Polyurethane with self-assembly and deep blue light emission characteristics and preparation method and application thereof

Abstract

The present application relates to the technical field of organic photoelectric material, in particular to polyurethane with self-assembly and deep blue light emitting characteristics, and its preparation method and application. The polyurethane comprises a conjugated structure formed by diarylfluorene, and a flexible non-conjugated structure formed by saturated aliphatic alkyl chain or ether chain, and has a structure shown in formula (I), and a number average molecular weight of 10000-100000. The polyurethane is prepared by introducing straight chain or ether chain through traditional polycondensation method, has unique inter-chain hydrogen bond driven self-assembly behavior, and the polyurethane film presents deep blue light emission. After being made into light emitting diode, the brightness is high after optimization, the light color output is relatively stable in the process of voltage change, and good application potential is shown.

Description

Technical Field

[0001] This invention relates to the field of organic optoelectronic materials technology, specifically to polyurethane with self-assembly and deep blue light emission characteristics, its preparation method and application. Background Technology

[0002] Polyurethane (PU) is a high-molecular-weight material with excellent mechanical properties, formed by the condensation reaction of polyols and polyisocyanates. It is highly malleable and mainly classified into polyether, polyester, polyimide, and polyurea types. Polyurethane itself typically does not emit deep blue light, but through specific chemical modifications or the introduction of luminescent components (such as rare-earth complexes and mechanosensitive dyes), it can emit blue or even deep blue light under illumination or stress. Blue light emission refers to the phenomenon where, after a material absorbs energy, electrons transition from a high energy level to a low energy level, releasing visible light with wavelengths between 400 and 500 nm. Blue light emission is one of the core elements for achieving white light illumination and full-color displays because, among the three primary colors of red, green, and blue, blue light has the highest energy and presents the greatest technical challenge.

[0003] Existing technologies typically prepare conjugated polymers via Suzuki-Miyaura or Stille coupling. However, the cost of preparing conjugated polymers via noble metal-catalyzed coupling is high, hindering large-scale manufacturing. Furthermore, research on organic light-emitting polymers mainly focuses on introducing non-conjugated flexible segments from the main chain or side chains, or blending with elastomers to impart mechanical flexibility to rigid conjugated polymers. However, when conjugated polymers are blended with elastomers, phase separation easily occurs, resulting in poor stability, hindered charge transport, and degraded device performance. Since interchain hydrogen bonding interactions, solution gelation behavior, and self-assembly microstructure all affect photoelectric properties in polyurethane-based light-emitting materials, researching light-emitting polymer materials that combine good mechanical flexibility with high-efficiency photoelectric performance is quite challenging.

[0004] Therefore, studying the intrinsic relationship between chain segment structure and photoelectric properties, and developing a polyurethane material that combines efficient deep blue light emission with excellent spectral stability, has significant research and application value. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a polyurethane with self-assembly and deep blue light emission characteristics, its preparation method, and its applications. The polyurethane is synthesized using a traditional polycondensation method, and the photoluminescence quantum yield of the polyurethane is improved by introducing a luminescent conjugated structure. After standing in an organic solvent, it spontaneously forms a gel with a microsphere structure, realizing a unique interchain hydrogen bond-driven self-assembly behavior, thereby solving the technical problems mentioned in the background art.

[0006] This invention is achieved through the following technical solution: A polyurethane with self-assembly and deep blue light emission properties comprises a conjugated structure formed by diarylfluorene and a flexible non-conjugated structure formed by saturated aliphatic alkyl chains or ether chains, having the structure shown in formula (I):

[0007] In the formula, R is a non-conjugated structural unit, selected from C6-C18 alkyl straight-chain groups or polyethylene glycol chains containing 2-10 ethylene glycol units; The number-average molecular weight of the polyurethane shown in formula (Ⅰ) is 10,000-100,000.

[0008] Preferably, R is selected from a dodecyl chain or a hexaethylene glycol chain.

[0009] As a further embodiment of the present invention, the polyurethane is uniformly mixed with an organic solvent to prepare a solution of 1~10 mg / mL. After the solution is allowed to stand, a gel with a microsphere structure is formed, the critical gel concentration of which is 2~4 mg / mL and the microsphere particle size is 0.1~1 μm.

