Advances in Liquid Crystals

Volumes 428-429

doi: 10.4028/www.scientific.net/KEM.428-429

Paper Title Page

Authors: Sang Wook Lee, Yu Jin Na, Won Suk Choi, Sin Doo Lee
Abstract: The fundamental aspects of the wettability and the elasticity of soft matters, particularly, functional polymer solutions, lipid membranes, and biological cells in the development of new technologies are overviewed from the basic principles and underlying physics. The key concept is how to control interfacial interactions between solid substrates and soft matters through surface modification. Two representative examples are demonstrated to discuss the underlying physics behind the pattern and domain formation; one of them is multi-dimensional generation of heterogeneous organic arrays and the other is micro-patterning of red blood cells on lipid membranes
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Authors: Yuan Ming Huang
Abstract: We demonstrated that a homologous series of banana-shaped liquid crystals, 1,3-phenylene bis(4-alkyloxybenzylideneamine), could assemble themselves into various kinds of groove-free diffraction gratings when their isotropic melts were slowly cooled into mesophases between two pieces of glass substrates. The groove-free diffraction gratings included one-dimensional parallel gratings, two-dimensional crossed gratings, two-dimensional fan-shaped gratings and two-dimensional circular gratings. Characterization by means of polarized optical microscopy showed that a pattern of periodic modulation of the refractive index was developed in the thin films formed by the banana-shaped compound. Our laser light diffraction experiments confirmed that these groove-free gratings could effectively diffract the incident red light from a helium-neon laser. On the basis of the diffraction equations derived for the self-assembled groove-free optical gratings, the diffraction patterns were simulated for the parallel gratings, orthogonally crossed gratings, fan-shaped gratings and circular gratings, respectively, and good agreement was achieved. The mechanisms on the self-assembly of the banana-shaped molecules were discussed in terms of intermolecular interactions. Our work provides an alternative method for manufacturing diffraction gratings by harnessing the self-assembly of banana-shaped molecules.
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Authors: Shin Ying Lu, Liang Chy Chien
Abstract: We demonstrate a polymer-stabilized cholesteric liquid crystal (PSChLC) where the reflected color can be electrically-switched to reflect a different color at a shorter wavelength (blue-shift). A polymerizable additive formulation is used to ensure a wider range of color tuning and anisotropic reflection where on side reflects and the other side transmits the incident light in response to applied voltage. A second electrically switched color based on polymer-stabilized blue phase (PSBP) liquid crystal is also demonstrated. Applying an electric field across the cell results in a red-shift in Bragg reflected wavelength due to the electrostriction effect. These switchable color devices of are color filters and polarizers free which are suitable for electronic papers.
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Authors: S. Krishna Prasad
Abstract: Employing actinic light to alter/stabilize a particular thermodynamic phase via the photo-isomerization of the constituent molecules is an interesting tool to investigate soft matter from a new dimension. This article focuses on the influence of different parameters, such as pressure, confinement, applied electric field, etc., on the dynamics associated with both the photochemical transition driving the equilibrium nematic to the non-equilibrium isotropic phase and the thermal back relaxation recovering the nematic phase.
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Authors: Hui Zhou, Wen Hao Yu, Bi Qin Wang, Ping Hu, Ke Qing Zhao
Abstract: Pd-Cu catalyzed homocoupling reaction has been used for the synthesis of symmetrical triphenylene discotic liquid crystal dimers, [C18H6(OCnH2n+1)5(O2CC6H4C≡C-)]2 (n = 4, 5, 6, 7, 8, 9), which connected two triphenylene discogens via a long rigid spacer. The purity and structure of monomers and dimers have been characterized with 1H NMR, IR and high resolution Mass. Their fine thermal stability has been confirmed by the results of thermogravimetry analysis (TGA). Polarized optical microscopy (POM) and differential scanning calorimetry (DSC) results have shown that the monomers and dimers exhibit columnar mesophases (Col). The dimers display wide mesophase ranges and are room temperature liquid crystals, and their clearing points increased with the lengthening of peripheral alkyl chain.
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Authors: Bao You Liu, Hui Long Yang, Yi Ping Wang, Yuan Yuan Wang, Zhi Jie Wu, Fu Xiang Wei
Abstract: Sonogashira coupling of phenylacetylenes with phenyl iodides in 1-butyl-3-methyl- imidazolium bromide (BMImBr) was explored. Using CuI/Pd(PPh3)4 as a catalyst and Im as the base, the expected substituted acetylenes were obtained with good to excellent yields (61%-95%) under mild conditions (4h, 60oC). After the product was isolated, the left ionic liquid can been readily recovered and reused in the subsquent runs with almost the same efficiency. The reactivity of different iodoarenes with terminal alkynes was also discussed.
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Authors: Jie Han, Feng Yan Zhang, Juan Yu Wang
Abstract: The synthesis and characterization of a series of heterocyclic compounds 2a-2d based on 1,3,4-oxadiazole/ thiadiazole, furan and thiophene units are reported. The thermal behaviors of these compounds were investigated by means of differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and thermogravimetric analysis (TGA). The 1,3,4-thiadiazole derivative 2b exhibited enantiotropic smectic C and A mesophases with wide temperature range and good thermal stability, while all of the other compounds did not show liquid crystalline behaviors. The results indicate that 1,3,4-thiadiazole-based compounds are more beneficial to form stable mesophases than the corresponding 1,3,4-oxadiazole analogues, and the compounds with a central furan unit as the rigid core may result in the loss of the meosgenic behaviors due to the non-linear molecular structure.
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Authors: Yuan Ming Huang, Qing Lan Ma, Bao Gai Zhai
Abstract: A homologous series of three-benzene-ring containing bent-cores compounds 1,3-phenylene-bis[4-(alkylcarboyloxyl)benzylideneamine] were synthesized. In these molecules the terminal ester chains CH3(CH2)n-2COO-, where n was the number of carbon atoms in the terminal chains, were linked to the central three-benzene-ring containing bent-core. As n changed from 1-12, the melting temperatures and clearing points were in the high temperature ranges of 136-206oC. As n changed in the range of 14-19, the melting temperatures and clearing points were dramatically dropped in a low temperature ranges 60-82oC.
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