Preparation of Thermochromic Polymer Nanocomposite Films from Polymerizable Organogels of Oligothiophene-Based Organogelators

최태진,장지영 한국고분자학회 2016 Macromolecular Research Vol.24 No.11

Thermochromic polymer nanocomposite films were prepared from polymerizable organogels. Organogelator 1 had a structure which 3,4,5-tris(ω-decenyl)benzamide groups were attached to a quarterthiophene core through amide bonds. Organogelator 2 had the same structure except that tris(ω-decenyl) groups were replaced by tris(n-decanyl) groups. The PMMA nanocomposite films were prepared by the photopolymerization of the organogels formed in methyl methacrylate (MMA). The film containing 1 (0.5 wt%) showed reversible thermochromism. The emission under 365 nm irradiation was changed to bright green from orange by heating up to 120 oC and returned to its initial orange by cooling. To the contrary, the PMMA composite film prepared from the organogel of 2 (0.5 wt%) did not show a reversible thermochromic property. Organogelator 1 with polymerizable terminal vinyl groups was covalently embedded in the PMMA matrix, but 2 was not. The reversible thermochromism was likely caused by the thermally reversible conformational change of quarterthiophene units in the polymer fibers.

Preparation of Thermochromic Polymer Nanocomposite Films from Polymerizable Organogels of Oligothiophene-Based Organogelators

최태진,장지영 한국고분자학회 2016 Macromolecular Research Vol.24 No.12

Thermochromic polymer nanocomposite films were prepared from polymerizable organogels. Organogelator 1 had a structure which 3,4,5-tris(ω-decenyl)benzamide groups were attached to a quarterthiophene core through amide bonds. Organogelator 2 had the same structure except that tris(ω-decenyl) groups were replaced by tris(n-decanyl) groups. The PMMA nanocomposite films were prepared by the photopolymerization of the organogels formed in methyl methacrylate (MMA). The film containing 1 (0.5 wt%) showed reversible thermochromism. The emission under 365 nm irradiation was changed to bright green from orange by heating up to 120 oC and returned to its initial orange by cooling. To the contrary, the PMMA composite film prepared from the organogel of 2 (0.5 wt%) did not show a reversible thermochromic property. Organogelator 1 with polymerizable terminal vinyl groups was covalently embedded in the PMMA matrix, but 2 was not. The reversible thermochromism was likely caused by the thermally reversible conformational change of quarterthiophene units in the polymer fibers.

Structural-thermochromic relationship of polydiacetylene (PDA)/polyvinylpyrrolidone (PVP) nanocomposites: Effects of PDA side chain length and PVP molecular weight

Anothai Kamphan,Chanita Khanantong,Nisanart Traiphol,Rakchart Traiphol 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.46 No.-

Reversible thermochromic polydiacetylene (PDA)/polyvinylpyrrolidone (PVP) nanocomposites areprepared by using 6 diacetylene (DA) monomers. The use of relatively low molecular weight (MW)PVP provides the nanocomposites with reversible thermochromism. The shortening of PDA alkyl tailcauses the decrease of color-transition temperature, ranging from 75 to 85 C. The shortening of alkylsegment adjacent to PDA carboxylic head group, however, does not provide the same trend. Thenanocomposites constituting PDAs with 8, 6 and 4 methylene units exhibits color-transition at about thesame temperature. The increase of PVP MW reduces the color-transition temperature and also affectsthermochromic reversibilty of the PDA/PVP nanocomposites.

Kinetic Investigation of Thermochromic Transition, Proton Transfer Reaction, and Crystal-Crystal Phase Transformation in 1,3-bis(hydroxyethylamino)-4,6-dinitrobenzene

Han, Jae-Il,Chung, Ihn-Hee,Lee, Sang-Cheol 한국섬유공학회 2011 FIBERS AND POLYMERS Vol.12 No.7

This study investigated the main origin of the thermochromism of a novel compound, 1,3-bis(hydroxyethylamino)-4,6-dinitrobenzene (BDB). In order to unravel the relative dependence of reversible color change between yellow and orange on proton transfer reaction and crystal-crystal phase transformation, kinetic experiments were executed. The recovery rates of thermochromic transition, proton transfer reaction, and crystal-crystal phase transformation were calculated from the data measured through UV-vis spectrophotometry, IR spectrometry, and X-ray diffractometry with a lapse of time at fixed-temperatures (30, 40, and $50^{\circ}C$) after cooling from heated temperature ($150^{\circ}C$). The kinetic experiments revealed that the recovery takes place more quickly at lower temperature. At each fixed-temperature, the recovery rate is in the order of the crystal-crystal phase transformation > the proton transfer reaction > the thermochromic transition. It is concluded that the proton transfer reaction is the main origin for thermochromism of BDB in solid state and the crystal-crystal phase transformation is a collateral one.

