A photosensitive diamine monomer containing a polyphenyl skeleton and a flexible bridging chain, and a preparation method and application thereof

Abstract

The application discloses a photosensitive diamine monomer containing a polycene skeleton and a flexible bridging chain, and a preparation method and application thereof, and belongs to the technical field of organic photosensitive functional materials. The monomer is composed of a polycene diamine hub, a flexible bridging chain and a 4-(trifluoromethyl) coumarin photosensitive fragment which are sequentially connected by ether bonds, and synthesis thereof comprises three steps: a diaminopolycene phenol hub intermediate is prepared from a dihalogenated polycene phenol through Suzuki coupling; a terminal halogenated flexible ether chain precursor is prepared from 7-hydroxy-4-(trifluoromethyl) coumarin through Williamson etherification; and then the two are assembled into the target monomer through nucleophilic substitution into ether. By changing the number of benzene rings and the amino substitution site of the hub, and the length of the flexible chain and the type of the bridging atom, a series of photosensitive diamine monomers with different structures can be obtained. The monomer can be crosslinked through intermolecular [2+2] photocycloaddition of the coumarin fragment thereof under irradiation of 365 nm ultraviolet light, and has good thermal stability, and can be used as a diamine monomer of a photosensitive polyimide precursor material.

Description

Technical Field

[0001] This invention relates to photosensitive functional monomers, their preparation methods and applications, specifically to a photosensitive diamine monomer containing a polyphenylene aromatic skeleton, a flexible bridging chain and a 7-hydroxy-4-(trifluoromethyl)coumarin photosensitive group, its modular synthesis method and application, belonging to the technical fields of organic photosensitive functional materials and polyimide precursor materials. Background Technology

[0002] Polyimide (PI) possesses good thermal stability, mechanical properties, electrical insulation, and chemical resistance, making it widely used in microelectronics and optoelectronics. In recent years, with the development of advanced integrated circuit packaging, flexible electronics, and microelectronics manufacturing, photosensitive polyimide (PSPI), which also has photo-patterning capabilities, has attracted increasing attention.

[0003] The performance of photosensitive polyimides largely depends on the molecular structure design of their precursors (such as photosensitive diamines or photosensitive dianhydrides). Existing photosensitive monomer or precursor systems still suffer from the following shortcomings in practical applications: First, the tunability of structure and properties is limited, often making it difficult to achieve a balance between heat resistance, solubility, and processability—increasing the rigidity of the aromatic skeleton, while beneficial for heat resistance, often comes at the cost of sacrificing solubility and processability; second, some negatively photosensitive systems require the addition of small-molecule photoinitiators or sensitizers for crosslinking, potentially leading to compatibility complexity, residues, and limited process windows; third, the synthetic pathway lacks flexibility, making it difficult to achieve serialized control of molecular structure (such as rigid skeleton length, amino substitution sites, flexible segment types, or linkage modes) through simple raw material substitution.

[0004] Regarding photoresponsive groups, coumarin compounds exhibit clear photoinduced [2+2] cycloaddition characteristics and can achieve photocrosslinking without introducing additional small-molecule photoinitiators, thus making them one of the candidate photoresponsive groups for constructing photosensitive monomers. Regarding aromatic skeletons, the fully aromatic structure of polyphenylene compounds helps improve the heat resistance and rigidity of the molecule, but excessive rigidity of the skeleton is often detrimental to dissolution and processing. Introducing flexible bridging chains between the rigid skeleton and the photoresponsive group, and adjusting molecular polarity through the introduction of fluorine substituents, is expected to improve solubility and processability while maintaining heat resistance, achieving a balance between rigidity and flexibility.

[0005] However, existing systems and methods are still insufficient to effectively integrate the three functional units—the polyphenyl aromatic skeleton, the flexible bridging chain, and the coumarin photoresponsive group—into the same diamine monomer with controllable linking sites, and to achieve serialized regulation of skeleton length, substitution sites, and flexible chain structure.

