Kooperativer Bibliotheksverbund

Berlin Brandenburg

and
and

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
Type of Medium
Language
Year
  • 1
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 01 February 2011, Vol.108(5), pp.1810-4
    Description: Micelles are the simplest example of self-assembly found in nature. As many other colloids, they can self-assemble in aqueous solution to form ordered periodic structures. These structures so far all exhibited classical crystallographic symmetries. Here we report that micelles in solution can self-assemble into quasicrystalline phases. We observe phases with 12-fold and 18-fold diffraction symmetry. Colloidal water-based quasicrystals are physically and chemically very simple systems. Macroscopic monodomain samples of centimeter dimension can be easily prepared. Phase transitions between the fcc phase and the two quasicrystalline phases can be easily followed in situ by time-resolved diffraction experiments. The discovery of quasicrystalline colloidal solutions advances the theoretical understanding of quasicrystals considerably, as for these systems the stability of quasicrystalline states has been theoretically predicted for the concentration and temperature range, where they are experimentally observed. Also for the use of quasicrystals in advanced materials this discovery is of particular importance, as it opens the route to quasicrystalline photonic band gap materials via established water-based colloidal self-assembly techniques.
    Keywords: Diffraction -- Research ; Symmetry (Physics) -- Research ; Crystals -- Chemical Properties;
    ISSN: 00278424
    E-ISSN: 1091-6490
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 23 April 2013, Vol.110(17), pp.6706-11
    Description: The flow orientation of anisotropic particles through narrow channels is of importance in many fields, ranging from the spinning and molding of fibers to the flow of cells and proteins through thin capillaries. It is commonly assumed that anisotropic particles align parallel to the flow direction. When flowing through narrowed channel sections, one expects the increased flow rate to improve the parallel alignment. Here, we show by microfocus synchrotron X-ray scattering and polarized optical microscopy that anisotropic colloidal particles align perpendicular to the flow direction after passing a narrow channel section. We find this to be a general behavior of anisotropic colloids, which is also observed for disk-like particles. This perpendicular particle alignment is stable, extending downstream throughout the remaining part of the channel. We show by microparticle image velocimetry that the particle reorientation in the expansion zone after a narrow channel section occurs in a region with considerable extensional flow. This extensional flow is promoted by shear thinning, a typical property of complex fluids. Our discovery has important consequences when considering the flow orientation of polymers, micelles, fibers, proteins, or cells through narrow channels, pipes, or capillary sections. An immediate consequence for the production of fibers is the necessity for realignment by extension in the flow direction. For fibrous proteins, reorientation and stable plug flow are likely mechanisms for protein coagulation.
    Keywords: Micelles ; Colloids -- Chemistry ; Microfluidics -- Methods
    ISSN: 00278424
    E-ISSN: 1091-6490
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Language: English
    In: The journal of physical chemistry. B, 09 January 2014, Vol.118(1), pp.344-50
    Description: Films of the semiconducting polymer poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]] with 40% fluorinated monomers, denoted PTB7-F40, are spin coated out of different solvents onto PEDOT:PSS films. The influence of the used solvents chlorobenzene, 1,2-dichlorobenzene, and 1,2,4-trichlorobenzene as well as the influence of the additive 1,8-diiodooctane (DIO) is probed with grazing incidence small- and wide-angle X-ray scattering (GISAXS and GIWAXS). As seen with GISAXS, without DIO, the films are homogeneous and show roughness correlation with the PEDOT:PSS film surface. With DIO, an inner film structure with a size of 50-75 nm is found and the roughness correlations weaken. In addition, as seen in GIWAXS, the crystalline part of the films is influenced by the used solvent if DIO is added.
    Keywords: Scattering (Physics) -- Usage ; Semiconductors (Materials) -- Research ; Solvents -- Influence;
    ISSN: 15206106
    E-ISSN: 1520-5207
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    In: Physical Chemistry Chemical Physics, 2014, Vol.16(14), pp.6583-6592
    Description: Characterization of mesoporous adsorbents is traditionally performed in terms of the pore size distribution with bulk methods like physisorption and mercury intrusion. But their application relies on assumptions regarding the basic pore geometry. Although novel tools have enabled the quantitative interpretation of physisorption data for adsorbents having a well-defined pore structure the analysis of disordered mesoporosity still remains challenging. Here we show that small angle X-ray scattering (SAXS) combined with chord length distribution (CLD) analysis presents a precise and convenient approach to determine the structural properties of two-phase (solidvoid) systems of mesopores. Characteristic wall (solid) and pore (void) sizes as well as surface areas are extracted without the need to assume a certain pore shape. The mesoporous structure of modern, commercially available fully porous and coreshell adsorbent particles is examined by SAXS/CLD analysis. Mean pore size and surface area are compared with results obtained from nitrogen physisorption data and show excellent agreement.