Effect of Alkyl Chain Length on Thermochromism of Novel Nitro Compounds

Lee, Sang-Cheol,Jeong, Young-Gyu,Jang, Suk-Hyun,Jo, Won-Ho The Korean Fiber Society 2007 Fibers and polymers Vol.8 No.2

A series of novel nitro compounds containing different alkyl chain length ($x=2{\sim}5$), 1,5-bis(hydroxyalkylamino)-2,4-dinitrobenzene (BDBx), are synthesized and their thermochromic behavior is investigated by using differential scanning calorimetry and optical microscopy. All the BDBx crystals synthesized show yellow color at room temperature. BDBx ($x=2{\sim}4$) samples display orange color even in the solid when heated above respective thermochromic transition temperature, while the yellow color of BDB5 changes to orange with melting. The orange color of BDBx crystals returns to yellow when cooled down to room temperature, indicating that the thermochromic behavior of BDBx is reversible. The thermochromic transition temperatures of BDBx crystals are found to be decreased with increasing the alkyl chain length, exhibiting even-odd fluctuation.

Synthesis of Cr-doped Al₂O₃ by Pechini sol-gel method and its application for reversible thermochromic sensors

Nguyen, Duy Khiem,Bach, Quang-Vu,Kim, Buyoung,Lee, Heesoo,Kang, Choonghyun,Kim, In-Tae Elsevier 2019 Materials chemistry and physics Vol.223 No.-

<P><B>Abstract</B></P> <P>Aluminum oxide doped with a small amount of chromium is known as “ruby” or “ruby solution” and can be used as a thermochromic material. The Pechini sol-gel process is applied to synthesize this advanced material. The crystal structure, chemical composition, and morphology of the synthesized materials are analyzed using X-ray diffraction, scanning electron microscopy coupled with energy-dispersive X-ray spectrometry, and Fourier transform infrared (FT-IR) spectroscopy. The color performance of the synthesized material is analyzed using UV-VIS spectrometry. Finally, the thermochromism exhibited by the pigment powders at high temperatures is investigated. The pigment exhibits exceptional thermochromic properties, transitioning from pink to gray in a temperature range of 25–600 °C. The change in color is reversible and is dependent on the temperature and chromium concentration; however, it is independent of the exposure time. This novel property of Cr-doped Al<SUB>2</SUB>O<SUB>3</SUB> can be potentially employed in reversible thermochromic sensors that could be used not only for warning users of damage due to overheating when the environmental temperature exceeds certain limits, but also for detecting and monitoring the temperature of various devices, such as aeronautical engine components, hotplates, and furnaces.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Cr-doped Al<SUB>2</SUB>O<SUB>3</SUB> powders were prepared by Pechini sol-gel method. </LI> <LI> The Cr<SUP>3+</SUP> contents influence slightly the phase transition temperature but control the brightness of the powders. </LI> <LI> The powder exhibits reversible thermochromic properties in a temperature range of 25–600 °C. </LI> <LI> The color change is dependent on the temperature but independent of the exposure time. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Investigation of reversible self-thermochromism in microencapsulated fluoran-based materials

Kim, Ick Jin,Ramalingam, Manivannan,Son, Young-A. Elsevier 2018 Dyes and pigments Vol.151 No.-

<P><B>Abstract</B></P> <P>In the present study, eight self-thermochromic fluorans (<B>STC1-STC8</B>) were synthesized, and their reversible thermochromic properties were investigated without the use of a color developer. This work demonstrated the role of the phenol group on ring c on the thermochromic reversibility of the fluorans. Furthermore, the two-component mixtures that contained fluorans and methyl stearate were used to examine the thermochromic behaviors of the fluorans with steady heating and cooling rates. The thermochromic properties of the fluorans were evaluated using solid-state UV-Vis, reflectance and FT-IR spectroscopic techniques. DFT calculations were conducted to justify the optical behaviors of the fluorans in their spirolactam forms (<B>STC1-STC8</B>) and cationic forms (<B>STC1+- STC8+</B>). Finally, <B>STC1</B> was successfully microencapsulated and applied in acrylic fiber to use as thermal indicators.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Eight new self-thermochromic fluorans (<B>STC1-STC8</B>) were designed and synthesized. </LI> <LI> The system exhibit a striking color change from colorless (heating) to deep red (cooling). </LI> <LI> <B>STC1</B> was microencapsulated and used as a thermal indicator. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Intense pulsed light sintering of vanadium dioxide nanoparticle films and their optical properties for thermochromic smart window