[0006] Therefore, it is necessary to provide a photosensitive diamine monomer with a well-defined structure, controllable connection sites, and modular construction capability, as well as its synthesis method, to meet the structural design requirements of photosensitive polyimide precursor materials. Summary of the Invention

[0007] The purpose of this invention is to provide a photosensitive diamine monomer compound, as well as a modular synthesis method and application of the compound. This monomer compound uses polyphenylene diamine as the hub, a flexible bridging chain as the connecting unit, and 4-(trifluoromethyl)coumarin as the photosensitive segment, all three linked sequentially via ether bonds. While maintaining the activity of diamine polycondensation, it introduces a photoresponsive unit that can be cross-linked via ultraviolet photoinduced [2+2] cycloaddition. By changing the number of benzene rings and amino substitution sites in the hub, as well as the chain length and bridging atom type of the flexible bridging chain, a series of monomers with different structures can be obtained.

[0008] To achieve the above objectives, in a first aspect, the present invention provides a photosensitive diamine monomer containing a polyphenylene backbone and a flexible bridging chain, having a molecular structure represented by general formula (I): (I), where: Ar represents the phenyl unit, and the Ar units are connected by carbon-carbon single bonds to form a polyphenyl aromatic skeleton; the curved bond represents the linking site, which is independently selected from the ortho, meta or para position of the corresponding Ar unit; m and n are independently selected from 1, 2 or 3, and I is selected from 1 or 2; the two -NH2 are independently located at the ortho, meta or para position of the corresponding terminal Ar unit. –O–(CH2) p –Z–(CH2)q–O– is a flexible bridging chain, with one end connected to an ether-oxygenated intermediate Ar unit and the other end connected to the 7-position of the coumarin fragment via an ether-oxygenated group. p and q are each independently selected from integers 1 to 6, and Z is selected from a single bond, –O–, –S–, or –NH–. Here, “single bond” indicates that no atom is inserted at the Z position, i.e., (CH2). p The flexible bridging chain is directly connected to (CH2)q via carbon-carbon single bonds, and the overall structure is represented as "–O–(CH2)p". + The structure of a pure methylene ether chain is q–O–; while –O–, –S–, and –NH– represent the insertion of an ether oxygen, thioether, or secondary amine group as a heteroatom spacer at that position, respectively.

[0009] Specifically, if the flexible bridging chain is omitted (i.e., p=q=0, with the coumarin fragment directly connected to the polyphenylene skeleton), the resulting purely rigid structure will suffer from a significant decrease in the solubility of the monomer in commonly used polar aprotic solvents such as DMAc and NMP due to the strong π-π stacking effect between the polyphenylene skeletons, which is very detrimental to the use and processing of the monomer. If the flexible segment is too short (p+q<2) or the polar contribution of the heteroatom spacer group is insufficient, the above improvement effect is limited and the structural design goal of achieving both rigidity and flexibility cannot be fully realized. This invention introduces -O-(CH2) p The -Z-(CH2)qO- flexible bridging chain effectively disrupts the regular π-π stacking between molecules, giving the monomer good solubility and processability, while retaining the excellent heat resistance given by the rigid skeleton of polyphenylene, thus achieving the structural design goal of "combining rigidity and flexibility".

[0010] As a further preferred technical solution of the present invention, in general formula (I): p and q are each independently selected from integers of 2 to 4; Z is selected from single bond, –O– or –NH–; both –NH2 are located at the para or meta position of the corresponding terminal Ar unit.

[0011] As a further preferred embodiment of the present invention, the polyphenyl aromatic skeleton is a terphenyl, tetraphenyl, or pentphenyl skeleton.

[0012] As a further preferred embodiment of the present invention, the photosensitive diamine monomer is selected from any one of the following compounds (a) to (d): (a) is 7-[4-(3,5-bis(4-aminophenyl)phenoxy)butoxy]-4-(trifluoromethyl)-2H-chromen-2-one, with the structural formula shown below: ; (b) is 7-{3-[(3-(3,5-bis(4-aminophenyl)phenoxy)propyl)amino]propoxy}-4-(trifluoromethyl)-2H-chromen-2-one, with the structural formula shown below: ; (c) is 7-{4-[3,5-bis(3′-amino-[1,1′-biphenyl]-4-yl)phenoxy]butoxy}-4-(trifluoromethyl)-2H-chromen-2-one, with the structural formula shown below: ; (d) is 7-(2-{2-[(4,4″-diamino-5′-phenyl-[1,1′:3′,1″-terphenyl]-2′-yl)oxy]ethoxy}ethoxy)-4-(trifluoromethyl)-2H-chromen-2-one, with the structural formula shown below: .

