Reconfigurable self-assembly through chiral control of interfacial tension

Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Nature Publishing Group for personal use, not for redistribution. The definitive version was published in Nature 481 (2012): 348–351, doi:10.1038/nature10769.From determining optical properties of simple molecular crystals to establishing preferred handedness in highly complex vertebrates, molecular chirality profoundly influences the structural, mechanical, and optical properties of both synthetic and biological matter at macroscopic lengthscales1,2. In soft materials such as amphiphilic lipids and liquid crystals, the competition between local chiral interactions and global constraints imposed by the geometry of the self-assembled structures leads to frustration and the assembly of unique materials3-6. An example of particular interest is smectic liquid crystals, where the 2D layered geometry cannot support twist, expelling chirality to the edges in a manner analogous to the expulsion of a magnetic field from superconductors7-10. Here, we demonstrate a previously unexplored consequence of this geometric frustration which leads to a new design principle for the assembly of chiral molecules. Using a model system of colloidal membranes11, we show that molecular chirality can control the interfacial tension, an important property of multi-component mixtures. This finding suggests an analogy between chiral twist which is expelled to the edge of 2D membranes, and amphiphilic surfactants which are expelled to oil-water interfaces12. Similar to surfactants, chiral control of interfacial tension drives the assembly of myriad polymorphic assemblages such as twisted ribbons with linear and circular topologies, starfish membranes, and double and triple helices. Tuning molecular chirality in situ enables dynamical control of line tension that powers polymorphic transitions between various chiral structures. These findings outline a general strategy for the assembly of reconfigurable chiral materials which can easily be moved, stretched, attached to one another, and transformed between multiple conformational states, thus enabling precise assembly and nano-sculpting of highly dynamical and designable materials with complex topologies.This work was supported by the National Science Foundation (NSF-MRSEC-0820492, NSF-DMR-0955776, NSF-MRI 0923057) and Petroleum Research Fund (ACS-PRF 50558-DNI7).2012-07-0

NACA Technical Notes

Report presenting results for a continuation of a research program in the high-speed 7- by 10-foot tunnel to investigate the aerodynamic characteristics in pitch, sideslip, and steady roll of model configurations with variations in wing geometric parameters. This particular report contains aerodynamic characteristics in pitch of wing-fuselage combinations with wings of aspect ratio 4, a sweepback angle of 45 degrees, and three different taper ratios. Results regarding lift characteristics, pitching-moment characteristics, drag characteristics, and lift-drag ratios are provided

NACA Research Memorandums

Report presenting a continuation of the program in the high-speed 7- by 10-foot tunnel to investigate the aerodynamic characteristics in pitch, sideslip, and steady roll of model configurations with variations in wing geometric parameters. This report contains the aerodynamic characteristics in pitch of wing-fuselage combinations with wings of aspect ratio 4, sweepback angle of 45 degrees, and three different taper ratios. Results regarding lift characteristics, pitching-moment characteristics, drag characteristics, and lift-drag ratio are provided

NACA Research Memorandums

Report discussing an investigation to determine the effects of changes in aspect ratio and tail height on the longitudinal stability characteristics of a model with a 32.6-degree sweptback wing. The effects of a leading-edge discontinuity were also examined

NACA Research Memorandums

Report presenting an investigation of a nacelle at various chordwise positions and vertical locations on a semispan model of a wing with and without a fuselage through a range of Mach numbers. The investigation was made to determine the interference characteristics between the nacelle and the model and to determine the effect of the fuselage on nacelle interference

NACA Research Memorandums

From Introduction: "This paper presents the results of the investigation of the wing-alone and wing-fuselage configurations employing a wing with the quarter-chord line swept back 45^o, aspect ratio 4, taper ratio 0.3, and an NACA 65A006 airfoil section parallel to the stream.