Four-ring achiral unsymmetrical bent core molecules forming strongly fluorescent smectic liquid crystals with spontaneous polar and chiral ordered B7 and B1 phases

Deb, Rajdeep; Nath, Rahul Kanti; Paul, M. K.; Rao, N. V. S.; Tuluri, Francis; Shen, Yongqiang; Shao, Renfan; Chen, Dong; Zhu, Chenhui; Smalyukh, Ivan I.; Clark, Noel A.

doi:10.1039/c0jm01539c

Cited by 64 publications

(33 citation statements)

References 40 publications

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“…Banana-shaped molecules from two homologous series reported to exhibit the B7 phase were prepared to achieve the goal (Fig. 1A) (19)(20)(21). The molecular architectures with bent-core and flexible alkyl terminated tails exhibit smectic phases with molecules of spontaneously polar order (polar direction, p) and tilt (tilt direction, c) to make them chiral (Fig.…”

Section: Resultsmentioning

confidence: 99%

Organization of the polarization splay modulated smectic liquid crystal phase by topographic confinement

Yoon

Deb

Chen

et al. 2010

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

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Recently, the topographic patterning of surfaces by lithography and nanoimprinting has emerged as a new and powerful tool for producing single structural domains of liquid crystals and other soft materials. Here the use of surface topography is extended to the organization of liquid crystals of bent-core molecules, soft materials that, on the one hand, exhibit a rich, exciting, and intensely studied array of novel phases, but that, on the other hand, have proved very difficult to align. Among the most notorious in this regard are the polarization splay modulated (B7) phases, in which the symmetry-required preference for ferroelectric polarization to be locally bouquet-like or "splayed" is expressed. Filling space with splay of a single sign requires defects and in the B7 splay is accommodated in the form of periodic splay stripes spaced by defects and coupled to smectic layer undulations. Upon cooling from the isotropic phase this structure grows via a first order transition in the form of an exotic array of twisted filaments and focal conic defects that are influenced very little by classic alignment methods. By contrast, growth under conditions of confinement in rectangular topographic channels is found to produce completely new growth morphology, generating highly ordered periodic layering patterns. The resulting macroscopic order will be of great use in further exploration of the physical properties of bent-core phases and offers a route for application of difficult-to-align soft materials as are encountered in organic electronic and optical applications.topographical confinement | monodomain | banana shaped | anchoring L iquid crystals (LCs) of bent-core "banana-shaped" molecules have come under intense investigation following the discovery of smectic phases in which polar ordering and macroscopic chirality appear as spontaneously broken symmetries (1, 2). Among the more exotic of these are the B7 phases, in which the polarization field exhibits a periodic splay modulation, leading, in combination with the fluid smectic layering, to intricate textures in bulk samples (3-6). As for many smectics appearing upon cooling directly from the isotropic phase via a first order transition, i.e., having no intervening nematic phase, the B7s are not easily aligned into macroscopically oriented domains of any sort with the anisotropic surface treatment methods such as optical-or mechanical-rubbed polymer surfaces or obliquely deposited silicon monoxide (SiOx) (7-11) that are typically useful for aligning LCs. Topographic patterning has been demonstrated to align LCs (12-14) and has recently emerged as an effective alignment technique for both nematic and smectic LCs, and in particular for layered LC phases growing directly from the isotropic (15)(16)(17)(18).In this paper we report the successful use of topographical confinement to control the spatial organization of the B7 smectic phase, employing linear micron-scale channels of rectangular cross-section etched into the surface of silicon wafers. Smectic layer orientat...

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Section: Resultsmentioning

confidence: 99%

Organization of the polarization splay modulated smectic liquid crystal phase by topographic confinement

Yoon

Deb

Chen

et al. 2010

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

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“…[10][11][12] Recently, we reported the structure and phase behavior of two series of asymmetric as well as isomeric four-ring bentcore mesogens with an ester linkage at the molecular bend. [13] From the molecular architectural point of view, these materials deviate not only from the usual linear molecular architecture of liquid crystals (LCs), but are also quite different from the conventional bent-core molecules derived from the 1,3-phenyl ring, [14][15][16] or those based on the "hockey-stick" molecular architecture. [17][18][19] The molecules reported here are able to form smectic LC phases with spontaneously chiral and polar layers (SmCP phases); including the PSM (B7) variants.…”

