Reversible Thermochromism Research Articles

Facile route for large-scale synthesis of reversible thermochromic polydiacetylene/zinc(II) assemblies: The effect of zinc(II) precursors

Polydiacetylenes (PDAs) are stimuli-responsive polymers that have shown potential for colorimetric detection of various stimuli. Commercially available PDAs often exhibit irreversible blue-to-red thermochromism, limiting their applications. In this study, we develop a facile method, involving the co-assembly of zinc (Zn2+) ions and PDAs in an aqueous medium, for creating reversible thermochromic materials. We have found that the Zn2+ precursors play a crucial role on achieving a reversible thermochromism. The PDA/Zn2+ assemblies prepared from Zn(CN)2 and Zn(CH3COO)2 exhibit reversible thermochromism whereas other Zn2+ precursors such as ZnCl2, Zn(NO3)2 and ZnSO4 do not yield reversibility. The reversible thermochromic PDA/Zn2+ assemblies can be synthesized via the solution mixing method in ambient conditions, making them suitable for large-scale production. The color-transition temperature can be tuned from 60 to 120 °C by changing PDA side chains. The synthesis of reversible thermochromic PDA/Zn(CN)2 assemblies in the liquid phase allows the fabrication of smart inks, sprayed coatings, and nanofibers, extending their fields of applications.

Integrated Reversible Thermochromism, High Tc , Dielectric Switch and Narrow Band Gap in One Multifunctional Ferroic.

Organic-inorganic Hybrid (OIH) materials for multifunctional switchable applications have attracted enormous attention in recent years due to their excellent optoelectronic properties and good structural tunability. However, it still remains challenging to fabricate one simple OIH compound with multi-functionals properties, such as dielectric switching, thermochromic properties, semiconductor characteristics and ferroelasticity. Under this context, we successfully synthesized [2-(2-fluorophenyl)ethan-1- ammonium]2 SnBr6 (compound 1), which has a higher phase transition temperature of 427.7 K. Additionally, it exhibits a semiconducting property with an indirect band gap of 2.36 eV. Combining ferroelastic, narrow band gap, thermochromic, and dielectric properties, compound 1 can be considered as a rarely reported multi-functional ferroelastic material, which is expected to give inspiration for broadening the applications in the smart devices field.

Sn2P2S6: A lead-free reversible thermochromic ferroelectric with high near-infrared reflectance

Multifunctional thermochromic materials integrated optical, ferroelectric, and/or magnetic properties have been long envisioned and played an invaluable role in signal processing and non-contact optical information storage in smart windows. However, poor materials stability, together with high discoloration temperature, absence of ferroelectric, or magnetic behaviors, impedes most thermochromic materials for practical applications. Here, the thermochromic behavior of all-inorganic lead-free ferroelectric Sn2P2S6 (SPS) is extensively studied, which exhibits a reversible color change between light orange and red around the ferroelectric-paraelectric phase transition temperature (∼ 67 °C). In situ powder X-ray diffraction (PXRD) and Raman spectroscopy indicate the change of P-S and Sn-S bond distance, and thus result in the modification of (P2S6) octahedral geometry and the coordination environment of Sn2+ ions along with the evolution of thermochromism (TCM). Additionally, the first-principles calculations reveal that, the Sn 5s2 stereochemically active lone pair electrons evoke negative lattice expansion comparable to that of the known ZrW2O8 at warming and is responsible for the reversible TCM of SPS. SPS also possesses high near-infrared reflectance (R > 80 %, 1100-2500 nm). The integration of ferroelectricity, high near-infrared reflectance, and TCM below 100 °C renders potential applications of the titled compound in multifunctional optical smart windows.

Bifunctional bimetal-POSS films integrating UV-IR shielding and reversible thermochromism

Bifunctional bimetal-POSS films integrating UV-IR shielding and reversible thermochromism

Thermo‐Tautochromic Polymer Architectures from Tertiary Methyl Red Amides

Thermo‐Tautochromic Polymer Architectures from Tertiary Methyl Red Amides

Effect of Fluorane Microcapsule Content on Properties of Thermochroic Waterborne Topcoat on Tilia europaea.

