Direct observation of domain structure in condensed monolayer phases

Qiu, Xia; Ruíz-García, Jaime; Stine, Keith J.; Knobler, Charles M.; Selinger, Jonathan V.

doi:10.1103/physrevlett.67.703

Cited by 149 publications

(98 citation statements)

References 10 publications

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“…When the chiral symmetry of an achiral system is broken, a handedness is established, and materials with different handedness commonly exhibit distinct and useful properties (10)(11)(12)(13)(14) relevant for applications ranging from chemical sensors (15,16) to photonics (17)(18)(19). To date, considerable effort has been expended to control handedness in materials (for example, by chiral separation of racemic mixtures or chiral amplification of small enantiomeric imbalances) (1,8,(20)(21)(22).…”

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confidence: 99%

Chiral structures from achiral liquid crystals in cylindrical capillaries

Jeong

Kang

Davidson

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

109

103

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We study chiral symmetry-broken configurations of nematic liquid crystals (LCs) confined to cylindrical capillaries with homeotropic anchoring on the cylinder walls (i.e., perpendicular surface alignment). Interestingly, achiral nematic LCs with comparatively small twist elastic moduli relieve bend and splay deformations by introducing twist deformations. In the resulting twisted and escaped radial (TER) configuration, LC directors are parallel to the cylindrical axis near the center, but to attain radial orientation near the capillary wall, they escape along the radius through bend and twist distortions. Chiral symmetry-breaking experiments in polymercoated capillaries are carried out using Sunset Yellow FCF, a lyotropic chromonic LC with a small twist elastic constant. Its director configurations are investigated by polarized optical microscopy and explained theoretically with numerical calculations. A rich phenomenology of defects also arises from the degenerate bend/twist deformations of the TER configuration, including a nonsingular domain wall separating domains of opposite twist handedness but the same escape direction and singular point defects (hedgehogs) separating domains of opposite escape direction. We show the energetic preference for singular defects separating domains of opposite twist handedness compared with those of the same handedness, and we report remarkable chiral configurations with a double helix of disclination lines along the cylindrical axis. These findings show archetypally how simple boundary conditions and elastic anisotropy of confined materials lead to multiple symmetry breaking and how these broken symmetries combine to create a variety of defects.mirror symmetry | parity symmetry | topological defects | chiral defects T he emergence of chirality from achiral systems poses fundamental questions about which we have limited mechanistic understanding (1-11). When the chiral symmetry of an achiral system is broken, a handedness is established, and materials with different handedness commonly exhibit distinct and useful properties (10-14) relevant for applications ranging from chemical sensors (15, 16) to photonics (17-19). To date, considerable effort has been expended to control handedness in materials (for example, by chiral separation of racemic mixtures or chiral amplification of small enantiomeric imbalances) (1,8,(20)(21)(22). Recently and in a different vein, identification and elucidation of pathways by which achiral building blocks spontaneously organize to create chiral structures have become an area of active study. Examples of these pathways include packing with multiple competing length scales (8-10, 23, 24), reconfiguration through mechanical instabilities of periodic structures (20,25,26), and helix formation of flexible cylinders through inter-and intracylinder interactions (27,28). In addition, the system of a broken chiral symmetry often consists of domains of opposite handedness with defects separating the domains.Liquid crystals (LCs) are soft materials composed ...

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confidence: 99%

Chiral structures from achiral liquid crystals in cylindrical capillaries

Jeong

Kang

Davidson

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

109

103

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“…The helical structure obtained from the achiral molecule was possible an occurrence of statistical fluctuations in the intermolecular self-assembly process, which could lead to an accidental excess of one helical direction [15][16][17][18]. After one helical direction was formed, the new aggregates would follow to form a helical secondary structure along with the same direction by chiral autocatalysis [14].…”

Section: Resultsmentioning

confidence: 99%

Formation and regulation of supramolecular chirality in organogel via addition of tartaric acid

et al. 2012

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A new 1,8-naphthalimide derivative was prepared in which the C-4 position was substituted by pyridin-4-ol. This derivative shows good gelation property that can gelate most of polar solvents. As an achiral molecule, helical fibre morphology was observed when the compound gelated acetone solvent. When 0.5 eq of D-tartaric acid or L-tartaric acid was added to the gel, the helical morphology was changed from left-handed to right-handed structure. This result was further proved by circular dichroism measurement. FT-IR experiment showed the formation of intermolecular H-bond between the gelator and tartaric acid. The photophysical properties of gelator had no difference before and after addition of tartaric acid; whereas the lamellar structure was varied by addition of tartaric acid.

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“…It has long been known from thermodynam ic and spectroscopic data that when a lipid monolayer is compressed isothermally it undergoes a series of phase transitions. The two phase coexistence re gion in the first-order transition from a liquid expanded phase (LE) to a liquid condensed phase (L C ) has been studied intensively, especially after the discovery that the morphology of the LC dom ains can be imaged by fluores cence microscopy [1][2][3][4] and Brewster angle microscopy [5,6]. Some specific features make this system unique from the point of view of pattern formation studies.…”

Section: Surface-tension-gradient-induced Pattern Formation In M Onolmentioning

confidence: 99%

“…First, the morphology of LC dom ains varies from com pact to dendritic and fractal patterns [2][3][4]7], which can now be studied in situ experimentally. Second, since this system is truly two dimensional, it is a challenge to inter pret the development of the boundaries between LC and LE phases with theories of dendritic growth [7,8] and faceted crystal growth [9].…”

Section: Surface-tension-gradient-induced Pattern Formation In M Onolmentioning

confidence: 99%