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Calcium carbonate monohydrate-like ACC was made by ball-milling with ethanol as auxiliary solvent. IR and solid-state NMR, diffraction and total scattering show that defects of the hydrate network due to partial displacement of water by ethanol are crucial for amorphization.

Ternary oxides NaMO2 (M = Cr, Fe, Co, Al) were prepared by microfluidic processing in water-in-oil emulsions followed by a short annealing step.

Localized surface plasmon resonance properties in unconventional materials like metal oxides or chalcogenide semiconductors have been studied for use in signal detection and analysis in biomedicine and photocatalysis. We devised a selective synthesis of the tungsten oxides WO3-x and (NH4)xWO3 with tunable plasmonic properties. We selectively synthesized WO3-x nanorods with different aspect ratios and hexagonal tungsten bronzes (NH4)xWO3 as truncated nanocubes starting from ammonium metatungstate (NH4)6H2W12O40·xH2O. Both particles form from the same nuclei at temperatures >200 °C; monomer concentration and surfactant ratio are essential variables for phase selection. (NH4)xWO3 was the preferred reaction product only for fast heating rates (25 K min-1), slow stirring speeds (∼150 rpm) and high precursor concentrations. A proton nuclear magnetic resonance (1H-NMR) spectroscopic study of the reaction mechanism revealed that oleyl oleamide, formed from oleic acid and oleylamine upon heating, is a key factor for the selective formation of WO3-x nanorods. Since oleic acid and oleylamine are standard surfactants for the wet chemical synthesis of many metal and oxide nanoparticles, the finding that oleyl oleamide acts as a chemically active reagent above 250 °C may have implications for many nanoparticle syntheses. Oriented attachment of polyoxotungstate anions is proposed as a model to rationalize phase selectivity. Magic angle spinning (MAS) 1H-NMR and powder X-ray diffraction (PXRD) studies of the bronze after annealing under (non)inert conditions revealed an oxidative phase transition. WO3-x and (NH4)xWO3 show a strong plasmon absorption for near infra-red light between 800 and 3300 nm. The maxima of the plasmon bands shift systematically with the nanocrystal aspect ratio.

Selective oxidation of thioethers is an important reaction to obtain sulfoxides as synthetic intermediates for applications in the chemical industry, medicinal chemistry and biology or the destruction of warfare agents. The reduced Magneli-type tungsten oxide WO3−x possesses a unique oxidase-like activity which facilitates the oxidation of thioethers to the corresponding sulfoxides. More than 90% of the model system methylphenylsulfide could be converted to the sulfoxide with a selectivity of 98% at room temperature within 30 minutes, whereas oxidation to the corresponding sulfone was on a time scale of days. The concentration of the catalyst had a significant impact on the reaction rate. Reasonable catalytic effects were also observed for the selective oxidation of various organic sulfides with different substituents. The WO3−x nanocatalysts could be recycled at least 5 times without decrease in activity. We propose a metal oxide-catalyzed route based on the clean oxidant hydrogen peroxide. Compared to other molecular or enzyme catalysts the WO3−x system is a more robust redox-nanocatalyst, which is not susceptible to decomposition or denaturation under standard conditions. The unique oxidase-like activity of WO3−x can be used for a wide range of applications in synthetic, environmental or medicinal chemistry.

Calcium sulfate is an important construction material. More than 1600 million square meters of interior surfaces are covered with plasterboards in Europe each year. Plasterboard is manufactured by transforming mined or recycled gypsum (CaSO4 × 2 H2O) to bassanite (CaSO4 × ½H2O) in a time- and energy-consuming heating process. A fast and sustainable way to produce bassanite by solvent-assisted milling, thereby eliminating the need for energy-intensive dehydration, is described. The milling reaction is complete after ≈200 min. Kinetic studies revealed that gypsum crystals transform to bassanite by shear forces during milling. 1H nuclear magnetic resonance (NMR) spectroscopic techniques and Fourier-transform infrared spectroscopy (FT-IR) show that the resulting bassanite nanocrystals are stabilized by surface functionalization with the auxiliary solvent methanol. Bassanite particles produced over extended milling times of 990 min form long-term stable dispersions without stabilizers and no signs of precipitation. Addition of water to bassanite leads to instant agglomeration, followed by a phase change to gypsum. The dispersibility in volatile methanol and the elucidation of the crystallization mechanism allow also for applications of the bassanite nanocrystals in hybrid materials. © 2022 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH.

