A thermochromic polymer elastomer material and its preparation method

Abstract

This invention discloses a thermochromic elastomer and its preparation method. The method includes the following steps: First, a methacrylic acid monomer containing a 1,10-phenanthroline structure is synthesized and mixed with acrylic acid or acrylate coordinating monomers and flexible monomers to form a homogeneous system. Then, a fluorescent rare earth metal salt, a temperature-insensitive or low-sensitivity fluorescent emitting substance, and a photoinitiator are added and stirred evenly to form a precursor solution. The precursor solution is placed in a mold and subjected to a free radical polymerization reaction under ultraviolet light irradiation to obtain the thermochromic elastomer. This invention fully utilizes the coordination crosslinking effect and dynamics of fluorescent rare earth particles, and regulates the temperature response of rare earth ion fluorescence through the coordination crosslinking network to achieve high strength, high toughness, efficient self-healing, and high temperature-sensitive fluorescent color-changing properties of the elastomer.

Description

Technical Field

[0001] This invention belongs to the field of materials science and technology, specifically relating to a thermochromic polymer elastomer material and its preparation method. Background Technology

[0002] With the rapid development of flexible electronic devices, smart wearable systems, and visual sensing technologies, the development of temperature sensing materials that combine flexibility, self-healing properties, and high sensitivity has become a research hotspot. Among these, temperature-responsive materials based on fluorescence signal changes have attracted widespread attention due to their advantages such as non-contact detection, rapid response, and high visualization. Existing thermoluminescent materials mainly include systems of inorganic phosphors, organic dyes, and rare earth complexes, among which rare earth ions (such as Tb) are particularly important. 3+ Eu 3+ Due to its narrow-band emission, long lifetime, and good photostability, fluorescence is considered an important luminescent unit for constructing high-performance fluorescence temperature sensing systems. Furthermore, by introducing organic dyes to form a dual-emission system, ratiometric fluorescence detection can be achieved by utilizing the differences in temperature response at different emission centers, thereby effectively improving measurement accuracy and anti-interference capabilities. However, most existing research systems focus on solutions, rigid matrices, or inorganic composite materials, lacking good flexibility and self-healing properties, making it difficult to meet the application requirements of flexible devices.

[0003] In recent years, introducing coordination crosslinking structures into polymer materials has become an important strategy for regulating material properties. Through coordination, on the one hand, coordination crosslinking can be generated, endowing materials with strong and tough mechanical properties and self-healing properties; on the other hand, it can sensitize the fluorescence of rare earth metals and endow their fluorescence intensity with responsiveness to external stimuli, achieving synergistic regulation of structure and properties. However, existing technologies usually only focus on achieving a single function, and it is difficult to simultaneously achieve mechanical properties, self-healing, and fluorescence response sensitivity. If the mechanical properties are strong, the fluorescence color change and self-healing properties will decrease significantly. For example, polymer materials with high coordination crosslinking dynamics have good self-healing properties and high responsiveness, but very low mechanical properties. Therefore, existing technologies lack synergistic design among the three factors of "coordination dynamic reversibility-luminescence behavior-polymer mechanical properties," making it difficult to balance temperature response sensitivity, mechanical toughness, and self-healing properties in materials. Therefore, there is an urgent need to develop a novel material system based on dynamic coordination, thermosensitive fluorescence and elastomer network structure, so as to organically unify the temperature sensitivity of rare earth coordination luminescence with the mechanical properties and self-healing properties of flexible polymers, thereby obtaining a functional elastomer material with high sensitivity of thermo-fluorescent color change, toughness and self-healing properties. Summary of the Invention

[0004] The purpose of this invention is to provide a thermochromic polymer elastomer material and its preparation method, so as to overcome the problem that the existing technology usually only focuses on the realization of a single function, and it is difficult to take into account mechanical properties, self-healing and fluorescence response sensitivity at the same time.

