Reactive Additive Capillary Stamping with Double Network Hydrogel-Derived Aerogel Stamps under Solvothermal Conditions.

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.

Guanosine Nucleolipids: Synthesis, Characterization, Aggregation and X-Ray Crystallographic Identification of Electricity-Conducting G-Ribbons.

The lipophilization of ß-d-riboguanosine (1) with various symmetric as well as asymmetric ketones is described (→3a-3f). The formation of the corresponding O-2',3'-ketals is accompanied by the appearance of various fluorescent by-products which were isolated chromatographically as mixtures and tentatively analyzed by ESI-MS spectrometry. The mainly formed guanosine nucleolipids were isolated and characterized by elemental analyses, 1 H-, 13 C-NMR and UV spectroscopy. For a drug profiling, static topological polar surface areas as well as 10 logPOW values were calculated by an increment-based method as well as experimentally for the systems 1-octanol-H2 O and cyclohexane-H2 O. The guanosine-O-2',3'-ketal derivatives 3b and 3a could be crystallized in (D6 )DMSO - the latter after one year of standing at ambient temperature. X-ray analysis revealed the formation of self-assembled ribbons consisting of two structurally similar 3b nucleolipid conformers as well as integrated (D6 )DMSO molecules. In the case of 3a ⋅ DMSO, the ribbon is formed by a single type of guanosine nucleolipid molecules. The crystalline material 3b ⋅ DMSO was further analyzed by differential scanning calorimetry (DSC) and temperature-dependent polarization microscopy. Crystallization was also performed on interdigitated electrodes (Au, distance, 5 µm) and visualized by scanning electron microscopy. Resistance and amperage measurements clearly demonstrate that the electrode-bridging 3b crystals are electrically conducting. All O-2',3'-guanosine ketals were tested on their cytostatic/cytotoxic activity towards phorbol 12-myristate 13-acetate (PMA)-differentiated human THP-1 macrophages as well as against human astrocytoma/oligodendroglioma GOS-3 cells and against rat malignant neuroectodermal BT4Ca cells.

Synthesis, Characterization, and Antimicrobial Properties of Peptides Mimicking Copolymers of Maleic Anhydride and 4-Methyl-1-pentene.

Synthetic amphiphilic copolymers with strong antimicrobial properties mimicking natural antimicrobial peptides were obtained via synthesis of an alternating copolymer of maleic anhydride and 4-methyl-1-pentene. The obtained copolymer was modified by grafting with 3-(dimethylamino)-1-propylamine (DMAPA) and imidized in a one-pot synthesis. The obtained copolymer was modified further to yield polycationic copolymers by means of quaternization with methyl iodide and dodecyl iodide, as well as by being sequentially quaternized with both of them. The antimicrobial properties of obtained copolymers were tested against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus epidermidis, and Staphylococcus aureus. Both tested quaternized copolymers were more active against the Gram-negative E. coli than against the Gram-positive S. aureus. The copolymer modified with both iodides was best when tested against E. coli and, comparing all three copolymers, also exhibited the best effect against S. aureus. Moreover, it shows (limited) selectivity to differentiate between mammalian cells and bacterial cell walls. Comparing the minimum inhibitory concentration (MIC) of Nisin against the Gram-positive bacteria on the molar basis instead on the weight basis, the difference between the effect of Nisin and the copolymer is significantly lower.

Synthesis of Terpolymers with Homogeneous Composition by Free Radical Copolymerization of Maleic Anhydride, Perfluorooctyl and Butyl or Dodecyl Methacrylates: Application of the Continuous Flow Monomer Addition Technique.

Terpolymers of homogeneous composition were prepared by free radical copolymerization of butyl or dodecyl methacrylate, 1H,1H,2H,2H-perfluorodecyl methacrylate and maleic anhydride using the continuous monomer addition technique. The copolymerization reactions were performed at 65 °C in the presence of azobisisobutyronitrile as an initiator in a mixture of methyl ethyl ketone and 1,3-bis (trifluoromethyl)benzene. The monomers and initiator are added to the reaction mixture with the same rate they are consumed in 5- and 10-fold excess compared to the initial monomer stock. The obtained terpolymers with molecular weights Mn = 50,000⁻70,000 are of uniform composition, close to the composition determined in low conversion experiments, proving the principle of the chosen concept. The kinetic data necessary for the design of the continuous addition experiment were obtained from binary copolymerization experiments at low monomer conversion (to avoid compositional drift). In addition, the so-called terpolymerization parameter was determined from ternary copolymerization experiments.