New monomethine, unsymmetrical styryl dyes consisting of benzothiazole and N-methylpiperazine or N-phenylpiperazine scaffolds were synthesized, and their binding affinities for different ds-polynucleotides and G-quadruplex were studied. Substitution of piperazine unit with methyl or phenyl group strongly influenced their binding modes, binding affinities, spectroscopic responses and antiproliferative activities. Compounds with N-methylpiperazine substituents showed a significant preference for AT-DNA polynucleotides and demonstrated AT-minor groove binding, which manifested in strong fluorescence increase, significant double helix stabilization, and positive induced circular dichroism spectra. These compounds formed complexes with G-quadruplex by π-π stacking interactions of dye with the top or bottom G-tetrad. Bulkier compounds with N-phenylpiperazine function are probably bound to ds-polynucleotide by partial intercalation between base pairs. On the other hand, they showed stronger stabilization of G-quadruplex compared to methyl-substituted compounds. Fluorimetric titrations pointed to possible mixed stoichiometry’s: 1:1 complex with π-π stacking interactions of dye on the top or bottom G- tetrad and 1:2 complex with dye positioned between two G-quadruplex molecules. Bulkier dyes with N-phenylpiperazine fragments demonstrated micromolar and submicromolar antiproliferative activity that was especially pronounced for leukaemia and lymphoma. Flow cytometric assay shows dose- and time-dependent increase in SubG0/G1 phase. Furthermore, the compounds enter the cells readily and accumulate in the mitochondrial space, co-localize with the standard mitochondrial markers.

Functional microgels provide a versatile basis for synthetic in vitro platforms as alternatives to animal experiments. The tuning of the physical, chemical, and biological properties of synthetic microgels can be achieved by blending suitable polymers and formulating them such to reflect the heterogenous and complex nature of biological tissues. Based on this premise, this paper introduces the development of volume-switchable core-shell microgels as 3D templates to enable cell growth for microtissue applications, using a systematic approach to tune the microgel properties based on a deep conceptual and practical understanding. Microscopic microgel design, such as the tailoring of the microgel size and spherical shape, is achieved by droplet-based microfluidics, while on a nanoscopic scale, a thermoresponsive polymer basis, poly(N-isopropylacrylamide) (PNIPAAm), is used to provide the microgel volume switchability. Since PNIPAAm has only limited cell-growth promoting properties, the cell adhesion on the microgel is further improved by surface modification with polydopamine, which only slightly affects the microgel properties, thereby simplifying the system. To further tune the microgel thermoresponsiveness, different amounts of N-hydroxyethylacrylamide are incorporated into the PNIPAAm network. In a final step, cell growth on the microgel surface is investigated, both at a single microgel platform and in spheroidal cell structures.

Modifying the surfaces of metal oxide nanoparticles (NPs) with monolayers of ligands provides a simple and direct method to generate multifunctional coatings by altering their surface properties. T...

Solid state reactions are slow because the diffusion of atoms or ions through the reactant, intermediate and crystalline product phases is the rate-limiting step. This requires days or even weeks of high temperature treatment, and consumption of large amounts of energy. We employed spark-plasma sintering, an engineering technique that is used for high-speed consolidation of powders with a pulsed electric current passing through the sample to carry out the fluorination of niobium oxide in minute intervals. The approach saves time and large amounts of waste energy. Moreover, it allows the preparation of fluorinated niobium oxides on a gram scale using poly(tetrafluoroethylene) (®Teflon) scrap and without toxic chemicals. The synthesis can be upscaled easily to the kg range with appropriate sintering equipment. Finally, NbO2F and Nb3O7F prepared by spark plasma sintering show significant photoelectrocatalytic (PEC) oxygen evolution from water in terms of photocurrent density and incident photon-to-current efficiency (% IPCE), whereas NbO2F and Nb3O7F prepared by conventional high temperature chemistry show little to no PEC response. Our study is a proof of concept for the quick, clean and energy saving production of valuable photocatalysts from plastic waste.