[0005] This invention provides a method for preparing a thermochromic polymer elastomer material, comprising the following steps: Step 1, Monomer Synthesis: In a dry 100 mL three-necked flask, add 2.0 g (approximately 10 mmol) of 5-amino-1,10-phenanthroline and 30 mL of anhydrous N,N-dimethylformamide (DMF). Under stirring and nitrogen protection, ensure complete dissolution. Then, add 1.2–1.8 equivalents of glycidyl methacrylate, a trace amount of triethylamine (approximately 0.1–0.3 equivalents) as a catalyst, and a small amount of hydroquinone (approximately 200–300 ppm) as a polymerization inhibitor. Place the reaction system in an oil bath at 50–65 °C and stir for 12–24 minutes. After the reaction was completed and cooled to room temperature, the reaction solution was slowly poured into a large amount of ice water to precipitate a solid product. The precipitate was collected by filtration and repeatedly washed with deionized water to remove solvent and unreacted small molecules. After washing with a small amount of ethanol, it was dried under vacuum at 40°C to obtain the product 5-[2-hydroxy-3-(methacryloyloxy)propylamino]-1,10-phenanthroline, abbreviated as Phen-GMA monomer. The reaction equation is as follows: ; The second step is the synthesis of the thermochromic elastomer: The synthesized Phen-GMA monomer, acrylic acid (AA, providing carboxyl groups as ligands), and n-butyl acrylate (BA, flexible monomer) are added to a dry reaction flask in a certain molar ratio (e.g., Phen-GMA:AA:BA = 1:2:7). The mixture is stirred at room temperature to form a homogeneous and transparent liquid. Then, an appropriate amount of rhodamine B (0.01–0.05 wt%) is added as a red fluorescent reference with low temperature sensitivity, and terbium nitrate (at a molar ratio of Tb) is added. 3+ Phen (0.2–0.5%) was used as the green coordination luminescent center, and Irgacure 2959 (1–2 wt%) was added as the photoinitiator. The mixture was stirred for 30 min under light-protected conditions to ensure that all components were fully dissolved and uniformly dispersed. The resulting homogeneous precursor solution was then poured into a pre-prepared mold, sealed with a transparent polyester film, and placed under a UV light source (365 nm, light intensity approximately 10–20 mW·cm). -2 In-situ free radical photopolymerization was carried out by irradiation for 30–60 min to obtain cross-linked elastomers. After the reaction was completed, the samples were taken out and vacuum post-treated at 40 °C for 10–24 hours to finally obtain thermochromic elastomer materials.

[0006] The present invention also provides a thermochromic polymer elastomer material, which is prepared by the above preparation method.

[0007] Compared with the prior art, the beneficial effects of the present invention are: The thermochromic polymer elastomer material of this invention, on the one hand, introduces monomers containing sensitizing ligands such as 1,10-phenanthroline into the polymer elastomer network to enhance fluorescence and impart high temperature sensitivity to fluorescent rare earth ions, while providing strong cross-linking; on the other hand, it uses monomers containing weaker ligands such as acrylic acid to provide energy-dissipative coordination cross-linking. These two types of coordination cross-linking achieve strong and tough mechanical properties, sensitive fluorescence emission, and good self-healing properties in the elastomer. Furthermore, the red fluorescence of Rhodamine B is relatively stable to temperature; by constructing a ratiometric fluorescence response through a dual-emission system, visualization and highly sensitive detection of temperature changes are achieved. This preparation method employs photoinitiated free radical polymerization, which features mild reaction conditions, rapid reaction speed, and easy processing and molding. It can achieve rapid material preparation at room temperature or low temperature, exhibiting good process adaptability. By controlling the monomer ratio and rare earth ion content, the fluorescence color, response sensitivity, and mechanical properties can be synergistically controlled, demonstrating strong designability and broad application potential. The prepared elastomer possesses excellent flexibility, high strength, high toughness, highly sensitive thermochromic color change properties, and self-healing properties, making it widely applicable in fields such as temperature sensing, flexible electronics, smart wearable devices, and security and anti-counterfeiting. Attached Figure Description

[0008] Figure 1 The fluorescence emission spectra of the fluorescent color-changing elastomer prepared according to Example 1 at 25°C and 100°C are shown. Figure 2 This is a schematic diagram showing the changes in chromaticity coordinates of the fluorescent color-changing elastomer prepared according to Example 1 at 25 °C and 100 °C. Figure 3 The stress-strain curves of the fluorescent color-changing elastomer prepared according to Example 1 and the stress-strain curves after cutting and repair and then stretching are shown. Figure 4 The changes in fluorescence color of the elastomers in Examples 1-3 under 254 nm ultraviolet light irradiation; Figure 5 The diagram shows the stretching of the joint after self-repair at the joint of the elastomer shown in Example 3 (left side) and the elastomer shown in Example 1 after being cut open; Figure 6 This is a color-changing diagram of an elastomer; Figure 7 The data are rheological test data during the curing process of the elastomer in Example 1. Detailed Implementation

