Thermal activation delayed fluorescence polymer material based on octahydrobinaphthalene skeleton and optical strain film sensor thereof

Abstract

The invention discloses a thermal activation delayed fluorescence polymer material based on an octahydrobinaphthalene skeleton and an optical strain film sensor thereof. A pair of chiral thermally activated delayed fluorescence polymers (R / S)-Fr are synthesized through iodination, nucleophilic substitution and Suzuki coupling copolymerization with octahydrobinaphthol as a chiral unit, and the chiral thermally activated delayed fluorescence polymers (R / S)-Fr have good film-forming property, thermal stability and thermally activated delayed fluorescence characteristics. The obtained thermally activated delayed fluorescent material is blended with an elastomer SEBS, an optical strain film sensor is prepared through a spin-coating process, the sensor is in linear response within the strain range of 0%-30% and 30%-60%, the maximum fluorescence amplification reaches 26 times, and the cycling stability and the environmental stability are excellent. The preparation method is simple in process and high in operability, and has a wide application prospect in the field of optical sensing.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of cross between thermally activated delayed fluorescence (TADF) material and optical strain sensing, in particular to the synthesis of chiral TADF polymer material based on octahydrobinaphthyl skeleton, and the preparation of optical strain film sensor based on the blending of TADF material and elastomer. BACKGROUND

[0002] In recent years, the technology of organic light-emitting diode (OLED) has developed rapidly in the field of display and lighting. However, the low exciton utilization efficiency of traditional fluorescent materials and the high cost caused by the dependence on noble metals (such as iridium and platinum complexes) in phosphorescent materials have seriously restricted the performance upgrade. Thermally activated delayed fluorescence (TADF) material, which can theoretically achieve 100% exciton utilization rate through the reverse intersystem crossing (RISC) process and does not require the participation of noble metals, has become the core of the research and development of the new generation of functional luminescent materials. This feature makes it possible to expand to cross-field applications such as sensing while maintaining excellent optoelectronic properties.

[0003] However, existing TADF materials are mostly focused on the optimization of OLED devices, and their application in the field of optical strain sensing has not been fully explored. Traditional fluorescent strain sensing materials (such as organic crystals, dynamic covalent networks, and ordinary fluorescent / elastomer composites) generally have common defects: (1) lack of rigid skeleton (to ensure stability), good film-forming property, and strain response sensitivity, resulting in poor linear response of sensing signal and low switching ratio; (2) insufficient compatibility between elastomer and luminescent material, which easily causes cracking during stretching and obvious cycle fatigue, making it difficult to meet the needs of high-precision strain detection and human-computer interaction.

[0004] In particular, the existing sensing materials have a narrow strain response range, making quantitative detection difficult and having weak environmental adaptability. If luminescent materials with TADF characteristics can be effectively combined with elastomers, it is expected to break through the performance bottleneck of traditional sensing films by taking advantage of their high fluorescent performance and structural adjustability. Therefore, developing a new type of optical strain sensing system based on TADF materials, designing TADF polymers with rigid structure and flexible adaptability, and optimizing the blending process of TADF materials and elastomers to achieve the unity of linear response, high switching ratio, and excellent cycle stability, is the key to promoting the intelligent and multifunctional upgrade of strain sensors. It also fills the gap of TADF materials in the field of sensing, and becomes an important topic in the field of material science and engineering. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application provides a thermal-activated delayed fluorescence polymer material based on octahydrobinaphthyl skeleton and an optical strain film sensor thereof, aiming to: design a chiral synthesis strategy based on octahydrobinaphthyl skeleton, take octahydrobinaphthol (OBN) as a chiral unit, and synthesize a chiral polymer material (R / S)-Fr (i.e. (R)-Fr or (S)-Fr) with a rigid molecular skeleton, good film-forming property and TADF characteristics through iodination, nucleophilic substitution, Suzuki coupling copolymerization and other reactions, to provide a high-performance light-emitting core for optical strain sensing; construct a blending system of the TADF polymer material (R / S)-Fr and an elastomer, realize controllable response of the fluorescence intensity of the fluorescent film under tensile strain by means of the strain-sensitive characteristics of the TADF molecule and the flexible regulation of the elastomer, solve the problems of poor linearity, easy cracking and insufficient cycle stability of the traditional sensing film, and finally obtain a high-performance optical strain film sensor to meet the high-precision strain detection requirement.