Localized surface plasmon resonance properties in unconventional materials like metal oxides or chalcogenide semiconductors have been studied for use in signal detection and analysis in biomedicine and photocatalysis. We devised a selective synthesis of the tungsten oxides WO

New analogs of the commercial asymmetric monomethine cyanine dyes thiazole orange (TO) and thiazole orange homodimer (TOTO) with hydroxypropyl functionality were synthesized and their properties in the presence of different nucleic acids were studied. The novel compounds showed strong, micromolar and submicromolar affinities to all examined DNA ds-polynucleotides and poly rA–poly rU. The compounds studied showed selectivity towards GC-DNA base pairs over AT-DNA, which included both binding affinity and a strong fluorescence response. CD titrations showed aggregation along the polynucleotide with well-defined supramolecular chirality. The single dipyridinium-bridged dimer showed intercalation at low dye-DNA/RNA ratios. All new cyanine dyes showed potent micromolar antiproliferative activity against cancer cell lines, making them promising theranostic agents.

Temperature-responsive polyurethane (PU) hydrogels represent a versatile material platform for modern tissue engineering and biomedical applications. However, besides intrinsic advantages such as high mechanical strength and a hydrolysable backbone composition, plain PU materials are generally lacking bio-adhesive properties. To overcome this shortcoming, the authors focus on the synthesis of thermoresponsive PU hydrogels with variable mechanical and cell adhesive properties obtained from linear precursor PUs based on poly(ethylene glycol)s (pEG) with different molar masses, isophorone diisocyanate, and a dimerizable dimethylmaleimide (DMMI)-diol. The cloud point temperatures of the dilute, aqueous PU solutions depend linearly on the amphiphilic balance. Rheological gelation experiments under UV-irradiation reveal the dependence of the gelation time on photosensitizer concentration and light intensity, while the finally obtained gel strength is determined by the polymer concentration and spacing of the crosslinks. The swelling ratios of these soft hydrogels show significant changes between 5 and 40 °C whereby the extent of this switch increases with the hydrophobicity of the precursor. Moreover, it is shown that the incorporation of a low amount of catechol groups into the networks through the DMMI dimerization reaction leads to strongly improved cell adhesive properties without significantly weakening the gels.

A general method to carry out the fluorination of metal oxides with poly(tetrafluoroethylene) (PTFE, Teflon) waste by spark plasma sintering (SPS) on a minute scale with Teflon is reported. The potential of this new approach is highlighted by the following results. i) The tantalum oxyfluorides Ta

Crystal growth & design 20(10), 6831 - 6846 (2020). doi:10.1021/acs.cgd.0c00912, Amorphous calcium carbonate (ACC) is an important precursor in the biomineralization of crystalline CaCO$_{3}$. In nature, it serves as a storage material or as a permanent structural element, whose lifetime is regulated by an organic matrix. The relevance of ACC in materials science is primarily related to our understanding of CaCO3 crystallization pathways and CaCO$_{3}$/(bio)polymer nanocomposites. ACC can be synthesized by liquid���liquid phase separation, and it is typically stabilized with macromolecules. We have prepared ACC by milling calcite in a planetary ball mill. Phosphate ���impurities��� were added in the form of monetite (CaHPO$_{4}$) to substitute the carbonate anions, thereby stabilizing ACC by substitutional disorder. The phosphate anions do not simply replace the carbonate anions. They undergo shear-driven acid/base and condensation reactions, where stoichiometric (10%) phosphate contents are required for the amorphization to be complete. The phosphate anions generate a strained network that hinders ACC recrystallization kinetically. The amorphization reaction and the structure of BM-ACC were studied by quantitative Fourier transform infrared spectroscopy and solid state $^{31}$P, $^{13}$C, and $^{1}$H magic angle spinning nuclear magnetic resonance spectroscopy, which are highly sensitive to symmetry changes of the local environment. In the first���and fast���reaction step, the CO$_{3}$$^{2���}$ anions are protonated by the HPO$_{4}$$^{2���}$ groups. The formation of unprecedented hydrogen carbonate (HC$_{3}$ $^{-}$ ) and orthophosphate anions appears to be the driving force of the reaction, because the phosphate group has a higher Coulomb energy and the tetrahedral PO43��� unit can fill space more efficiently. In a competing second���and slow���reaction step, pyrophosphate anions are formed in a condensation reaction. No pyrophosphates are formed at higher carbonate contents. High strain leads to such a large energy barrier that any reaction is suppressed. Our findings aid in the understanding of the mechanochemical amorphization of calcium carbonate and emphasize the effect of impurities for the stabilization of the amorphous phases in general. Our approach allowed the synthesis of new amorphous alkaline earth defect variants containing the unique HCO$_{3}$ $^{-}$ anion. Our approach outlines a general strategy to obtain new amorphous solids for a variety of carbonate/phosphate systems that offer promise as biomaterials for bone regeneration., Published by ACS Publ., Washington, DC

