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Nonlocal effect in liquid crystals
박진해 충청수학회 2014 충청수학회지 Vol.27 No.3
In this paper, we investigate the role of nonlocal inter-action energy on nucleations of periodic solutions in a one-dimensionalproblem arising in smectic liquid crystals.
NONLOCAL EFFECT IN LIQUID CRYSTALS
Park, Jinhae Chungcheong Mathematical Society 2014 충청수학회지 Vol.27 No.3
In this paper, we investigate the role of nonlocal interaction energy on nucleations of periodic solutions in a one-dimensional problem arising in smectic liquid crystals.
박승범,Tai-Yon Cho,Kyung-Hwan Yoon,장지영,Rudolf Zentel,윤도영 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.8
We have synthesized and characterized the first cyclic co-oligomeric ferroelectric liquid crystals (FLCs) based on cyclic siloxanes and found that the co-oligomer containing two different mesogenic units exhibits SmC^*mesophase over a wide temperature range from 65 ^oC to 135 ^oC, much wider than those of the monomer counterparts and the cyclic homo-oligomers. The cyclic co-oligomeric liquid crystal readily filled the display cell and exhibited fast switching times in the range of 4 ms to 6 ms over the entire SmC^* phase. Moreover, the practical absence of layer shrinkage, attributed to de Vries-type transition, shows an additional significant advanage for cyclic co-oligomeric FLCs in LCD applications.
Park, Seung-Beom,Cho, Tai-Yon,Yoon, Kyung-Hwan,Chang, Ji-Young,Zentel, Rudolf,Yoon, Do-Y. Korean Chemical Society 2011 Bulletin of the Korean Chemical Society Vol.32 No.suppl8
We have synthesized and characterized the first cyclic co-oligomeric ferroelectric liquid crystals (FLCs) based on cyclic siloxanes and found that the co-oligomer containing two different mesogenic units exhibits $SmC^*$ mesophase over a wide temperature range from $65^{\circ}C$ to $135^{\circ}C$, much wider than those of the monomer counterparts and the cyclic homo-oligomers. The cyclic co-oligomeric liquid crystal readily filled the display cell and exhibited fast switching times in the range of 4 ms to 6 ms over the entire $SmC^*$ phase. Moreover, the practical absence of layer shrinkage, attributed to de Vries-type transition, shows an additional significant advanage for cyclic co-oligomeric FLCs in LCD applications.
Sudarshan Kundu,Taponita Datta (nee Ray),Prasenjit Nayek,Tapas Pal Majumder,Subir Kumar Roy 한국물리학회 2008 Current Applied Physics Vol.8 No.5
Liquid crystal mixtures of non-mesogenic polar molecule with a commercial ferroelectric liquid crystal (FLC) mixture were prepared. Two mixtures were prepared by mixing 0.5% (w/w) and 1% (w/w) of polar molecules with commercial FLC mixture. Comprehensive studies of dielectric and electro-optic properties of the commercial FLC mixture and the polar molecules doped FLC mixtures have been made as a function of temperatures. Our studies reveal a higher tilt angle in lower concentration (0.5%) mixture but in case of 1% mixture tilt angle is decreased in comparison to 0.5% mixture. The spontaneous polarization of the commercial FLC mixture and other two mixtures is almost equal in magnitude at all temperatures. At the lower temperature region of SmC* phase, Goldstone mode (GM) dielectric strength of the commercial FLC mixture and low concentration (0.5%) mixture is found almost equal but it is slightly higher in case of high concentration (1%) mixture. With the increase of temperature GM dielectric strength of both the doped mixtures rapidly converges at different temperatures which are much lower than the temperature of transition (TC) from SmC* – SmA phase. The results have been discussed. Liquid crystal mixtures of non-mesogenic polar molecule with a commercial ferroelectric liquid crystal (FLC) mixture were prepared. Two mixtures were prepared by mixing 0.5% (w/w) and 1% (w/w) of polar molecules with commercial FLC mixture. Comprehensive studies of dielectric and electro-optic properties of the commercial FLC mixture and the polar molecules doped FLC mixtures have been made as a function of temperatures. Our studies reveal a higher tilt angle in lower concentration (0.5%) mixture but in case of 1% mixture tilt angle is decreased in comparison to 0.5% mixture. The spontaneous polarization of the commercial FLC mixture and other two mixtures is almost equal in magnitude at all temperatures. At the lower temperature region of SmC* phase, Goldstone mode (GM) dielectric strength of the commercial FLC mixture and low concentration (0.5%) mixture is found almost equal but it is slightly higher in case of high concentration (1%) mixture. With the increase of temperature GM dielectric strength of both the doped mixtures rapidly converges at different temperatures which are much lower than the temperature of transition (TC) from SmC* – SmA phase. The results have been discussed.