[0006] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions: The present application first provides a thermal-activated delayed fluorescence polymer material based on octahydrobinaphthyl skeleton, wherein the thermal-activated delayed fluorescence polymer material takes octahydrobinaphthol (OBN) as a chiral unit, and the structure is shown in formula (1): .

[0007] The thermal-activated delayed fluorescence polymer material based on octahydrobinaphthyl skeleton of the present application has a donor-acceptor (D-A) structure. The donor (D) is an electron-rich polycyclic aromatic hydrocarbon (containing octahydrobinaphthyl), the acceptor (A) is an electron-deficient unit containing a cyano group and a nitrogen heterocycle, the donor and the acceptor are connected through an ether bond, and the molecule contains a long alkyl side chain (-C8H 17 ). The singlet and triplet energy level difference (ΔE st ) of the polymer is 0.04 eV, and the polymer has TADF characteristics.

[0008] The octahydrobinaphthyl unit is a rigid fused ring structure, which is introduced into the polymer main chain to increase the molecular rigidity and conjugation degree, improve the chemical stability, and regulate the molecular packing mode through steric hindrance and electronic effect; the long alkyl side chain is used to increase the intermolecular flexibility, improve the solubility (which is beneficial to solution processing and film forming), and at the same time regulate the main chain conjugated plane packing; the cyano group (-CN) enhances the D-A electron push-pull effect, widens the absorption spectrum, and improves the charge separation efficiency; the nitrogen heterocycle regulates the electrochemical properties by changing the electron cloud distribution and energy level, and optimizes the carrier injection and transport efficiency.

[0009] The preparation method of the thermal-activated delayed fluorescence polymer material based on octahydrobinaphthyl skeleton of the present application comprises the following steps: Step 1: synthesis of intermediate (R)-1 or (S)-1 The starting material (R)-5,5',6,6',7,7',8,8'-octahydrobinaphthol or (S)-5,5',6,6',7,7',8,8'-octahydrobinaphthol, morpholine, and elemental iodine were dissolved in dichloromethane at a molar ratio of 1:5.5-6.5:2.0-2.1 under room temperature, and stirred for 8-12 hours. After the reaction was completed, dilute hydrochloric acid was added for quenching, and dichloromethane and water were used for extraction. The organic phase was washed with saturated sodium thiosulfate solution for 2-4 times, and concentrated under reduced pressure. Dichloromethane / petroleum ether (1:1, by volume) was used as the eluent, and the intermediate (R)-1 or (S)-1 was obtained by column chromatography. Step 2: Synthesis of intermediate (R)-2 or (S)-2 The intermediate (R)-1 or (S)-1, tetrachloro-p-phenylenedinitrile, and potassium carbonate were dissolved in dry N,N-dimethylformamide (DMF) at a molar ratio of 1:1.0-1.1:1.8-2.2 under an argon atmosphere, and heated and stirred at 30-35°C for 20-24 hours. The reaction solution was diluted with water, and extracted with ethyl acetate. The organic phase was concentrated under reduced pressure, and petroleum ether / dichloromethane (7:2, by volume) was used as the eluent. The intermediate (R)-2 or (S)-2 was obtained by column chromatography. Step 3: Synthesis of monomer (R)-3 or (S)-3 before polymerization The intermediate (R)-2 or (S)-2, carbazole, and cesium carbonate were dissolved in dry DMF at a molar ratio of 1:2.0-2.2:4.0-4.5 under an argon atmosphere, and stirred at 40-45°C for 20-24 hours. The reaction solution was diluted with water, and extracted with dichloromethane. The organic phase was concentrated under reduced pressure, and first purified by column chromatography using petroleum ether / dichloromethane (2:1, by volume) as the eluent, and then recrystallized using an ethanol / ethyl acetate mixed solvent to obtain the monomer (R)-3 or (S)-3 before polymerization. Step 4: Synthesis of polymer material (R)-Fr or (S)-Fr The monomer (R)-3 or (S)-3, 9,9-di-n-octylfluorene-2,7-diboronic acid pinacol ester, palladium tetra(triphenylphosphine), potassium carbonate are dissolved in a dry 1,4-dioxane and deionized water mixed solution in a molar ratio of 1:1:0.08-0.12:8-12 under an argon atmosphere, and stirred at 80-85°C for 68-72 hours; then benzene boronic acid is added and reacted for 2 hours, and iodobenzene is added and reacted for 2-3 hours, the amount of benzene boronic acid is 0.18-0.22 times the molar amount of the monomer, and the amount of iodobenzene is 0.08-0.12 times the molar amount of the monomer; then sodium diethyldithiocarbamate trihydrate dissolved in deionized water is added, and the temperature is raised to 90-95°C for continued reaction for 20-24 hours, and then cooled to room temperature; the reaction solution is diluted with water, extracted with dichloromethane, and the organic phase is concentrated under reduced pressure; the concentrated product is dissolved in dichloromethane, added dropwise into stirring methanol, and then filtered after standing overnight; the filter cake is sequentially subjected to soxhlet extraction with acetone, n-hexane, and dichloromethane, the dichloromethane soxhlet extract is collected and concentrated under reduced pressure, dichloromethane and petroleum ether are added again, and then concentrated under reduced pressure to obtain the thermal-activated delayed fluorescence polymer material (R)-Fr or (S)-Fr based on an octahydrobinaphthalene skeleton, wherein the (R)-Fr and (S)-Fr are enantiomeric structures; the number average molecular weight of (R)-Fr is 6014 Da, and the molecular weight distribution coefficient PDI is 1.52; the number average molecular weight of (S)-Fr is 4839 Da, and the molecular weight distribution coefficient PDI is 1.39.