[0009] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0010] Example 1: First, the monomer was synthesized. 2.0 g (approximately 10 mmol) of 5-amino-1,10-phenanthroline and 30 mL of anhydrous N,N-dimethylformamide were added to a dry 100 mL three-necked flask. Nitrogen gas was bubbled through the flask under stirring until completely dissolved. Then, 1.2 equivalents of glycidyl methacrylate, 0.1 equivalents of triethylamine, and 200 ppm of hydroquinone were added. The mixture was reacted at 50 °C for 12 h. After the reaction, the reaction solution was poured into ice water to precipitate a solid. The solid was filtered, washed with water and ethanol, and dried under vacuum at 40 °C to obtain the Phen-GMA monomer. Next, the elastomer was prepared. The above monomer, acrylic acid, and n-butyl acrylate were mixed in a molar ratio of 1:2:7. After stirring to form a homogeneous liquid, 0.02 wt% of Rhodamine B and a molar ratio of Tb were added. 3+ Terbium nitrate with a phen content of 0.2% was added, followed by 1 wt% photoinitiator Irgacure 2959. After stirring in the dark for 30 minutes, the mixture was poured into a mold and sealed. The mixture was then incubated under 365 nm ultraviolet light (10 mW·cm⁻¹). -2 Photopolymerization was carried out by irradiation for 45 minutes to obtain an elastomer film, which was then vacuum dried at 40°C for 12 hours to obtain a thermochromic elastomer.

[0011] like Figures 1-3 As shown, this elastomer exhibits significant thermo-fluorescent color change, high strength and toughness, and good self-healing properties.

[0012] Example 2: A method for preparing a thermochromic elastomer, the steps of which are basically the same as those in Example 1, except that: in the monomer synthesis process, the amount of glycidyl methacrylate is 1.5 equivalents, the amount of triethylamine is 0.2 equivalents, the amount of hydroquinone is 250 ppm, the reaction temperature is 60 ℃, and the reaction time is 18 h; in the elastomer preparation process, the molar ratio of Phen-GMA, acrylic acid, and n-butyl acrylate is 1:1.5:7.5, the amount of rhodamine B is 0.03 wt%, and the amount of terbium nitrate added is Tb. 3+ Phen=0.35, photoinitiator dosage is 1.5 wt%, under 365 nm ultraviolet light (15 mW·cm⁻¹) -2 Polymerization was completed by irradiation for 60 min. The resulting elastomer was vacuum dried at 40 °C for 18 h to obtain the target material. The material showed a more obvious change in fluorescent color from green to orange-red during temperature change.

[0013] Example 3: A method for preparing a thermochromic elastomer, the steps of which are basically the same as those in Example 1, except that: in the monomer synthesis, the amount of glycidyl methacrylate is 1.8 equivalents, the amount of triethylamine is 0.3 equivalents, the amount of hydroquinone is 300 ppm, the reaction temperature is 65 ℃, and the reaction time is 24 h; in the elastomer preparation, the molar ratio of Phen-GMA, acrylic acid, and n-butyl acrylate is 1:1:8, the amount of rhodamine B is 0.05 wt%, and the amount of terbium nitrate added is Tb. 3+ Phen=0.5, photoinitiator dosage is 2 wt%, under 365 nm ultraviolet light (20 mW·cm⁻¹) -2 Rapid curing was achieved by irradiation for 30 minutes, and the resulting elastomer was obtained after vacuum drying at 40 °C for 24 h. This material has higher flexibility and a wider thermo-fluorescent response range.

[0014] like Figure 4 The values ​​'ac' in the figures represent the fluorescence color changes of the elastomers in Examples 1-3 under 254 nm ultraviolet light. Due to the different contributions of the green fluorescence from Tb ions and the added red fluorescence, the fluorescence colors differ at room temperature. The figures also show that the color-changing temperature ranges of the three different elastomers are significantly different. Example 1's color-changing range is 70-80°C. o Around C, while Example 3 is below 40. o C indicates that a color change occurs, meaning the color change range is wide enough.

[0015] Depend on Figure 5 It can be seen that this elastomer has good self-healing ability. The different colors on both sides clearly show the effect of the elastomer's self-healing. Figure 3 The diagram shows the stress-strain curves of the elastomer before and after self-healing in Example 1. It can be seen that the repaired elastomer exhibits mechanical properties very close to its initial state. This result also indicates that the elastomer possesses excellent tensile properties, with an elongation at break reaching nearly 6000%, demonstrating good flexibility.