[0010] Preferably, the organic solvents mentioned above include, but are not limited to, chlorobenzene.

[0011] This invention also provides a method for preparing the above-mentioned polyurethane with self-assembly and deep blue light emission properties, specifically including the following steps: S1. Dissolve 9,9-bis[4-(6-hydroxyhexyloxy)phenyl]-2,7-dibromofluorene and 9,9-diphenylfluorene-2-boronic acid pinacol ester in an organic solvent, and obtain hydroxyl-functionalized trimerfluorene by Suzuki coupling reaction in the presence of a base and a palladium catalyst. Its structural formula is shown in formula (II).

[0012] S2. In the presence of an aprotic polar solvent and a catalyst, the compound of formula (II) obtained in S1, the diol, and the hexamethylene diisocyanate are subjected to a polycondensation reaction to obtain the polyurethane of structural formula (I).

[0013] As a further embodiment of the present invention, in step S1, the molar ratio of 9,9-bis[4-(6-hydroxyhexyloxy)phenyl]-2,7-dibromofluorene, 9,9-diphenylfluorene-2-boronate pinacol ester and palladium catalyst is 1:(3~5):(0.05~0.1).

[0014] As a further embodiment of the present invention, in step S1, the organic solvent is selected from tetrahydrofuran or toluene, the base is selected from K2CO3, tetraethylammonium hydroxide or trimethylsilanolate potassium, and the catalyst is selected from tetra(triphenylphosphine)palladium, methanesulfonic acid (tri-tert-butylphosphine) (2'-methylamino-1,1'-biphenyl-2-yl)palladium (II) or a complex of palladium acetate and tricyclohexylphosphine; in step S2, the aprotic polar solvent is N,N-dimethylformamide (DMF), the catalyst is dibutyltin dilaurate (DBTDL), and the diol is the diol corresponding to the non-conjugated structural unit R in formula (I), used as a chain extender.

[0015] Preferably, in step S1, the organic solvent is tetrahydrofuran, the base is K2CO3, and the catalyst in step S1 is tetra(triphenylphosphine)palladium.

[0016] As a further aspect of the present invention, in step S2, the molar ratio of the compound shown in formula (II), the diol and the hexamethylene diisocyanate is (6~8):(2~4):10.

[0017] Preferably, in step S2, the molar ratio of the compound shown in formula (II), the diol, and the hexamethylene diisocyanate is 7:3:10.

[0018] As a further embodiment of the present invention, in step S1, the reaction temperature is 35~85℃ and the reaction time is 48~72 h; in step S2, the reaction temperature is 35~85℃ and the reaction time is 12~24 h.

[0019] The present invention also provides the application of the above-mentioned polyurethane in the preparation of polyurethane films, light-emitting diodes or electronic display devices.

[0020] The present invention also provides a polyurethane film made of the above-mentioned polyurethane with self-assembly and deep blue light emission characteristics, wherein the polyurethane film emits deep blue light with a peak wavelength of 398~406 nm.

[0021] The present invention also provides a light-emitting diode, comprising an anode, a hole injection layer, a light-emitting layer (EML layer), an electron transport layer, an electron injection layer, and a cathode, wherein the light-emitting layer comprises the aforementioned polyurethane, and the electroluminescence spectrum of the light-emitting diode has a CIE coordinate offset Δx ≤ 0.02 and Δx ≤ 0.17 as a function of voltage.