[0010] The application further provides a preparation method of an optical strain film sensor based on the thermal-activated delayed fluorescence polymer material, comprising the following steps: Step 1: dissolving and mixing the thermal-activated delayed fluorescence polymer material and the elastomer uniformly in a blending solvent to obtain a precursor solution; Step 2: coating the precursor solution on a substrate to obtain an optical strain film sensor after annealing.

[0011] Preferably, the elastomer comprises at least one of polystyrene-based elastomers (such as SBS and SEBS), polyurethane-based elastomers (such as TPU), polyolefin-based elastomers (such as TPE and TPV), polyamide-based thermoplastic elastomers (such as PA1212 and PA1012), thermoplastic rubber materials (such as TPR), and polydimethylsiloxane (PDMS).

[0012] Preferably, in step 1, the concentrations of the thermal-activated delayed fluorescence polymer material and the elastomer in the precursor solution are 5-10 mg / mL respectively, and the mass percentage of the two is 10%-75%:90%-25%.

[0013] Preferably, in step 2, the substrate is subjected to ultraviolet ozone cleaning treatment for 15-20 min.

[0014] Preferably, in step 2, the spin-coating speed of the precursor solution is 2000-2500 rpm, and the spin-coating time is 35-40 seconds.

[0015] Preferably, in step 2, the annealing temperature is 110-120℃, and the annealing time is 15-20 minutes.

[0016] Compared with the prior art, the present application has the following advantages: The present application provides a method for preparing an optical strain film sensor by hot-activating a fluorescent polymer material and an elastomer, which has the advantages of simple process, easy operation, strong controllability and outstanding practicability, and does not require complex equipment and harsh reaction conditions. The obtained sensing film has a precise linear response relationship between the fluorescence intensity and the strain under the action of tensile strain, and has excellent cycle stability, environmental adaptability (water immersion resistance, wide temperature range stability) and mechanical reliability, and has broad industrial application prospects in the fields of flexible wearable display, high-precision optical strain sensing, intelligent flexible electronics, etc., and provides an efficient and feasible technical scheme for the development and application of a new generation of flexible sensing material. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figures 1-4 The synthesis route of the polymer material (R)-Fr or (S)-Fr is shown in the figure, wherein (R / S) represents (R) or (S); Figure 5 The GPC test spectrum of the polymer material (S)-Fr prepared in Example 1 of the present application is shown in the figure.

