Induction of ‘banana phases’ in binary systems composed of bent-core and calamitic mesogen

Haddawi, S.; Tamba, Maria-Gabriela; Pelzl, G.; Weißflog, W.; Baumeister, Ute

doi:10.1039/b916685h

Cited by 8 publications

(2 citation statements)

References 39 publications

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“…The modular conception does not need such high expenditure of synthetic work. Broad heterophasic ranges in the diagrams show a disadvantage of this approach [49][50][51][52][53][54][55].…”

Section: Introductionmentioning

confidence: 99%

Banana-calamitic Dimers: Further Variations of the Bent-core Mesogenic Unit

et al. 2014

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Banana-calamitic dimers are a topic in the field of bent-core mesogens. New materials were prepared by chemical variations at the bent-core fragment that is by a cyano group terminally attached to the bent-core fragment, by lateral substitution with a chlorine atom and methyl group, respectively, and by increasing the number of phenyl rings from five to six. The bent-core and the calamitic mesogenic moieties are connected by aliphatic spacers of different length. The materials were investigated by optical microscopy, DSC, X-ray diffraction studies and electro-optical measurements. This way nematic, smectic and various types of polar columnar phases have been characterized. The low temperature phase in a sequence of two nematic phases exhibiting different properties can be classified as a nematic twist-bend phase. Such NTB phases are only formed if a bend exists along the molecular long axes. This prerequisite can be doubly achieved in banana-calamitic dimers: by the intrinsic bend of one of the mesogenic fragments and by an odd-numbered spacer.

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“…The modular conception does not need such high expenditure of synthetic work. Broad heterophasic ranges in the diagrams show a disadvantage of this approach [49][50][51][52][53][54][55].…”

Section: Introductionmentioning

confidence: 99%

Banana-calamitic Dimers: Further Variations of the Bent-core Mesogenic Unit

et al. 2014

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“…To overcome these problems and regulate the temperature range and some material parameters of the liquid crystalline phases, it has been suggested to mix BC and calamitic compounds. As a matter of fact, in recent years the polymorphism of binary systems composed of a BC and a rodlike mesogen has been extensively studied with the aim of investigating the effect of mixing these two types of compounds on mesophase formation, including the induction of new mesophases. − These systems have shown interesting properties such as the induction of anticlinic order (SmC A or SmC A *) over synclinic order (SmC or SmC*) in smectics, ,,,, the induction of banana phases, ,,,, and a complete miscibility of smectic bent-core and nematic rod-shaped substances . These mixtures have been mainly characterized by optical microscopy, DSC, and X-ray diffraction measurements, and the induction of anticlinic (SmC A ) ordering in an untilted smectic (SmA) phase has also been proven by Monte Carlo simulations .…”

Section: Introductionmentioning

confidence: 99%

Orientational Order, Molecular Organization, and Dynamics in Mixtures of Bent-Core and Rod-Shaped Mesogens: A ²H NMR Study

et al. 2010

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Mixtures of a bent-core mesogen (ClPbis10BB) and a calamitic mesogen (6OO8), showing a nematic phase over the entire compositional range and one or two smectic phases (namely, SmA, SmC, or SmC(A)) below the nematic one over a wide concentration range, were investigated by means of (2)H NMR spectroscopy, exploiting selectively deuterated isotopomers of both mesogens. The analysis of (2)H NMR spectra recorded in the liquid crystalline phases on several representative mixtures gave information on the orientational order properties and the molecular organization within the phases as well as on the alignment properties upon application of a magnetic field. On the other hand, the analysis of (2)H longitudinal relaxation times (T(1Z) and T(1Q)) in 6OO8-d(2)/ClPbis10BB mixtures and pure 6OO8-d(2) allowed the influence of the bent-core mesogen on the dynamics of the calamitic one to be highlighted.

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Laterally Alkyl‐ and Aryl‐Substituted, Swallow‐Tailed, and Polycatenar Mesogens: Structural Features and Functionalities

Weißflog

2014

Handbook of Liquid Crystals

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Long‐chain groups additionally attached to calamitic mesogens change the shape of the molecules and, therefore, their attractive and repulsive interactions. While compounds bearing lateral alkyl groups mostly exhibit nematic phases, lateral substitution with aryl‐containing groups means a qualitative jump by special packing in layer structures. Polycatenar mesogens can be wedge or dumbbell shaped depending on the number and positions of hydrocarbon chains at one or both terminal positions. Phasmidic and double‐swallow‐tailed mesogens are not able to exhibit smectic A phases for steric reasons, which can be induced, however, in mixtures with small rodlike molecules. Lateral alkyl chains attached to bent‐core mesogens reduce the tendency to form polar switchable layer phases, whereas polycatenar bent molecules form columnar structures. Equipping the molecules under discussion with functional groups in any ω‐standing position allows the lateral or terminal connection of mesogens, for example, to dendrimers, polymers, or metallic surfaces such as gold. In general, increasing the number of aliphatic chains often decreases melting points, increases solubility, and, therefore, allows better processability of functional materials.

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Induction of ‘banana phases’ in binary systems composed of bent-core and calamitic mesogen

Cited by 8 publications

References 39 publications

Banana-calamitic Dimers: Further Variations of the Bent-core Mesogenic Unit

Banana-calamitic Dimers: Further Variations of the Bent-core Mesogenic Unit

Orientational Order, Molecular Organization, and Dynamics in Mixtures of Bent-Core and Rod-Shaped Mesogens: A ²H NMR Study

Laterally Alkyl‐ and Aryl‐Substituted, Swallow‐Tailed, and Polycatenar Mesogens: Structural Features and Functionalities

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Induction of ‘banana phases’ in binary systems composed of bent-core and calamitic mesogen

Cited by 8 publications

References 39 publications

Banana-calamitic Dimers: Further Variations of the Bent-core Mesogenic Unit

Banana-calamitic Dimers: Further Variations of the Bent-core Mesogenic Unit

Orientational Order, Molecular Organization, and Dynamics in Mixtures of Bent-Core and Rod-Shaped Mesogens: A 2H NMR Study

Laterally Alkyl‐ and Aryl‐Substituted, Swallow‐Tailed, and Polycatenar Mesogens: Structural Features and Functionalities

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Orientational Order, Molecular Organization, and Dynamics in Mixtures of Bent-Core and Rod-Shaped Mesogens: A ²H NMR Study