• Title, Summary, Keyword: nematic phase

Search Result 99, Processing Time 0.069 seconds

The Physical Properties of Thermotropic Side-Chain Triblock Copolymers of n-Butyl Acrylate and a Comonomer with Azobenzene Group

  • Dan, Kyung-Sik;Kim, Byoung-Chul;Han, Yang-Kyoo
    • Macromolecular research
    • /
    • v.17 no.5
    • /
    • pp.313-318
    • /
    • 2009
  • The side chain liquid crystal triblock copolymers (TBCs), which underwent phase transitions below their decomposition temperature, were prepared by copolymerization of poly(n-butyl acrylate) and a comonomer containing the mesogenic azobenzene group. The physical properties of TBCs in the distinctive transition temperature ranges were investigated in terms of the liquid crystal (LC) content in the copolymers. The phase transition temperatures traced optically, thermally and rheologically were well coincided one another and clearly exhibited the phase transition of smectic-nematic-isotropic with increasing temperature. In the smectic phase, increasing temperature made the liquid crystal system more elastic, but viscosity (${\eta}'$) remained almost constant. In the nematic phase, increasing temperature abruptly decreased ${\eta}'$ and G', ultimately leading to isotropic phase. Both smectic and nematic phases exhibited Bingham viscosity behavior but the former gave much greater yield stress at the same LC content.

Theoretical Prediction of the Thermodynamic Properties of Liquid-Crystalline p-Azoxyanisole (액정 p-Azoxyanisole의 열역학적 성질에 대한 이론적인 예측)

  • Youngkyu Do;Mu Shik Jhon;Taikyue Ree
    • Journal of the Korean Chemical Society
    • /
    • v.20 no.2
    • /
    • pp.118-128
    • /
    • 1976
  • The significant structure theory of liquids and the Bragg-Williams approximation of phase transition theory have been applied to the calculation of the thermodynamic properties of p-azoxyanisole which exhibits a liquid crystal phase of the nematic type. The isotropic phase was treated as a normal liquid; and for the nematic phase, in addition to its liquidity, the effect due to the arrangement of molecular-dipoles was considered. The liquidity of the p-azoxyanisole was described by the significant structure theory of liquids, and the Bragg-Williams approximation was used to consider the effect due to the arrangement of molecular-dipoles. The molar volume, vapor pressure, heat capacity at constant pressure, thermal expansion coefficient, compressibility, entropy and enthalpy change at the nematic-isotropic phase transition point, absolute entropy, and absolute Helmholtz free energy were calculated over the temperature range of the nematic and isotropic phases. The calculated results of the thermodynamic properties were compared with the experimental data.

  • PDF

Thermo-Recording for The Composite System of (Disk-Like Molecules and Liquid Crystals)

  • Jeong, Hwan-Kyeong
    • Journal of the Korean Applied Science and Technology
    • /
    • v.19 no.3
    • /
    • pp.245-249
    • /
    • 2002
  • A (disk-like liquid crystal (DLC) monomer/liquid crystals(LCs)/chiral dopant/dichroic dye) composite was irradiated with ultraviolet (UV) light. The (DLC network/LCs/chiral dopant/dichroic dye) was formed in the homeotropically oriented smectic A(SA) phase by the surface orientation treatment and the electric field. A focal-conic texture exhibiting strong light scattering appeared in the heat-induced chiral nematic phase(N${\ast}$) of the composite upon heating. Thermo-recording in the composite system has been realized by using a He-Ne laser. The laser irradiation was induced the phase transitions from SA phase to chiral nematic(N${\ast}$) phase in the composite system.

Holographic s forage of random-phase-modulation-added binary amplitude data (랜덤 위상변조가 가미된 이진 진폭 데이터 영상의 홀로그래픽 저장)

  • 오용석;신동학;장주석
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
    • /
    • /
    • pp.489-492
    • /
    • 2001
  • We studied a method to use a variable discrete random phase mask in 2-D binary data representation for efficient holographic data storage. The variable phase mask is realized by use of a twisted nematic liquid crystal display.

  • PDF

Formation of 3-Dimensional Networks of Colloidal Particles in a Nematic Host

  • West, John L.;Glushchenko, Anatoliy;Zhang, Ke;Reznikov, Yuri
    • 한국정보디스플레이학회:학술대회논문집
    • /
    • /
    • pp.191-192
    • /
    • 2002
  • We reported pushing of colloidal particles by a moving isotropic-nematic phase boundary. Here, we report tailoring the structure of 3-dimensional networks formed by these particles by adjusting the rate of phase transition and by application of an electric field. The resulting networks affect the electro-optic performance of liquid crystal devices.

  • PDF

Theoretical Estimates for Elastic Properties of Biaxial Nematics

  • Allender, David W.
    • 한국정보디스플레이학회:학술대회논문집
    • /
    • /
    • pp.195-198
    • /
    • 2005
  • Using theoretical analysis based on Landau theory, it is shown that only five phenomenological parameters are necessary to describe the twelve bulk elastic constants of a biaxial nematic phase. Further, a simple method for determining the values of these five parameters experimentally is given. Comparison with the values of the well-known splay, twist, and bend elastic constants of the uniaial nematic is made.