[0018] Figure 6 The ultraviolet-visible absorption spectrum of the polymer material (S)-Fr prepared in Example 1 of the present application is shown in the figure.

[0019] Figure 7 The transient photoluminescence spectrum of the polymer material (S)-Fr prepared in Example 1 of the present application is shown in the figure.

[0020] Figure 8 The metallographic microscope pictures of the pure (S)-Fr film (100%:0%) and the (S)-Fr / SEBS blended film (33.3%:66.7%) prepared in Example 3 of the present application under different tensile strains are shown in the figure.

[0021] Figure 9 The atomic force microscope pictures of the pure (S)-Fr film (100%:0%) and the (S)-Fr / SEBS blended film (33.3%:66.7%) prepared in Example 3 of the present application under different tensile strains are shown in the figure.

[0022] Figure 10The fluorescence properties of the pure (S)-Fr film (100%:0%) and the (S)-Fr / SEBS blend film (33.3%:66.7%) prepared in Example 3 of this invention under different tensile strains are shown in (a) and (b), which are fluorescence spectra and fluorescence intensity comparison diagrams of the pure (S)-Fr film; and (c) and (d), which are fluorescence spectra and fluorescence intensity comparison diagrams of the (S)-Fr / SEBS blend film.

[0023] Figure 11 The fluorescence spectra of the (S)-Fr / SEBS blend film (33.3%:66.7%) prepared in Example 3 of this invention under different tensile strains are shown. Figure 11 (a) and the linear fitting plot of fluorescence intensity ( Figure 11 (b) in the middle.

[0024] Figure 12 The image shows the tensile cycling stability of the (S)-Fr / SEBS blend film (33.3%:66.7%) prepared in Example 3 of this invention, where (a) represents the fluorescence performance under different strain cycles and (b) represents the fluorescence performance under 30% strain cycles.

[0025] Figure 13 The fluorescence intensity change of the (S)-Fr / SEBS blend film (33.3%:66.7%) prepared in Example 3 of this invention during immersion in water for 30 days. Figure 13 (a) and the changes in fluorescence intensity at different temperatures ( Figure 12 (b) in the middle.

[0026] Figure 14 The fluorescence spectra of (S)-Fr and SEBS at different blending ratios in Example 4 of this invention are shown below. Figure 14 (a) and fluorescence intensity comparison diagram ( Figure 14 (b) in the middle. Detailed Implementation

[0027] The embodiments of the TADF-type material Fr and the optical strain thin film sensor based thereon, as described below with reference to the accompanying drawings, are described in detail. The embodiments provide the specific structure of the material, the synthesis steps and related experimental procedures, but the scope of protection of the present invention is not limited to the following embodiments.

