Color-transition Temperature Research Articles

Influences of solvent media on chain organization and thermochromic behaviors of polydiacetylene assemblies prepared from monomer with symmetric alkyl tails

This contribution investigates thermochromic behaviors and morphologies of polydiacetylene(PDA) assemblies prepared from a diacetylene monomer constituting symmetric alkyl tails. Properties of solvent media strongly affects molecular organization during the preparation process. The use of water provides PDA assemblies with irregular shape while a sheet-like structure forms in butanol. Thermal analysis and X-ray diffraction detect the variation of crystalline fraction and interlamellar spacing in these structures. The change of solvent media significantly affects their thermochromic behaviors. Thin film of PDA assemblies prepared in butanol exhibits reversible thermochromism with much higher color-transition temperature compared to the system of water.

Thermochromic Ion-Exchange Micelles Containing H+ Chromoionophores.

Thermochromic composites constitute a classical subfamily of stimuli responsive materials. We report here the thermochromic effect in Pluronic F-127 (F127) micelles containing hydrophobic ion-exchanger and H+ chromoionophores. The highly versatile and reversible thermochromism is attributed to the temperature-induced hydration-dehydration of the peripheral layer of the micelles, which in turn controls the ion-exchange process between the core and the periphery of the micelles. The color typically changes abruptly within 3-5 °C, and the color transition temperature can be tuned within 5-25 °C upon varying the F127 concentrations. This work lays the foundation of a new variety of thermochromic materials involving ion-exchange.

Color Transition Properties of Water Dispersible Polydiacetylene Particles Conjugated with the Thermosensitive Polymer

An assembly of diacetylene molecules is necessary to progress a topochemical reaction as UV-irradiated polymerization. In this study, we attempt to regularly assemble 10, 12- pentacosadiynoic acid (PCDA) by freezing the solution, followed by lyophilization. Dried PCDA assembly was easily dispersed in aqueous solution by sonication. Irradiation of UV light can promote polymerization reaction of PCDA judging from a color change of the solution into blue. A color transition of the polyPCDA-dispersed solution from blue to red was observed at approximately 56°C due to distortion of its π-conjugated system. A color transition temperature could be controlled by hybridization with thermosensitive hydroxypropyl cellulose, of which lower critical solution temperature appears around 38-39°C. By synchronizing to coli-globule transition of HPC in aqueous media, blue-red transition response of water-dispersed polyPCDA could be induced by changing conformation of surrounded polymer.

Facile preparation of Prussian blue analogue Co3[Co(CN)6]2with fine-tuning color transition temperature as thermochromic material

For thermochromic materials, a fine-tuning thermochromic property is always pursued to in order to realize their full potential. However, to date, realizing the fine-tuning still remains a great challenge and is seldom reported. In the present work, the Prussian blue analogue, Co3[Co(CN)6]2, with fine-tuning color transition temperature is synthesized through a facile wet-chemical method. By simply adjusting the amount of sodium citrate in the system, part of the ligand water molecules coordinated to lattice Co(II) can be substituted by citrate, which is confirmed by DFT calculations and experimental results, resulting in a color transition versus temperature as a response to a coordination environmental change of the Co(II). Finally, a fine-tuning color transition temperature from 40 to 80 °C is realized with the color changing from pink to blue upon heating. In addition to the tunable color transition temperature, a high color transition speed and long term stability were also achieved due to the porous and stable lattice structure of Co3[Co(CN)6]2. To the best of our knowledge, this is the first report of a metal–organic framework (MOF) with a fine-tuning reversible thermochromic property, and the present controlled strategy might be expanded to the preparation of other similar materials.

Role of Zn2 + ion on the formation of reversible thermochromic polydiacetylene/zinc oxide nanocomposites

Polydiacetylene (PDA)/zinc oxide (ZnO) nanocomposite is a class of materials that exhibit reversible thermochromism with controllable color-transition temperature. The nanocomposite also changes color upon exposure to various types of acids and bases. In our continuing efforts to develop this material, we obtain evidences that reveal true nature of the nanocomposite formation. X-ray diffraction (XRD) technique detects a significant increase of the interlamellar distance within the nanocomposite comparing to that of the pure constituent PDA. The investigation of the nanocomposite systems prepared from 10,12-tricosadiynoic acid and 10,12-pentacosadiynoic acid provides consistent results. This indicates an intercalation of the Zn2+ ions, leaking out of the ZnO nanoparticles, between the PDA layers. An atomic absorption spectroscopy confirms the existence of Zn2+ ions in the aqueous solution. The XRD result also shows that using only Zn2+ ions to prepare the nanocomposite can provide the intercalated PDA/Zn2+ structure. However, the enhanced inter- and intrachain interactions within this system is not sufficient to provide reversible thermochromism. An infrared spectroscopy detects the variation of vibrational frequencies of carboxylate head groups within the systems of PDA/ZnO nanocomposite and PDA/Zn2+ assemblies, corresponding to different types of interactions. Therefore, the strong interfacial interaction between PDA head groups and ZnO nanoparticle is essential for obtaining the reversible thermochromism. We also attempt to prepare the nanocomposites by using a combination of Zn2+ ions and various types of substrates including TiO2, SiO2 and Al2O3 nanoparticles.

