1,492 research outputs found
Supramolecular modification of ABC triblock terpolymers in confinement assembly
The self-assembly of AB diblock copolymers in three-dimensional (3D) soft confinement of nanoemulsions has recently become an attractive bottom up route to prepare colloids with controlled inner morphologies. In that regard, ABC triblock terpolymers show a more complex morphological behavior and could thus give access to extensive libraries of multicompartment microparticles. However, knowledge about their self-assembly in confinement is very limited thus far. Here, we investigated the confinement assembly of polystyrene-block-poly(4-vinylpyridine)-block-poly(tert-butyl methacrylate) (PS-b-P4VP-b-PT or SVT) triblock terpolymers in nanoemulsion droplets. Depending on the block weight fractions, we found spherical microparticles with concentric lamella–sphere (ls) morphology, i.e., PS/PT lamella intercalated with P4VP spheres, or unusual conic microparticles with concentric lamella–cylinder (lc) morphology. We further described how these morphologies can be modified through supramolecular additives, such as hydrogen bond (HB) and halogen bond (XB) donors. We bound donors to the 4VP units and analyzed changes in the morphology depending on the binding strength and the length of the alkyl tail. The interaction with the weaker donors resulted in an increase in volume of the P4VP domains, which depends upon the molar fraction of the added donor. For donors with a high tendency of intermolecular packing, a visible change in the morphology was observed. This ultimately caused a shape change in the microparticle. Knowledge about how to control inner morphologies of multicompartment microparticles could lead to novel carbon supports for catalysis, nanoparticles with unprecedented topologies, and potentially, reversible shape changes by light actuation
Nascent polypeptide chains on mitochondrial ribosomes and their integration into the inner membrane
Detection of t(7;12)(q36;p13) in paediatric leukaemia using dual colour fluorescence in situ hybridisation
The identification of chromosomal rearrangements is of utmost importance for the diagnosis and classification of specific leukaemia subtypes and therefore has an impact on therapy choices in individual cases. The t(7;12)(q36;p13) is a cryptic rearrangement that is difficult to recognise using conventional cytogenetic methods and is often undetected by reverse transcription polymerase chain reaction due to the absence of a fusion transcript in many cases. Here we present a reliable and easy to use dual colour fluorescence in situ hybridisation assay for the detection of the t(7;12)(q36;p13) rearrangement. A comparison with previous similar work is given and advantages and limitations of this novel approach are discussed
Ortho-Fluorination of azophenols increases the mesophase stability of photoresponsive hydrogen-bonded liquid crystals
Photoresponsive liquid crystals (LCs) whose alignment can be controlled with UV-Visible light are appealing for a range of photonic applications. From the perspective of exploring the interplay between the light response and the self-assembly of the molecular components, supramolecular liquid crystals are of particular interest. They allow elaborating the structure-property relationships that govern the optical performance of LC materials by subtle variation of the chemical structures of the building blocks. Herein we present a supramolecular system comprising azophenols and stilbazoles as hydrogen-bond donors and acceptors, respectively, and show that ortho-fluorination of the azophenol dramatically increases the thermal stability of the LC phases, an important characteristics in their further utilization in photonics. The systems exhibit fast photoinduced order-disorder transitions, and rapid recovery of the liquid-crystalline state once the light irradiation is ceased, due to the photochemical properties of azophenols
Improving the mesomorphic behaviour of supramolecular liquid crystals by resonance-assisted hydrogen bonding
A systematic structure-property relationship study on hydrogen-bonded liquid crystals was performed, revealing the impact of resonance-assisted hydrogen bonds (RAHBs) on the self-assembling behavior of the supramolecular architecture. The creation of a six-membered intramolecular hydrogen-bonded ring acts as a counterpart to the self-organization between hydrogen bond donators and acceptors and determines thus the suprastructure. Variation of the hydrogen-bonding pattern allowed us to significantly improve the temperature range of the reported liquid crystalline assemblies
Electron concentration effects on the Shastry-Sutherland phase stability in Ce_{2-x}Pd_{2+y}In_{1-z} solid solutions
The stability of a Shastry-Sutherland ShSu phase as a function of electron
concentration is investigated through the field dependence of thermal and
magnetic properties of the solid solution Ce_{2-x}Pd_{2+y}In_{1-z} in the
antiferromagnetic branch. In these alloys the electronic (holes) variation is
realized by increasing concentration. The AF transition T_M decreases from
3.5K to 2.8K as concentration increases from y=0.2 to y=0.4. By applying
magnetic field, the ShSu phase is suppressed once the field induced
ferromagnetic polarization takes over at a critical field B_{cr} which
increases with content. A detailed analysis around the critical point
reveals a structure in the maximum of the dM/dB derivative, which is related
with incipient steps in the magnetization M(B) as predicted by the theory for
the ShSu lattice. The crossing of M(B) isotherms, observed in ShSu prototype
compounds, is also analyzed. The effect of substitution by is
interpreted as an increase of the number of 'holes' in the conduction band and
results in a unique parameter able to describe the variation of the magnetic
properties along the studied range of concentration.Comment: 8 pages, 11 figure
Hydrogen-bonded liquid crystals with broad-range blue phases
We report a modular supramolecular approach for the investigation of chirality induction in hydrogen-bonded liquid crystals. An exceptionally broad blue phase with a temperature range of 25 °C was found, which enabled its structural investigation by solid state 19F-NMR studies and allowed us to report order parameters of the blue phase I for the first time
Halogen bonding enhances nonlinear optical response in poled supramolecular polymers
We demonstrate that halogen bonding strongly enhances the nonlinear optical response of poled supramolecular polymer systems. We compare three nonlinear optical chromophores with similar electronic structures but different bond-donating units, and show that both the type and the strength of the noncovalent interaction between the chromophores and the polymer matrix play their own distinctive roles in the optical nonlinearity of the systems
New evidence on the link between ethnic fractionalization and economic freedom
Among the determinants of economic freedom, the presence of different ethnic groups within a country has sometimes been explored by the empirical literature, without conclusive evidence on the sign of the relation, its drivers, and the conditions under which it holds. This paper offers new evidence by empirically modelling how ethnic fragmentation is related to economic freedom, as measured by the Economic Freedom Index and by each of its numerous areas, components and sub-components. The results provide insights on the components driving the effect and, interestingly, detect notable differences between developed and developing countries
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