Phase behaviour and Janus hierarchical supramolecular structures based on asymmetric tapered bisamide

Lee

Jung

et al. 2016

Sci Rep

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For the advancement in multi-stimuli responsive optical devices, we report the elaborate molecular engineering of the dual photo-functionalized amphiphile (abbreviated as AZ1DA) containing both a photo-isomerizable azobenzene and a photo-polymerizable diacetylene. To achieve the efficient photochemical reactions in thin solid films, the self-assembly of AZ1DA molecules into the ordered phases should be precisely controlled and efficiently utilized. First, the remote-controllable light shutter is successfully demonstrated based on the reversible trans-cis photo-isomerization of azobenzene group in the smectic A mesophase. Second, the self-organized monoclinic crystal phase allows us to validate the photo-polymerization of diacetylene moiety for the photo-patterned thin films and the thermo-responsible color switches. From the demonstrations of optically tunable thin films, it is realized that the construction of strong relationships between chemical structures, molecular packing structures and physical properties of the programmed molecules is the core research for the development of smart and multifunctional soft materials.

Section: Resultssupporting

confidence: 75%

Photochemical Isomerization and Topochemical Polymerization of the Programmed Asymmetric Amphiphiles

Lee

Jung

et al. 2016

Sci Rep

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“…Note that the lower d ‐spacing values of AZ 3 DLC molecule indicative of either a tilted arrangement along the long axis of the smectic phase or interdigitaion of the smectic layers 11. However, the q ‐values of low angle diffractions are 1:2:3 and the broad scattering halo (liquid‐like lateral short‐range ordering within the layer) is detected in the high‐angle region 12. It is realized that AZ 3 DLC keeps the ribbon‐shaped chiral dendritic conformation in the presence of a bicyclic diol center as a chiral group between the dendronized azobenzene moieties.…”

Section: Resultsmentioning

confidence: 97%

“…[11] However, the q-values of low angle diffractions are 1:2:3 and the broad scattering halo (liquid-like lateral short-range ordering within the layer) is detected in the high-angle region. [12] It is realized that AZ 3 DLC keeps the ribbon-shaped chiral dendritic conformation in the presence of a bicyclic diol center as a chiral group between the dendronized azobenzene moieties. From the experimental results and careful analysis, AZ 3 DLC should be a low-ordered chiral smectic (Sm*) LC phase between 77 and 121 8C.…”

Section: Resultsmentioning

confidence: 99%

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

Lee

Choi

et al. 2014

Chemistry A European J

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A ribbon-shaped chiral liquid crystalline (LC) dendrimer with photochromic azobenzene mesogens and an isosorbide chiral center (abbreviated as AZ3 DLC) was successfully synthesized and its major phase transitions were studied by using differential scanning calorimetry (DSC) and linear polarized optical microscopy (POM). Its ordered structures at different temperatures were further identified through structure-sensitive diffraction techniques. Based on the experimental results, it was found that the AZ3 DLC molecule exhibited the low-ordered chiral smectic (Sm*) LC phase with 6.31 nm periodicity at a high-temperature phase region. AZ3 DLC showed the reversible photoisomerization in both organic solvents and nematic (N) LC media. As a chiral-inducing agent, it exhibited a good solubility, a high helical-twisting power, and a large change in the helical-twisting power due to its photochemical isomerization in the commercially available N LC hosts. Therefore, we were able to reversibly "remote-control" the colors in the whole visible region by finely tuning the helical pitch of the spontaneously formed helical superstructures.

“…The origins of two sets of diffractions need to be resolved by further 2D SAXS experiments. 28,29 The shifting and narrowing of the high-angle scattering halo during cooling indicate the increase of the correlation length and the closer molecular lateral packing. Upon further cooling to 25 °C, the 1D SAXS peak with the d spacing = 7.18 nm slightly shifts to the d spacing = 7.28 nm in the 1D SAXS patterns (Figure 3a), indicating the formation of highly ordered phase structures.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Self-Assembled Hierarchical Superstructures from the Benzene-1,3,5-Tricarboxamide Supramolecules for the Fabrication of Remote-Controllable Actuating and Rewritable Films

Choi

ACS Appl. Mater. Interfaces

Park

et al. 2016

Self Cite

The well-defined hierarchical superstructures constructed by the self-assembly of programmed supramolecules can be organized for the fabrication of remote-controllable actuating and rewritable films. To realize this concept, we newly designed and synthesized a benzene-1,3,5-tricarboxamide (BTA) derivative (abbreviated as BTA-3AZO) containing photoresponsive azobenzene (AZO) mesogens on the periphery of the BTA core. BTA-3AZO was first self-assembled to nanocolumns mainly driven by the intermolecular hydrogen-bonds between BTA cores, and these self-assembled nanocolumns were further self-organized laterally to form the low-ordered hexagonal columnar liquid crystal (LC) phase below the isotropization temperature. Upon cooling, a lamello-columnar crystal phase emerged at room temperature via a highly ordered lamello-columnar LC phase. The three-dimensional (3D) organogel networks consisted of fibrous and lamellar superstructures were fabricated in the BTA-3AZO cyclohexane-methanol solutions. By tuning the wavelength of light, the shape and color of the 3D networked thin films were remote-controlled by the conformational changes of azobenzene moieties in the BTA-3AZO. The demonstrations of remote-controllable 3D actuating and rewritable films with the self-assembled hierarchical BTA-3AZO thin films can be stepping stones for the advanced flexible optoelectronic devices.