[0013] In compound (a), p=4, q=0, and Z are single bonds, and the flexible bridging chain is -O-(CH2)4-O-; in compound (b), p=3, q=3, and Z are -NH-, and the flexible bridging chain is -O-(CH2)3-NH-(CH2)3-O-; in compound (c), p=4, q=0, and Z are single bonds, and the flexible bridging chain is -O-(CH2)4-O-; in compound (d), p=2, q=2, and Z are -O-, and the flexible bridging chain is -O-(CH2)2-O-(CH2)2-O-.

[0014] According to a second aspect of the present invention, the present invention also provides a method for preparing a photosensitive diamine monomer containing a polyphenylene backbone and a flexible bridging chain, comprising the following steps: (1) Preparation of hub module: Dihalopolyphenols are coupled with amino-containing arylboronic acid or its derivatives in an organic solvent under the presence of palladium catalyst and base to obtain a diaminopolyphenol intermediate with phenolic hydroxyl group, which is used as the hub module. (2) Preparation of functional module: 7-hydroxy-4-(trifluoromethyl)coumarin and the dihalogenated flexible bridging chain shown in general formula (a) are subjected to Williamson etherification reaction in an organic solvent in the presence of a phase transfer catalyst and a base, so that the coumarin is etherified through its 7-position oxygen atom to obtain a terminal halogenated coumarin flexible ether chain precursor, which serves as the functional module.

[0015] (a) Wherein: X and Y are each independently selected from chlorine, bromine or iodine, p and q are each independently selected from integers from 1 to 6, and Z is selected from single bond, –O–, –S– or –NH–; (3) Module assembly: In the presence of a Lewis base and in an organic solvent, the phenolic hydroxyl group of the hub module obtained in step (1) undergoes a nucleophilic substitution reaction with the terminal halogen of the functional module obtained in step (2) to form an ether, thereby obtaining the photosensitive diamine monomer compound shown in general formula (I).

[0016] As a further preferred embodiment of the present invention, the hub module has a structure as shown in general formula (b):

[0017] (b) Wherein: Ar represents a phenyl unit, and each Ar unit is connected by a carbon-carbon single bond to form a polyphenyl aromatic skeleton; the curved bond represents a linking site, which is independently selected from the ortho, meta or para position of the corresponding Ar unit; m and n are independently selected from 1, 2 or 3, and I is selected from 1 or 2; the two -NH2 are independently located at the ortho, meta or para position of the corresponding terminal Ar unit; the phenolic hydroxyl group connected by the curved bond is -OH, which is used as the active site for the nucleophilic substitution reaction in step (3).

[0018] As a further preferred embodiment of the present invention, the dihalopolyphenol is selected from any one of 3,5-dibromophenol, 3,5-bis(4-bromophenyl)phenol, and 3,5-dibromo-[1,1′-biphenyl]-4-phenol; and / or, the amino-containing arylboronic acid or its derivative is selected from any one of 2-aminophenylboronic acid, 3-aminophenylboronic acid, 4-aminophenylboronic acid, 4-aminophenylboronic acid pinacol ester, and 3-aminophenylboronic acid pinacol ester; and / or, the dihaloflexible bridging chain is selected from any one of 1,4-dibromobutane and bis(2-bromoethyl) ether.

[0019] As a further preferred technical solution of the present invention, the palladium catalyst in step (1) is selected from any one of tetra(triphenylphosphine)palladium, dichlorobis(triphenylphosphine)palladium, palladium acetate, and palladium on carbon; the base is selected from at least one of potassium carbonate, sodium carbonate, and cesium carbonate. And / or, the phase transfer catalyst in step (2) is selected from any one of tetrabutylammonium iodide, tetraethylammonium bromide, octadecanoic acid, and benzyltriethylammonium chloride; the base is selected from at least one of potassium carbonate, sodium carbonate, and cesium carbonate; And / or, the Lewis base in step (3) is selected from any one of sodium hydride, potassium carbonate, sodium carbonate, and cesium carbonate; And / or, the organic solvents in steps (1) to (3) are each independently selected from any one or a mixture of two or more of the following solvents: methanol, ethanol, acetone, tetrahydrofuran, acetonitrile, chloroform, ethyl acetate, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, and 1,4-dioxane.