Seng Kue Lee*,Masatoshi Tokita,Yoshio Shimbo,Kyung-Tae Kang,Hideo Takezoe,Junji Watanabe 대한화학회 2007 Bulletin of the Korean Chemical Society Vol.28 No.12
A new series of chiral bent-shaped liquid crystals with an asymmetric central core based on 1,6-dihydroxynaphthalene and chiral terminal chain prepared from (S)-(-)-2-methyl-1-butanol, 1,6-naphthalene bis[4-(4-alkoxyphenyliminomethyl)]benzoates [N(1,6)-n-O-PIMB(n-2)*-(n-4)O (n = 8-11)] were synthesized. Their mesomorphic properties and phase structures were investigated by means of electro-optical, polarization reversal current, and second harmonic generation measurements in order to confirm the relationship between the molecular structure and phase structure. All odd n (n = 9 and 11) compounds, N(1,6)-9-O-PIMB7*-5O and N(1,6)-11-O-PIMB9*-7O exhibit antiferroelectric phase, whereas even n (n = 8 and 10) compounds was flexible, N(1,6)-10-O-PIMB8*-6O exhibits the ferroelectric phase but N(1,6)-8-O-PIMB6*-4O exhibits the antiferroelectric phase. These results come from the decrease of the closed packing efficiency within a layer and the lack of uniform interlayer interaction between adjacent layers, which were caused by the asymmetrical naphthalene central core. Thus, we concluded that the structure of central core as well as the terminal chain plays an important role for the emergence of particular polar ordering in phase structures.
Swadesh Kumar Gupta,Dharmendra Pratap Singh,Rajiv Manohar 한국물리학회 2013 Current Applied Physics Vol.13 No.4
Effect of single wall carbon nanotubes (SWCNTs) on electro-optical performance of a ferroelectric liquid crystal (FLC) has been studied. Voltage dependent spontaneous polarization and response time measurement has been made for the pure and SWCNT doped FLC system. Dielectric measurement has also been performed to understand the existing interaction between SWCNTs and FLC molecules. The results have shown increase in the value of spontaneous polarization and relative permittivity with slight slower response for the doped system. The observed properties of doped system revealed that the SWCNTs can perform well with FLC at low applied electric field to enhance the performance of LC devices.
Cell thickness dependence of liquid crystal parameters
Sood, Nitin,Khosla, Samriti,Singh, Darshan,Bawa, S.S. The Korean Infomation Display Society 2012 Journal of information display Vol.13 No.1
Ferroelectric liquid crystal parameters, spontaneous polarization, and transition temperature were studied as a function of cell thickness. These parameters were found to increase with increasing cell thickness, but an exception was observed for the transition temperature in the case of a thin cell. A simple Landau model is presented to interpret the theoretical and experimental observations. The anomalous behavior is attributed to the electroclinic effect and is explained using the Landau model.
Dielectric behavior of carbon-nanotube-doped ferroelectric liquid crystal mixture
Samriti Khosla,Arti Sharma 한국정보디스플레이학회 2013 Journal of information display Vol.14 No.4
The dielectric spectra of pure and 0.1% multi-walled-carbon-nanotube-(MWCNT)-doped ferroelectric liquid crystal (FLC)mixture KCFLC10S materials were studied in the 50 Hz to 1MHz frequency range at different bias voltages. An unusual behavior-increase of ε with increasing E was observed in both samples. It was found that although the relaxation mode was not observable in the MWCNT-FLC sample, the increased effect of the bias voltage on the FLC with the addition of MWCNTs is clearly visible. A theory is presented to explain this effect of MWCNTs in the FLC material.
A. Chaudhary,R.K. Shukla,P. Malik,R. Mehra,K.K. Raina 한국물리학회 2019 Current Applied Physics Vol.19 No.12
Nanocomposites comprises of nano sized zinc oxide (ZnO, size ~10 nm) particles and ferroelectric liquid crystal (FLC) material have been prepared and studied. The concentration of the dopant (ZnO nanoparticles) in FLC matrix varied from 0.0 to 1 wt%. Distinct nanocomposites have been used to fabricate memory device and studied through dielectric spectroscopy, optical microscopy and electro-optical methods to explore electro-optic and memory parameters. Experimental results reveal that doping of ZnO nanoparticles in FLC leads to long lasting memory and low deriving voltage in nanocomposites. The achieved prolonged memory effect in nanocomposites may attribute to the charge transfer at the interfaces. Another reason, application of applied field may lead to ion trapping effect at ZnO surface which in turn minimize the depolarized field and enhance the memory effect in nanocomposites.