Solubility, Emulsification and Surface Properties of Maleic Anhydride, Perfluorooctyl and Alkyl Meth-Acrylate Terpolymers.

The solubility of terpolymers containing alkyl, and perfluoroalkyl side chains as well as succinic acid moieties in the main chain, P[RFMA0.2-co-RHMA0.65-co-MAH0.15] (RH = C4H9- or C12H25-, RF- = C10H4F19-) with ca. 20 mol % fluorinated side chains and 10⁻22 mol % of succinic anhydride rings was tested in a number of solvents varying from water to non polar mineral oils. The polymers are well soluble in fluorinated solvents like Freon-113® and 1,3-bis(trifluoromethyl) benzene, in semi-polar solvents like chloroform, THF or lower esters and also in hydrocarbons with polymers containing dodecyl methacrylate. In self-emulsification experiments, a stable water emulsion of P[F8H2MA0.2-co-BMA0.65-co-MAH0.15] was obtained. The dispersability and emulsification of these polymers in mixtures of organic solvents and water yielded stable emulsions in the presence of additional surfactant. Thin films coated from organic solutions as well as from emulsions on glass resulted in water and oil-repelling surfaces with contact angles up to 140° against water and 71° against hexadecane. An enhancing effect of annealing was not observed.

The effect of the shape of the mesogenic group on the structure and phase behavior of 2,3,4-tris(dodecyloxy)benzenesulfonates with alkaline cations.

Synthesis and mesophase structure characterisation are reported for a group of alkali salts of 2,3,4-tris(dodecyloxy)benzenesulfonic acid. As revealed by a combination of polarizing optical microscopy, differential scanning calorimetry and X-ray scattering, variation of the effective mesogen shape due to changes of the cation size leads to systematic transformation of the materials' phase behaviour. Thermotropic mesophases of different types and dimensionalities were observed: 1D (smectic bilayers), 2D (ordered and disordered columnar phases), and 3D (high-temperature micellar mesomorphic phase, low-temperature crystalline one). Cubic packing prevails when the cation size is small and, thus, the effective mesogen shape is close to the conic one. With increasing ion size, the mesogen shape becomes more tapered, and columnar mesophases appear to be more stable.

3-Methyl-ideneoxolane-2,5-dione.

The title compound (itaconic anhydride), C5H4O3, consists of a five-membered carbon-oxygen ring in a flat envelope conformation (the unsubstituted C atom being the flap) with three exocyclic double bonds to two O atoms and one C atom. In contrast to the bond lengths, which are very similar to those in itaconic acid in its pure form or in adducts with other mol-ecules, the bond angles differ significantly because of the effect of ring closure giving rise to strong distortions at the C atoms involved in the exocyclic double bonds. In the crystal, C-H⋯O inter-actions link the mol-ecules, forming an extended three-dimensional network.

Dimer/tetramer motifs determine amphiphilic hydrazine fibril structures on graphite.

Fibril structures are produced at a solvent-graphite interface by self-assembly of custom-designed symmetric and asymmetric amphiphilic benzamide derivatives bearing C(10) aliphatic chains. Scanning tunnelling microscopy (STM) studies reveal geometry-dependent internal structures for the elementary fibrils of the two molecules that are distinctly different from known mesophase bulk structures. The structures are described by building-block models based on hydrogen-bonded dimer and tetramer precursors of hydrazines. The closure and growth in length of building units into fibrils takes place through van der Waals forces acting between the dangling alkyl chains. The nanoscale morphology is a consequence of the basic molecular geometry, where it follows that a closure to form a fibril is not always likely for the doubly substituted hydrazine. Therefore, we also observe crystallite formation.

Surface modification of luminescent lanthanide phosphate nanorods with cationic "Quat-primer" polymers.

"Quat-primer" polymers bearing cationic groups were investigated as a surface modifier for Tb-doped cerium phosphate green-emitting fluorescent nanorods (NRs). The NRs were synthesized by a microwave process without using any complex agents or ligands and were characterized with different analytical tools such as X-ray diffraction, transmission electron microscopy, and fluorescence spectroscopy. Poly(ethyleneimine) partially quarternized with glycidyltrimethylammonium chloride was synthesized separately and characterized in detail. (1)H and (13)C NMR spectroscopic studies revealed that the quaternary ammonium group was covalently attached to the polymer. UV-vis spectroscopy was used to examine the stability of the colloidal dispersions of the bare NRs as well as the modified NRs. ζ potential, thermogravimetric analysis, and atomic force microscopy studies were carried out to confirm that the positively charged Quat-primer polymer is adsorbed on the negatively charged surface of the NRs, which results in high dispersion stability. Emission spectra of the modified NRs indicated that there was no interference of the Quat-primer polymer with the fluorescence behavior.