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

Abstract Reversible thermochromic polydiacetylene (PDA)/polyvinylpyrrolidone (PVP) nanocomposites are prepared 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 tail causes the decrease of color-transition temperature, ranging from 75 to 85 °C. The shortening of alkyl segment adjacent to PDA carboxylic head group, however, does not provide the same trend. The nanocomposites constituting PDAs with 8, 6 and 4 methylene units exhibits color-transition at about the same temperature. The increase of PVP MW reduces the color-transition temperature and also affects thermochromic reversibilty of the PDA/PVP nanocomposites.

Versatile route to prepare reversible thermochromic polydiacetylene nanocomposite using low molecular weight poly(vinylpyrrolidone)

Abstract This contribution introduces a simple method to prepare polydiacetylene(PDA)-based materials with reversible thermochromism. The incorporation of low molecular weight poly(vinylpyrrolidone) (PVP10) into the PDA assemblies, prepared from 10,12-pentacosadiynoic acid (PCDA) monomer, enhances inter- and intrachain interactions within the system. The PVP10 is simply added during conventional preparation methods without requiring any other treatments. X-ray diffraction technique reveals the increase of interlamellar distance, which indicates the intercalation of PVP10 chains with the poly(PCDA) layers. The resultant poly(PCDA)/PVP10 nanocomposite exhibits higher color-transition temperature compared to that of the pure poly(PCDA) assemblies. In addition, the blue-to-purple color transition of poly(PCDA)/PVP10 nanocomposite in aqueous solution is fully reversible during 10 consecutive heating/cooling cycles. When the poly(PCDA)/PVP10 nanocomposite is fabricated into thin film, it exhibits two-steps color transition, reversible blue-to-purple at 90 °C and reversible purple-to-red at 150 °C. The complete color reversibility of this system persists up to 200 °C. Raman scattering spectroscopy is utilized to investigate color stability and the change of PDA backbone conformation within the nanocomposite during the color-transition process. We also demonstrate that the preparation conditions such as the PVP10 concentration and incubation time significantly affect the color reversibility of the resultant nanocomposites. Their size and shape are influenced by the PCDA/PVP10 mixing process.

Fine tuning the colorimetric response to thermal and chemical stimuli of polydiacetylene vesicles by using various alcohols as additives

Abstract In this study, we demonstrate a simple approach for fine tuning the color-transition behaviors of polydiacetylene (PDA) vesicles when exposed to thermal or chemical stimuli. The strength of inter- and intrachain interactions within PDA vesicles, fabricated by using 10,12-tricosadiynoic acid (TCDA) and 10,12-pentacosadiynoic acid (PCDA), are manipulated by mixing with 1-butanol, 1-pentanol or 2-methyl-1-butanol. The swelling of alcohol molecules weakens the interactions within the PDA layers, which in turn affects the color-transition behaviors. We observe that the resultant PDA vesicles exhibit color-transition temperatures ranging from about 35 °C to 55 °C, depending on concentration and structure of the added alcohols. The color-transition temperature and alcohol concentration exhibits linear correlation, where its slope varies with the alcohol structure. This approach is further utilized for controlling the color-transition behaviors of these PDA vesicles upon exposure to chemical stimuli including tetrahydrofuran, pyridine, ethylamine and phenol. The color transition of PDA vesicles at desired concentration of each chemical stimulus can be achieved by varying the concentration of alcohol additives. The ability to control the color-transition behaviors of PDA vesicles is very important for their development as chromatic sensor, extending their utilization in various applications.