[0020] As a further preferred technical solution of the present invention, steps (1) to (3) are all performed under inert gas protection and satisfy the following: The Suzuki coupling reaction in step (1) is carried out at a temperature of 70–100 °C for 8–24 hours, and the molar ratio of the dihalopolyphenol to the aminoarylboronic acid or its derivative is 1:2.0–1:2.5. The Williamson etherification reaction in step (2) is carried out at a temperature of 60–90 °C for 8–24 hours, and the molar ratio of 7-hydroxy-4-(trifluoromethyl)coumarin to the dihalogenated flexible bridging chain is 1:2.0–1:3.0. The nucleophilic substitution reaction in step (3) is carried out at a temperature of 70–95 °C for 8–24 hours, and the molar ratio of the hub module to the functional module is 1:1.0 to 1:1.2.

[0021] According to a third aspect of the present invention, the present invention also provides the application of the photosensitive diamine monomer containing a polyphenylene backbone and a flexible bridging chain prepared by the methods of the first and second aspects in the preparation of photosensitive polyimides.

[0022] Compared with the prior art, the present invention can achieve the following beneficial effects: (1) Modularization and serialization: This invention divides the target monomer into three parts: hub module, functional module and assembly steps, and connects them in a directional manner via ether bonds. Under the premise of maintaining the consistency of the reaction framework, by changing the substitution sites of dihalogenated polyphenols, arylboronic acid and dihalogenated flexible bridging chains, the length of the polyphenyl skeleton, amino substitution sites and flexible chain structure can be adjusted to obtain a series of photosensitive diamine monomers with different structures. (2) Photoresponsiveness: The obtained monomer contains a 4-(trifluoromethyl)coumarin fragment, which can be cross-linked by intermolecular [2+2] photo-enhancing through its coumarin unit under ultraviolet light irradiation. The ultraviolet-visible spectrum shows that the process has a clear isoabsorption point and a single conversion pathway, indicating that it has photocross-linking reactivity. (3) Thermal stability: After the active halogen end groups of the functional modules are converted into stable aryl ether bonds through assembly, the initial thermal decomposition temperature of the obtained monomer is significantly higher than that of the halogenated precursor, and it still maintains good thermal stability while embedding the photoresponse unit. (4) Controllable route: First, the terminal halogenated functional module is prepared and then assembled with the hub module containing phenolic hydroxyl group, which helps to reduce site competition and side reactions caused by multi-site parallel reactions and facilitates the separation and purification of target monomers. Attached Figure Description

[0023] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0024] Figure 1 The 1H NMR spectrum (¹H NMR, 500MHz, DMSO-d6) of the terphenyl intermediate E (hub module) obtained in Example 1 is shown to confirm the structure of the phenolic intermediate containing diamino groups.

[0025] Figure 2The 1H NMR spectrum (¹H NMR, 500 MHz, CDCl3) of the coumarin precursor F (functional module) obtained in Example 1 is shown to confirm the structure of the terminally brominated coumarin-butyl ether flexible chain precursor.

[0026] Figure 3 The image shows the 1H NMR spectrum (¹H NMR, 500 MHz, DMSO-d6) of the target photosensitive diamine monomer obtained in Example 1, used to confirm the covalent connection between the coumarin photosensitive motif and the terphenyldiamine backbone after modular assembly.

[0027] Figure 4 The thermogravimetric analysis (TGA) curve of the target photosensitive diamine monomer obtained in Example 1 is shown. The test conditions were: nitrogen atmosphere, heating rate of 10℃ / min, temperature range of 30℃ to 600℃, and normalization based on the mass at 150℃ to characterize the thermal stability of the monomer.

[0028] Figure 5 This is the UV-Vis spectrum of the target photosensitive diamine monomer obtained in Example 1 in DMAc solution. Test conditions: concentration approximately 10. -5 The photodimerization behavior and photosensitivity of coumarin groups were characterized by irradiation with a mol / L, 365 nm ultraviolet light source for different durations.