Rutile-type nanorods of SnO2 were obtained in a one-pot hydrothermal synthesis starting from SnCl4·5H2O and HCl in a temperature range between 200 and 240°C. Although the nanorods are polydisperse, the average length of the nanorods could be adjusted from 13 to 65 nm by varying of the reaction temperature. The resulting anisotropic nanocrystals were characterized using powder X-ray diffraction (PXRD), (high resolution-) transmission electron microscopy (HR-TEM), and selected area electron diffraction (SAED). The particle growth proceeds via a dissolution-recrystallization process with soluble [SnCl5(H2O)]− intermediates, as confirmed by PXRD, Raman spectroscopy, and magic angle spinning nuclear magnetic resonance (MAS-NMR).

Crystallization via metastable phases plays an important role in chemical manufacturing, biomineralization, and protein crystallization, but the kinetic pathways leading from metastable phases to the stable crystalline modifications are not well understood. In particular, the fast crystallization of amorphous intermediates makes a detailed characterization challenging. To circumvent this problem, we devised a system that allows trapping and stabilizing the amorphous intermediates of representative carbonates (calcium, strontium, barium, manganese, and cadmium). The long-term stabilization of these transient species enabled a detailed investigation of their composition, structure, and morphology. Total scattering experiments with high-energy synchrotron radiation revealed a short-range order of several angstroms in all amorphous intermediates. From the synchrotron data, a structural model of amorphous calcium carbonate was derived that indicates a lower coordination number of calcium compared to the crystalline polymorphs. Our study shows that a multistep crystallization pathway via amorphous intermediates is open to many carbonates. We could isolate and characterize these transient species, thereby providing new insights into their crystallization mechanism.

Amorphous intermediates play a crucial role during the crystallization of alkaline earth carbonates. We synthesized amorphous carbonates of magnesium, calcium, strontium, and barium from methanolic solution. The local environment of water and the strength of hydrogen bonding in these hydrated modifications were probed with Fourier transform IR spectroscopy

Amorphous calcium carbonate (ACC) is an important precursor in the biomineralization of crystalline CaCO3. The lifetime of transient ACC in nature is regulated by an organic matrix, to use it as an intermediate storage buffer or as a permanent structural element. The relevance of ACC in material science is related to our understanding of CaCO3 crystallization pathways. ACC can be obtained by liquid–liquid phase separation, and it is typically stabilized with the help of macromolecules. We have prepared ACC by milling calcite in a planetary ball mill. The ball-milled amorphous calcium carbonate (BM-ACC) was stabilized with small amounts of Na2CO3. The addition of foreign ions in form of Na2CO3 is crucial to achieve complete amorphization. Their incorporation generates defects that hinder recrystallization kinetically. In contrast to wet-chemically prepared ACC, the solvent-free approach makes BM-ACC an anhydrous modification. The amorphization process was monitored by quantitative Fourier transform infrare...

Surface functionalization of nanoparticles (NPs) plays a crucial role in particle solubility and reactivity. It is vital for particle nucleation and growth as well as for catalysis. This raises the quest for functionalization efficiency and new approaches to probe the degree of surface coverage. We present an (in situ) proton nuclear magnetic resonance (1H NMR) study on the ligand exchange of oleylamine by 1-octadecanethiol as a function of the particle size and repeated functionalization on Au NPs. Ligand exchange is an equilibrium reaction associated with Nernst distribution, which often leads to incomplete surface functionalization following “standard” literature protocols. Here, we show that the surface coverage with the ligand depends on the (i) repeated exchange reactions with large ligand excess, (ii) size of NPs, that is, the surface curvature and reactivity, and (iii) molecular size of the ligand. As resonance shifts and extensive line broadening during and after the ligand exchange impede the ev...

Superoxide dismutases (SOD) are a group of enzymes that catalyze the dismutation of superoxide (O2−) radicals into molecular oxygen (O2) and H2O2 as a first line of defense against oxidative stress. Here, we show that glycine-functionalized copper(II) hydroxide nanoparticles (Gly-Cu(OH)2 NPs) are functional SOD mimics, whereas bulk Cu(OH)2 is insoluble in water and catalytically inactive. In contrast, Gly-Cu(OH)2 NPs form water-dispersible mesocrystals with a SOD-like activity that is larger than that of their natural CuZn enzyme counterpart. Based on this finding, we devised an application where Gly-Cu(OH)2 NPs were incorporated into cigarette filters. Cigarette smoke contains high concentrations of toxic reactive oxygen species (ROS, >1016 molecules per puff) including superoxide and reactive nitrogen species which lead to the development of chronic and degenerative diseases via oxidative damage and subsequent cell death. Embedded in cigarette filters Gly-Cu(OH)2 NPs efficiently removed ROS from smoke, thereby protecting lung cancer cell lines from cytotoxic effects. Their stability, ease of production and versatility make them a powerful tool for a wide range of applications in environmental chemistry, biotechnology and medicine.