[0022] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: 1. This invention uses a traditional polycondensation method to prepare polyurethane by introducing straight or ether chains. The synthesis route is short, the catalyst cost is low, and it can be widely used in large-scale manufacturing. 2. The polyurethane provided by this invention can spontaneously form a gel with a microsphere structure after standing in an organic solvent, with a critical gel concentration as low as 2~4 mg / mL. The microspheres are uniform in size and exhibit unique inter-chain hydrogen bond-driven self-assembly behavior. 3. The polyurethane film provided by this invention emits deep blue light with a peak wavelength of 398~406 nm; 4. The polyurethane light-emitting diodes provided by this invention have high brightness after optimization, small CIE coordinate shift in the electroluminescence spectrum during voltage changes, and stable and consistent light and color output, showing good application potential. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the polyurethane synthesis route provided in Embodiment 1 of the present invention; Figure 2 These are the NMR spectra of polyurethane provided in Embodiment 1 of the present invention at different temperatures; Figure 3 This is a scanning electron microscope (SEM) image of polyurethane provided in Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the device structure of the light-emitting diode provided by the present invention; Figure 5 These are the photoluminescence (PL) spectra of polyurethane in dilute solution and thin film states provided in Example 1 of the present invention (a) and the photoluminescence (PL) spectra of polyurethane in dilute solution and thin film states provided in Example 2 of the present invention (b). Figure 6 The graphs (a) and (b) are provided by the present invention, showing the current density versus voltage curve and the brightness versus voltage curve of the light-emitting diode. Figure 7 The electroluminescence spectrum (a) and color coordinate variation diagram (b) of the light-emitting diode provided by the present invention are shown. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0026] Unless otherwise specified, the raw materials and reagents used in the examples are readily available commercially, and the experimental methods used are all conventional methods in the art.

[0027] Example 1 This embodiment provides a polyurethane with self-assembly and deep blue light emission properties, named PUTRF-C12, which comprises a conjugated structure formed by diarylfluorene and a flexible non-conjugated structure formed by saturated aliphatic alkyl chains, and has the structure shown in formula (I): ; In the formula, R is a C12 alkyl straight chain, and the number-average molecular weight of the polyurethane shown in formula (Ⅰ) is 10.8 kDa.

[0028] This embodiment also provides a method for preparing the above-mentioned polyurethane, such as... Figure 1 As shown, it specifically includes the following steps: S1. The starting materials 9,9-bis[4-(6-hydroxyhexyloxy)phenyl]-2,7-dibromofluorene (2.0 g, 2.82 mmol), 9,9-diphenylfluorene-2-boronate pinacol ester (3.763 g, 8.47 mmol), and the catalyst tetra(triphenylphosphine)palladium (0.12 g, 0.104 mmol) were mixed and placed in a Schlenk tube. After purging with nitrogen three times, 6 mL of K2CO3 aqueous solution (2M concentration) and 20 mL of tetrahydrofuran were injected, and the reaction was carried out at 85°C in the dark for 48 hours. After the reaction was completed, the mixture was extracted with dichloromethane, and the organic phase was dried with anhydrous sodium sulfate. After rotary evaporation, the organic phase was purified by silica gel column chromatography (eluent: petroleum ether / ethyl acetate = 1:1) to obtain hydroxyl-functionalized trimerfluorene, the structure of which is shown in formula (II). The theoretical molecular weight is 1182.56, and the actual molecular weight, as determined by MALDI-TOF-MS, is 1182.71.

[0029] ;

[0030] S2. The hydroxyl-functionalized trimerfluorene (0.5 g), 1,12-dihydroxydodecane (0.036 g), and hexamethylene diisocyanate (0.10 g) obtained in step 1 were added to a Schlenk tube in a molar ratio of 7:3:10. After purging with nitrogen three times, 3 mL of anhydrous DMF and 1 drop of DBTDL catalyst were injected, and the reaction was carried out at 85 °C for 12 hours. After the reaction was completed, the reaction solution was concentrated, precipitated in methanol, purified by Soxhlet extractor (acetone as eluent), and vacuum dried to obtain a white polymer powder, which is the polyurethane shown in formula (I), wherein R is a dodecyl chain.

[0031] According to gel permeation chromatography (GPC), the polyurethane prepared in this example has a number-average molecular weight of 10.8 kDa and a polydispersity index (PDI) of 1.44. The NMR spectra of the polyurethane prepared in this example at different temperatures are shown below. Figure 2 As shown, by Figure 2 It can be seen that as the temperature increases, the chemical shift moves to a higher field, but does not exceed the normal range, and no new characteristic peaks appear, indicating that the conjugated structure of the polyurethane PUTrF-C12 prepared in this embodiment has good stability.

[0032] The polyurethane prepared in this example was dissolved in chlorobenzene to prepare a solution of 1-10 mg / mL. After standing for 10-20 minutes, a gel formed. The critical gel concentration was determined to be 2-4 mg / mL. The resulting gel was then placed in ethanol, and ethanol was used to replace the chlorobenzene, taking advantage of the miscibility of ethanol and chlorobenzene. The gel was then freeze-dried and observed using a scanning electron microscope (SEM). Figure 3 As shown, the polyurethane forms a uniformly dispersed microsphere structure with a microsphere size of 0.1~1 μm, indicating that the polyurethane provided in this embodiment has excellent inter-chain hydrogen bond-driven self-assembly capability.