[0028] Example 1: Preparation of thermally activated delayed fluorescent polymer material (S)-Fr Step 1: Synthesis of intermediate (S)-1 At room temperature, ( S )-5,5',6,6',7,7',8,8'-octahydrobinaphthol (5.89 g, 20.0 mmol, ( S) in 177 mL of dichloromethane, then morpholine (10.45 g, 120 mmol) was added, and finally iodine (10.24 g, 40.3 mmol) was added in three batches with an interval of 2 hours. After stirring to mix the system, the reaction was continuously stirred at room temperature (25 °C) for 12 hours. After the reaction was completed, 50 mL of dilute hydrochloric acid was added to quench the reaction, followed by extraction separation with dichloromethane (3x150 mL) and water (300 mL); the organic phase was collected and washed with saturated sodium thiosulfate solution for 3 times, and then the organic phase was concentrated under reduced pressure to obtain the crude product. The crude product was purified by column chromatography with dichloromethane / petroleum ether (v / v =1 / 1) as the eluent, and finally the white solid intermediate (S)-1 was obtained with a yield of 66%. The synthesis route is shown in Figure 1 . 1 H NMR (500 MHz, CDCl3): δ 7.44 (s, 2H), 2.65 (t, J =5.0 Hz, 4H), 2.22-2.17 (m, 2H), 2.05-2.00 (m, 2H), 1.66-1.54 (m, 8H). Step 2: Synthesis of intermediate (S)-2 Under an argon protective atmosphere, dry DMF (50 mL) was added to a dry reaction vessel as a solvent, and then intermediate (S)-1 (5.46 g, 10.0 mmol), tetrachloro-p-phenylenedinitrile (2.10 g, 10.5 mmol), and potassium carbonate (2.76 g, 20.0 mmol) were sequentially added. After stirring to mix, the reaction was heated and stirred at 30 °C for 24 hours, and after the reaction was completed, the reaction was naturally cooled to room temperature. Water (300 mL) was added to the cooled reaction solution to dilute it, and then extraction was performed with ethyl acetate (3x300 mL), and all the organic phases were combined and concentrated under reduced pressure to obtain the crude product. The crude product was purified by column chromatography with petroleum ether / dichloromethane (v / v = 7 / 2) as the eluent, and finally the white solid intermediate (S)-2 was obtained with a yield of 96.5%. The reaction formula is shown in Figure 2 . 1 H NMR(500 MHz, CDCl3): δ 7.62 (s, 2H), 2.85-2.76 (m, 4H), 2.55-2.49 (m,2H), 2.35-2.31 (m, 2H), 1.84-1.66 (m, 8H). Step 3: Synthesis of monomer (S)-3 before polymerization Into a dry reaction vessel, dry DMF (50 mL) was added as a solvent under an argon atmosphere, followed by the addition of intermediate (S)-2 (3.53 g, 5.0 mmol), carbazole (1.84 g, 11.0 mmol), cesium carbonate (7.17 g, 22.0 mmol) sequentially. After stirring well, the reaction system was placed in an environment of 45 °C, and stirring was continued for 24 hours. After the reaction was completed, the reaction solution was naturally cooled to room temperature. Water (300 mL) was added to the cooled reaction solution to dilute it, followed by extraction with dichloromethane (3 x 300 mL). All the organic phases were combined and concentrated under reduced pressure to obtain a crude product. The crude product was first purified by column chromatography using petroleum ether / dichloromethane (v / v = 2 / 1) as an eluent, and the yield was 55.3%. The product after the preliminary purification was recrystallized with ethanol / ethyl acetate mixed solvent, and the recrystallization operation was repeated 3 times, and finally a high-purity white solid of polymerization precursor (S)-3 was obtained. The reaction formula is shown in Figure 3 . 1 H NMR (500 MHz, CDCl3): δ 7.78 (s, 2H), 7.72 (d, J =6.5 Hz, 2H), 7.62 (d, J = 6.0 Hz, 2H), 7.45 (d, J = 7.0 Hz, 2H), 7.28 (t, J =6.5 Hz, 2H), 7.15 (t, J = 6.5 Hz, 2H), 6.93 (t, J = 6.5 Hz, 2H), 6.79 (t, J =6.5 Hz, 2H), 6.70 (d, J = 7.0 Hz, 2H), 2.93-2.83 (m, 4H), 2.61-2.56 (m, 2H),2.43-2.38 (m, 2H), 1.90-1.79 (m, 6H), 1.74-1.67 (m, 2H). Step 4: Synthesis of polymer material (S)-Fr Under the protection of argon atmosphere, a dry reaction vessel was added with a mixed solution of dry 1,4-dioxane (12 mL) and deionized water (3 mL) as a solvent, and then sequentially added with monomer (S)-3 (0.31 g, 0.3 mmol), 9,9-di-n-octylfluorene-2,7-diboronic acid bis(pinacol ester) (0.19 g, 0.3 mmol), tetrakis(triphenylphosphine)palladium (0.035 g, 0.03 mmol), and potassium carbonate (0.42 g, 3.0 mmol). After being stirred uniformly, the reaction system was placed in an environment at 85°C, and continuously stirred for 72 hours. After the reaction was completed, benzeneboronic acid (0.06 mmol, 7.32 mg) was added to the system, and continuously stirred for 2 hours. Then, iodobenzene (0.03 mmol, 6.12 mg) was added, and continuously stirred for another 2 hours. Subsequently, 1 g of sodium diethyldithiocarbamate trihydrate was dissolved in 20 mL of deionized water, and the aqueous solution was added to the reaction system. The reaction temperature was increased to 90°C, and continuously stirred for 24 hours. After the reaction was completed, the system was naturally cooled to room temperature.

