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  • 1
    Language: English
    In: Angewandte Chemie International Edition, 29 October 2012, Vol.51(44), pp.10933-10933
    Description: Wiley‐VCH, Weinheim, 2011. 372 pp., hardcover, € 139.00.—ISBN 978‐3527323210
    Keywords: Monograph Supramolecular Chemistry
    ISSN: 1433-7851
    ISSN: Angewandte Chemie International Edition
    E-ISSN: 1521-3773
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  • 2
    In: Epilepsia, October 2011, Vol.52(10), pp.1857-1867
    Description: Regional variations and temporal trends in the incidence of new‐onset epilepsy are clinically important and may offer clues on how to prevent epilepsy. We examined regional differences and secular trends in the incidence of new‐onset epilepsy in the Finnish population based on the nationwide full‐refundable antiepileptic drug registry and the population registry in the years 1986–2008. The overall incidence of epilepsy was significantly higher in eastern Finland than in middle [risk ratio (RR) 1.08 (95% confidence interval, CI 1.05–1.12)), p 〈 0.0001] and western Finland [RR 1.32 (1.30–1.35), p 〈 0.0001] but it was declining from 1986 to 2008 in all regions [RR 0.83 (0.81–0.84), p 〈 0.0001]. The mean annual decline was 0.6%. Although the incidence of epilepsy was falling from 1986 to 2008 in childhood [annual decline 1.9%, RR 0.80 (0.75–0.86), p 〈 0.0001] and in middle age [annual decline 0.8%, RR 0.88 (0.84–0.93), p 〈 0.0001], it increased significantly in the elderly (age 65 years or older) in all of Finland [annual increase 3.5%, RR 1.25 (1.18–1.33), p 〈 0.0001], and particularly in east versus west Finland [RR 1.48 (1.42–1.55), p 〈 0.0001]. As a result, starting with the year 2000, the incidence rate of epilepsy was higher in the elderly than in children for all of Finland. In view of the falling incidence of epilepsy in childhood and middle‐age in all of Finland from 1986 to 2008, the significant increase in the incidence of epilepsy in the elderly is of concern. The regional increase of epilepsy may offer clues for allocating resources and, possibly, population epileptogenesis between west and east Finland and for strategies to prevent epilepsy in the elderly.
    Keywords: Epilepsy ; Incidence Of Epilepsy ; Regional Changes ; Secular Trends ; Epidemiology ; Antiepileptic Drug
    ISSN: 0013-9580
    E-ISSN: 1528-1167
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  • 3
    Language: English
    In: Journal of the American Chemical Society, 07 November 2012, Vol.134(44), pp.18157-60
    Description: A route to fully miscible polyethylene (PE) nanocomposites has been established based on polymer-brush-coated nanoparticles. These nanoparticles can be mixed with PE at any ratio, with homogeneous dispersion, and without aggregation. This allowed a first systematic study of the thermomechanical properties of PE nanocomposites without interference from aggregation effects. We observe that the storage modulus in the semicrystalline state and the softening temperature increase significantly with increasing nanoparticle content, whereas the melt viscosity is unaltered by the presence of nanoparticles. We show that the complete miscibility with the semicrystalline polymer matrix and the improvement of thermomechanical properties in the solid state is caused by the PE-coated nanoparticles being nucleating agents for the crystallization of PE. This provides a general route to fully miscibility nanocomposites with semicrystalline polymers.
    Keywords: Crystalline Polymers -- Structure ; Crystalline Polymers -- Mechanical Properties ; Crystalline Polymers -- Thermal Properties ; Crystallization -- Analysis ; Polyethylene -- Structure ; Polyethylene -- Mechanical Properties ; Polyethylene -- Thermal Properties ; Viscosity -- Analysis;
    ISSN: 00027863
    E-ISSN: 1520-5126
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  • 4
    In: Chemical Communications, 2012, Vol.49(3), pp.267-269
    Description: Using 13 C double quantum solid-state NMR spectroscopy, we were able to observe nuclei of a supramolecular BTA based additive on the nanoscale in a matrix of i -PP at a concentration of only 0.09 wt%. These nuclei exhibit the analogous structural features as the crystalline phase of the neat additive.