    Keywords: X-Ray ; Adsorbent ; Pore-Size-Distribution ; Quantitative-Analysis ; Surface-Area:Mathematics ; Physisorptions ; Hydrargyrum ; Nitrogen ; Pore-Structure ; Pore-Shape ; Middle-Porosity ; Pore-Size ; Röntgenstrahl ; Adsorptionsmittel ; Porengrößenverteilung ; Quantitative Analyse ; Flächeninhalt ; Physisorption ; Quecksilber ; Stickstoff ; Porenstruktur ; Porenform ; Mesoporosität ; Porengröße ; Chemistry;
    ISSN: 1463-9076
    E-ISSN: 1463-9084
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    Language: English
    In: Polymer, 2011, Vol.52(17), pp.3819-3826
    Description: Recent investigations have shown that an anthracene containing poly( -arylene-ethynylene)-alt-poly( -arylene-vinylene) statistical copolymer consisting of a well defined conjugated backbone, along which linear and branched alkoxy side chains are attached in a random manner, yields, compared to its counterparts with regular side chain substitution, an improved performance in polymer [6,6]:-phenyl-C -butyric acid methyl ester (PCBM) bulk-heterojunction solar cells. The microscopic origin for the improved power conversion efficiency (  ≈ 3.8%) of the statistical copolymer – which is the best in its material class – has not been resolved. We conducted grazing incidence wide-angle x-ray scattering investigations in order to correlate the nanomorphology of the active layers to the photovoltaic performance of the device. A comparison of the results obtained for the statistical copolymer to those obtained for the corresponding regular copolymers shows that the improved performance of the former may be attributed to a combination of the following structural characteristics: 1. well, ordered stacked domains that promote backbone planarization, 2. partly face-on alignment of domains relative to the electrodes for an improved active layer-electrode charge transfer, and 3. a more isotropic domain orientation throughout the active layer that ensures that the backbone alignment direction has components perpendicular and parallel to the electrodes in order to compromise between light absorption and efficient intra-chain charge transport. The regular copolymers exhibiting inferior performance lack either sufficient stacking order or face-on alignment of the domains. None of them shows isotropic domain orientation.
    Keywords: Grazing Incidence X-Ray Scattering ; Conjugated Polymers ; Bulk-Heterojunction Solar Cells ; Engineering ; Chemistry
    ISSN: 0032-3861
    E-ISSN: 1873-2291
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    Language: English
    In: Langmuir : the ACS journal of surfaces and colloids, 29 March 2016, Vol.32(12), pp.2928-36
    Description: We report synchrotron-based small-angle X-ray scattering experiments on a template-grown porous silica matrix (Santa Barbara Amorphous-15) upon in situ sorption of fluorinated pentane C5F12 along with volumetric gas sorption isotherm measurements. Within the mean-field model of Saam and Cole for vapor condensation in cylindrical pores, a nitrogen and C5F12 sorption isotherm is well described by a bimodal pore radius distribution dominated by meso- and micropores with 3.4 and 1.6 nm mean radius, respectively. In the scattering experiments, two different periodicities become evident. One of them (d1 = 11.5 nm) reflects the next nearest neighbor distance in a 2D-hexagonal lattice of tubular mesopores. A second periodicity (d2 = 11.4 nm) found during in situ sorption and freezing experiments is traced back to a superstructure along the cylindrical mesopores. It is compatible with periodic pore corrugations found in electron tomograms of empty SBA-15 by Gommes et al. ( Chem. Mater. 2009, 21, 1311 - 1317). A Rayleigh-Plateau instability occurring at the cylindrical blockcopolymer micelles characteristic of the SBA-15 templating process quantitatively accounts for the superstructure and thus the spatial periodicity of the pore wall corrugation. The consequences of this peculiar morphological feature on the spatial arrangement of C5F12, in particular the formation of periodically arranged nanobubbles (or voids) upon adsorption, desorption, and freezing of liquids, are discussed in terms of capillary bridge formation and cavitation in tubular but periodically corrugated pores.