Self-assembled structures formed by a wedge-shaped molecule in 2D and 3D: the role of flexible side chains and polar head groups.

A wedge-shaped amphiphilic molecule, 3,4,5-tridodecyloxycinnamic acid, was used as a model system to explore the role of different constitutive elements of the chemical structure in the formation of 2D and 3D self-assemblies. The polar heads forming cyclic hydrogen-bonded dimers determine the two largest unit cell parameters, which depend only slightly on the dimensionality of the system (i.e. 2D versus 3D) and on the sample thermal history. By contrast, the structure of the alkyl side chains is very sensitive to the phase transformations, and is likely to be responsible for the rich polymorphic behaviour of the studied compound. Thus, in the monotropic SmC phase, the alkyl chains form a liquid-crystalline sub-lattice with hexagonal symmetry that can further crystallize either in a triclinic sub-cell (metastable crystalline phase) or in an orthorhombic sub-cell (stable crystalline phase). In 2D, at the interface with the graphite surface the molecular orientation is guided by the epitaxy. Although the largest lattice parameters are close to those in the bulk, the alkyl chains adopt a particular alternating orientation. In one molecule of the dimer, two alkyl chains have their molecular planes parallel to the substrate while the third chain is perpendicular to it, and the other way around for the other molecule of the dimer. To our knowledge, such alternating orientation of the alkyl chains in the monolayer is reported for the first time.

Self-organization of polybases neutralized with mesogenic wedge-shaped sulfonic acid molecules: an approach toward supramolecular cylinders.

Complexes consisting of poly(4-vinylpyridine) and mesogenic wedge-shaped ligands 4'-[3",4",5"-tris(dodecyloxy)benzoyloxy]azobenzene-4-sulfonic acid and 4'-[3",4",5"-tris(octyloxy)benzoyloxy]azobenzene-4-sulfonic acid have been prepared with different monomer/ligand ratios. Upon protonation of the poly(4-vinylpyridine) chains by the wedge-shaped sulfonic acid molecules a hypsochromic and hyperchromic effect was observed with the pi-pi* transition of the azo-chromophor, allowing us to monitor the neutralization process by means of UV-vis spectroscopy in solution. The changes of the absorption characteristics implied a conformational change of the polymer backbone. In the bulk the interaction between pyridine and sulfonic acid moieties was proved by FT-IR spectroscopy. Polarizing optical microscopy, differential scanning calorimetry, and X-ray diffraction measurements were used to study the bulk structure of the complexes. The complexes formed a liquid crystalline lamellar phase at low degrees of substitution, while a hexagonal columnar mesophase was observed at degrees of neutralization of 80% and higher.

Creation of a mixed-valence state from one-dimensionally aligned TTF utilizing the self-assembling nature of a low molecular-weight gel.

One-dimensional TTF assemblies have been obtained through the design of low molecular-weight gels, which show a characteristic absorption band at around 1750 nm upon I2 doping, assignable to a mixed-valence state of the TTF assemblies.

Field-gradient NMR diffusometry in poly(ethylene oxide) melts confined to nanoscopic pores of solid methacrylate matrices.

Depending on the choice of matrix constituents, the diameters of strands of linear, monodisperse poly(ethylene oxide) confined to nanoscopic pores of cross-linked methacrylate matrices can be varied considerably. The samples were characterized by DSC, TEM, SEM and fringe field-gradient NMR diffusometry with respect to the strand diameter. A formalism evaluating diffusive spin echo attenuation curves based on the tube/reptation model allows the determination of the strand diameter. Values in the range 8-58 nm were found in accordance with TEM and SEM micrographs of shadow-cast freeze-fractured surfaces of the samples.

Wedge-shaped molecules with a sulfonate group at the tip--a new class of self-assembling amphiphiles.

The synthesis of 4-N-[3',4',5'-tris(dodecyloxy)benzamido]benzene-4-sulfonic acid (1) and 4'-[3",4",5"-tris(dodecyloxy)benzoyloxy]azobenzene-4-sulfonic acid (2) is described. Pure acid 1 is stable, while 2 can be stored only in solution. Both acids were obtained from their sodium salts and were quantitatively transformed into the pyridinium salts. The phase behavior of these acids, as well as the sulfonates was investigated by differential scanning calorimetry and polarizing optical microscopy. The investigated compounds exhibit columnar mesophases. The formation of columnar superstructures was demonstrated for the sodium sulfonates by scanning force microscopy, gelation experiments, and proton magnetic resonance spectroscopy.