    Keywords: Additives ; Crystal Structure ; NMR Spectroscopy ; Nanocomposites ; Nanomaterials ; Nanostructure ; Nuclei ; Polypropylenes ; Miscellaneous Sciences (So) ; Components and Materials (General) (Ea);
    ISSN: 1359-7345
    E-ISSN: 1364-548X
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  • 5
    Language: English
    In: Polymer, 15 February 2010, Vol.51(4), pp.913-921
    Description: This paper presents 1,3,5-benzenetrisamides as colorless α–nucleating agents for poly(vinylidene fluoride). In order to screen a large variety of 1,3,5-benzenetrisamide derivatives with respect to their nucleating potential an efficient and reliable test based on polarized light microscopy was established. For selected promising compounds the concentration dependence of the PVDF crystallization temperature, the dissolution behavior of the additive in the polymer melt, and the crystallization of the additive from the polymer melt was investigated in a concentration range between 1 wt% (10,000 ppm) and 70 ppm. It was found, that only two of the investigated compounds were able to raise the crystallization temperature about 8 °C at a concentration of 140 ppm and 580 ppm, respectively. These trisamides have the advantage being soluble in the polymer melt, not featuring absorption of visible light and therefore allowing the preparation of uniform and colorless PVDF products.
    Keywords: Pvdf ; Nucleating Agents ; 1,3,5-Benzenetrisamides ; Engineering ; Chemistry
    ISSN: 0032-3861
    E-ISSN: 1873-2291
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  • 6
    Language: English
    In: Polymer, 30 November 2012, Vol.53(25), pp.5754-5759
    Description: 1,3,5-Benzenetrisamides (BTAs) are a prominent class of low-molecular weight compounds in supramolecular chemistry. They are well-known to self-assemble into micro- and nanofibers in a bottom–up approach. At the same time, BTAs are also suitable for top-down processing by melt electrospinning. In this work, we demonstrate for the first time that both approaches lead to mechanically robust BTA fibers. We compare self-assembled and electrospun fibers of N,N,N″-tripropyl-1,3,5-benzenetricarboxamide on multiple length scales. X-ray diffraction (XRD) reveals the same crystal structure independently from the preparation method. Using scanning electron microscopy (SEM), we observe significantly different morphologies of both fiber types on the sub-micron-scale. However, atomic force microscopy (AFM) bending experiments show that despite differences in morphology, Young's modulus is comparable for both types and in the lower GPa range (3–5 GPa). Thus, both top–down and bottom–up techniques with their complementary features in terms of accessible structures and potential applications are available for this class of materials.
    Keywords: 1,3,5-Benzenetrisamides ; Melt Electrospinning ; Self-Assembly ; Engineering ; Chemistry
    ISSN: 0032-3861
    E-ISSN: 1873-2291
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  • 7
    Language: English
    In: Langmuir : the ACS journal of surfaces and colloids, 27 November 2018, Vol.34(47), pp.14249-14253
    Description: Controlled wrinkling is a rather simple method of fabricating surface topographies. The production process is based on the spontaneous formation of wrinkles upon compression of a hard film attached to a soft elastic substrate. Controlled wrinkling typically features large-scale wrinkled samples with a discrete wavelength and amplitude. In this report, we employ an approach utilizing linear metal layer thickness gradients for the controlled formation of gradient wrinkle patterns. The observed wavelength modulation was experimentally achieved by preparing layer thickness gradients of gold, chromium, and indium by physical vapor deposition in combination with a poly(dimethyl siloxane) elastomer substrate. In case of chromium and indium, a thin SiO surface layer was sufficient to ensure adhesion. However, in case of gold, an additional thin chromium adhesion layer was required. For the wrinkled gradient gold film, it was possible to tune the wavelength from 3.4 to 12.2 μm on a single substrate. The experimental data correspond well to the theoretical bilayer model from Stafford et al. Chromium has a significant higher Young's modulus and melting temperature than gold. However, chromium was successfully evaporated and gradient wrinkle patterns with wavelengths from 1.0 to 3.5 μm were realized. In contrast, indium has a considerable lower Young's modulus than gold and chromium, respectively. Consequently, lower wavelengths (0.6-1.0 μm) of the wrinkled gradient indium film were observed. These tunable wrinkled gradient metal films can be envisioned as components in sensors and optical and electro-optical devices.