In a particular temperature range, 1, 2-benzo-6-diethylamino-fluorane microcapsules (fluorane microcapsules) exhibit a good color-changing function. For the coating on wood surfaces, embedding fluorane microcapsules, good weather resistance, light retention, color retention, impact resistance, and wear resistance are essential. However, the effect of fluorane microcapsule content on its properties has not been verified. Therefore, in this paper, the orthogonal test is designed with the fluorane microcapsule content, drying temperature, and drying time as test factors to identify the most influential factors. Then, by embedding microcapsules into the waterborne coating on wood substrates, the performance of the waterborne topcoat was investigated. The results show that the color of the waterborne topcoat with fluorane microcapsules on a basswood (Tilia europaea) surface can change between yellow and colorless when the temperature rises and falls, achieving reversible thermochromism. The activation temperature was 32 °C, and the range of discoloration temperature was 30–32 °C. The topcoat with a 15% fluorane microcapsule content had the best comprehensive performance. The color difference was 71.9 at 32 °C, the gloss was 3.9% at 60°, the adhesion grade was 0, the hardness was 2H, the impact resistance was 10 kg·cm, the elongation at the break was 15.56%, and liquid resistance was outstanding. After aging tests, the color difference of the topcoat with 15% fluorane microcapsules was more obvious. The damaged area of the topcoat with the addition of 15% fluorane microcapsules was smaller, indicating it had a better aging resistance. The experimental results lay the foundation for the preparation of intelligence-indicating and decorative waterborne coating.

Cotton fabrics treated with acylhydrazone-based polyviologen to create innovative multi-stimulus responsive textiles

Novel multi-stimuli responsive cotton fibers were developed via spray-coating with an acylhydrazone-based polyviologen (AHPV). Polyviologen was prepared by supramolecular condensation polymerization of bipyridinium dialdehyde with a hydroxyl-substituted aryldihydrazide in an acidified aqueous medium. Transparent AHPV/resin nanocomposite film was deposited onto the surface of cotton fabric by well-dispersion of AHPV as a chromogenic substance in a resin binding agent. Increasing the temperature of the AHPV-coated cotton fabric from room temperature to 85 °C reversibly triggered a change in color from pale yellow (437 nm) to green (607 nm), respectively. The transparent layer immobilized onto the white cotton surface transformed into green under ultraviolet source as demonstrated by CIE Lab parameters. The photochromic impacts were explored at various AHPV. In addition, the AHPV-coated cotton immediately displayed a vapochromic activity upon exposure to NH3(g), and then recovered to pale yellow after removing the ammonia source away. The current AHPV-coated cotton fabric displayed a limit of detection (LOD) to NH3(aq) in the range of 50–150 ppm. The spray-coated cotton fabrics demonstrated a reversible photochromism, thermochromism and vapochromism with high stability. The produced AHPV nanoparticles were also studied by transmission electron microscopy (TEM), demonstrating particle diameter of 74–92 nm. The mechanical and morphological properties of the spray-coated cotton fabrics were also explored. The surface morphology of AHPV-finished samples was examined by Fourier-transform infrared (FTIR) and scanning electron microscopy (SEM). No considerable defects were observed in permeability to air and bending length of AHPV-finished samples. Additionally, high colorfastness was monitored for the AHPV-finished cotton substrates. The cytotoxic activity of the AHPV-finished cotton was also examined. Mechanistic study accounting for the multichromic activity of acylhydrazone-based polyviologen is explored.

Competitive Dual-Emission-Induced Thermochromic Luminescence in Organic-Metal Halides.

Lead-free Halides, especially Mn-based ones, are preferred as hotspots in the exploration of photoluminescent materials. However, there are few reports on sensitive reversible thermochromism and switchable dual emission originating from self-trapped exciton emission in pure Mn-Based materials. Here, we report a new Mn-based hybrid material [TMPA]2MnI4 (TMPA = trimethylphenylammonium), which shows two emission peaks at 545 and 660 nm benefitting from the d-d orbital transition of Mn2+ and the generation of self-trapped excitons, respectively. Due to the different sensitivity to temperature, the stages of thermal activation and thermal quenching of the two emission types are also inconsistent, showing a certain competition relationship and dominating the emission colors in different temperature ranges, resulting in adjustable green-orange-green thermochromic luminescence from 100 to 403 K (both high and low temperatures correspond to green, and orange is displayed at near room temperature). Therefore, thermochromic luminescence can be easily achieved by controlling the temperature under the guidance of excited states. This work provides new insights into the synthesis and application of thermochromic materials. Therefore, it is certain that regulating temperature while being guided by excited states will achieve thermochromic luminescence. This research offers fresh perspectives on the development and potential of thermochromic materials.

