• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.10
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• pp.69-74
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• 2017

In this study, cholesteryl 4-n-alkoxybenzoates (Chol-n), with alkyl groups used for controlling the temperature of transition to the liquid crystal phase, were synthesized, and the effects of the length of the alkyl groups on the physical properties of the liquid crystal compounds were investigated. The chemical structures and thermal and liquid crystalline properties of the synthesized compounds were investigated by Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance spectroscopy ($^1H$-NMR), differential scanning calorimetry (DSC), and polarizing optical microscopy (POM). The synthesized compounds showed melting transition temperatures ($T_m$) in the range of $103^{\circ}C$ to $143^{\circ}C$ and all of the compounds except Chol-6 exhibited a wide liquid crystal phase temperature range of about $60^{\circ}C$ to $100^{\circ}C$. No correlation between the number of carbon atoms in the molecule and the thermal properties of the compounds was found. All of the synthesized compounds showed an enantiotropic cholesteric phase, which was accompanied by a chiral smectic phase in the compounds Chol-6, Chol-8, Chol-9, and Chol-10. All of the compounds exhibited thermochromism in the liquid crystal state, and their color changed from red to blue as the temperature was increased.

• Journal of the Korean Chemical Society
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• v.54 no.5
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• pp.500-505
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• 2010

Two different dyes containing the same molecular weight but different chemical structure have been utilized for the study of thermodynamic parameters. In this study, {3-(4-(diethylamino)phenyl)-3-(1-ethyl-2-methyl-1H-indol-3-yl)isobenzofuran-1(3H)-one} (Blue 502) and {3-(4-(diethylamino)-2-methylphenyl)-3-(1,2-dimethyl-1H-indol-3-yl)isobenzofuran-1(3H)-one} (Blue 402) were used. It has been performed by measuring UV spectra of the two dyes. In general, the blue shift has been observed from both dyes in higher carbon number alcohol solvents. Interestingly, Blue 502 showed higher stability than Blue 402 in the same conditions used in this study. And, the equilibrium constants (0.9~1.0) of the dyes depending upon temperature change were also calculated using UV absorbance. The standard enthalpy calculated from equilibrium constants and molar absorptivity($\varepsilon$) are 10.94 kJ/mol in Blue 402 and 9.010 kJ/mol in Blue 502, respectively.

• Journal of the Korean Chemical Society
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• v.38 no.12
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• pp.864-872
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• 1994

Absorption spectra of thermochromic spiropyran and spirooxazine derivatives were investigated. The effects of solvent polarity on the absorption spectra indicate that the merocyanine-like form of non-substituted spiro compound is likely to the quinoid type. However, the merocyanine-like form of electron-withdrawing substituted spiro compound is likely to the zwitter-ion type. The enthalpy changes between the closed and merocyanine-like forms were measured. The enthalpy change of spiro compound decreases as the solvent polarity increases. The UV-Vis spectrum of merocyanine-like form was resolved into three Lorentzian-Gaussian product bands. The solvent dependence of the amount of the three band was also examined.

• Fire Science and Engineering
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• v.22 no.5
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• pp.61-66
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• 2008

In this research, gel compounds containing thermochromic ingredients were manufactured and evaluated to prevent the transition hazards of fire and explosion, which they are one of the methods for detecting abnormal conditions caused by overheating of special materials early. And also, compounds of viscoelastic and brushing types were manufactured as the kind and content of raw materials, and manufacturing process to enlarge the application for overheat-detecting targets. Test methods were conducted as chromism test, viscosity profile, starting time of thermochromism, and FT-IR analysis. Thermochromic gel materials exhibit chromism properties that can detect abnormal conditions effectively, and then they are possible to various applications.

• Applied Chemistry for Engineering
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• v.28 no.2
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• pp.230-236
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• 2017

We synthesized liquid crystalline polymers containing isosorbide group as a cholesteric derivative and methylene group for controlling the transition temperature to the liquid crystal phase. Effects of the concentration of the isosorbide group and the position of the methylene group on the properties of the liquid crystalline polymer were investigated. Among all the synthesized polymers, polymers (MnHI-x) with a methylene group in the main chain showed higher melting transition temperature and thermal stability than those (SnBI-x) with a methylene group in the side chain. All the synthesized polymers showed an enantiotropic liquid crystal phase. The polymers having 10 mol% isosorbide as a cholesteric liquid crystal phase derivative showed nematic phase, and those having 20 mol% or more isosorbide showed a cholesteric or chiral smectic phase. Thus, we can conclude that the isosorbide group plays a role as a cholesteric liquid crystal phase derivative.

• Resources Recycling
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• v.26 no.5
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• pp.61-66
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• 2017

Vanadium Dioxide has been investigated for use as a "spectrally-selective" window coating to block infrared transmission and reduce the loss of building interior heat through windows. The preparation of thermochromic $VO_2$ powder by the reductive reaction with hydrogen was studied. The reductive reaction method has many advantages of easy and mass production of $VO_2$ powder according to controlled reaction without semi-conductor equipments like sputter and beam evaporator. The reaction temperature, time, concentration of reductive gas, post-annealing condition and W addition as dopant would affect the characterization of $VO_2$ powder and its thermochromism. Many applications for electrical device and energy-saving technologies is expected.

• Journal of the Korea Convergence Society
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• v.12 no.11
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• pp.291-299
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• 2021

Recently, due to environmental problems caused by densification and high rise of urban areas, interests in air flow is increasing and appropriate shape and layout design of buildings is required. Therefore, in this study, we intend to propose an experimental method that can observe the air flow around a building using thermochromic pigment. Thermochromic pigments have limitations in observing precise temperature changes due to the characteristic that the color changes only with respect to a specific temperature, but they have the advantages of easy configuration of experimental equipment and short time required for experiments. In this study, the air flow tendencies around a building was examined by performing CFD analysis for a simple model and then compared with the thermochromic experiment results in order to review the usefulness of the proposed experimental method. As a result of the experiment, it was possible to observe the formation of separated flow and vortex region generated by buildings using the charateristics of thermochromic pigment and it was confirmed that the proposed method can be useful for buildings design and urban city planning.