[0029] Figure 6 This is the UV-Vis spectrum of the control diamine monomer a' (without CF3) in DMAc solution in Comparative Example 1. The test conditions were the same as in Example 1 (concentration approximately 10). -5 Irradiation with 365 nm ultraviolet light source (mol / L, continuous recording from 0 to 60 min) was used to compare the photoresponse performance with that of the CF3-containing monomer obtained in Example 1, and to characterize the effect of the CF3 substituent on the photocycloaddition activity of coumarin.

[0030] The objectives, features, and advantages of this invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0031] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0032] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art to which this invention pertains. Unless otherwise specified, the experimental reagents used in the following embodiments are conventional biochemical reagents; and the experimental methods described are conventional methods.

[0033] Example 1: Coumarin photosensitive diamine monomer with a para-terphenyl backbone and a butyl ether flexible chain This embodiment provides the synthesis of a coumarin photosensitive diamine monomer with a highly rigid core and a medium-length flexible chain, and the specific method is as follows: Step 1. Composition of the hub module (intermediate E): In a 250 mL double-necked flask, 3,5-dibromophenol (1.00 g, 3.97 mmol), 4-aminophenylborate (1.38 g, 7.94 mmol), tetra(triphenylphosphine)palladium (0.23 g, 0.20 mmol, 5 mol%), and potassium carbonate (3.28 g, 23.8 mmol) were added sequentially, followed by tetrahydrofuran (40 mL) and water (10 mL). The mixture was stirred under nitrogen protection in the dark. The temperature was raised to 80 °C, and the reaction was allowed to proceed for 12 hours. After the reaction was complete as monitored by TLC, the mixture was cooled to room temperature. The reaction mixture was filtered, and the filter cake was washed 3–4 times with tetrahydrofuran. The filtrates were combined and extracted with saturated brine (50 mL × 3) and ethyl acetate (50 mL × 3). The organic phase was dried over anhydrous sodium sulfate, concentrated under reduced pressure, and purified by silica gel column chromatography (petroleum ether / ethyl acetate = 3:1, v / v) to give 1.01 g of a pale yellow solid product (intermediate E), with a yield of 92%. The 1H NMR spectrum is shown below. Figure 1 As shown.

[0034] The specific reaction equation for this step is as follows:

[0035] Step 2. Preparation of the functional module (intermediate F, i.e., coumarin-butyl ether-bromine precursor): In a 250 mL double-necked flask, 7-hydroxy-4-(trifluoromethyl)coumarin (1.00 g, 4.35 mmol), 1,4-dibromobutane (1.86 g, 8.61 mmol), cesium carbonate (2.24 g, 6.87 mmol), cesium iodide (0.15 g, 0.57 mmol), and tetrabutylammonium iodide (0.21 g, 0.57 mmol) were added, followed by 18 mL of anhydrous tetrahydrofuran under nitrogen protection. The mixture was heated to 80 °C and reacted for 12 hours. After the reaction was complete as monitored by TLC, it was cooled to room temperature. The reaction solution was filtered, and the filtrate was concentrated by rotary evaporation under reduced pressure at 35 °C to obtain the crude product. The crude product was washed three times with anhydrous diethyl ether and dried under vacuum at 60 °C for 12 hours to obtain 1.52 g of a pale yellow solid product (coumarin-butyl ether-bromine precursor), with a yield of 96%. The 1H NMR spectrum is shown below. Figure 2 As shown.

[0036] The specific reaction equation for this step is as follows:

[0037] Step 3, Module Assembly (Target Unit): In a 100 mL double-necked flask, intermediate E (0.50 g, 1.81 mmol) prepared in step 1, the coumarin-butyl ether-bromine precursor (0.66 g, 1.81 mmol) prepared in step 2, and sodium carbonate (0.57 g, 5.43 mmol) were added, followed by 20 mL of anhydrous acetone under nitrogen protection. The mixture was heated to 80 °C and reacted for 12 hours. After the reaction was complete as monitored by TLC, it was cooled to room temperature. The reaction mixture was filtered, and the filter cake was washed with a small amount of ethyl acetate. The filtrates were combined and concentrated by rotary evaporation under reduced pressure at 30 °C to obtain the crude product. The crude product was purified by silica gel column chromatography (dichloromethane / petroleum ether = 5:1, v / v), and dried under vacuum at 60 °C for 12 hours to obtain 0.92 g of the target photosensitive diamine monomer as a yellow solid, with a yield of 91%. The 1H NMR spectrum is shown below. Figure 3 As shown.

