Long‐Lived Supramolecular Helices Promoted by Fluorinated Photoswitches

Huang, He; Orlova, Tetiana; Matt, Benjamin; Katsonis, Nathalie

doi:10.1002/marc.201700387

Cited by 29 publications

(22 citation statements)

References 34 publications

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“…Potential applications of such nanodevices powered by sunlight may range from autonomous self‐propelling machines to self‐cleaning surfaces. Supramolecular helicity in nonpolymeric liquid crystals can be also controlled with light (Figure b) …”

Section: Photoresponsive Materials and Nanostructuresmentioning

confidence: 99%

Recent Implementations of Molecular Photoswitches into Smart Materials and Biological Systems

Pianowski

2019

Chemistry A European J

273

226

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Light is a nearly ideal stimulus for molecular systems. It delivers information encoded in the form of wavelengths and their intensities with high precision in space and time. Light is a mild trigger that does not permanently contaminate targeted samples. Its energy can be reversibly transformed into molecular motion, polarity, or flexibility changes. This leads to sophisticated functions at the supramolecular and macroscopic levels, from light‐triggered nanomaterials to photocontrol over biological systems. New methods and molecular adapters of light are reported almost daily. Recently reported applications of photoresponsive systems, particularly azobenzenes, spiropyrans, diarylethenes, and indigoids, for smart materials and photocontrol of biological setups are described herein with the aim to demonstrate that the 21st century has become the Age of Enlightenment—“Le siècle des Lumières”—in molecular sciences.

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Section: Photoresponsive Materials and Nanostructuresmentioning

confidence: 99%

Recent Implementations of Molecular Photoswitches into Smart Materials and Biological Systems

Pianowski

2019

Chemistry A European J

273

226

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“…One of the easiest ways to obtain the cholesteric mesophase is by doping the nematic matrix with chiral components (Figure ). Variation of structure of chiral molecules by external stimuli leading, for examples, to the photoisomerization, is effectively used for fine tuning of the helix pitch . In addition, the application of an electric field also provides a convenient opportunity to change optical properties of the CLC phase .…”

Section: Introductionmentioning

confidence: 99%

Cholesteric Liquid Crystal Materials for Tunable Diffractive Optics

Ryabchun

Bobrovsky

2018

Advanced Optical Materials

185

106

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refractive, diffraction and optical fiber components. In particular, diffraction grating (DG) is one of the key elements for the design and creation of modern optoelectronic devices. One of the most prominent materials for the creation of DGs is liquid crystals. The main feature of these systems is that liquid crystals combine properties such as optical anisotropy inherent for crystals and molecular mobility. High sensitivity to an external field, in particular to an electric field, makes liquid crystals very useful for the creation of DGs with tunable properties. The combination of these properties enables easy control of optical characteristics of such systems and opens wide perspectives for the design of new materials for diffractive optics.Among the different types of liquid crystalline (LC) phases, cholesteric liquid crystal (CLC) phase possesses intrinsic periodicity in the form of the helical supramolecular structure (Figure 1). With the realization of definite alignment conditions, this periodicity has been exploited for generation of DGs. [8,9] Another remarkable feature of the cholesteric mesophase is selective light reflection with the reflection wavelength determined by the simple Equation (1) where n is the average refractive index, and P is the helix pitch. The specific value of helix pitch depends on the chemical structure of the molecules forming the cholesteric phase and concentration of chiral moieties. One of the easiest ways to obtain the cholesteric mesophase is by doping the nematic matrix with chiral components (Figure 1). Variation of structure of chiral molecules by external stimuli leading, for examples, to the photoisomerization, is effectively used for fine tuning of the helix pitch. [10][11][12][13][14][15][16][17] In addition, the application of an electric field also provides a convenient opportunity to change optical properties of the CLC phase. [18][19][20][21] These unique properties enable to design a great variety of optical elements and devices based on CLC layers, films, or cells. Among them it is necessary to mention the media for photo-optical data recording, [22][23][24][25] electrically switchable mirrors, [26,27] optically controllable linearpolarization rotators, [28] coatings with controllable friction and adhesion, [29] materials for display technology, [23,30] secure Modern optics and photonics constantly require break-through materials and designs in order to achieve miniature, lightweight, highly tunable, and effective optical devices. One of the basic optical components is the diffraction grating (DG), widely used for the dispersion of light, beam steering, etc. This review gathers research efforts on diffractive optical elements based on cholesteric liquid crystal (CLC) materials with a supramolecular helical architecture. All main types and fabrication approaches of periodic diffractive structures from CLCs are classified and described. Key optical properties of DGs, their advantages and drawbacks are considered. Special attention is paid on the tunability of DG...

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“…An efficient method widely used to prepare CLCs is doping nematic LC mixtures with chiral additives that induce a helical structure [2,8]. For photosensitive chiral dopants (photoswitches), their helical twisting power and thus the CLC equilibrium helix pitch P 0 can be controlled by light through photoinduced changes in chiral molecular switch conformation that influence the LC's helical twisting power [11][12][13][14][15][16][17][18]. Phototunability of the helix pitch leads to a variety of technologically promising effects such as the phototunable selective reflection, i.e.…”

Section: Introductionmentioning

confidence: 99%

Multiple minimum-energy paths and scenarios of unwinding transitions in chiral nematic liquid crystals

Tenishchev¹,

Kiselev²,

Ivanov³

et al. 2019

Phys. Rev. E

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We apply the minimum energy paths (MEPs) approach to study the helix unwinding transition in chiral nematic liquid crystals. A mechanism of the transition is determined by a MEP passing through a first order saddle point on the free energy surface. The energy difference between the saddle point and the initial state gives the energy barrier of the transition. Two starting approximations for the paths are used to find the MEPs representing different transition scenarios: (a) the director slippage approximation with in-plane helical structures; and (b) the anchoring breaking approximation that involves the structures with profound out-of-plane director deviations. It is shown that, at sufficiently low voltages, the unwinding transition is solely governed by the director slippage mechanism with the planar saddle point structures. When the applied voltage exceeds its critical value below the threshold of the Fréedericksz transition, the additional scenario through the anchoring breaking transitions is found to come into play. For these transitions, the saddle point structure is characterized by out-of-plane deformations localized near the bounding surface. The energy barriers for different paths of transitions are computed as a function of the voltage and the anchoring energy strengths. * tenischev.

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Long‐Lived Supramolecular Helices Promoted by Fluorinated Photoswitches

Cited by 29 publications

References 34 publications

Recent Implementations of Molecular Photoswitches into Smart Materials and Biological Systems

Recent Implementations of Molecular Photoswitches into Smart Materials and Biological Systems

Cholesteric Liquid Crystal Materials for Tunable Diffractive Optics

Multiple minimum-energy paths and scenarios of unwinding transitions in chiral nematic liquid crystals

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