Novel synthesis of PVA/NaCl hydrogel for reversible thermochromism

Hydrogel is a three-dimensional network which contains a high water content. It is widely applied to numerous fields such as health care, architecture and agriculture by virtue of excellent biocompatibility, simple preparation method and proper mechanical properties. Functional modification on hydrogels affords special physical and chemical properties which further spans their applications. Herein we report a novel strategy to prepare temperature-sensitive compound hydrogel using polyvinyl alcohol (PVA) and NaCl as raw materials, and borax as the crosslinking agent. It is found that the temperature response characteristic can be well realized by the variational solubility of NaCl under different temperatures. That is, these PVA/NaCl hydrogels present white at low temperature while they become transparent when temperature rise. In addition, the higher NaCl content is, the faster color changes.

Green Thermochromic Materials: A Brief Review

AbstractGreen thermochromic materials are of great interest in many applications. Thermochromic and phase change materials are commonly used as smart devices to facilitate temperature sensing and passive heating/cooling systems, respectively. Since most of the current thermochromic materials are nondegradable, toxic, and/or nongreen, there is great opportunity to develop greener materials with high performance considering the wide range of materials that can exhibit thermochromism. This concise review distinguishes the different forms, phases, and chemical structures of thermochromic materials. A brief history of thermochromism is reviewed and a general distinction between reversible and irreversible thermochromism is provided. A general definition of green materials is provided, recent advances in the emerging field are critically discussed as well as future applications. This review also provides brief but thorough understanding of mechanistic pathways of this phenomenon in materials and the constituent requirements of green materials such that new systems can be designed using nontoxic, biobased, and/or biodegradable materials. Such green thermochromic materials will expand their use significantly.

Zero-dimensional antimony(III) halides templated by ruthenium complexes: photoluminescence, thermochromism and photo/electrical performances

Zero dimensional antimony(III) halides have captured more and more attention as broadband emitters. Herein, Using photochemically active ruthenium complexes as templates, two new antimony(III) halide based hybrids have been prepared and structurally determined, i.e., [Ru(bipy)3](Sb2Cl6O) (1) and [Ru(phen)3](SbI5) (2). Both the (Sb2Cl6O)2- and (SbI5)2-are rare examples of antimony halides, in which Sb centers are in square pyramidal environments with stereochemically active lone pairs. The (Sb2Cl6O)2- ion bearing secondary Sb···Cl interactions are further stabilized by C-H···Cl hydrogen bonds to give a quasi-3D network. The (SbI5)2- anions are anchored in the 1D[Ru(phen)3]n 2n+ chains based on strong π···π stacking interactions among phenanthroline ligands, which are the reason for the formation of its square pyramid geometry.1 exhibits bright red luminescence but 2produces weak blue emission. This trend might be assigned to the larger conjugated system of phenanthroline in 2, which is dominant by ruling out the contribution of antimony(III) halide. Besides, reversible thermochromism can be found in 1. Furthermore, good electrical chemical and photocurrent performance can be detected. The photoluminescence modulation by controlling the conjugated degree of organic ligands is an efficient strategy for the precise preparation of new luminescent materials.

Study on the halide effect of MA4PbX6·2H2O hybrid perovskites – From thermochromic properties to practical deployment for smart windows

Thermochromic smart windows empowered by the unique material properties and reversible thermochromism of dihydrated methylammonium lead halide hybrid perovskites (MA4PbX6·2H2O; X: halide) have risen as novel yet promising candidates for thermochromic smart windows, in which the halide plays a crucial role to the functionality and performance. In this study, the effects of halide types and mixing ratios on the thermochromic properties and practical deployment of MA4PbX6·2H2O halide hybrid perovskites are comprehensively studied by extensive fabrication and characterization processes as well as fundamental and applicational investigation tools. The potential perovskite compositions for thermochromic smart window applications are identified with respect to the desired optical properties (i.e. luminous transmittance and solar modulation ability) and transitional properties (i.e. transition temperature, hysteresis width and transition time). Moreover, thermal-regulating performance of the applicable candidate mixed halide hybrid perovskite MA4PbI5Br1·2H2O is demonstrated in a model-house field investigation. This work provides not only an inclusive database of the thermochromic properties of MA4PbX6·2H2O halide hybrid perovskites, but also an application manual about their deployment for thermochromic smart windows, facilitating the development of smart windows and sustainable buildings.