High color stability and reversible thermochromism of polydiacetylene/zinc oxide nanocomposite in various organic solvents and polymer matrices

Abstract Polydiacetylene (PDA)-based materials exhibit color transition when subjected to external stimuli, making them attractive for sensing technology. The utilization of PDA-based materials can be largely extended by fabricating in different polymer matrices, which normally involves organic solvents as media. Recently, our group has developed PDA/zinc oxide (ZnO) nanocomposites, exhibiting reversible thermochromism in aqueous medium. In this contribution, we demonstrate that the PDA/ZnO nanocomposite can be dispersed in various organic solvents including 1,2-dichlorobenzene, chlorobenzene, toluene, ethanol, butanol, hexanol, chloroform and tetrahydrofuran. The color of pure PDA changes from blue to red in these solvents while the PDA/ZnO nanocomposite remains blue after 30 days. The color reversibility and color-transition temperature of the PDA/ZnO nanocomposite are hardly affected in these organic solvents compared to the system of aqueous medium. We further demonstrate that the PDA/ZnO nanocomposite can be embedded in common polymer matrices such as poly(styrene), poly(methyl methacrylate), poly(ethylene) and poly(vinyl alcohol) by using a simple mixing process. We have found that color reversibility of the PDA/ZnO nanocomposite depends on property of the polymer matrices and persists up to about 200 °C in some systems. The ability to prepare PDA-based materials in different organic solvents and polymer matrices is very important for their utilization in various applications.

Fine tuning the color-transition temperature of thermoreversible polydiacetylene/zinc oxide nanocomposites: The effect of photopolymerization time

An ability to control the thermochromic behaviors of polydiacetylene (PDA)-based materials is very important for their utilization. Recently, our group has developed the PDA/zinc oxide (ZnO) nanocomposites, which exhibit reversible thermochromism (Traiphol et al., 2011). In this study, we present our continuation work demonstrating a rather simple method for fine tuning their color-transition temperature. The PDA/ZnO nanocomposites are prepared by varying photopolymerization time, which in turn affects the length of PDA conjugated backbone. We have found that the increase of photopolymerization time from 1 to 120min results in systematically decrease of the color-transition temperature from about 85 to 40°C. These PDA/ZnO nanocomposites still exhibit reversible thermochromism. The PDA/ZnO nanocomposites embedded in polyvinyl alcohol films show two-step color-transition processes, the reversible blue to purple and then irreversible purple to orange. Interestingly, the increase of photopolymerization time causes an increase of the irreversible color-transition temperature. Our method is quite simple and cheap, which can provide a library of PDA-based materials with controllable color-transition temperature.

Influences of structural mismatch on morphology, phase transition temperature, segmental dynamics and color-transition behaviors of polydiacetylene vesicles

In this contribution, we report a systematic study of polydiacetylene (PDA) vesicles fabricated by mixing two types of monomers, 10,12-tricosadiynoic acid (TCDA) and 10,12-pentacosadiynoic acid (PCDA). These diacetylene (DA) monomers constitute the same head group but different alkyl chain length, which in turn causes structural mismatch within the PDA layers. The PCDA:TCDA ratios are 100, 75, 50, 25 and 0mol%. Morphologies and properties of these PDA vesicles are explored by utilizing laser light scattering, transmission electron microscopy, differential scanning calorimetry, temperature-dependent nuclear magnetic resonance spectroscopy (NMR) and spin–lattice relaxation time (T1) measurements. An increase in DA mole ratio to 50mol% leads to significant increase in particle size. The mixed PDA vesicles also exhibit irregular shape with rather rough surface. The mismatch of alkyl side chain causes the drop of phase transition temperature. For the system of mixed poly(PCDA50:TCDA50), its transition temperature is lower than those of the pure PDAs. The NMR line shape analysis detects an abrupt change of proton signal adjacent to the PDA head group during the blue/red color-transition process. The T1 measurements also reveal different local environments of PDA alkyl side chains in the blue and red phases. The mismatch of PDA side chains causes significant drop of the color-transition temperature.

Reversible chromatic sensor fabricated by inkjet printing TCDA-ZnO on a paper substrate

A flexible reversible color change poly-(10,12-tricosadiynoic acid) TCDA-ZnO (2.5wt%) composite based chromatic sensor was successfully designed and fabricated by inkjet printing. Fabricated sensors showed good reversibility and stable chromatic properties with color transition temperature at 70°C. Attenuated Total Reflection (ATR) – Fourier Transform Infrared (FTIR) spectra show chelate formation between TCDA and ZnO. Temperature-dependent Raman spectra indicate that the blue-red phase of poly-TCDA-ZnO (2.5wt%) is thermally triggered at 70°C and the amorphous phase is formed near 120°C. An inkjet printed Quick Response (QR) code using poly TCDA-ZnO demonstrates a sensory functionality which can be incorporated in these codes.

