenols as building blocks for supramolecular liquid crystals – substitution pattern dominates mesomorphism

A modular supramolecular approach towards hydrogen-bonded liquid crystalline assemblies based on naturally occurring polyphenols is reported. The combination of experimental observations, crystallographic studies and semi-empirical analyses of the assemblies provides insight into the structure–property relationships of these materials. Here a direct correlation of the number of donor OH-groups as well as their orientation with the mesomorphic behavior is reported. We discovered that the number and orientation of the OH-groups have a stronger influence on the mesomorphic behavior of the supramolecular assemblies than the connectivity (e.g. stilbenoid or chalconoid) of the hydrogen bond donor…

The Catalytic Effect of Fluoroalcohol Mixtures Depends on Domain Formation

In the present contribution, we investigated catalytically active mixtures of 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) and aqueous H2O2 by molecular dynamics simulations. It is clearly observable that the HFIP molecule strongly binds to the H2O2, which is necessary for the desired catalytic reaction to occur. Upon the addition of the substrate cyclooctene to the solution, this interaction is enhanced, which suggests that the catalytic activity is increased by the presence of the hydrocarbon. We could clearly observe the microheterogeneous structure of the mixture, which is the result of the separation of the hydroxyl groups, water, and H2O2 from the fluorinated alkyl moiety in the form of l…

Structure and Dynamics of Confined Liquids: Challenges and Perspectives for the X-ray Surface Forces Apparatus

Preprint of the open access article Weiss, H., Cheng, H.-W., Mars, J., Li, H., Merola, C., Renner, F. U., Honkimäki, V., Valtiner, M., & Mezger, M. (2019). Structure and Dynamics of Confined Liquids: Challenges and Perspectives for the X-ray Surface Forces Apparatus. Langmuir, 35(51), 16679–16692. https://doi.org/10.1021/acs.langmuir.9b01215

A modular approach towards functional supramolecular aggregates - subtle structural differences inducing liquid crystallinity.

Herein we report an efficient modular approach to supramolecular functional materials. Hierarchical self-assembly of azopyridine derivatives and hydrogen-bond donors yielded discotic assemblies. Subtle differences in the core units introduced mesomorphic behaviour and fast photo-response of the liquid crystals based on phloroglucinol. The presented results prove the benefits of a modular methodology towards highly responsive materials with tailor-made properties.

On the impact of linking groups in hydrogen-bonded liquid crystals – a case study

The impact of the linking group in hydrogen-bonded liquid crystals is systematically studied by a modular approach. POM and DSC results exhibited tremendous differences in the mesomorphic behaviour of the assemblies, due to the versatile linkages of the side chains, which were correlated with structural features and the elctronical nature of the side chains.

Humidity-Induced Grain Boundaries in MAPbI3 Perovskite Films

Methylammonium lead halide perovskites (MAPbI3) are very sensitive to humid environments. We performed in situ scanning force microscopy and in situ X-ray diffraction measurements on MAPbI3 films to track changes in the film morphology and crystal structure upon repeated exposure to a high relative humidity environment (80%). We found that the appearance of monohydrate (MAPbI3·H2O) Bragg reflections coincided with the appearance of additional grain boundaries. Prolonging the exposure time to humidity induced more grain boundaries and steps in the MAPbI3 films, and the peak intensities of the monohydrate MAPbI3·H2O increased. The monohydrate was not stable under dry atmosphere and could be r…

Vitamin C Loaded Polyethylene: Synthesis and Properties of Precise Polyethylene with Vitamin C Defects via Acyclic Diene Metathesis Polycondensation

A polyethylene-like polymer with an in-chain vitamin C group was synthesized by olefin metathesis polymerization. Here, we describe both the synthesis and a comprehensive physical characterization. Because of the olefin metathesis synthesis, the vitamin C groups are equidistantly arranged in the polyethylene (PE) main chain. Their separation was adjusted to 20 CH2 units. After hydrogenation, a semicrystalline polymer is obtained that is soluble in polar solvents. Because of its size and steric effect, the vitamin C acts as a chain defect, which is expelled from the crystal lattice, yielding a lamellar crystal with a homogeneous thickness corresponding to the interdefect distance. The physic…