    Keywords: Chrom ; Gold ; Indium ; Physikalische Dampfphasenbeschichtung ; Adhäsion ; Dimethylsiloxan ; Elastomer ; Produktionsprozess ; Gradientendünnschicht ; Amplitude ; Experimentelle Daten ; Wellenlänge ; Metallschicht ; Oberflächenschicht ; Oberflächentopographie ; Hartstoffüberzug ; Elektrooptisches Bauelement ; Chemistry;
    ISSN: 07437463
    E-ISSN: 1520-5827
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  • 8
    Language: English
    In: Langmuir : the ACS journal of surfaces and colloids, 15 May 2018, Vol.34(19), pp.5535-5544
    Description: Efficient hydrogelators will gel water fast and at low concentrations. Small molecule gelling agents that assemble into fibers and fiber networks are particularly effective hydrogelators. Whereas it is straightforward to determine their critical concentration for hydrogelation, the kinetics of hydrogelation is more difficult to study because it is often very fast, occurring on the subsecond time scale. We used a 3D focusing microfluidic device combined with fluorescence microscopy and in situ small-angle X-ray scattering (SAXS) to study the fast pH-induced gelation of a model small molecule gelling agent at the millisecond time scale. The gelator is a 1,3,5-benzene tricarboxamide which upon acidification assembles into nanofibrils and fibril networks that show a characteristic photoluminescence. By adjusting the flow rates, the regime of early nanofibril formation and gelation could be followed along the microfluidic reaction channel. The measured fluorescence intensity profiles were analyzed in terms of a diffusion-advection-reaction model to determine the association rate constant, which is in a typical range for the small molecule self-assembly. Using in situ SAXS, we could determine the dimensions of the fibers that were formed during the early self-assembly process. The detailed structure of the fibers was subsequently determined by cryotransmission electron microscopy. The study demonstrates that 3D focusing microfluidic devices are a powerful means to study the self-assembly on the millisecond time scale, which is applied to reveal early state of hydrogelation kinetics. In combination with in situ fluorescence and X-ray scattering, these experiments provide detailed insights into the first self-assembly steps and their reaction rates.
    Keywords: Microfluidics ; X-Ray ; Kinetics ; Gels ; Reactor-Model ; Molecular-Self-Assembly ; Photoluminescence ; Gelation ; Nanofibril ; Millisecond-Range ; Reaction-Channel ; Self-Assembly ; Reaction-Rate ; Mikrofluidik ; X-Strahl ; Kinetik ; Gel ; Reaktionsmodell ; Molekulare Selbstassemblierung ; Photolumineszenz ; Gelbildung ; Nanofibrille ; Millisekunde ; Reaktionsweg ; Selbstassemblierung ; Reaktionsgeschwindigkeit ; Chemistry;
    ISSN: 07437463
    E-ISSN: 1520-5827
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  • 9
    In: Nature, 2015, Vol.523(7559), p.196
    Description: Efficient transport of excitation energy over long distances is a key process in light-harvesting systems, as well as in molecular electronics (1-3). However, in synthetic disordered organic materials, the exciton diffusion length is typically only around 10 nanometres (refs 4, 5), or about 50 nanometres in exceptional cases (6,7), a distance that is largely determined by the probability laws of incoherent exciton hopping. Only for highly ordered organic systems has the transport of excitation energy over macroscopic distances been reported--for example, for triplet excitons in anthracene single crystals at room temperature (8), as well as along single polydiacetylene chains embedded in their monomer crystalline matrix at cryogenic temperatures (at 10 kelvin, or -263 degrees Celsius) (9). For supramolecular nanostructures, uniaxial long-range transport has not been demonstrated at room temperature. Here we show that individual self-assembled nanofibres with molecular-scale diameter efficiently transport singlet excitons at ambient conditions over more than four micrometres, a distance that is limited only by the fibre length. Our data suggest that this remarkable long-range transport is predominantly coherent. Such coherent long-range transport is achieved by one-dimensional self-assembly of supramolecular building blocks, based on carbonyl-bridged triarylamines (10), into well defined H-type aggregates (in which individual monomers are aligned cofacially) with substantial electronic interactions. These findings may facilitate the development of organic nanophotonic devices and quantum information technology.
    Keywords: Nanotechnology – Research;
    ISSN: 0028-0836
    E-ISSN: 1476-4687
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  • 10
    Language: English
    In: Journal of the American Chemical Society, 2016, Vol.138(33), pp.urn:issn:0002-7863
    Description: Abstract Image Functional supramolecular systems like carbonyl-bridged triarylamine (CBT) trisamides are known for their long-range energy transport at room temperature. Understanding the complex self-assembly processes of this system allows for control over generated structures using controlled supramolecular polymerization. Here, we present two novel CBT trisamides with (S)- or (R)-chiral side chains which show a two-pathway self-assembly behavior in solution. Depending on the thermal profile during the self-assembly process, two different stable states are obtained under otherwise identical conditions. A kinetically trapped state A is reached upon cooling to 7 °C, via a proposed isodesmic process. In addition, there is a thermodynamically stable state B at 7 °C that is induced by first undercooling to −5 °C, via a nucleation-elongation mechanism. In both cases, helical supramolecular aggregates comprising H-aggregated CBTs are formed. Additionally, controlled supramolecular polymerization was achieved by mixing the two different states (A and B) from the same enantiomer, leading to a conversion of the kinetically trapped state to the thermodynamically stable state. This process is highly enantioselective, as no conversion is observed if the two states consist of opposite enantiomers. We thus show the importance and opportunities emerging from understanding the pathway complexity of functional supramolecular systems.
    Keywords: Journal Article ; Research Support, Non-U.S. Gov'T
    ISSN: 0002-7863
    ISSN: 1520-5126
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