[0029] The cooled reaction solution was diluted with water (50 mL), and then extracted with dichloromethane (3 x 50 mL) for multiple times. All the organic phases were combined and concentrated under reduced pressure. To the concentrated product, 4 mL of dichloromethane was added to completely dissolve the product. The solution was added dropwise to 100 mL of methanol being stirred, and then left to stand overnight. After that, the filter cake was collected by suction filtration.

[0030] The filter cake was placed in a Soxhlet extractor, and sequentially extracted with acetone, n-hexane, and dichloromethane. The dichloromethane phase was collected, and concentrated under reduced pressure. To the concentrated product, 10 mL of dichloromethane was added to dissolve the product, and then 200 mL of petroleum ether was added. Subsequently, the mixture was concentrated under reduced pressure again, and finally a yellow-green solid product, chiral TADF polymer material (S)-Fr based on octahydrobinaphthyl skeleton, was obtained. Figure 4

[0031] As shown in Figure 5 , the number average molecular weight (Mn) of the product (S)-Fr was 4839 Da, and the molecular weight distribution coefficient (PDI) was 1.39.

[0032] Figure 6 The UV-Vis absorption spectrum of the polymer material (S)-Fr prepared in this example.

[0033] Figure 7 The transient photoluminescence spectrum of the polymer material (S)-Fr prepared in this example is shown in the figure. As can be seen from the figure, the material has the characteristic of thermal activated delayed fluorescence.

[0034] Example 2: Preparation of thermal activated delayed fluorescence polymer material (R)-Fr​ In this embodiment, the thermally activated delayed fluorescence polymer material (R)-Fr was prepared using the same method as in Example 1, except that the raw material used in step 1 was (R)-5,5',6,6',7,7',8,8'-octahydronaphthol. The steps sequentially yielded (R)-1, (R)-2, (R)-3, and (R)-Fr. The number-average molecular weight (Mn) of this product (R)-Fr was 6014 Da, and the molecular weight distribution coefficient (PDI) was 1.52.

[0035] Example 3: Fabrication of an optical strain thin-film sensor The polymer (S)-Fr and the elastomer SEBS were dissolved in toluene and mixed in two ratios: 100%:0% (pure (S)-Fr) and 33.3%:66.7% ((S)-Fr / SEBS) by mass to prepare a blend solution with a total concentration of 10 mg / mL.

[0036] In air, a PVA sacrificial layer was first spin-coated onto the surface of a silicon substrate. After drying, the aforementioned blend solution was spin-coated onto the surface of the PVA layer (spin-coating parameters: 2000 rpm, duration 40 seconds). The sample was then placed in a vacuum oven and dried at room temperature to remove the solvent. The dried sample was then heat-annealed at 120°C for 15 minutes and slowly cooled to room temperature in the oven. The film on the silicon substrate was then inverted onto the PDMS surface, and deionized water was dropped from the edge of the substrate (to dissolve the PVA sacrificial layer) to separate the film from the silicon substrate. The film was then transferred to an elastically loaded PDMS, and the change in fluorescence intensity under tensile strain was measured using a tensile online fluorescence spectrometer.

[0037] Performance test results 1. Microstructure and mechanical stability: such as Figure 8 , Figure 9 As shown, the pure (S)-Fr film exhibits significant cracks at 50% strain, and the cracks further propagate at 100% strain; however, after blending with SEBS, no obvious cracks were observed in the film at either 50% or 100% strain. The micro-phase structure formed by the introduction of SEBS can effectively suppress crack initiation and propagation, significantly improving the mechanical stability of the film.