Dendritic Mesoporous Silica Nanoparticles for pH-Stimuli-Responsive Drug Delivery of TNF-Alpha

Tumor necrosis factor-alpha (TNF-α) is a pleiotropic immune stimulatory cytokine and natural endotoxin that can induce necrosis and regression in solid tumors. However, systemic administration of TNF-α is not feasible due to its short half-life and acute toxicity, preventing its widespread use in cancer treatment. Dendritic mesoporous silica nanoparticles (DMSN) are used coated with a pH-responsive block copolymer gate system combining charged hyperbranched polyethylenimine and nonionic hydrophilic polyethylenglycol to encapsulate TNF-α and deliver it into various cancer cell lines and dendritic cells. Half-maximal effective concentration (EC50 ) for loaded TNF-α is reduced by more than two…

Ferroelastic Fingerprints in Methylammonium Lead Iodide Perovskite

Methylammonium lead iodide (MAPbI3) perovskite shows an outstanding performance in photovoltaic devices. However, certain material properties, especially the possible ferroic behavior, remain unclear. We observed distinct nanoscale periodic domains in the piezoresponse of MAPbI3(Cl) grains. The structure and the orientation of these striped domains indicate ferroelasticity as their origin. By correlating vertical and lateral piezoresponse force microscopy experiments performed at different sample orientations with X-ray diffraction, the preferred domain orientation is suggested to be the a1–a2-phase. The observation of these ferroelastic fingerprints appears to strongly depend on the film t…

Correction: Surface induced smectic order in ionic liquids – an X-ray reflectivity study of [C22C1im]+[NTf2]−

Physical chemistry, chemical physics 20(37), 24494 - 24495 (2018). doi:10.1039/C8CP91851A

Drug Delivery: Dendritic Mesoporous Silica Nanoparticles for pH-Stimuli-Responsive Drug Delivery of TNF-Alpha (Adv. Healthcare Mater. 13/2017)

Tuneable Transient Thermogels Mediated by a pH- and Redox-Regulated Supramolecular Polymerization.

A multistimuli-responsive transient supramolecular polymerization of β-sheet-encoded dendritic peptide monomers in water is presented. The amphiphiles, which contain glutamic acid and methionine, undergo a glucose oxidase catalyzed, glucose-fueled transient hydrogelation in response to an interplay of pH and oxidation stimuli, promoted by the production of reactive oxygen species (ROS). Adjusting the enzyme and glucose concentration allows tuning of the assembly and the disassembly rates of the supramolecular polymers, which dictate the stiffness and transient stability of the hydrogels. The incorporation of triethylene glycol chains introduces thermoresponsive properties to the materials. …

Surface induced smectic order in ionic liquids - an X-ray reflectivity study of [C(22)C(1)im](+)[NTf2](-)

Physical chemistry, chemical physics 19(39), 26651 - 26661 (2017). doi:10.1039/C7CP04852A

Photo-switching and -cyclisation of hydrogen bonded liquid crystals based on resveratrol

A series of hydrogen-bonded liquid crystals based on resveratrol and resveratrone is reported and investigated with respect to their photo-switchability (at 405 nm) and photo-cyclisation (at 300 nm).

Alteration of the structural properties of inulin gels

Abstract In this work, inulin particle gels, prepared with a type of long chain inulin, were examined in terms of their structural properties and mechanical response, depending on the applied shear rates and temperature during gel preparation. The results are interpreted on the basis of a particle gel model, which takes into account the varying gel structure, depending on the sample preparation parameters. X-ray measurements of the inulin powder, used for the experiments, revealed a mostly amorphous powder. The temperature profiles for the sample preparation, chosen from 25 °C to 60 °C with constant stirring at 600 rpm, yielded viscoelastic particle gels with decreasing hardness. By applica…

Single-crystal I h ice surfaces unveil connection between macroscopic and molecular structure

