Study on Helical Structure of the B<sub>4</sub> Phase Formed from Achiral Banana-Shaped Molecule

Thisayukta, Jirakorn; Takezoe, Hideo; Watanabe, Junji

doi:10.1143/jjap.40.3277

Cited by 132 publications

(146 citation statements)

References 38 publications

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“…[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. [7,8] The bentcore molecules form well-defined smectic layers with in-plane hexatic order, the coupling of macroscopic polarization and tilt of the molecular planes making the layers chiral (Figure 1 a).…”

Section: Introductionmentioning

confidence: 86%

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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Section: Introductionmentioning

confidence: 86%

Structure of the B4 Liquid Crystal Phase near a Glass Surface

Chen¹,

Heberling²,

Nakata³

et al. 2011

ChemPhysChem

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“…[41][42][43][44][45] The polarity and chirality as well as frustration have become a world wide topics in the liquid crystalline field. 46 It should be emphasized that studies on these exotic phases start from the studies on the polymeric effects in main-chain LC polymers.…”

Section: Layer Structure Responsible For Distinct X-ray Pattern Showimentioning

confidence: 99%

Several Interesting Fields Exploited through Understanding of Polymeric Effects on Liquid Crystals of Main-Chain Polyesters

Tokita

Watanabe

2006

Polym J

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ABSTRACT:We review our experimental results on the structural characteristics of polymeric liquid crystals collected through our studies on the main-chain liquid crystalline polyesters with mesogenic biphenyl groups connected by flexible alkyl spacer. The polyesters studied, designated as BB-n where n is the number of carbon atoms in the alkyl spacer unit, form smectic mesophases. Of interest is that the type of smectic phase alters depending on the odd-even parity of n. An ordinal smectic A phase is formed by BB-n with even n, whereas BB-n with odd n forms a new type of smectic phase, so called smectic CA phase, in which the long axis of the mesogen is tilted against the layer normal and the tilting direction is opposite between neighboring layers. Finding of smectic CA phase with specific packing symmetry leads to a distinct discovery of ferroelectric and antiferroelectric phases in achiral molecular systems. In these smectic phases, the polymer chain assumes more extended conformation. Such an extended conformation, however, does not continue over the whole length of the polymer and hairpin folding arises to gain entropy. In the smectic phases, the hairpin foldings are located at a limited space, forming chain folded lamellae. Unusual shear flow orientation and anomalous crystallization behavior are explained based on the chain folded lamellar structure. Solid state morphology of liquid crystalline polymer is also presented. Since the degree of liquid crystallinity is almost 100%, the solid phase cooled through the formation of liquid crystals is composed of crystal and liquid crystal glass. Liquid crystal glass is studied and properties are discussed in a comparison with those of conventional isotropic glass.

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“…shaped molecules can be observed in their unique mesophases such as B 2 phase with electro-optical switchable property (the smectic layered chirality induced by the existence of the polar direction and the tilting molecular director with respect to the layer normal) [36][37][38][39][40] , B 4 phase with opposite optical activity (the different chiral domains formed from the helical morphology which is similar to the twist grain boundary phase), [41][42][43][44] and B 7 phase with macroscopic spiral and more complicated textures. [45][46][47][48][49] Watanabe and co-workers suggested that the asymmetric twisting conformation which is resulted from the ester linkage groups connecting the central phenyl ring with the side wings seems to be one of the origins for the formation of the helical morphology.…”

Section: Introductionmentioning

confidence: 99%

Hierarchical Superstructures with Helical Sense in Self‐Assembled Achiral Banana‐Shaped Liquid Crystalline Molecules

Lin

et al. 2008

Adv Funct Materials

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The self‐assembly of 1,3‐phenylene bis[4‐(4‐n‐heptyloxybenzoyloxy)‐benzoates] (BC7) is studied to examine the formation of helical morphologies from achiral banana‐shaped liquid crystal molecules at different self‐assembling levels. Various hierarchical superstructures including flat‐elongated lamellar crystal, left‐ and right‐handed helical ribbons, and tubular texture are observed while the BC7 molecules self‐assemble in THF/H2O solution. By contrast, only plate‐like morphology is observed in the self‐assembly of achiral linear shaped 1,4‐phenylene bis[4‐(4‐n‐heptyloxybenzoyloxy)‐benzoates] (LC7) molecules, indicating that the chirality of the self‐assembled texture is strongly dependent upon the molecular geometry of the achiral molecules. The formation of the helical superstructures, namely hierarchical chirality, is attributed to the conformational chirality from the achiral banana‐shaped liquid crystalline molecules, as evidenced by significant optical activity in time‐resolved circular dichroism experiments. Selective area electron diffraction is performed to examine the structural packing of the hierarchical superstructures. As observed, the molecular disposition of the lamellar crystal is identical to that of the helical superstructure. Also, the diffraction patterns of the helical superstructures appeared arc‐like patterns consisting of a series of reflections, suggesting that the helical morphology resulted from the curving of the lamellar crystals through a twisting and bending mechanism. Consequently, the model of molecular disposition in the self‐assembled helical superstructures from the achiral banana‐shaped molecules is proposed. The morphological evolution in this study may provide further understanding with respect to the chiral information transfer mechanism from specific molecular geometry to hierarchical chirality in the achiral banana‐shaped molecules.

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Study on Helical Structure of the B₄ Phase Formed from Achiral Banana-Shaped Molecule

Cited by 132 publications

References 38 publications

Structure of the B4 Liquid Crystal Phase near a Glass Surface

Structure of the B4 Liquid Crystal Phase near a Glass Surface

Several Interesting Fields Exploited through Understanding of Polymeric Effects on Liquid Crystals of Main-Chain Polyesters

Hierarchical Superstructures with Helical Sense in Self‐Assembled Achiral Banana‐Shaped Liquid Crystalline Molecules

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Study on Helical Structure of the B4 Phase Formed from Achiral Banana-Shaped Molecule

Cited by 132 publications

References 38 publications

Structure of the B4 Liquid Crystal Phase near a Glass Surface

Structure of the B4 Liquid Crystal Phase near a Glass Surface

Several Interesting Fields Exploited through Understanding of Polymeric Effects on Liquid Crystals of Main-Chain Polyesters

Hierarchical Superstructures with Helical Sense in Self‐Assembled Achiral Banana‐Shaped Liquid Crystalline Molecules

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Study on Helical Structure of the B₄ Phase Formed from Achiral Banana-Shaped Molecule