Physical gels made of liquid crystalline B4 phase

Zep, Anna; Salamończyk, Mirosław; Vaupotič, Nataša; Pociecha, Damian; Górecka, Ewa

doi:10.1039/c3cc41225c

Cited by 54 publications

(55 citation statements)

References 22 publications

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“…The correlation length is about 20 nm. The additional smaller peaks at q 2 = 0.276 Å −1 and q 3 = 0.414 Å −1 are harmonics of the first peak indicating the lamellar structure of the HNF phase …”

Section: Resultsmentioning

confidence: 95%

“…The collected TEM images of the unichiral materials show structures typical for HNF phases ( Figure ), where the twisted ribbons are made of a several layers perpendicular to the local twist axis . Due to the smectic character of the HNF phase, the layers work as a sponge and organogels are observed . The formation of HNFs starts on the layer edges (Figure a).…”

Section: Resultsmentioning

confidence: 99%

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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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Section: Resultsmentioning

confidence: 95%

Section: Resultsmentioning

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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“…The B4 phase responds to the imperative to grow in nanometer-scale channels by growing single HNFs in each channel, a robust outcome that is generic, relying only on the phase structure and not on the specific details of the LC molecular structure. The very low solubility of all but other bent core molecules within the HNF layering (19,33) enables the growth of channels with virtually any dopant deposited in the chiral channels from an initial B4 host/dopant mixture.…”

Section: Resultsmentioning

confidence: 99%

“…In this case the HNF growth will be very fast, with the released heat conducted to the cold end by the pore walls. Within a pore with a growing filament, the combination of heat release from growth and the isothermal boundary condition produces a strong tendency for growth to occur near the pore wall, where the principal heat flux is into the wall, effectively thermally short-circuiting the tip-splitting process, similar to the HNF growth in a solvent medium (33). This condition also changes the basic growth mode of the filaments from the twisted ribbon mode having the centroid of the filament along a straight line to the telephone cord mode where the centroid is on a helical line, enabling the growing filament to remain in contact with the pore wall as it grows along the pore.…”

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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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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“…1f) that is completely homochiral, that is, every HNF grown in a given domain has the same handedness 45,46 . In each chiral domain, the guest material is nanoconfined to the pores of the HNF network, which has a large surface-area-to-volume ratio (B100 m 2 cm À 3 , comparable to aerogel) 40,41 . This geometry suggests that HNF networks might be useful in chiral separations or catalysis 47 , if the appropriate chemical distinctions can be exhibited by the HNF surface.…”

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confidence: 99%

Diastereomeric liquid crystal domains at the mesoscale

et al. 2015

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In many technologies used to achieve separation of enantiomers, chiral selectors are designed to display differential affinity for the two enantiomers of a chiral compound. Such complexes are diastereomeric, differing in structure and free energy for the two enantiomers and enabling chiral discrimination. Here we present evidence for strong diastereomeric interaction effects at the mesoscale, manifested in chiral liquid crystal guest materials confined in a chiral, nanoporous network of semi-crystalline helical nanofilaments. The nanoporous host is itself an assembly of achiral, bent-core liquid crystal molecules that phase-separate into a conglomerate of 100 micron-scale, helical nanofilament domains that differ in structure only in the handedness of their homogeneous chirality. With the inclusion of a homochiral guest liquid crystal, these enantiomeric domains become diastereomeric, exhibiting unexpected and markedly different mesoscale structures and orientation transitions producing optical effects in which chirality has a dominant role.

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Physical gels made of liquid crystalline B4 phase

Cited by 54 publications

References 22 publications

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

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

Multistep hierarchical self-assembly of chiral nanopore arrays

Diastereomeric liquid crystal domains at the mesoscale

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