[0038] The specific reaction equation for this step is as follows: .

[0039] Test 1: Individual Thermal Performance Test To investigate the effect of modular assembly on thermal stability, thermogravimetric analysis (TGA) was performed on the hub module (intermediate E), functional module (intermediate F, i.e., coumarin-butyl ether-bromine precursor) and target photosensitive diamine monomer obtained in Example 1.

[0040] Test conditions: nitrogen atmosphere, heating rate 10 ℃ / min, temperature range 30–600 ℃, normalized based on the mass at 150 ℃, the temperature corresponding to 5% weight loss (Td5%) was taken as the initial thermal decomposition temperature, and the residual mass (carbon residue) at 600 ℃ was recorded. Test results are as follows: Figure 4 As shown in Table 1.

[0041] Table 1

[0042] Thermogravimetric analysis results show that, through modular assembly, this invention eliminates the active halogen end groups of the functional modules, significantly increasing the initial thermal decomposition temperature of the target monomer compared to the precursor. Furthermore, while successfully embedding the coumarin photoresponsive unit, it maintains the target monomer's good thermal stability at 267℃ and the smoothest decomposition behavior. Thus, at the molecular level, both photosensitive functionality and thermal stability are simultaneously achieved, laying the structural foundation for the subsequent preparation of photosensitive polyimide materials with both photopatterning capabilities and heat resistance.

[0043] Test 2: Characterization of Single-Unit Photoresponse Performance Depend on Figure 5 It can be seen that the CF3-containing photosensitive diamine monomer obtained in Example 1 has a clear and controllable ultraviolet light response characteristic in DMAc solution, which is as follows: when not irradiated, the monomer exhibits the π→π of the coumarin C=C conjugated system at approximately 308–312 nm. The absorption peak was observed; with prolonged irradiation time at 365 nm UV light (0–32 min), the intensity of this peak continuously and monotonically decreased, with a decrease of approximately 31%, indicating that intermolecular [2+2] photo-addition occurred in the coumarin units, and the C=C double bond conjugation was disrupted; the curves at each time point intersected at the same isoabsorption point at approximately 263 nm, proving that the photocrosslinking process has a single pathway, no byproducts are generated, and the reaction is clean and controllable. In summary, the monomer obtained in this embodiment possesses good photocrosslinking reactivity and can achieve rapid and clean UV photocrosslinking without introducing additional photoinitiators.

[0044] Comparative Example 1: Synthesis of a coumarin photosensitive diamine monomer without -CF3 substituent To verify the contribution of the -CF3 substituent in 4-(trifluoromethyl)coumarin to the photoresponse performance, a control diamine monomer (denoted as monomer a') without -CF3 was synthesized by replacing 7-hydroxy-4-(trifluoromethyl)coumarin with only 7-hydroxycoumarin, following the exact same route and conditions as in Example 1.

[0045] Under the same test conditions as in Example 1 (DMAc solution, concentration approximately 10), -5 The monomer a' was characterized by UV-Vis spectra under irradiation with a mol / L, 365 nm ultraviolet light source, and the irradiation time was extended to 60 min for continuous recording (results are shown in Figure 1). Figure 6 As shown below, the data for the -CF3-containing monomer obtained in Example 1 are compared with the following: (1) Absorption peak position: The characteristic peak of the monomer containing -CF3 is located at about 308-312 nm, while the control monomer a' is blue-shifted to about 295-300 nm, with a difference of about 10-15 nm. The electron-withdrawing effect of -CF3 reduces the HOMO-LUMO band gap of coumarin and red-shifts the peak position, making the CF3-containing monomer more effective at absorbing 365 nm excitation light.