Ferroelasticity, thermochromism, semi-conductivity, and ferromagnetism in a new layered perovskite: (4-fluorophenethylaminium)2[CuCl4

A new A2BX4-type layered perovskite, (4-fluorophenethylaminium)2[CuCl4], exhibits multi-channel properties including above-room-temperature ferroelasticity, reversible thermochromism, indirect semi-conductivity, and low-temperature ferromagnetism.

Reversible thermochromism to tune the bandgap of organic–inorganic hybrid materials

Here, we report a series of organic–inorganic hybrid halide materials, with rare and fully reversible thermochromism, narrow bandgaps, and near-infrared luminescence. Thermochromism induced bandgap narrowing provide new insights for the further of organic–inorganic hybrid materials.

Reversible thermochromism, temperature-dependent conductivity and high stability for a laminated bismuth(iii)–silver(i) hybrid double perovskite

We report here a new two-dimensional bimetallic double perovskite with reversible thermochromism, enhanced electrical conductivity and outstanding stability.

Ultra-low-temperature reversible thermochromism and contactless bacterial sensing by chalcone-functionalized polydiacetylene

HCl-treated chalcone-polydiacetylene films exhibit ammonia-induced pronounced visible color and fluorescence transformations employed for visible detection of food spoilage.

Mixed-halide copper-based perovskite R2Cu(Cl/Br)4 with different organic cations for reversible thermochromism

Mechanically exfoliated flakes of mixed-halide Cu-based perovskite crystals, R2Cu(Cl/Br)4, with three alkyl chains exhibit reversible thermochromic behavior with differences in crystal lattice behavior depending on the organic spacer used.

Multiple stimulus responsive Co-AIE framework materials with reversible solvatochromic and thermochromic behaviors: molecular design, synthesis and characterization

A novel Co-AIE-MOF (Co-tcbpe) based on TPE derivatives is designed and synthesized. And it shows a multi-stimuli response in the application of reversible solvatochromism and thermochromism.

A Quasi‐Two‐Dimensional Copper Based Organic‐Inorganic Hybrid Perovskite with Reversible Thermochromism and Ferromagnetism

AbstractTwo‐dimensional (2D) organic‐inorganic hybrid perovskites (OHPs) have been gaining more and more attention for their unique optical, electrical and magnetic behaviors. Herein, we report a multifunctional quasi‐2D hybrid perovskite, 1, 6‐hexanediammonium tetrachlorocuprate ((1, 6‐HDA)CuCl4), which exhibit reversible thermochromic behavior, temperature‐dependent conductivity and ferromagnetism. Changing temperature results in the reversible color change of (1, 6‐HDA)CuCl4 between yellow and brown. A screen‐printing ink is prepared by using (1, 6‐HDA)CuCl4 and used to print thermochromic patterns. The reversible thermochromism originates from the CuCl6 octahedron distortions and lattice expansion in the crystal structure. The conductivity varies more than two orders of magnitude upon temperature change. (1, 6‐HDA)CuCl4 also shows ferromagnetic property with Curie temperatures around 12 K.

Strong π-stacking causes unusually large anisotropic thermal expansion and thermochromism

π-stacking in ground-state dimers/trimers/tetramers of N-butoxyphenyl(naphthalene)diimide (BNDI) exceeds 50 kcal ⋅ mol-1 in strength, drastically surpassing that for the *3[pyrene]2 excimer (∼30 kcal ⋅ mol-1; formal bond order = 1) and similar to other weak-to-moderate classical covalent bonds. Cooperative π-stacking in triclinic (BNDI-T) and monoclinic (BNDI-M) polymorphs effects unusually large linear thermal expansion coefficients (α a , α b , α c , β) of (452, -16.8, -154, 273) × 10-6 ⋅ K-1 and (70.1, -44.7, 163, 177) × 10-6 ⋅ K-1, respectively. BNDI-T exhibits highly reversible thermochromism over a 300-K range, manifest by color changes from orange (ambient temperature) toward red (cryogenic temperatures) or yellow (375 K), with repeated thermal cycling sustained for over at least 2 y.