    Keywords: Dampfkondensation ; Porenradienverteilung ; Riffelbildung ; Brückenbildung ; X-Strahl ; Kapillare ; Hexagonales Kristallgitter ; Elektron ; Periodizität ; Poröses Silicium ; Pentan ; Stickstoff ; Synchrotron ; Sorptionsisotherme ; Kavitation ; Räumliche Anordnung ; Chemistry;
    ISSN: 07437463
    E-ISSN: 1520-5827
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 7
    Language: English
    In: The journal of physical chemistry. B, 20 March 2014, Vol.118(11), pp.3207-17
    Description: Supramolecular assembly allows for enhanced control of bulk material properties through the fine modulation of intermolecular interactions. We present a comprehensive study of a cross-linkable amphiphilic wedge molecule based on a sulfonated trialkoxybenzene with a sodium counterion that forms liquid crystalline (LC) phases with ionic nanochannel structures. This compound exhibits drastic structural changes as a function of relative humidity (RH). Our combined structural, dynamical, and transport studies reveal deep and novel information on the coupling of water and wedge molecule transport to structural motifs, including the significant influence of domain boundaries within the material. Over a range of RH values, we employ (23)Na solid-state NMR on the counterions to complement detailed structural studies by grazing-incidence small-angle X-ray scattering. RH-dependent pulsed-field-gradient (PFG) NMR diffusion studies on both water and the wedge amphiphiles show multiple components, corresponding to species diffusing within LC domains as well as in the domain boundaries that compose 10% of the material. The rich transport and dynamical behaviors described here represent an important window into the world of supramolecular soft materials, carrying implications for optimization of these materials in many venues. Cubic phases present at high RH show fast transport of water (2 × 10(-10) m(2)/s), competitive with that observed in benchmark polymeric ion conductors. Understanding the self-assembly of these supramolecular building blocks shows promise for generating cross-linked membranes with fast ion conduction for applications such as next-generation batteries.
    Keywords: Strukturumwandlung ; Röntgenstrahl ; Diffusion ; Natrium ; Ionenkanal ; Relative Feuchtigkeit ; Dynamisches Verhalten ; Ionenleitung ; Baugruppe ; Selbstassemblierung ; Membran ; Chemistry;
    ISSN: 15206106
    E-ISSN: 1520-5207
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 8
    Language: English
    In: Langmuir : the ACS journal of surfaces and colloids, 04 October 2011, Vol.27(19), pp.12197-200
    Description: The influence of solvent annealing on microscopic deformational behavior of a styrene/n-butyl acrylate copolymer latex film subjected to uniaxial tensile deformation was studied by small-angle X-ray scattering. It was demonstrated that the microscopic deformation mechanism of the latex films transformed from a nonaffine deformation behavior to an affine deformation behavior after solvent annealing. This was attributed to the interdiffusion of polymeric chains between adjacent swollen latex particles in the film. It turns out that solvent annealing is much more efficient than thermal annealing due to a much slow evaporation process after solvent annealing.
    Keywords: Membranes, Artificial ; Latex -- Chemistry
    ISSN: 07437463
    E-ISSN: 1520-5827
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 9
    Language: English
    In: Chemistry of Materials, 05/25/2010, Vol.22(10), pp.3079-3085
    ISSN: 0897-4756
    E-ISSN: 1520-5002
    Source: American Chemical Society (via CrossRef)
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 10
    Language: English
    In: Macromolecules, 26 August 2014, Vol.47(16), pp.5711-5718
    Description: The reorientation of lamellae and the dependence of the lamellar spacing, , on polymer volume fraction, ϕ, ∝ ϕ, in diblock copolymer thin films during solvent vapor annealing (SVA) are examined by combining white light interferometry (WLI) and grazing-incidence small-angle X-ray scattering (GISAXS). A thin film of lamellae-forming poly(styrene--butadiene) prepared by spin-coating features lamellae of different orientations with the lamellar spacing depending on orientation. During annealing with ethyl acetate (EAC) vapor, it is found that perpendicular lamellae behave differently from parallel ones, which is due to the fact that their initial lamellar thicknesses differ strongly. Quantitatively, the swelling process is composed of three regimes and the drying process of two regimes. The first two regimes of swelling are associated with a significant structural rearrangement of the lamellae; i.e., the lamellae first become thicker, and then perpendicular and randomly oriented lamellae vanish, which results in a purely parallel orientation at the end of the swelling process. The rearrangement is attributed to the increase of mobility of the polymer chains imparted by the solvent and to a decrease of total free energy of the thin film. In the third regime of swelling, the scaling exponent is found to be β = -0.32. During drying, the deswelling is nonaffine which may be a consequence of the increase of nonfavorable segmental interactions as the solvent is removed.
    Keywords: Chemistry;
    ISSN: 0024-9297
    E-ISSN: 15205835
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. Further information can be found on the KOBV privacy pages