[0038] 2. Fluorescence intensity strain response: such as Figure 10 As shown, the fluorescence intensity of the pure (S)-Fr film (without SEBS blend) decreased to 0.481 times the initial value under 50% tensile strain; when the strain increased to 100%, the fluorescence intensity further decreased to 0.06 times the initial value; while the fluorescence intensity of the (S)-Fr / SEBS blend film increased to 9.33 times the initial value under 50% tensile strain, and the fluorescence intensity increased to 13.5 times the initial value under 100% strain.

[0039] 3. Sensing performance optimization and environmental stability: As shown in Figure 11 , 12 , by reducing the concentration of the blended solution (the total concentration of materials in the blended solution is 5 mg / mL), the initial fluorescence intensity of the (S)-Fr / SEBS blended film was regulated, and further sensing performance tests were carried out. The results showed that in the two working intervals of 0%-30% and 30%-60%, the fluorescence intensity and the tensile strain showed good linear correlation; when the strain increased to 60%, the fluorescence intensity increased by 26 times of the initial value. In addition, the film showed excellent fluorescence intensity stability under different strain cycles, as shown in Figure 13 , after soaking in water for 30 days and under variable temperature environment of 25-120℃, the fluorescence performance could be stably maintained.

[0040] Example 4 The optical strain sensor was prepared according to the same method as in Example 3, with the only difference being that the ratio of TADF polymer (S)-Fr to elastomer SEBS was regulated to 75%:25%, 50%:50%, 25%:75%, and 10%:90%, respectively. The fluorescence spectrum of the obtained film under no stretching condition is shown in Figure 14 . As compared with Example 3, it can be seen that the (S)-Fr / SEBS blended film under the condition of 33.3%:66.7% has the best fluorescence performance.

[0041] In summary, the present application realizes the preparation of an optical strain sensor based on thermally activated delayed fluorescence / elastomer through a simple and efficient blending strategy. The introduction of SEBS effectively regulates the change trend of the fluorescence intensity of the film under tensile strain and improves the mechanical properties of the film. At the same time, the film has good strain sensing cycle stability and environmental stability, providing a new idea for the preparation of optical strain sensors with high sensitivity, linearity, and good stability.