Kim, Kwang-Seok,Son, Eun-Won,Youn, Ji Won,Kim, Dae Up Elsevier 2019 Materials & Design Vol.176 No.-

<P><B>Abstract</B></P> <P>As cost-efficient and large-scalable fabrication, solution processing has been developed to prepare vanadium dioxide (VO<SUB>2</SUB>) films for thermochromic smart windows that can modulate infrared radiation in response to changes in ambient temperature while maintaining visible transmittance. Herein, we report for fabrication of VO<SUB>2</SUB> films from ball-milled VO<SUB>2</SUB> nanoparticle ink using intense pulsed light (IPL) sintering. The VO<SUB>2</SUB> films on quartz substrates were prepared by spin coating. The prepared films were sintered by IPL in air with various voltages from 1400 to 2000 V with the fixed conditions of 4 ms, 400 pulses and 1 Hz. IPL sintering of VO<SUB>2</SUB> nanoparticle ink led to granular films which were sintered at higher voltages since IPL irradiation was able to evaporate solvent including polymers in the ink, and sinter VO<SUB>2</SUB> nanoparticles. The VO<SUB>2</SUB> films IPL sintered at 2000 V exhibit luminous transmittance of over 46.3% and solar transmittance modulation of 11.2%. These results reveal that IPL sintering is substantial progress in terms of long-time and high-temperature post annealing for fabrication of solution-based thermochromic films.</P> <P><B>Highlights</B></P> <P> <UL> <LI> VO<SUB>2</SUB> nanoink and IPL sintering were utilized for fabrication of thermochromic films. </LI> <LI> IPL sintering improves the crystallinity and thermochromic performance of VO<SUB>2</SUB> films. </LI> <LI> Visible and luminous transmittance of VO<SUB>2</SUB> films is 63.6% and 46.3%, respectively. </LI> <LI> VO<SUB>2</SUB> films exhibit 47% infrared modulation and 11.2% solar transmittance modulation. </LI> <LI> IPL sintered VO<SUB>2</SUB> films facilitate commercialization of thermochromic applications. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Morphology-dependent luminescent behavior of hexacatenar Luminogens based on naphthalenyl and 1,2,3-triazolyl groups

Nguyen, Manh Linh,Kim, Suwoong,Kim, Ho-Joong,Cho, Byoung-Ki Elsevier 2019 Dyes and pigments Vol.160 No.-

<P><B>Abstract</B></P> <P>The columnar assemblies and thermochromic properties of a hexacatenar molecule consisting of naphthalenyl and 1,2,3-triazolyl units were evaluated. The molecule formed 3D monoclinic crystalline (Cry<SUB>mono</SUB>) and hexagonal columnar LC (Col<SUB>hex</SUB>) phases as a function of temperature. Photoluminescence (PL) study revealed a noticeable change in the emission color at the Cry<SUB>mono</SUB>-to-Col<SUB>hex</SUB> transition. The aromatic cores in the Cry<SUB>mono</SUB> phases were stacked in an edge-to-face geometry and thereby exhibited a monomeric emission in the ultra-violet (UV) region. In contrast, a bluish excimer emission was observed for the Col<SUB>hex</SUB> phase with face-to-face stacking. Consequently, the fluorescent molecule exhibited different assembly features as a function of temperature, giving rise to distinct thermochromic phenomenon.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A thermochromic hexacatenar molecule consisting of naphthalenyl and 1,2,3-triazolyl units was prepared through click chemistry. </LI> <LI> An emission change from ultra-violet to bluish color was observed at the crystal-to-liquid crystalline phase transition. </LI> <LI> The thermochromic property is attributed to the aromatic stacking transformation. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Facile Evaluation of Thermodynamic Parameters for Reverse Thermochromism of Indolinobenzospiropyran-6-carboxylates in Aqueous Binary Solvents

금삼록,So-Young Ma,Hyun-Woo Lim,Tae-Hwi Han,Kyu-Hyun Choi 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.8

The position of the thermodynamic equilibrium for reverse thermochromic spiropyran 6-carboxylates (SPCOOHs) was easily determined in aqueous binary mixtures, such as water-methanol, water-acetonitrile and water-dimethyl sulfoxide. The existence of more than one type of interconvertible species of the ring-opened form of SP-COOH in aqueous binary solvents enables us to evaluate the molar extinction coefficients of the ring-opened species of SP-COOH and to obtain the thermodynamic parameters.