[0033] Example 2

[0034] This embodiment provides a polyurethane with self-assembly and deep blue light emission properties, named PUTRF-CO6, which comprises a conjugated structure formed by diarylfluorene and a flexible non-conjugated structure formed by hexaethylene glycol chains, and has the structure shown in formula (I): ;

[0035] In the formula, R is a hexaethylene glycol chain, and the number-average molecular weight of the polyurethane shown in formula (Ⅰ) is 24.1 kDa.

[0036] This embodiment also provides a method for preparing the above-mentioned polyurethane, which is similar to that of Example 1, except that in step S2, 1,12-dihydroxydodecane is replaced with hexaethylene glycol, and hydroxyl-functionalized trimeron (0.5 g), hexaethylene glycol (0.051 g), and hexamethylene diisocyanate (0.10 g) are mixed in a molar ratio of 7:3:10. The remaining steps are the same as in Example 1, and the polyurethane shown in formula (Ⅰ) is finally obtained, wherein R is a hexaethylene glycol chain.

[0037] According to gel permeation chromatography (GPC) testing, the polyurethane prepared in this example has a number-average molecular weight of 24.1 kDa and a polydispersity index (PDI) of 2.26.

[0038] The polyurethane prepared in this embodiment was dissolved in chlorobenzene and subjected to gel testing similar to that in Example 1. The results obtained by scanning electron microscopy (SEM) were consistent with those in Example 1. The polyurethane formed a uniformly dispersed microsphere structure with a microsphere size of 0.1~1 μm, indicating that the polyurethane provided in this embodiment has excellent inter-chain hydrogen bond-driven self-assembly capability.

[0039] Example 3 This embodiment provides a light-emitting diode, the structure of which is as follows: Figure 4 As shown, the structure includes an anode (ITO), a hole injection layer (PEDOT:PSS, 40 nm), a light-emitting layer (40-50 nm), an electron transport layer (TPBi, 20 nm), an electron injection layer (LiF, 1 nm), and a cathode (Al, 100 nm). The light-emitting layer is prepared using polyurethane obtained in Example 1 or Example 2, and the specific steps are as follows: (1) Clean and dry the patterned ITO substrate, and then treat it with ultraviolet light and ozone for 15 minutes; (2) Spin-coat the treated ITO with PEDOT:PSS (AI 4083) solution and anneal at 120°C for 20 minutes; (3) Dissolve the polyurethane prepared in Example 1 or Example 2 in chlorobenzene at a concentration of 10 mg / mL, spin coat it onto the PEDOT:PSS layer at a speed of 1500 rpm for 60 seconds, and then anneal it at 120°C for 10 minutes to form a thin film, which is the light-emitting layer. (4) In high vacuum (<1×10 -5 At mbar, TPBi, LiF and Al electrodes were deposited sequentially by vacuum thermal evaporation to obtain a light-emitting diode; In step (3), polyurethane was dissolved in chlorobenzene to obtain a dilute solution with a concentration of 10 mg / mL. After annealing, a thin film was formed. Photoluminescence (PL) detection was performed on the polyurethane provided in Examples 1 and 2 in the dilute solution and thin film states, respectively. The spectra are shown below. Figure 5 As shown. By Figure 5 It can be seen that the polyurethane dilute solution and polyurethane film prepared in Examples 1 and 2 both emit deep blue light with a peak wavelength of 398~406 nm.

[0040] The performance of the light-emitting diode provided in this embodiment is tested. For example... Figure 6 As shown, the turn-on voltage of the LED using polyurethane PUTrF-C12 as the light-emitting layer is 5.2 V, while the turn-on voltage of the LED using polyurethane PUTrF-CO6 as the light-emitting layer is 4.5 V. Their luminous intensity is similar, and the maximum brightness of the device can reach 538 cd / m². -2 The external quantum efficiency is 0.77%.Figure 7 As shown, the light-emitting diode emits deep blue light at an initial voltage of 6V, with the main peak at 424 nm. As the applied voltage increases to 12V, the CIE coordinates change from (0.16, 0.07) to (0.18, 0.24). That is, the CIE coordinate shift of the electroluminescence spectrum of the light-emitting diode with voltage change is Δx≤0.02 and Δx≤0.17, which proves that the light output of the light-emitting diode provided in this embodiment is relatively stable and shows good application potential.