Claims

1. A thermally activated delayed fluorescence polymer material based on an octahydrobinaphthyl skeleton, characterized in that, The heat-activated delayed fluorescence polymer material takes octahydrobinol OBN as a chiral unit, and the structure is shown as formula (1): 。 2. A method for producing the thermally activated delayed fluorescence polymer material based on an octahydrodipyrenyl skeleton according to claim 1, characterized by, The method comprises the following steps: Step 1: synthesis of intermediate (R)-1 or (S)-1 At room temperature, the raw materials (R)-5, 5', 6, 6', 7, 7', 8, 8'-octahydrobinol or (S)-5, 5', 6, 6', 7, 7', 8, 8'-octahydrobinol, morpholine, and elemental iodine are dissolved in dichloromethane in a molar ratio of 1:5.5-6.5:2.0-2.1, and stirred for 8-12 hours; after the reaction is completed, dilute hydrochloric acid is added for quenching, dichloromethane and water are used for extraction, the organic phase is washed with saturated sodium thiosulfate solution for 2-4 times, and after concentration under reduced pressure, dichloromethane / petroleum ether (1:1, by volume) is used as an eluent, and column chromatography is used for purification to obtain the intermediate (R)-1 or (S)-1; Step 2: synthesis of intermediate (R)-2 or (S)-2 Under an argon atmosphere, the intermediate (R)-1 or (S)-1, tetrafluoro-p-phenylenedinitrile, and potassium carbonate are dissolved in dry N, N-dimethylformamide (DMF) in a molar ratio of 1:1.0-1.1:1.8-2.2, and heated and stirred at 30-35 DEG C for 20-24 hours, and then cooled to room temperature; the reaction solution is diluted with water, extracted with ethyl acetate, and the organic phase is concentrated under reduced pressure, and petroleum ether / dichloromethane (7:2, by volume) is used as an eluent, and column chromatography is used for purification to obtain the intermediate (R)-2 or (S)-2; Step 3: synthesis of monomer (R)-3 or (S)-3 before polymerization Under an argon atmosphere, the intermediate (R)-2 or (S)-2, carbazole, and cesium carbonate are dissolved in dry DMF in a molar ratio of 1:2.0-2.2:4.0-4.5, and stirred at 40-45 DEG C for 20-24 hours, and then cooled to room temperature; the reaction solution is diluted with water, extracted with dichloromethane, and the organic phase is concentrated under reduced pressure, first eluted with petroleum ether / dichloromethane (2:1, by volume) by column chromatography, and then recrystallized with an ethanol / ethyl acetate mixed solvent to obtain the monomer (R)-3 or (S)-3 before polymerization; Step 4: synthesis of polymer material (R)-Fr or (S)-Fr The monomer (R)-3 or (S)-3, 9,9-di-n-octylfluorene-2,7-diboronic acid pinacol ester, tetrakis(triphenylphosphine)palladium, potassium carbonate are dissolved in a mixed solution of dry 1,4-dioxane and deionized water in a molar ratio of 1:1:0.08-0.12:8-12 under an argon atmosphere, and stirred at 80-85°C for 68-72 hours; then benzene boronic acid is added and reacted for 2 hours, and iodobenzene is added and reacted for 2-3 hours, the amount of benzene boronic acid is 0.18-0.22 times the molar amount of the monomer, and the amount of iodobenzene is 0.08-0.12 times the molar amount of the monomer; then sodium diethyldithiocarbamate trihydrate dissolved in deionized water is added, and the reaction is continued at 90-95°C for 20-24 hours, and then cooled to room temperature; the reaction solution is diluted with water, extracted with dichloromethane, and the organic phase is concentrated under reduced pressure; the concentrated product is dissolved in dichloromethane, added dropwise into stirring methanol, and filtered after standing overnight; the filter cake is sequentially subjected to soxhlet extraction with acetone, n-hexane, and dichloromethane, the dichloromethane soxhlet extract is collected and concentrated under reduced pressure, dichloromethane and petroleum ether are added again, and concentrated under reduced pressure again to obtain the thermal activated delayed fluorescence polymer material (R)-Fr or (S)-Fr based on octahydrobinaphthalene skeleton, wherein the (R)-Fr and (S)-Fr are enantiomeric structures.

3. The method of claim 2, wherein: The number average molecular weight of (R)-Fr is 6014 Da, and the molecular weight distribution coefficient PDI is 1.52; the number average molecular weight of (S)-Fr is 4839 Da, and the molecular weight distribution coefficient PDI is 1.

39.

4. A method for the production of an optical strain film sensor based on the thermally activated delayed fluorescence polymer material according to claim 1, characterized in that Comprising the following steps: Step 1: dissolving and uniformly mixing the thermal activated delayed fluorescence polymer material and the elastomer in a blending solvent to obtain a precursor solution; Step 2: coating the precursor solution on a substrate to obtain an optical strain film sensor after annealing.

5. The method of claim 4, wherein: The elastomer comprises at least one of polystyrene-based elastomer, polyurethane-based elastomer, polyolefin-based elastomer, polyamide-based thermoplastic elastomer, thermoplastic rubber material, and polydimethylsiloxane.

6. The method of claim 4, wherein: In step 1, the concentrations of the thermal activated delayed fluorescence polymer material and the elastomer in the precursor solution are 5-10 mg / mL respectively, and the mass percentage of the two is 10%-100%:90%-0%.

7. The preparation method according to claim 4, characterized in that, In step 2, the substrate is subjected to ultraviolet ozone cleaning treatment for 15-20 minutes.

8. The preparation method according to claim 4, characterized in that, In step 2, the spin coating speed of the precursor solution is 2000-2500 rpm, and the spin coating time is 35-40 seconds.

9. The preparation method according to claim 4, characterized in that, In step 2, the annealing temperature is 110-120°C, and the annealing time is 15-20 minutes.

10. An optical strain film sensor prepared by the preparation method of any one of claims 4-9.

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