Modifying the surfaces of metal oxide nanoparticles (NPs) with monolayers of ligands provides a simple and direct method to generate multifunctional coatings by altering their surface properties. This works best if the composition of the monolayers can be controlled. Mussel-inspired, noninnocent catecholates stand out from other ligands like carboxylates and amines because they are redox-active and allow for highly efficient surface binding and enhanced electron transfer to the surface. However, a comprehensive understanding of their surface chemistry, including surface coverage and displacement of the native ligand, is still lacking. Here, we unravel the displacement of oleate (OA) ligands on hydrophobic, OA-stabilized TiO

A general method to carry out the fluorination of metal oxides with poly(tetrafluoroethylene) (PTFE, Teflon) waste by spark plasma sintering (SPS) on a minute scale with Teflon is reported. The potential of this new approach is highlighted by the following results. i) The tantalum oxyfluorides Ta3 O7 F and TaO2 F are obtained from plastic scrap without using toxic or caustic chemicals for fluorination. ii) Short reaction times (minutes rather than days) reduce the process time the energy costs by almost three orders of magnitude. iii) The oxyfluorides Ta3 O7 F and TaO2 F are produced in gram amounts of nanoparticles. Their synthesis can be upscaled to the kg range with industrial sintering equipment. iv) SPS processing changes the catalytic properties: while conventionally prepared Ta3 O7 F and TaO2 F show little catalytic activity, SPS-prepared Ta3 O7 F and TaO2 F exhibit high activity for photocatalytic oxygen evolution, reaching photoconversion efficiencies up to 24.7% and applied bias to photoconversion values of 0.86%. This study shows that the materials properties are dictated by the processing which poses new challenges to understand and predict the underlying factors.

Gemische aus Alkyllithium und Alkoxiden der schweren Alkalimetalle eignen sich zur Herstellung der entsprechenden Alkylverbindungen. Sie zeichnen sich ebenfalls durch ihre Reaktivitat bei Metallierungsreaktionen aus. Diese metallorganischen Mischungen werden oft als LiC-KOR-Superbasen bezeichnet, doch trotz vieler Bemuhungen ist nur wenig uber ihren Aufbau bekannt. Hier werden dimetallische Alkalimetall-Alkyl/Alkoxy-Verbindungen vorgestellt, die durch die Reaktion von Neopentyllithium und Kalium-tert-butoxid gebildet werden. Dank guter Loslichkeit in Alkanen und Temperaturbestandigkeit der Neopentylverbindungen konnten die Losungen in n-Hexan bei Umgebungstemperatur gehandhabt werden und ermoglichten die Isolierung durch Kristallisation. Die Verbindungen konnten durch Rontgendiffraktometrie und NMR-Spektroskopie sowohl in fester Form als auch in Losung als Li/K-Neopentyl/tert-Butoxy-Aggregate mit veranderlicher Zusammensetzung LixKyNpz(OtBu)x+y−z identifiziert werden.

The batch-to-melt conversion in batches of sand, soda ash and corundum (C), alumina spinel (A), boehmite (B), or gibbsite (G) as Al2O3 carrier are studied using thermal analysis, X-ray diffraction, and 27Al nuclear magnetic resonance spectroscopy. Laboratory-scaled batches are either heated continuously or quenched from 1600°C in a series of increasing dwell times. The results show that the conversion from the raw materials to the fresh melt proceeds in two kinetic stages. During the first stage (3–5 min), fast conversion of nearly 95% by mass occurs and the conversion coefficient increases in the order G < C ≈ A < B. The second stage is controlled by the slow dissolution of intermediate crystal phases, such as cristobalite, carnegieite, sodium metasilicate, and diaoyudaoite, which leads to an increase in the total batch-to-melt turnover time of up to 10 min. No direct correlation between the kinetic parameters characterizing the first stage and the fraction and dissolution speed of intermediate crystals of the second stage could be established.

