Liang H.-L.,Johannes Gutenberg University Mainz |
Liang H.-L.,Martin Luther University of Halle Wittenberg |
Noh J.,Seoul National University of Science and Technology |
Zentel R.,Johannes Gutenberg University Mainz |
And 3 more authors.
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences | Year: 2013
Thin liquid crystalline shells surrounding and surrounded by aqueous phases can be conveniently produced using a nested capillary microfluidic system, as was first demonstrated by Fernandez- Nieves et al. in 2007. By choosing particular combinations of stabilizers in the internal and external phases, different types of alignment, uniform or hybrid, can be ensured within the shell. Here, we investigate shells in the nematic and smectic phases under varying boundary conditions, focusing in particular on textural transformations during phase transitions, on the interaction between topological defects in the director field and inclusions in the liquid crystal (LC), and on the possibility to relocate defects within the shell by rotating the shell in the gravitational field. We demonstrate that inclusions in a shell can seed defects that cannot form in a pristine shell, adding a further means of tuning the defect configuration, and that shells in which the internal aqueous phase is not density matched with the LC will gently rearrange the internal structure upon a rotation that changes the influence of gravity. Because the defects can act as anchor points for added linker molecules, allowing self-assembly of adjacent shells, the various arrangements of defects developing in these shells and the possibility of tuning the result by modifying boundary conditions, LC phase, thickness and diameter of the shell or applying external forces make this new LC configuration very attractive. © 2013 The Author(s) Published by the Royal Society. All rights reserved. Source
Lagerwall J.P.F.,Korea Advanced Institute of Science and Technology |
Lagerwall J.P.F.,Advanced Institute of Convergence Technologies |
Schutz C.,University of Stockholm |
Schutz C.,Wallenberg Wood Science Center |
And 7 more authors.
NPG Asia Materials | Year: 2014
Cellulose nanocrystals (CNCs), produced by the acid hydrolysis of wood, cotton or other cellulose-rich sources, constitute a renewable nanosized raw material with a broad range of envisaged uses: for example, in composites, cosmetics and medical devices. The intriguing ability of CNCs to self-organize into a chiral nematic (cholesteric) liquid crystal phase with a helical arrangement has attracted significant interest, resulting in much research effort, as this arrangement gives dried CNC films a photonic band gap. The films thus acquire attractive optical properties, creating possibilities for use in applications such as security papers and mirrorless lasing. In this critical review, we discuss the sensitive balance between glass formation and liquid crystal self-assembly that governs the formation of the desired helical structure. We show that several as yet unclarified observations - some constituting severe obstacles for applications of CNCs - may result from competition between the two phenomena. Moreover, by comparison with the corresponding self-assembly processes of other rod-like nanoparticles, for example, carbon nanotubes and fd virus particles, we outline how further liquid crystal ordering phenomena may be expected from CNCs if the suspension parameters can be better controlled. Alternative interpretations of some unexpected phenomena are provided, and topics for future research are identified, as are new potential application strategies. © 2014 Nature Publishing Group. Source
Scalia G.,Korea Advanced Institute of Science and Technology |
Scalia G.,Advanced Institute of Convergence Technologies |
Enz E.,Martin Luther University of Halle Wittenberg |
Calo O.,ENEA |
And 5 more authors.
Macromolecular Materials and Engineering | Year: 2013
By electrospinning liquid crystals coaxially inside a polymer sheath, responsive fibers with application potential, e.g., in wearable sensors can be produced. We conduct a combined scanning electron/polarizing microscopy study of such fibers, concluding that a match between the properties of the sheath solution and that of the core fluid is vital for achieving well-formed and well-filled fibers. Problems that may otherwise arise are fibers that are continuously filled, but partially collapsed; or fibers in which the core breaks up into droplets due to a mismatch in elongational viscosity between inner and outer fluids. Liquid-crystal-functionalized core-sheath fibers produced by coaxial electrospinning can exhibit novel optical properties and strong response function. These fibers could be used in wearable sensors, but a careful matching between core and sheath fluids is required for ensuring optimum fiber morphology, strength, and a continuous core. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source
Hwang B.S.,Kunsan National University |
Kim H.S.,Kunsan National University |
Yih W.,Kunsan National University |
Yih W.,Advanced Institute of Convergence Technologies |
And 3 more authors.
Organic Letters | Year: 2014
Acuminolide A (1), along with pectenotoxin II (PTX-2), dinophysistoxin I (DTX-1), okadaic acid (OA), and 7-epi-PTX-2 seco acid, was isolated from a large-scale cultivation of the dinoflagellate Dinophysis acuminata. The new 33-membered macrolide 1 was characterized by detailed analysis of 2D NMR and MS data. Its relative stereochemistry was elucidated on the basis of ROESY correlations and J-based analysis. In contrast to the other well-known toxins that were isolated, 1 showed no cytotoxicity against four cancer cell lines but caused potent stimulation of actomyosin ATPase activity. (Chemical Equation Presented). © 2014 American Chemical Society. Source