[0016] Depend on Figure 6 As can be seen, this elastomer has excellent flexibility and can be wrapped around the arm. It glows green without hot air, turning red when hot air is applied. In the final image, placing a hand on the elastomer immediately creates a finger pattern; this is because the fingers block the hot air, causing the blocked portion to revert to green.

[0017] like Figure 7As shown in the figure, the rheological test data during the curing process of the elastomer in Example 1 show that the formation of the cross-linked network can be seen after about 10 minutes of UV irradiation (the intersection of the storage modulus G' and the loss modulus G" in the figure). After about 45 minutes, the storage modulus G' and the loss modulus G" basically leveled off, indicating that the curing reaction has basically completed the rapid curing process.

[0018] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A thermochromic elastomer, characterized in that, The elastomer is formed by photoinitiated polymerization of the following components: a methacrylic acid monomer containing a 1,10-phenanthroline structure, an acrylic acid or acrylate coordinating monomer, a flexible monomer, a fluorescent rare earth metal salt, and a temperature-insensitive or low-sensitive fluorescent emitting material. The methacrylic acid monomer containing a 1,10-phenanthroline structure contains a 1,10-phenanthroline group that can coordinate with rare earth ions and a carbon-carbon double bond structure that can participate in free radical polymerization. The rare earth ions in the rare earth salt can form dynamic coordination bonds with the 1,10-phenanthroline group and produce temperature-sensitive fluorescence emission. The fluorescence intensity of the temperature-insensitive or low-sensitive fluorescent emitting material is insensitive to temperature changes or has low sensitivity, and when mixed with rare earth metal fluorescent colors, it can produce other different colors, achieving a thermochromic fluorescence function.

2. The thermochromic elastomer according to claim 1, characterized in that, The methacrylic acid monomer containing the 1,10-phenanthroline structure is 5-[2-hydroxy-3-(methacryloyloxy)propylamino]-1,10-phenanthroline or its structural analogue, obtained by reacting 5-amino-1,10-phenanthroline with a vinyl monomer containing an epoxy group, or an acrylate / methacrylate monomer, with a trace amount of triethylamine as a catalyst and a small amount of hydroquinone as a polymerization inhibitor.

3. The thermochromic elastomer according to claim 1, characterized in that, The acrylic or acrylate coordinating monomer is selected from one or more of acrylic acid, vinylimidazole, or 4-vinylpyridine.

4. The thermochromic elastomer according to claim 1, characterized in that, The flexible monomer is selected from one or more of n-butyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, butyl methacrylate, or isooctyl acrylate.

5. The thermochromic elastomer according to claim 1, characterized in that, The fluorescent rare earth metal salt is a Tb-containing salt. 3+ Or Eu 3+ Inorganic salts, which are nitrates or chlorides.

6. The thermochromic elastomer according to claim 1, characterized in that, The temperature-insensitive or low-sensitivity fluorescent emitting material is selected from one or more of rhodamine dyes, nilored, fluorescein, and curcumin.

7. The thermochromic elastomer according to claim 1, characterized in that, The proportions of each component are as follows: the molar ratio of rare earth ions to 1,10-phenanthroline groups is 0.1 to 1.0; the amount of fluorescent emitting material that is insensitive or has low sensitivity to temperature is 0.001 wt% to 0.1 wt% of the total mass of the elastomer.

8. The thermochromic elastomer according to claim 1, characterized in that, It also includes a photoinitiator, which is selected from one or more of Irgacure 2959, Irgacure 1173, Irgacure 651, TPO or benzophenone initiators, and is used in an amount of 0.5 wt% to 3 wt% of the total monomer mass.

9. A method for preparing a thermochromic elastomer as described in any one of claims 1 to 8, characterized in that, Includes the following steps: (1) A homogeneous system is formed by mixing methacrylic acid monomers containing 1,10-phenanthroline structure, acrylic acid or acrylate coordinating monomers and flexible monomers; (2) Add fluorescent rare earth metal salt, temperature-insensitive or low-sensitivity fluorescent emitting material and photoinitiator, and stir evenly to form a precursor solution; (3) The precursor liquid is placed in a mold and subjected to free radical polymerization under ultraviolet light to obtain the thermo-fluorescent elastomer.

10. The preparation method according to claim 9, characterized in that, The rare earth ions coordinate with 1,10-phenanthroline groups and ligand groups of acrylic acid or acrylate monomers before or during polymerization, forming a dynamic coordination crosslinking network.

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