Thermal‐ and Photo‐Induced Phase‐Transition Behaviors of a Tapered Dendritic Liquid Crystal with Photochromic Azobenzene Mesogens and a Bicyclic Chiral Center

Kim, Dae‐Yoon; Lee, Sang‐Ah; Choi, Yu‐Jin; Hwang, Seok‐Ho; Kuo, Shiao‐Wei; Nah, Changwoon; Lee, Myong‐Hoon; Jeong, Kwang‐Un

doi:10.1002/chem.201303924

Cited by 46 publications

(30 citation statements)

References 51 publications

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“…This means that a highly ordered crystal (K 2 ) phase appears, forming the intracolumnar disc stacking interactions. Upon decreasing the temperature to 25 °C, diffraction peaks in the wide‐angle region are getting narrow and shifting to higher 2θ‐angles, indicating the formation of true crystal (K 1 ) phase . Since the structural change of the crystal‐to‐crystal phase transition requires a tremendous amount of energy, the molecular packing structure in the K 2 phase should resemble the K 1 phase .…”

Section: Resultsmentioning

confidence: 99%

Solid‐State Light Emission Controlled by Tuning the Hierarchical Superstructure of Self‐Assembled Luminogens

Kim

Koo

Lim

et al. 2018

Adv Funct Materials

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Solid-state luminescence is an important strategy for color generation via molecular self-assembly. Here, a new luminogen (AT 3 EMIS) containing both a rigid chromophore and a flexible dendron is designed and synthesized for multicolor emission. The emission energy of the target material is precisely controlled by adjusting three different columnar arrays through thermal and mechanical stimulation. With well-defined supramolecular organizations in different length scales, the luminescent properties of the light switch can be tuned.

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Section: Resultsmentioning

confidence: 99%

Solid‐State Light Emission Controlled by Tuning the Hierarchical Superstructure of Self‐Assembled Luminogens

Kim

Koo

Lim

et al. 2018

Adv Funct Materials

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“…To demonstrate remote‐controllable actuators, we designed and successfully synthesized a norbornene‐based polymer containing an azobenzene‐functionalized dendron ( Figure ). The targeted dendritic monomer was first synthesized by Williamson etherification of methyl gallate with azobenzene derivatives . The subsequent hydrolysis reaction provided a carboxylic acid‐modified dendron (AZ 3 D) in an aqueous base (Figure S1, Supporting Information).…”

Section: Resultsmentioning

confidence: 99%

From Smart Denpols to Remote‐Controllable Actuators: Hierarchical Superstructures of Azobenzene‐Based Polynorbornenes

Kim

Shin

Yoon

et al. 2017

Adv Funct Materials

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For the demonstration of remote-controllable actuators, a dendronized polymer (denpol) is newly designed and successfully synthesized by ringopening metathesis polymerization of azobenzene-based macromonomers. The incorporation of azobenzene mesogens into the denpols helps to construct finely tuned hierarchical superstructures with anisotropic physical properties and reversible photoisomerization. The polynorbornene backbones and azobenzene side chains in the uniaxially oriented films are aligned perpendicularly and parallel to the layer normal, respectively. Based on photoreversible actuation experiments combined with diffraction results, direct relationships between the chemical structures, hierarchical superstructures, and their corresponding photomechanical behaviors are proposed. Smart denpols possess great potential for practical applications in photoresponsive switches.

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“…Jeong and co‐workers reported a new ribbon‐shaped chiral LC dendrimer with photochromic azobenzene mesogens and an isosorbide chiral center (AZ3DLC). The presence of a bicyclic diol group at the center could provide molecular chirality and break the molecular packing symmetry.…”

Section: Photochromism In Artificial Supramolecular Self‐assembling Smentioning

confidence: 99%

Recent Progress in Photoswitchable Supramolecular Self‐Assembling Systems

Yao

Wang

et al. 2016

Advanced Optical Materials

169

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structures with response to internal factors or external environment stimuli either physically or chemically. Among different stimuli methods including temperature, pH and redox etc., light is the most attractive and convenient one with many advantages: 1) it does not introduce any foreign chemicals into the systems; 2) it can be conveniently switched on and off, and tuned precisely at different wavelengths and intensities; 3) it can be operated with high level of spatiotemporal resolution; 4) it can be conveniently applied as an orthogonal stimulus. Moreover, on the way to explore more sophisticated selforganizations under non-equilibrium conditions, light will act as more than a simple stimulus but as an energy input and medium for information, just like what happened in light-triggered or lightdriven biological processes such as vision and photosynthesis.Photochromic compounds, as one big family of photo-responsive compounds, can provide reversible switch of chemical or physical properties of supramolecular systems solely by light. Photochromism is defi ned as "reversible transformation of a chemical species induced in one or both directions by absorption of electromagnetic radiation between two forms, A and B, having different absorption spectra". [ 3 ] The key word "reversible" refl ects its signifi cant difference from irreversible photochemical processes in a broader realm of photo-responsive compounds. Depending on the relative thermal stability of the two isomers, the back reaction of photochromic compounds can be divided into T-type (thermal) photochromism and P-type (photochemical) one. Compounds with T-type photochromism are thermally unstable and revert to original thermal stable state spontaneously within milliseconds to a few minutes, while compounds with P-type photochromism are thermally stable in both states and need photo irradiation to recover. During the isomerization, the change of absorption spectra is the common but not only outcome which always accompanied by various changes in chemical or physical properties such as geometric structures, fl uorescence emission, conjugation, dipole moment, electron conductivity, electrochemical properties, and so forth. [ 4 ] Since the properties are usually switched between two distinct states, photochromic compounds are also referred to as photoswitches in many cases. These features make them good candidates for fabricating light-controlled materials [ 5 ] in various fi eldsThe rise of supramolecular chemistry has drawn great attention to the designed self-assembly of synthetic molecules. Supramolecular self-assembly has become an effi cient strategy in constructing well-ordered nanostructures using a bottom-up way in material science and has also shown its great potential in biological applications. Photochromic compounds are small organic molecules which can undergo reversible photochemical reactions between two chemical species with distinct properties. They have been incorporated into various materials for applications including optical devices, dat...

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Thermal‐ and Photo‐Induced Phase‐Transition Behaviors of a Tapered Dendritic Liquid Crystal with Photochromic Azobenzene Mesogens and a Bicyclic Chiral Center

Cited by 46 publications

References 51 publications

Solid‐State Light Emission Controlled by Tuning the Hierarchical Superstructure of Self‐Assembled Luminogens

Solid‐State Light Emission Controlled by Tuning the Hierarchical Superstructure of Self‐Assembled Luminogens

From Smart Denpols to Remote‐Controllable Actuators: Hierarchical Superstructures of Azobenzene‐Based Polynorbornenes

Recent Progress in Photoswitchable Supramolecular Self‐Assembling Systems

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