Spontaneous helix formation in smectic liquid crystals comprising achiral molecules

Sekine, Tomoko; Niori, Teruki; Watanabe, Junji; Furukawa, T.; Choi, Suk–Won; Takezoe, Hideo

doi:10.1039/a702026k

Cited by 186 publications

(134 citation statements)

References 6 publications

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“…Our choice for crystalline component is the recently characterized helical nanofilament (HNF) phase of bent-core mesogenic molecules, in which molecular monolayers grow from an isotropic melt or higher temperature LC phase in the form of linear HNFs made up of twisted crystalline monolayer ribbons (16,17). This growth mode is very robust, filling space with close packed parallel arrays of HNFs in the neat LC material, or forming porous networks of uniformly structured HNFs in mixtures, even at low concentration.…”

Section: Resultsmentioning

confidence: 99%

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Multistep hierarchical self-assembly of chiral nanopore arrays

Kim

Lee

Shin

et al. 2014

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

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A series of simple hierarchical self-assembly steps achieve selforganization from the centimeter to the subnanometer-length scales in the form of square-centimeter arrays of linear nanopores, each one having a single chiral helical nanofilament of large internal surface area and interfacial interactions based on chiral crystalline molecular arrangements.aluminum oxide | liquid crystal | chirality | nanoconfinement | bent-core C ontrolled nanoscale self-assembly (SA) is one of the most important subjects in chemistry, physics, and materials science and technology. Currently, soft matter systems such as block copolymers (BCPs), biomaterials, colloids, supramolecules, and liquid crystals (LCs) are widely explored as building blocks for self-assembly because of their diverse themes of nanostructural organization (1-3). Of particular interest in this effort are nanostructures that are hierarchically SA over a broad range of length scales, because these both advance basic SA science and promise practical uses in a broad array of materials applications (4). Here we present a composite nanomaterial system based on hierarchically template-assisted self-assembly (TSA) wherein, in absence of any predisposed pattern, a series of hierarchical steps spontaneously produces, over square centimeter areas, nanopore arrays with large internal surface areas of chiral crystal interfaces.This system is based on the marriage of two robust SA scenarios: (i) the formation of films of Al 2 O 3 populated with arrays of nanometer-scale pores by the anodic oxidation of aluminum, combined with (ii) the helical crystalline nanofilament formation of the B4 phase of bent-core mesogenic molecules (4). Anodic aluminum oxide (AAO) films are one of the most widely used nanoporous media, spontaneously forming uniform cylindrical pores, 5-450 nm in diameter and many microns long, with a high areal density (∼10 9 pores/cm 2 ) and low polydispersity in size (Materials and Methods) (5-7). Such AAO pores have been used as templates for the organization of soft matter nanostructures, such as BCP lamellae, cylinders, and other structures (8-10). In these and other AAO-based self-assembled nanosystems, fabrication extends down to the mesoscopic-length scales, the interfaces produced being fluid or amorphous solid structures. Approaches for generating intrapore interfaces with the controlled atom-scale organization required for many applications, for example, the electrodeposition of crystals (11,12), generally plug the pores. We sought to explore systems that combined robust crystalline ordering with a definitive crystal morphology that would enable the fabrication by SA of clear channels with crystal interfaces running through the length of the AAO pores. The helical nanofilaments reported here represent a striking realization of this goal, promising a host of chemical and photonic applications, for example in nonlinear optics (13)(14)(15).

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Section: Resultsmentioning

confidence: 99%

“…1 for 1,3-phenylenebis[4-(4-nonyloxyphenyliminonetyl)benzoate] (NOBOW), the well-studied bent-core molecule used here (16,17). NOBOW has two rigid arms (c: rigid aromatic core parts) and two tails (t: aliphatic groups) connected by the center aromatic ring.…”

Section: Resultsmentioning

confidence: 99%

Multistep hierarchical self-assembly of chiral nanopore arrays

Kim

Lee

Shin

et al. 2014

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

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“…[1][2][3] The formation of chiral smectic phases has been a key feature of achiral, banana-shaped molecules, with spontaneous symmetry breaking originally described in the B2 phase of P-9-OPIMB, also known as NOBOW. [4] The first observation of macroscopic chiral domains, however, was in the B4 phase of P-9-OPIMB homologs, [5] where large left-and right-handed chiral domains were distinguished under decrossed polarizer and analyzer. These domains immediately suggested some kind of helical structure [6] and it has since been confirmed that left-and right-handed helical nanofilaments are the structural basis of the B4 phase.…”

Section: Introductionmentioning

confidence: 99%

Structure of the B4 Liquid Crystal Phase near a Glass Surface

Chen¹,

Heberling²,

Nakata³

et al. 2011

ChemPhysChem

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The B4 liquid crystal phase of bent-core molecules, a smectic phase of helical nanofilaments, is one of the most complex hierarchical self-assemblies in soft materials. We describe the layer topology of the B4 phase of mesogens in the P-n-OPIMB homologous series near the liquid crystal/glass interface. Freeze-fracture transmission electron microscopy reveals that the twisted layer structure of the bulk is suppressed, the layers instead forming a structure with periodic layer undulations, with the topography depending on the distance from the glass. The surface layer structure is modeled as parabolic focal conic arrays generated by equidistant parabolas whose foci are defect lines along the glass surface. Nucleation and growth of toric focal conics near the glass substrate is also observed. Although the growth of twisted nanofilaments, the usual manifestation of structural chirality in the B4 phase, is suppressed near the surface, the smectic layers are intrinsically chiral, and the helical filaments that form on top of them grow with specific handedness.

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“…[1][2][3] Among them, numerous Schiff base type compounds show rich polymorphism of mesophases. [4] Although most of the materials have alkyl or alkyloxy terminal chains, there are examples with terminal chains containing sulfur, [5] carbonyl, [6] carbonate, [7] or carboxylate [8] moieties. The effect of the connecting groups on the phase behavior was also investigated in detail, and it was found that the sequence of the connecting groups has a decisive role on the mesophase formation.…”

Section: Introductionmentioning

confidence: 99%

Intercalated Smectic A Phases in Banana‐Shaped Liquid Crystals with Carbonate End Groups

et al. 2006

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Novel, symmetrical, bent-core mesogens, namely substituted 1,3-phenylenebis{4'-[(ethoxycarbonyl)oxy]-1,1'-biphenyl}-4-carboxylates, are prepared with carbonate groups at both ends of the molecules. The mesophase properties are investigated for different electron-donating and -withdrawing substituents connected to the central ring at different positions. These compounds exhibit nematic and/or smectic A intercalated (SmA(int)) mesophases. Electro-optical studies show a very significant electric-field-induced biaxiality that is fast (<1 ms) and large (0.03) associated with a high birefringence (0.33 at 500 nm, 10 V mum(-1) field) for the unsubstituted analogue. For one substance this effect is observable from above 100 degrees C down to room temperature. Such electric-field-induced biaxiality may find practical applications in fast electro-optic modulation devices.

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Spontaneous helix formation in smectic liquid crystals comprising achiral molecules

Cited by 186 publications

References 6 publications

Multistep hierarchical self-assembly of chiral nanopore arrays

Multistep hierarchical self-assembly of chiral nanopore arrays

Structure of the B4 Liquid Crystal Phase near a Glass Surface

Intercalated Smectic A Phases in Banana‐Shaped Liquid Crystals with Carbonate End Groups

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