Soluble inorganic aluminium compounds like aluminium sulfate or aluminium chloride have been challenged by the European Chemical Agency to induce germ cell mutagenicity. Before conducting mutagenicity tests, the hydrolysis products in water and in physiological solutions should be determined as a function of the concentration and pH. We used different 27Al NMR spectroscopic techniques (heteronuclear Overhauser effect spectroscopy (HOESY), exchange spectroscopy (EXSY), diffusion ordered (DOSY)) in this work to gain the information to study the aluminium species in solutions with Al2(SO4)3 concentrations of 50.0, 5.0, and 0.5 g/L and their pH and time dependent transformation. At low pH, three different species were present in all physiological solutions and water: [Al(OH)n(H2O)6 − n](3 − n)+ (n = 0–2), [Al(H2O)5SO4]+, and [Al2(OH)2(H2O)8]4+. Increasing pH reduced the amounts of the two monomer species, with a complete loss at pH 5 for solutions with a concentration of 50.0 g/L and at pH 4 for solutions with a concentration of 5.0 g/L. The dimer species [Al2(OH)2(H2O)8]4+ is present in a pH range between 3 and 6. Less symmetric oligomeric and probably asymmetric aluminium species are formed at pH of 5 and 6. The pH value is the driving force for the formation of aluminium species in all media, whereas the specific medium had only minor effect. No conclusive information could be obtained at pH 7 due to signal loss related to fast quadrupole relaxation of asymmetric aluminium species. A slight reduction of the content of the symmetric aluminium species due to the formation of oligomeric species was observed over a period of 6 weeks. Reference 27Al NMR experiments conducted on saturated water solutions of AlCl3 and those with a concentration of 50 g/L show that the type of salt/counter ion at the same concentration and pH influences the hydrolysis products formed.

The mechanisms by which amorphous intermediates transform into crystalline materials are not well understood. To test the viability and the limits of the classical crystallization, new model systems for crystallization are needed. With a view to elucidating the formation of an amorphous precursor and its subsequent crystallization, the crystallization of calcium oxalate, a biomineral widely occurring in plants, is investigated. Amorphous calcium oxalate (ACO) precipitated from an aqueous solution is described as a hydrated metastable phase, as often observed during low-temperature inorganic synthesis and biomineralization. In the presence of water, ACO rapidly transforms into hydrated whewellite (monohydrate, CaC2 O4 ⋅H2 O, COM). The problem of fast crystallization kinetics is circumvented by synthesizing anhydrous ACO from a pure ionic liquid (IL-ACO) for the first time. IL-ACO is stable in the absence of water at ambient temperature. It is obtained as well-defined, non-agglomerated particles with diameters of 15-20 nm. When exposed to water, it crystallizes to give (hydrated) COM through a dissolution/recrystallization mechanism.

The polymerization of alkoxy-substituted [2.2]paracyclophane-1,9-dienes via ring-opening metathesis polymerization (ROMP) to obtain soluble poly(p-phenylenevinylene)s is a versatile method due to its living nature which enables the possibility of block copolymerization and end group modification. However, detailed studies on the reactivity behavior and the polymerization process of alkoxy-substituted [2.2]paracyclophane-1,9-dienes have not been reported so far. Herein we present a detailed study on the varying tendencies of the four isomers of dimethoxy-(2-ethylhexyloxy)-[2.2]paracyclophane-1,9-diene to undergo ROMP. Therefore, we carried out polymerization combining all individual isomers with five different metathesis catalysts and collected initiation and propagation kinetics for various combinations. Furthermore, we revealed a specific coordination of the monomer repeating unit to the catalyst during the polymerization process and succeeded to polymerize not only the pseudogeminal isomers but also one...

Calcareous biominerals typically feature a hybrid nanogranular structure consisting of calcium carbonate nanograins coated with organic matrices. This nanogranular organisation has a beneficial effect on the functionality of these bioceramics. In this feasibility study, we successfully employed a flow-chemistry approach to precipitate Mg-doped amorphous calcium carbonate particles functionalized by negatively charged polyelectrolytes&mdash, either polyacrylates (PAA) or polystyrene sulfonate (PSS). We demonstrate that the rate of Mg incorporation and, thus, the ratio of the Mg dopant to calcium in the precipitated amorphous calcium carbonate (ACC), is flow rate dependent. In the case of the PAA-functionalized Mg-doped ACC, we further observed a weak flow rate dependence concerning the hydration state of the precipitate, which we attribute to incorporated PAA acting as a water sorbent, a behaviour which is not present in experiments with PSS and without a polymer. Thus, polymer-dependent phenomena can affect flow-chemistry approaches, that is, in syntheses of functionally graded materials by layer-deposition processes.