  • PDF

Dimesogenic Compounds Consisting of Two Identical Terminal N-(4-Oxybenzylidene)-4-n-butylaniline Units and a Central Polymethylene Spacer

  • Jung-Il Jin;Bong Young Chung;Joo-Hoon Park
    • Bulletin of the Korean Chemical Society
    • /
    • v.12 no.5
    • /
    • pp.583-588
    • /
    • 1991
  • A series of dimesogenic compounds having two identical, terminal Schiff base type mesogens and a central polymethylene spacer were prepared and their properties were compared with those of the corresponding monomesogenic compounds. The mesomorphic properties of the compounds were studied by differential scanning calorimetry and on a hot-stage of a polarizing microscope. All of the dimesogenic compounds formed mesophases enantiotropically with the exception of pentamethylene-1,5-bis(4-oxybenzylidene 4-n-butylaniline). This compound was monotropic and formed only a nematic phase on heating the solid, whereas it formed nematic as well as smectic A phases on cooling the isotropic liquid. Those compounds containing longer (octamethylene and decamethylene) spacers favored the formation of nematic phase whereas those having shorter (dimethylene and tetramethylene) spacers formed smectic phases. In general, the variety of mesophase forms exhibited by the dimesogenic compounds was significantly less than that shown by the corresponding monomesogenic compounds.

  • PDF

Characteristic confirm of Compensated Film Characteristics using Reactive Rod-like Mesogen in Twisted Nematic mode (TN mode에서의 Reactive Rod-like Mesogen을 이용한 보상필름의 특성 확인)

  • Jeon, Eun-Jeong;Kwon, Dong-Won;Kang, Byeong-Gyun;Lim, Young-Jin;Kim, Jong-Hoon;Seong, Hyeon-Jun;Lee, Myong-Hoon;Lee, Seung-Hee
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
    • /
    • /
    • pp.271-272
    • /
    • 2009
  • We fabricated a hybrid aligned film using reactive rod-like mesogen to reduce light leakage of twisted nematic(TN) cell in off-axis of the dark state. We proved that the fabricated compensation film has hybrid alignment by changing phase retardation according to polar angle. In this paper, we confirmed characteristics of compensation film through simulation results and found the matching factor of simulation results and experimental result. In result, the maximum pretilt angle of hybrid compensated film is $19^{\circ}$ which has phase retardation 0.1445.

  • PDF

Optical Simulation of Viewing Angle Property of Biaxial Nematic Bent-Core Liquid Crystal

  • Yang, Seungbin;Lee, Ji-Hoon
    • Journal of the Optical Society of Korea
    • /
    • v.20 no.4
    • /
    • pp.510-514
    • /
    • 2016
  • The conventional liquid crystal displays (LCDs) have been using optically uniaxial liquid crystal (LC) medium and this often causes a significant image change at oblique viewing angles. We simulated the viewing angle properties of the biaxial nematic (Nb) phase of a bent-core liquid crystal (BLC) and compared the results with the vertically aligned (VA)- and the in-plane switching (IPS)-LCDs. The Nb phase of the BLC showed a smaller transmittance at the dark state as well as a greater contrast ratio at wide viewing angle. The viewing angle property of the Nb-mode without any compensation film was slightly superior to the IPS-mode with the compensation films eliminating the decross of the polarizers at oblique viewing angle.

Thermotropic Liquid Crystalline Properties of α,ω-Bis(4-cyanoazobenzene-4'-oxy)alkanes (α,ω-비스(4-사이아노아조벤젠-4'-옥시)알케인들의 열방성 액정 특성)

  • Jeong, Seung Yong;Kim, Hyo Gap;Ma, Yung Dae
    • Applied Chemistry for Engineering
    • /
    • v.22 no.4
    • /
    • pp.358-366
    • /
    • 2011
  • A homologous series of linear liquid crystal dimers, the ${\alpha},{\omega}$-bis(4-cyano-azobenzene-4'-oxy)alkanes (CATWETn, where n, the number of methylene units in the spacer, is 2~10) were synthesized, and their thermotropic liquid crystalline phase behavior were investigated. The CATWETn with n of 3 and 6 exhibited monotropic nematic phases, whereas other derivatives showed enantiotropic nematic phases. The nematic-isotropic transition temperatures of the dimers and their entropy variation at the phase transition showed a large odd-even effect as a function of n. This phase transition behavior was rationalized in terms of the change in the average shape of the spacer on varying the parity of the spacer. The thermal stability and degree of order in the nematic phase and the magnitude of the odd-even effect of CATWETn were similar to those for the methoxy-, nitro-, and pentyl-substituted dimers, while they were significantly different from those for the monomesogenic compounds, 1-{4-(4'-cyanophenylazo)phenoxy}alkylbromides and the side-chain liquid-crystalline polymers, the poly[1-{4-(4'-cyanophenylazo)phenoxyalkyloxy}ethylene]s. The results were discussed in terms of 'virtual trimer model' by Imrie.