Controlling the reversible thermochromism of polydiacetylene/zinc oxide nanocomposites by varying alkyl chain length

In this work, polydiacetylene (PDA)/ZnO nanocomposites are successfully fabricated by using three types of monomers with different alkyl chain length, 5,7-hexadecadiynoic acid, 10,12-tricosadiynoic acid, and 10,12-pentacosadiynoic acid. The monomers dispersed in aqueous medium spontaneously assemble onto the surface of ZnO nanoparticles, promoted by strong interfacial interactions. The PDA/ZnO nanocomposites obtained via photopolymerization process are characterized by scanning electron microscopy, laser light scattering, infrared spectroscopy, and uv/vis absorption spectroscopy. The strength of interfacial interactions and morphologies of the nanocomposites are found to vary with alkyl chain length of the monomers. The PDA/ZnO nanocomposites also exhibit rather different thermochromic behaviors compared to their pure PDA counterparts. All nanocomposites show reversible blue/purple color transition upon multiple heating/cooling cycles, while the irreversible blue/red color transition is observed in the systems of pure PDAs. The shortening of alkyl side chain in PDA/ZnO nanocomposites leads to a systematic decrease in their color-transition temperatures. Colors of the nanocomposites at elevated temperature also vary with the alkyl chain length. Our results provide a simple route for controlling the reversible thermochromism of PDA-based materials, allowing their utilization in a wider range of applications.

Tuning Down of Color Transition Temperature of Thermochromically Reversible Bisdiynamide Polydiacetylenes

A series of bisdiynamide lipids containing various lengths of methylene spacer (m = 2, 3 and 4) between the diynes and the diamide headgroup and number of methylene units (n = 6 and 9) in their hydrophobic tails are synthesized. All six lipids synthesized can be dispersed in water and photopolymerized by UV irradiation to give the corresponding polydiacetylene (PDA) sols. The color transitions from blue to red during heating−cooling cycles of the PDA sols are photographically recorded and monitored by UV−vis absorption spectroscopy. The bisdiynamide PDAs exhibit excellent thermochromic reversibility and the color transition temperature can be tuned between ca. 25−55 °C by the variation of m and n values. Temperature indicators can be obtained by applying a screen printing ink formulated from the bisdiynamide monomer on plastic substrates followed by UV irradiation to generate desired patterns of thermochromically reversible PDAs.

Time–temperature chromatic sensor based on polydiacetylene (PDA) vesicle and amphiphilic copolymer

Polydiacetylene (PDA) is an excellent color-changing indicator. In this paper, we demonstrate a new and interesting kind of time–temperature chromatic sensor based on PDA vesicle and amphiphilic polymer. In presence of amphiphilic polymers, PDA vesicles could gradually transit from blue to red, which was irreversible and regularly depended on the temperature, time, and properties of amphiphilic polymer (including the concentration, molecular weight, molecular structure, hydrophobicity, and thermo-sensitive property). Higher concentration of amphiphilic polymers resulted in lower color-transition temperature and faster color-transition. Also, higher temperature led to faster color-transition. The color-changing of PDA/amphiphilic polymer matrix may have resulted from the higher temperature and gradual insertion of amphiphilic polymer into PDA, synergistically perturbing the conformation of PDA. The prepared PDA/F127, PDA/F68, PDA/L35 and PDA/Tween-20 aqueous matrix showed potential application in time–temperature chromatic sensors at around 10–50 °C. This work provides a new method to design time–temperature chromatic sensors.

Tuning of Thermochromic Properties of Polydiacetylene toward Universal Temperature Sensing Materials through Amido Hydrogen Bonding

Mono- and diamides derivatives of 10,12-pentacosadiynoic acid (PCDA) were synthesized from condensation of PCDA with various aliphatic and aromatic diamines. Polydiacetylenes of the amido-PCDA derivatives were prepared by photopolymerization of their molecular assembly homogeneously dispersed in aqueous media. Thermochromic properties of the resulting polydiacetylene sol were studied by temperature variable UV−vis spectrometry along with photographic recording. The color transition temperatures and thermochromic reversibility of the polymers are varied depended on the number of amide groups and the structure of the aliphatic and aromatic linkers. The phenylenediamide and polymethylenediamide PCDA derivatives give polydiacetylenes with complete thermochromic reversibility, while the polydiacetylenes obtained from 1,2-cyclohexylene and glycolic chain diamide derivatives exhibited irreversible thermochromism, whereas the polymers attained from the aromatic monoamide analogues are partially reversible. The va...