Mixtures of alkyllithium and heavier alkali-metal alkoxides are often used to form alkyl compounds of heavier alkali metals, but these mixtures are also known for their high reactivity in deprotonative metalation reactions. These organometallic mixtures are often called LiC-KOR superbases, but despite many efforts their constitution remains unknown. Herein we present mixed alkali-metal alkyl/alkoxy compounds produced by reaction of neopentyllithium with potassium tert-butoxide. The key to success was the good solubility and temperature-stability of neopentyl alkali-metal compounds, leading to hexane-soluble mixtures, which allowed handling at ambient temperatures and isolation by crystallization. The compounds in solid state and in solution were identified by X-ray crystallography and NMR spectroscopy as mixtures of lithium/potassium neopentyl/tert-butoxy aggregates of varying compositions Lix Ky Npz (OtBu)x+y-z .

A distinct nanogranular fine structure is shared by a wealth of biominerals from several species, classes and taxa. This nanoscopic organization affects the properties and behavior of the biogenic ceramic material and confers on them attributes that are essential to their function. We present a set of structure-relationship properties that are rooted in the nanogranular organization and we propose that they rest on a common pathway of formation, a colloid-driven and hence nonclassical mode of crystallization. With this common modus operandi, we reveal the most fundamental and wide spread process-structure-property relationship in biominerals. With the recent increase in our understanding of nonclassical crystallization in vitro and in vivo, this significant process-structure-property relationship will serve as a source for new design approaches of bio-inspired materials.

Block copolypeptides with their inherent nanometer length scale of phase separation, provide means of manipulating the type (α-helices, β-strands) and persistence of peptide secondary structures. Two such examples are employed based on the α-helical poly( γ -benzyl- l -glutamate) (PBLG) polypeptide as one block and poly( l -leucine) (α-helical) or poly( O -benzyl- l -tyrosine) (POBT) (β-strands) as the second block. Although both secondary structures are present in the copolypeptides the effect of nano-scale confinement is to induce folding in the POBT β-sheets and to maintain the defected α-helices of PBLG and PLEU with a limited lateral coherence.

The hierarchical self-assembly at the submicrometer, nanometer and α-helical length scales has been studied in a miktoarm star rod−coil chimera composed of poly(γ-benzyl-l-glutamate) (PBLG), polystyrene, and polyisoprene blocks by X-ray scattering, solid state NMR, and transmission electron microscopy. The propensity of the rod block toward α-helices that are further hexagonally packed gives rise to pure PBLG domains and induces the partial mixing of the two amorphous blocks. These structural results were confirmed by independent dynamic probes at the segmental and α-helical level by NMR and dielectric spectroscopy, respectively.

Macromolecules is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Communication to the Editor Poly(#-benzyl-l-glutamate) Peptides Confined to Nanoporous Alumina: Pore Diameter Dependence of Self-Assembly and Segmental Dynamics Hatice Duran, Antonis Gitsas, George Floudas, Mihail Mondeshki, Martin Steinhart, and Wolfgang Knoll Macromolecules, 2009, 42 (8), 2881-2885• DOI: 10.1021/ma900119x • Publication Date (Web): 24 March 2009 Downloaded from http://pubs.acs.org on April 22, 2009

International audience; The thermotropic, structural, and morphological properties of blends of a disk-like liquid crystalline phthalocyanine derivative and a lath-shaped perylenetetracarboxidiimide mesogen derivative have been studied by combining differential scanning calorimetry, thermal polarized optical microscopy, X-ray diffraction, solidstate nuclear magnetic resonance, and atomic force microscopy. The two compounds are fully miscible for blends containing at least 60 mol % of the disk-like molecule. In such composition range, the homogeneous blends form a columnar hexagonal (Colh) mesophase for which the thermal stability is enhanced compared to that of the corresponding mesophase of the pure phthalocyanine. The miscible blends self-align homeotropically between two glass slides. For blends containing between 55 and 40 mol % of the diskshaped molecule, the two components are fully miscible at high temperature but the perylene derivative forms a separate crystalline phase when the temperature is decreased. Phase separation is systematically observed in blends containing less than 40 mol % of the discotic molecule. In this case, the resulting Colh mesophase is less stabilized compared to the blends containing a larger amount of the phthalocyanine derivative. These phase-separated blends do not show any homeotropic alignment. AFM investigations confirm the formation of a single columnar morphology in the phthalocyanine-rich blends, consistent with the full miscibility between the two compounds. Solid-state NMR measurements on the mixed phase show the influence of the presence of the perylene molecules on the molecular dynamics of the molecules; remarkably, the presence of the host molecules improves the local order parameter in the phthalocyanine columnar phase.

