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Polarized Light Emission from Uniaxially Oriented and Polymer-Stabilized AIE Luminogen Thin Films
Koo, Jahyeon,Lim, Seok-In,Lee, Seung Hee,Kim, Jin Soo,Yu, Yeon-Tae,Lee, Cheul-Ro,Kim, Dae-Yoon,Jeong, Kwang-Un American Chemical Society 2019 Macromolecules Vol.52 No.4
<P>Organic materials with linearly polarized luminescence (LPL) properties and good processability are critical to the development of advanced optical devices. To fabricate polymer-stabilized thin films with LPL properties, dicyanodistyrylbenzene-based reactive luminogens (abbreviated as DRL) containing both vinyl and thiol units were newly synthesized. On the basis of morphological observations combined with thermal and scattering analyses, it was found that DRL has a nematic liquid crystal mesophase. DRL molecules were uniaxially oriented by surface alignment layer and stabilized by thiol-ene click reaction. Uniaxially oriented and polymer-stabilized DRL thin films showed excellent chemical resistance as well as mechanical and thermal stability due to the chemically cross-linked polymer network. The DRL polymer film exhibited strong emission at 564 nm with remarkable LPL property. The polymer-stabilized films obtained from reactive luminogens with aggregation-induced enhanced emission (AIEE) properties have great potential for the application of advanced optical devices.</P> [FIG OMISSION]</BR>
Kim, Jongyoon,Koo, Jahyeon,Park, Jimin,Jeong, Kwang-Un,Lee, Ji-Hoon Elsevier 2019 Journal of molecular liquids Vol.277 No.-
<P><B>Abstract</B></P> <P>We synthesized a new liquid crystal (LC) dopant 4-[7-(4′-Cyanobiphenyl-4-yl)hexyloxy]bezoic acid (CBO7OBA) which can form dimers by hydrogen-bonding. We mixed the hydrogen-bondable CBO7OBA dopants with commercial nematic liquid crystal (NLC) mixtures and investigated the change of the flexoelastic ratio of the mixture. The flexoelastic ratio of the CBO7OBA-doped NLC mixture was increased up to 4.7 C/Nm, while that of the pure NLC was 2.0 C/Nm at room temperature. The greater flexoelastic ratio of the CBO7OBA-doped NLC mixture is thought to be due to the bent-shape and the large dipole moment of the CBO7OBA molecules.</P> <P><B>Highlights</B></P> <P> <UL> <LI> New liquid crystalline molecule which can form bimesogen through hydrogen-bonding was synthesized. </LI> <LI> Flexoelastic ratio of the bimesogen-doped nematic liquid crystal was measured using flexoelectro-optic method. </LI> <LI> Flexoelastic ratio was increased from 2.0 C/Nm to 4.7 C/Nm after doping the bimesogen molecules. </LI> </UL> </P>
Kang, Dong-Gue,Ko, Hyeyoon,Koo, Jahyeon,Lim, Seok-In,Kim, Jin Soo,Yu, Yeon-Tae,Lee, Cheul-Ro,Kim, Namil,Jeong, Kwang-Un American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.41
<P>For the development of anisotropic thermal interface materials (TIMs), a rod-shaped reactive monomer PNP-6MA is newly designed and successfully synthesized. PNP-6MA reveals a smectic A (SmA) mesophase between crystalline (K) and isotropic (I) phases. PNP-6MA can be oriented under a magnetic field (<I>B</I> = 2 T), and its macroscopic orientation can be robustly stabilized by in situ polymerization. Even without macroscopic orientations, the fabricated thermal conducting liquid crystal (TCLC) films show the outstanding thermal conductivity of 1.21 W/m K, which is higher than conventional organic materials. The thermal conductivity of uniaxially and macroscopically oriented TCLC films can be 2.5 W/m K along the long axis of mesogenic core. The newly developed TCLC film can be used as a TIM between a high-power light-emitting diode and a heat sink.</P> [FIG OMISSION]</BR>
Photoresponsive chiral molecular crystal for light-directing nanostructures
Kim, Dae-Yoon,Yoon, Won-Jin,Choi, Yu-Jin,Lim, Seok-In,Koo, Jahyeon,Jeong, Kwang-Un The Royal Society of Chemistry 2018 Journal of Materials Chemistry C Vol.6 No.45
<P>A photoresponsive chiral molecular crystal (abbreviated as PCMC) was programmed and synthesizied by localizing a chiral isosorbide at the core between two amphiphilic azobenzene building blocks. Owing to the bent-shaped geometry, the PCMC can self-organize into helical nanoribbons with a highly ordered smectic domain. Since the PCMC has not only an intrinsic molecular chirality but also a photoresponsive molecular function, the helical nanoribbons with single handedness were transformed to flat nanobelts by irradiation with ultraviolet light. Additionally, its chiroptical properties were fully recovered to the initial state upon exposure to visible light. Fine tuning the nanoarchitectures using the remote controllable feature of the PCMC presented in this work can lead the design of novel functional materials that are potentially applicable as optical sensors and biomimetic devices.</P>
Construction of light-responsive phase chirality from an achiral macrogelator
Choi, Yu-Jin,Yoon, Won-Jin,Park, Minwook,Kang, Dong-Gue,Bang, Geukcheon,Koo, Jahyeon,Lim, Seok-In,Park, Seohee,Jeong, Kwang-Un The Royal Society of Chemistry 2019 Journal of Materials Chemistry C Vol.7 No.11
<P>To realize light-responsive phase chirality from an achiral macrogelator in the solid state, a disc-shaped achiral macrogelator (B1AZ) was newly synthesized. B1AZ was self-assembled into a lamello-columnar structure in the bulk state, while single-handed helical fibrils (<I>H</I>F) with 400 nm of helical pitch were constructed by side-by-side lateral association of achiral B1AZ molecules in carvone chiral solvents. Even after the elimination of chiral solvents, the helical morphology and its chiroptical properties were precisely preserved. However, <I>H</I>F was not sensitive to UV light due to intense lateral packing. For remote-controlling the helical morphology, a single-helix (<I>H</I>S) with an 18 nm helical pitch was formed by utilizing <I>cis</I>-B1AZ sol. Upon irradiation with UV light, <I>H</I>S was transformed into spheroids (<I>S</I>) because of the <I>trans</I>-to-<I>cis</I> photo-isomerization of the azobenzene (AZ) of B1AZ. The photo-switchable phase chirality can be applied in light-responsive smart materials.</P>