[0041] In summary, this invention uses a traditional polycondensation method to prepare polyurethane by introducing straight or ether chains. It possesses unique interchain hydrogen bond-driven self-assembly behavior, and its polyurethane film emits deep blue light. After optimization, the brightness of the light-emitting diode is high, and the light output is relatively stable during voltage changes, showing good application potential.

[0042] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A polyurethane with self-assembly and deep blue light emission properties, characterized in that: It has the structure shown in equation (I): ； In the formula, R is selected from C6-C18 straight-chain alkyl groups or polyethylene glycol chains containing 2-10 ethylene glycol units; The number-average molecular weight of the polyurethane shown in formula (Ⅰ) is 10,000-100,000.

2. The polyurethane with self-assembly and deep blue light emission properties according to claim 1, characterized in that, The polyurethane is uniformly mixed with an organic solvent to prepare a solution of 1~10 mg / mL. After the solution is allowed to stand, a gel with a microsphere structure is formed, the critical gel concentration is 2~4 mg / mL, and the particle size of the microspheres is 0.1~1 μm.

3. The method for preparing polyurethane with self-assembly and deep blue light emission characteristics according to claim 1 or 2, characterized in that, Specifically, the following steps are included: S1. Dissolve 9,9-bis[4-(6-hydroxyhexyloxy)phenyl]-2,7-dibromofluorene and 9,9-diphenylfluorene-2-boronic acid pinacol ester in an organic solvent, and obtain hydroxyl-functionalized trimerfluorene by Suzuki coupling reaction in the presence of a base and a palladium catalyst. Its structural formula is shown in formula (II). ； S2. In the presence of an aprotic polar solvent and a catalyst, the compound of formula (II) obtained in S1, the diol, and the hexamethylene diisocyanate are subjected to a polycondensation reaction to obtain the polyurethane of structural formula (I).

4. The preparation method according to claim 3, characterized in that: In step S1, the molar ratio of 9,9-bis[4-(6-hydroxyhexyloxy)phenyl]-2,7-dibromofluorene, 9,9-diphenylfluorene-2-boronate pinacol ester and palladium catalyst is 1:(3~5):(0.05~0.1).

5. The preparation method according to claim 3, characterized in that: In step S1, the organic solvent is selected from tetrahydrofuran or toluene; the base is selected from K2CO3, tetraethylammonium hydroxide, or potassium trimethylsilanolate; and the catalyst is selected from tetra(triphenylphosphine)palladium, methanesulfonic acid (tri-tert-butylphosphine) (2'-methylamino-1,1'-biphenyl-2-yl)palladium(II), or a complex of palladium acetate and tricyclohexylphosphine; in step S2, the aprotic polar solvent is... N , N -Dimethylformamide, wherein the catalyst is dibutyltin dilaurate, and the diol is the diol corresponding to R.

6. The preparation method according to claim 3, characterized in that: In step S2, the molar ratio of the compound shown in formula (II), the diol, and the hexamethylene diisocyanate is (6~8):(2~4):

10.

7. The preparation method according to claim 3, characterized in that: In step S1, the reaction temperature is 35~85℃ and the reaction time is 48~72 h; in step S2, the reaction temperature is 35~85℃ and the reaction time is 12~24 h.

8. The application of the polyurethane with self-assembly and deep blue light emission properties as described in claim 1 or 2 in the preparation of polyurethane films, light-emitting diodes or electronic display devices.

9. A polyurethane film, characterized in that, Made of polyurethane with self-assembly and deep blue light emission characteristics as described in claim 1 or 2, the polyurethane film emits deep blue light with a peak wavelength of 398~406 nm.

10. A light-emitting diode, comprising an anode, a hole injection layer, a light-emitting layer, an electron transport layer, an electron injection layer, and a cathode, characterized in that, The light-emitting layer comprises the polyurethane with self-assembly and deep blue light emission characteristics as described in claim 1 or 2.

Images