The stability, persistence and dynamics of the peptide secondary motifs are investigated in a series of poly(γ-benzyl-l-glutamate)-b-polyalanine (PBLG-b-PAla) polypeptides through a combination of structural (X-rays, NMR) and dynamic (Dielectric Spectroscopy, NMR) probes. The unfavorable enthalpic interactions between the unlike blocks give rise to nanophase separation that results in the destabilization of PAla β-sheets. Contrary to this, the overall helicity of PBLG α-helices is enhanced. The dynamics of the “defected” amorphous segments and of the more ordered segments are studied by DS and 13C NMR, respectively. These probes provide information on the time scale and the mechanism of molecular and supramolecular motion.

The effect of chain topology on (i) the peptide secondary structure, (ii) the nanophase self-assembly, and (iii) the local segmental and global peptide relaxations has been studied in a series of model diblock and 3-arm star copolypeptides of poly(epsilon-carbobenzyloxy-L-lysine) (PZLL) and poly(gamma-benzyl-C-glutamate) (PBLG) with PZLL forming the core. Diblock copolypeptides are nanophase separated with PBLG and PZLL domains comprising a-helices packed in a hexagonal lattice. Star copolypeptides are only weakly phase separated, comprising PBLG and PZLL a-helices in a pseudohexagonal lattice. Phase mixing has profound consequences on the local and global dynamics. The relaxation of the peptide secondary structure speeds up, and the helix persistence length is further reduced in the stars, signifying an increased concentration of helical defects. Biomacromolecules

The self-assembly, the molecular dynamics, and the kinetics of structure formation are studied in dipole-functionalized hexabenzocoronene (HBC) derivatives. Dipole substitution destabilizes the columnar crystalline phase except for the dimethoxy- and monoethynyl-substituted HBCs that undergo a reversible transformation to the crystalline phase. The disk dynamics are studied by dielectric spectroscopy and site-specific NMR techniques that provide both the time-scale and geometry of motion. Application of pressure results in the thermodynamic phase diagram that shows increasing stability of the crystalline phase at elevated pressures. Long-lived metastability was found during the transformation between the two phases. These results suggest new thermodynamic and kinetic pathways that favor the phase with the highest charge carrier mobility.

We report on the self-assembly and molecular dynamics in a series of poly(γ-methyl-l-glutamate-co-γ-stearyl-l-glutamate) [poly(MLG-co-SLG)] using thermodynamic (differential scanning calorimetry), structural (wide-angle X-ray scattering and 13C solid-state NMR), as well as dynamic (dielectric spectroscopy and site-specific solid-state NMR) techniques. Stearyl crystallization takes place in the copolymers with wPSLG ≥ 18% which reflects changes of the hydrocarbon side chains conformation. Extruded fibers of the copolymers are composed of both α-helical and β-sheet secondary structures oriented along the fiber axis with a bottleneck structure with MLG/SLG sequences forming the neck and more distant SLG sequences forming the bottle. This supramolecular organization has direct consequences on the dynamics. Two dielectrically active processes with strong temperature dependences were found. Site-specific NMR allowed the identification of the geometry of motions. One is associated with small-amplitude motions of...

Amorphous calcium carbonate films synthesized by the polymer-induced liquid-precursor (PILP) process convert into crystallographically complex calcite spherulites. Tuning the experimental parameters allows for the generation of crystal lattice tilting similar to that found in calcareous biominerals. This contribution evidences the role of spherulitic growth mechanisms in pseudomorphic transformations of calcium carbonate.

We revisit the ultrastructural features of different calcareous biominerals and identify remarkable similarities: taxonomically very distant species show a common nanogranular structure, even if different extracellular secretion patterns are employed or calcium carbonate polymorphs formed. By these analyses, we elucidate the locus of the small fraction of intracrystalline organic matrix revealing its intergranular character and localize the intracrystalline amorphous calcium carbonate moiety commonly found in mesocrystalline biominerals and provide a first explanation for the pathway by which it is preserved.