Linkage-length dependent structuring behaviour of bent-core molecules in helical nanostructures

Kim, Hanim; Zep, Anna; Ryu, Seong Ho; Ahn, Hyungju; Shin, Tae Joo; Lee, Sang Bok; Pociecha, Damian; Górecka, Ewa; Yoon, Dong Ki

doi:10.1039/c5sm03100a

Cited by 16 publications

(22 citation statements)

References 32 publications

(31 reference statements)

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“…As reported previously, azobenzene containing bent dimeric molecules were synthesized, and showed the nematic and B4 phase ( Figure a) . The B4 phase, which is mechanically stable under 100 °C, exhibits twisted filament morphology with helical pitch of several hundred nanometers.…”

Section: Resultssupporting

confidence: 60%

“…To discriminate chirality by optical activity, which is the intrinsic property of chiral materials, we used a racemic chiral color reflector made of a robust chiral nanostructure, helical nanofilament (HNF), or B4 phase . Since the HNFs are composed of achiral molecules, they form either of left‐ or right‐handed micron scale domain in the sample in equal opportunity, and thus the HNF‐film reflects r‐ or l‐CPL.…”

Section: Introductionmentioning

confidence: 99%

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Direct Visualization of Optical Activity in Chiral Substances Using a Helical Nanofilament (B4) Liquid Crystal Phase

Park

Wolska

Pociecha

et al. 2019

Advanced Optical Materials

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Detecting the chirality of material is very important in material science, chemistry, pharmacology, and biomaterial science because it is useful for identifying and discarding unintended side effects. Here, directly visualized is the optical activity of chiral samples using an orientation‐controlled helical nanofilament (HNF, B4) liquid crystal (LC) phase made of achiral bent‐shaped molecules. The vertical orientation of the HNFs is induced by shining unpolarized UV light. Right‐ or left‐handed domains of the HNFs are formed because of the lack of molecular chirality, each single‐handed domain is large enough to be seen with the naked eye, up to ≈several mm2. The periodic arrays of aligned HNFs reflect a specific color, here green, due to the Bragg reflection. Such a reflector enables an easy detection of optical activity of a sample placed on it. The device is tested with naturally chiral substances, like fructose and glucose, which exhibit opposite sense of optical activity, as well as with structurally chiral nematic LC phase and reveals high sensitivity of a detection.

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Section: Resultssupporting

confidence: 60%

Section: Introductionmentioning

confidence: 99%

Direct Visualization of Optical Activity in Chiral Substances Using a Helical Nanofilament (B4) Liquid Crystal Phase

Park

Wolska

Pociecha

et al. 2019

Advanced Optical Materials

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“…To investigate the origin of the reflected colors of the helical nanostructure, simulations were performed using the finite element method (FEM). The numerical calculation in the frequency domain, based on the finite integration technique (FIT) first proposed by T. Weiland in 1976, uses the integral form of Maxwell's equation as follows 11 :…”

Section: Simulationmentioning

confidence: 99%

Directed self-assembly of a helical nanofilament liquid crystal phase for use as structural color reflectors

Park

Kim

et al. 2019

NPG Asia Mater

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The fabrication of molecular structures with a desired morphology, e.g., nanotubes, nanoribbons, nanosprings, and sponges, is essential for the advancement of nanotechnology. Unfortunately, realization of this objective is expensive and complicated. Here, we report that irradiating a film comprising azobenzene derivatives with UV light produces oriented arrays of helical nanofilaments via the photoisomerization-induced Weigert effect. As a result, structural colors are observed due to the extrinsic chiral reflection in the visible wavelength range, and the reflected color can be tuned by adjusting the molecular length of the azobenzene derivative. This simple fabrication method can be used for fabricating large, reversible, and patternable color reflectors, providing a new platform for interference-based structural coloration as it exists in nature, such as morpho butterflies, green-winged teal, and various beetles.

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“…This second twist, meaning stacked arrays of nanofilaments are not parallel but rotated with respect to each other (Figure e,f), can explain both the observed structural blue color of some HNF materials and their ambidextrous optical activity. Confinement in nanoporous anodic aluminum oxides was recently introduced as a means to tune the morphology (including the helical pitch, the layer spacing, and the number of layers) of confined single HNFs by adjusting the pore diameter of the confining nanopores . Hence, HNF phases are synthetic, self‐assembled superstructures that could serve as ideal model systems for many biomineralization processes, including the supramolecular assembly of B‐DNA helices in crystals, where the double helix structure directs the overall geometry by an encoded self‐fitting mechanism …”

Section: Introductionmentioning

confidence: 99%

A Dual Modulated Homochiral Helical Nanofilament Phase with Local Columnar Ordering Formed by Bent Core Liquid Crystals: Effects of Molecular Chirality

Salamończyk

Jákli

et al. 2016

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Helical nanofilament (HNF) phases form as a result of an intralayer mismatch between top and bottom molecular halves in bent-core liquid crystals (BC-LCs) that is relieved by local saddle-splay geometry. HNFs are immensely attractive for photovoltaic and chiral separation applications and as templates for the chiral spatial assembly of guest molecules. Here, the synthesis and characterization of two unichiral BC-LCs and one racemic mixture with tris-biphenyl-diester cores featuring chiral (R,R) and (S,S) or racemic 2-octyloxy aliphatic side chains are presented. In comparison to the achiral compound with linear side chains forming an intralayer modulated HNF phase (HNFmod ), synchrotron small angle X-ray diffraction indicates that the unichiral derivatives form a dual modulated HNF phase with intra- as well as interlayer modulations (HNFmod2 ) suggesting a columnar local structure of the nanofilaments. Transmission electron microscopy and circular dichroism spectropolarimetry confirm that the unichiral materials exclusively form homochiral HNFs with a twist sense-matching secondary twist. A contact preparation provides the first example of two identical chiral liquid crystal phases only differing in their handedness that do not mix and form an achiral liquid crystal phase with an entirely different structure in the contact zone.

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Linkage-length dependent structuring behaviour of bent-core molecules in helical nanostructures

Cited by 16 publications

References 32 publications

Direct Visualization of Optical Activity in Chiral Substances Using a Helical Nanofilament (B4) Liquid Crystal Phase

Direct Visualization of Optical Activity in Chiral Substances Using a Helical Nanofilament (B4) Liquid Crystal Phase

Directed self-assembly of a helical nanofilament liquid crystal phase for use as structural color reflectors

A Dual Modulated Homochiral Helical Nanofilament Phase with Local Columnar Ordering Formed by Bent Core Liquid Crystals: Effects of Molecular Chirality

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