A new method of producing date powder granules: Physicochemical characteristics of powder

A mixing technique was developed to produce free flowing powder granules from date. This method involved preparation of the paste from raw date, mixing with maltodextrin powder followed by an oven drying. In order to determine an optimum proportion of date paste and maltodextrin (DE 6) to produce stable granules, mixing was carried out at various levels of maltodextrin (MD) ranging between 0.54 kg and 1.0 kg per kg of date paste (dry weight basis). The date paste dried with 1.0 kg of maltodextrin/1.0 kg of date paste produced non sticky and free flowing powder. Several physicochemical parameters such as water activity, bulk density, color, hygroscopicity and glass transition temperatures of date powders were measured. The caking of date powders during storage at room temperature was explained using the concept of glass transition temperature.

Spray‐Drying of Amylase Hydrolyzed Sweetpotato Puree and Physicochemical Properties of Powder

ABSTRACT: Spray‐drying, which has been used for commercial production of functional ingredients from several fruits and vegetables, has not yet been studied for sweetpotato processing. Thus, the objective was to determine the effects of viscosity reduction of sweetpotato puree with alpha‐amylase, maltodextrin (MD) addition, and inlet air temperature on the physicochemical characteristics of spray‐dried sweetpotato powder. A face‐centered cube design was used to evaluate the effects of amylase level (0, 3.75, and 7.5 mL/kg puree), MD concentration (0%, 10%, and 20%), and inlet air temperature (150 °C, 190 °C, and 220 °C) on powder characteristics. Model‐fitting using response surface methodology was performed to examine the effects of independent variables on the moisture content, color, water absorption, solubility, particle size, bulk density, and glass transition temperature. The data were fit to a full second order polynomial equation. However, only the linear and quadratic terms proved to be significant for most dried powder attributes. MD significantly increased powder solubility, altered the hue value, and raised the glass transition temperature of the powder. Pretreatment with alpha‐amylase resulted in a lower glass transition temperature and a decrease in particle size. Overall, results show that good quality sweetpotato powders can be produced using this drying method, with potential applications in food and nutraceutical products.

Attempts to improve Mg2Ni hydrogen storage by aluminium addition

In an attempt to destabilize Mg2NiH4, the starting alloy, Mg2Ni, was doped with aluminium by ball milling before hydrogenation. The structure of Mg2NiH4 is based on an electron-rich d10 [NiH4]-complex stabilized by a Mg ion framework and from theoretical calculations it had been suggested that a further destabilization of the hydride could be obtained by substituting some Mg for Al. After hydrogenation, the structure, color and phase transition temperature of Mg2NiH4 was found to be affected by Al addition. The conventional monoclinic low-temperature (LT) structure of Mg2NiH4 was not observed by X-ray diffraction for Mg2−xAlxNiH4, which instead could be indexed with a cubic unit cell, a=6.519 Å, that is very close to the dynamically disordered, cubic, high-temperature (HT) phase of Mg2NiH4 (a=6.490 Å). In contrast, the Al-doped Mg2NiH4 is stable at room temperature. Furthermore, the typical orange color of Mg2NiH4 was not observed and differential scanning calorimetric measurements (DSC) of the Al-containing hydride showed a 10°C decrease in phase transition temperature. This is interpreted as a transition from a statically disordered pseudo-HT structure to the dynamically disordered HT phase. However, the monoclinic structure of the LT phase of Mg2NiH4 could again be observed at room temperature after 10 hydriding/dehydriding cycles, indicating that the Al-doping of Mg2NiH4 is counteracted by cycling and only has a temporary influence on the properties.

Radiation effects in organic solutions of cholesteryl nonanoate and cholesteryl decanoate

Abstract The products of γ radiolysis of solutions of cholesteryl nonanoate and cholesteryl decanoate cause a decrease in the color transition temperatures which is proportional to the absorbed dose. The rate of the lowering of the colour transition temperature depends strongly on the solvent and is inversely proportional to the concentration of the cholesteric esters. Carbon tetrachloride solutions of cholesteryl alkanoates from formate to decanoate were found to have the same G(HCl) both in the absence of air (G = 4.5 ± 0.4) or in the presence of air (G = 11 ± 1). G(CHC13) were found to be 2.7 ± 0.2 in the presence of air and 3.8 ± 0.2 in deaerated samples for all the above mentioned esters in a concentration of 0.1 M. The hydrogen abstracted to form CHCl3 is mostly the allylic hydrogen from the cholesterol skeleton.