Section: Introductionmentioning

confidence: 99%

Fluorescence Confocal Polarizing Microscopy of a Fluorescent Bent‐Core Liquid Crystal Exhibiting Polarization Splay Modulated (B7) Structures and Defects

et al. 2014

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The B7 phases of bent-core molecules are polarization splay modulated fluid smectics that exhibit an unusually complex variety of exotic macroscopic structures, textures, and defects visible in polarized light microscopy. Herein we describe optical studies of these structures using fluorescence confocal polarizing microscopy (FCPM) and depolarized transmission optical microscopy to probe their organization in three dimensions. These experiments utilize recently reported fluorescent bent-core molecules designed to give strong polarized fluorescence. This new bent-core molecular family provides the means for probing a variety of bent-core phases and structures by using FCPM and multiphoton fluorescence nonlinear imaging techniques. Comparative textural analysis of the B7 structures obtained using different types of imaging and the corresponding structural models are discussed.

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“…In general, a banana molecule includes five or six aromatic rings. It was also found that three-ring bent-core molecules can form LC phases [91,92], and four-ring molecules even display banana mesophases by incorporating lateral hydroxy groups [93]. This indicates the importance of lateral substituents to the design of bent-core molecules.…”

Section: General Molecular Structure Of Bent-core Lcsmentioning

confidence: 89%

Electric‐ and Light‐Responsive Bent‐Core Liquid Crystals: From Molecular Architecture and Supramolecular Nanostructures to Applications

Zhang¹

2013

Intelligent Stimuli‐Responsive Materials

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The three classic states of matter are well known and ubiquitous in everyday life: solid, liquid, and gas. Liquid crystals (LCs), an intermediate state between solid crystal and isotropic liquid, constitute a new fascinating class of condensed soft matter uniquely combining both fluidity and long-range order. The fluid-like mobility enables LCs to be switchable under external stimuli, and crystal-like long-range order bestows anisotropic physical properties on LCs. LCs can be divided into two main classes: thermotropic and lyotropic. Thermotropic LCs consist of individual molecules (or ion pairs) and exhibit phase transitions with the change of temperature. In this case, temperature is the fundamental thermodynamic factor determining mesophase formation. Lyotropic LCs are a special type of solution system that can form mesophases as a function of both temperature and concentration of LC molecules. The building block of a lyotropic phase is an aggregate (called a micelle) formed via self-assembly of many molecules (typically on the order of 100). Examples of LCs can be found both in the natural world and in technological applications. Thermotropic LCs find 189 190 ELECTRIC-AND LIGHT-RESPONSIVE BENT-CORE LIQUID CRYSTALS a wide variety of uses in displays, and an important example of lyotropic LCs is cell membranes formed by amphiphilic lipids. Surfactants in water (i.e., soap water) constitute another useful example of lyotropic LCs. Although the majority of LCs are organic molecules, there exist many LC materials incorporating metals into organic anisotropic molecules [1-3]. These organic-inorganic hybrid LC materials are described as metallomesogens and are recently called metallotropic LCs [4] as distinguished from two main LC classes. In fact, metallomesogens can be classified as either thermotropic or lyotropic LCs depending on their composition and conditions. However, it should be noted that metallomesogens offer a material platform to incorporate magnetic, electronic, optical, redox, and catalytic properties common to inorganic materials into LCs.Although thermotropic LCs have been known to scientists for over 100 years since a discovery by the Austrian botanical physiologist Friedrich Reintizer in 1888, it was only in the late 1960s that they began to be used in display applications. Today, they are best known for their exceptionally successful commercial applications in flat panel display products such as TVs, smart phones, computer displays, and digital projectors. Although today's LC display technology is becoming very advanced, LC materials used in display devices possess the simplest nematic (N) phase and their molecules have been variants on simple rod shapes (Fig. 6.1a). Besides nematic phases, LCs can exhibit other phases: smectic (Sm), columnar (Col), and cubic phases, depending on the orientational or positional orders of their molecules. Nematic phases have only long-range orientational order, smectic mesophases exhibit one-dimensional (1D) positional order and form two-dimensional (2D) layered ...

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Four-ring achiral unsymmetrical bent core molecules forming strongly fluorescent smectic liquid crystals with spontaneous polar and chiral ordered B7 and B1 phases

Cited by 64 publications

References 40 publications

Organization of the polarization splay modulated smectic liquid crystal phase by topographic confinement

Organization of the polarization splay modulated smectic liquid crystal phase by topographic confinement

Fluorescence Confocal Polarizing Microscopy of a Fluorescent Bent‐Core Liquid Crystal Exhibiting Polarization Splay Modulated (B7) Structures and Defects

Electric‐ and Light‐Responsive Bent‐Core Liquid Crystals: From Molecular Architecture and Supramolecular Nanostructures to Applications

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