[0046] (2) Photocycloaddition efficiency: The characteristic peak of the monomer containing -CF3 decreased by about 31% after irradiation for 32 min, while the decrease of the control monomer a' was only about 21% even after irradiation for 60 min. Considering the time required to achieve similar conversion, the photocycloaddition conversion efficiency of the monomer containing -CF3 was significantly higher than that of the control monomer (about 2.7 times that of the latter), indicating that -CF3 reduced the electron cloud density of the coumarin C=C double bond through the electron-withdrawing effect, and significantly improved the [2+2] photocycloaddition activity.

[0047] (3) Reaction selectivity: The monomer containing -CF3 has a clear isoabsorption point at about 263 nm, and the reaction pathway is single; no isoabsorption point was observed in the control monomer a' throughout the process, and the curves were intersected and dispersed, indicating that there is competition from side reactions when -CF3 is not present, and the conversion selectivity is significantly reduced.

[0048] Furthermore, after extensive comparative testing (the test subjects included the target monomers of Examples 2-4 below and their corresponding un-CF3 substituted monomers), it was found that, compared with the control monomers without -CF3, the monomers containing -CF3 of the present invention showed significant advantages in three aspects: photoresponse rate (efficiency improved by about 2.7 times), matching of absorption peak with excitation source, and reaction pathway selectivity. This fully confirms the necessity of the -CF3 substituent in the 4-(trifluoromethyl)coumarin fragment in the structural design of the present invention.

[0049] Example 2: Synthesis of a coumarin photosensitive diamine monomer with a flexible chain containing a secondary amine heteroatom and a para-terphenyl backbone This embodiment aims to verify the adaptability of the modular strategy to different flexible chain lengths, and to demonstrate the universality of the construction process by changing the catalytic system.

[0050] The specific module assembly reaction equation for this embodiment is as follows:

[0051] The specific synthesis steps are as follows: Step 1. Hub Module Preparation Intermediate E was prepared exactly according to the method in step 1 of Example 1.

[0052] Step 2. Preparation of the functional module (coumarin-bis(3-bromopropyl)amine precursor) In a 250 mL two-necked flask, 7-hydroxy-4-(trifluoromethyl)coumarin (TFMC, 1.00 g, 4.35 mmol), bis(3-bromopropyl)amine hydrobromide (2.78 g, 8.20 mmol), cesium carbonate (2.68 g, 8.20 mmol), potassium iodide (0.10 g, 0.60 mmol, catalytic amount), and tetraethylammonium bromide (0.12 g, 0.57 mmol) were added, followed by 18 mL of anhydrous acetonitrile under nitrogen protection. The mixture was heated to 80 °C and reacted for 18 hours. After the reaction was complete as monitored by TLC, it was cooled to room temperature. The reaction mixture was filtered, and the filtrate was concentrated by rotary evaporation under reduced pressure at 35 °C to obtain the crude product. The crude product was washed three times with anhydrous diethyl ether and dried under vacuum at 60 °C for 12 hours to obtain 1.58 g of a pale yellow solid product (coumarin-bis(3-bromopropyl)amine precursor), with a yield of approximately 89%.