Supramolecular polymerization and gel formation of bis(merocyanine) dyes driven by dipolar aggregation.

Two highly dipolar merocyanine dyes were tethered by a rigid tris(n-dodecyloxy)xylylene unit that preorganizes the dyes for a supramolecular polymerization process through intermolecular aggregation of the dyes. UV/vis spectroscopy revealed a solvent dependent equilibrium between monomeric dyes and two different types of dye aggregates that are characterized by hypsochromically shifted D- and H-type absorption bands. Taking into account the ditopic nature of the supramolecular building blocks, the occurrence of the D-band indicates the formation of an oligomeric/polymeric supramolecular chain whereas the observation of the H-band suggests a higher order assembly. For the H-aggregated dyes, intrinsic viscosities exceed 0.65 L g(-1) in methylcyclohexane, values typically found for macromolecular solutions. At higher concentration, further association of these aggregates takes place by entanglement of the alkyl groups leading to a substantial increase in viscosity and gelation. Rheology studies show linear viscoelastic behavior which was attributed to the formation of an entangled dynamic network. AFM and cryo-TEM studies of the gel reveal long and stiff rod-type assemblies. X-ray diffraction studies for a solid film show columnar mesomorphism. Based on these results, a structural model is proposed in which six helically preorganized strands of the supramolecular polymer intertwine to form a rod with a diameter of about 5 nm. Within these rods all dyes are tightly aggregated in a tubular fashion giving rise to delocalized excitonic states, and the pi-conjugated tube is jacketed by the tridodecyloxy groups.

Polymer dynamics under nanoscopic constraints: the "corset effect" as revealed by NMR relaxometry and diffusometry.

A spinodal demixing technique was employed for the preparation of linear poly(ethylene oxide) (PEO) confined in nanoscopic strands, which in turn are embedded in a quasi-solid methacrylate matrix impenetrable to PEO. Both the molecular weight of the PEO and the mean diameter of the strands are variable to a certain degree. Chain dynamics of the PEO in the molten state were examined with the aid of field-gradient NMR diffusometry and field-cycling NMR relaxometry. The dominating mechanism for translational displacements in the nanoscopic strands is shown to be reptation. A formalism for the evaluation of NMR diffusometry is presented, which permits the estimation of the mean PEO strand diameter. Samples of different composition revealed diameters in the range 9-58 nm, in reasonable agreement with electron micrographs. The time scale of the diffusion measurements was 10-300 ms. On the much shorter time scale of field-cycling NMR relaxometry, 10(-9)-10(-4)s, a frequency dispersion of the spin-lattice relaxation time characteristic for reptation clearly showed up in all samples. An effective tube diameter of only 0.6 nm was found even when the strand diameter was larger than the radius of gyration of the PEO chain random coils. The finding that the tube diameter effective on the short time scale of field-cycling NMR relaxometry is much smaller than the diameter of the confining structure is termed the "corset effect", and is traced back to the lack of local free-volume fluctuation capacity under nanoscale confinements. The order of magnitude of the 'pore' diameter, at which the cross-over from confined to bulk chain dynamics is expected, is estimated.

Surface orientation of 3,4,5-tris-substituted benzoic acid amphiphiles.

Regarding the molecular orientation on flat substrates, thin films have been studied of a series of wedge-shaped molecules (3,4,5-tris-substituted benzoate-benzo crown ether compounds) consisting of a hydrophobic outer rim and a polar group at the thin end which form columnar mesomorphic and crystalline structures. For most substrates studied here, autophobic dewetting is demonstrated to be caused by the formation of a monomolecular adlayer in which the molecules are oriented normal to the substrate surface with the hydrophobic tails directed away from the substrate. For thick films, this adlayer is shown to cause an "in-plane" orientation of the axis of the columnar state. An ordered in-plane oriented adlayer is observed only for highly ordered pyrolytic graphite as the substrate. In this case, specific interactions with the substrate cause formation of a well-ordered 2D pattern that might favor homeotropic orientation of the columnar structures but has to be optimized by further structural variation. The structure of the adsorbed monolayer is elucidated by combining contact angle measurements, plasmon resonance spectroscopy, and optical and scanning tunneling microscopy.