Physics and chemistry of ice surfaces are not only of fundamental interest but also have important impacts on biological and environmental processes. As ice surfaces—particularly the two prism faces—come under greater scrutiny, it is increasingly important to connect the macroscopic faces with the molecular-level structure. The microscopic structure of the ubiquitous ice Ih crystal is well-known. It consists of stacked layers of chair-form hexagonal rings referred to as molecular hexagons. Crystallographic unit cells can be assembled into a regular right hexagonal prism. The bases are labeled crystallographic hexagons. The two hexagons are rotated 30° with respect to each other. The linkage…

Isoprene/Styrene Tapered Multiblock Copolymers with up to Ten Blocks: Synthesis, Phase Behavior, Order, and Mechanical Properties

The living anionic copolymerization of isoprene and styrene in cyclohexane affords tapered block copolymers due to the highly disparate reactivity ratios of rI = 12.8 and rS = 0.051. Repeated addit...

Synthesis of Precision Poly(1,3-adamantylene alkylene)s via Acyclic Diene Metathesis Polycondensation

[Image: see text] Fully saturated, aliphatic polymers containing adamantane moieties evenly distributed along the polymer backbone are of great interest due to their exceptional thermal stability, yet more synthetic strategies toward these polymers would be desirable. Herein, we report for the first time the synthesis of poly(1,3-adamantylene alkylene)s based on α,ω-dienes containing bulky 1,3-adamantylene defects precisely located on every 11th, 17th, 19th, and 21st chain carbon via acyclic diene metathesis polycondensation. All saturated polymers revealed excellent thermal stabilities (452–456 °C) that were significantly higher compared to those of structurally similar polyolefins with al…

CCDC 1939466: Experimental Crystal Structure Determination

Related Article: Meik Blanke, Jan Balszuweit, Marco Saccone, Christoph Wölper, David Doblas Jiménez, Markus Mezger, Jens Voskuhl, Michael Giese|2020|Chem.Commun.|56|1105|doi:10.1039/C9CC07721A

CCDC 1886744: Experimental Crystal Structure Determination

Related Article: Marco Saccone, Michael Pfletscher, Sven Kather, Christoph Wölper, Constantin Daniliuc, Markus Mezger, Michael Giese|2019|J.Mater.Chem.C|7|8643|doi:10.1039/C9TC02787D

CCDC 1939467: Experimental Crystal Structure Determination

Related Article: Meik Blanke, Jan Balszuweit, Marco Saccone, Christoph Wölper, David Doblas Jiménez, Markus Mezger, Jens Voskuhl, Michael Giese|2020|Chem.Commun.|56|1105|doi:10.1039/C9CC07721A

CCDC 1455700: Experimental Crystal Structure Determination

Related Article: Michael Pfletscher, Christoph Wölper, Jochen S. Gutmann, Markus Mezger, Michael Giese|2016|Chem.Commun.|52|8549|doi:10.1039/C6CC03966A

CCDC 1942435: Experimental Crystal Structure Determination

Related Article: Jan Balszuweit, Meik Blanke, Marco Saccone, Markus Mezger, Constantin G. Daniliuc, Christoph Wölper, Michael Giese, Jens Voskuhl|2021|MSDE|6|390|doi:10.1039/D0ME00171F

CCDC 1886743: Experimental Crystal Structure Determination

Related Article: Marco Saccone, Michael Pfletscher, Sven Kather, Christoph Wölper, Constantin Daniliuc, Markus Mezger, Michael Giese|2019|J.Mater.Chem.C|7|8643|doi:10.1039/C9TC02787D

CCDC 1945777: Experimental Crystal Structure Determination

Related Article: Jan Balszuweit, Meik Blanke, Marco Saccone, Markus Mezger, Constantin G. Daniliuc, Christoph Wölper, Michael Giese, Jens Voskuhl|2021|MSDE|6|390|doi:10.1039/D0ME00171F

CCDC 1884535: Experimental Crystal Structure Determination

Related Article: Marco Saccone, Michael Pfletscher, Sven Kather, Christoph Wölper, Constantin Daniliuc, Markus Mezger, Michael Giese|2019|J.Mater.Chem.C|7|8643|doi:10.1039/C9TC02787D