[0053] Step 3. Module Assembly: In a 100 mL two-necked flask, intermediate E (0.50 g, 1.81 mmol), coumarin-bis(3-bromopropyl)amine precursor (0.74 g, 1.81 mmol), and cesium carbonate (1.77 g, 5.43 mmol) prepared above were added, along with anhydrous N,N-dimethylformamide (DMF, 20 mL). The mixture was stirred under nitrogen protection in the dark. The temperature was raised to 65 °C, and the reaction was allowed to proceed for 14 hours. After the reaction was complete as monitored by TLC, it was cooled to room temperature, and the reaction solution was poured into a large amount of ice water to precipitate the solid. The solid was filtered, washed with water, and the crude product was purified by silica gel column chromatography and dried under vacuum to obtain 0.99 g of the target photosensitive diamine monomer with a flexible chain containing nitrogen heteroatoms, with a yield of approximately 91%. Technical effect analysis: Example 2 replaced the pure carbon ether chain of Example 1 with a heteroatom chain containing secondary amine (-NH-) (Z=-NH-), introducing a secondary amine unit into the molecular backbone that can form hydrogen bonds and serve as a subsequent coordination / crosslinking site. The assembly steps were carried out using cesium carbonate as a weak base at a low temperature in the dark to avoid the influence of strong bases on coumarin lactones, demonstrating that this modular method is also suitable for nitrogen-containing heteroatom dihalogenated flexible chains. Example 2 has been successfully synthesized, and the resulting monomer containing secondary amine heteroatom flexible chains has been confirmed to have the correct structure by ¹H NMR. Thermogravimetric analysis showed that its initial thermal decomposition temperature (Td5%) was not lower than 250℃, exhibiting good thermal stability. This monomer is soluble in polar aprotic solvents such as DMAc and NMP, demonstrating superior solubility compared to the pure rigid polyphenylene diamine structure without flexible chains, thus meeting the processing concentration requirements for coating films. Under 365 nm UV irradiation, the characteristic absorption peak of coumarin showed significant attenuation, indicating that the introduction of the nitrogen-containing heteroatom flexible chain does not affect the photoinduced [2+2] cycloaddition activity of the coumarin fragment. These results demonstrate that the monomer obtained in Example 2 successfully achieved a synergistic design of a rigid polyphenylene skeleton and a flexible nitrogen-containing bridging chain, improving solubility and processability while maintaining heat resistance, achieving a design goal of "balancing rigidity and flexibility."

[0054] Example 3: Synthesis of a coumarin photosensitive diamine monomer with a meta-amino-substituted pentylene skeleton This embodiment aims to verify the modular strategy's ability to flexibly construct different spatial topological skeletons (such as meta-substitution) and longer rigid biphenyl cores (such as pentadienylbenzene).

[0055] The specific module assembly reaction equation for this embodiment is as follows:

[0056] The specific synthesis steps are as follows: Step 1. Preparation of the pivot module (me-aminopentaphenyl intermediate): Referring to step 1 of Example 1, the substitution sites of the core raw material and boric acid were changed.

[0057] In a 100 mL double-necked flask, 3,5-bis(4-bromophenyl)phenol (1.00 g, 2.47 mmol), 3-aminophenylboronic acid (0.75 g, 5.43 mmol), palladium acetate (0.028 g, 0.12 mmol), and potassium carbonate (2.04 g, 14.8 mmol) were added sequentially, followed by 1,4-dioxane (40 mL) and water (10 mL). The mixture was then protected with nitrogen. The temperature was raised to 95 °C, and the reaction was carried out for 14 hours. After the reaction was completed, the product was extracted, dried, and purified by column chromatography to obtain 0.96 g of a deep yellow solid product (me-aminopentaphenol intermediate), with a yield of 91%.

[0058] (Note: This intermediate has an ultra-long rigid core composed of 5 benzene rings, and the amino groups are located at the meta positions at both ends of the skeleton, exhibiting a "zigzag" spatial configuration.) Step 2. Preparation of the functional module (butyl ether flexible chain precursor): The terminal bromobutyl ether flexible chain precursor F was prepared by following the method in step 2 of Example 1 exactly.

[0059] Step 3. Modular assembly (target pentaphenyl monomer): In a 100 mL double-necked flask, the meta-aminopentaphenyl intermediate prepared in step 1 (0.50 g, 1.17 mmol), the coumarin-butyl ether-bromine precursor prepared in step 2 (0.43 g, 1.17 mmol), and cesium carbonate (1.14 g, 3.50 mmol) were added, followed by anhydrous N-methylpyrrolidone (NMP, 15 mL). The mixture was heated to 90 °C under nitrogen protection and reacted in the dark for 12 hours. After the reaction was complete, the reaction solution was added dropwise to a large amount of cold water to precipitate the solid. The solid was filtered, washed with water, purified by column chromatography or recrystallization, and dried under vacuum to obtain 0.76 g of the target photosensitive diamine monomer with a meta-amino group, with a yield of 91%.

[0060] Technical effect analysis: In Example 3, the amino group was introduced into the meta position using 3-aminophenylboronic acid to obtain a meta-substituted pentylene monomer, verifying the adaptability of this method to different amino substitution sites and longer polyphenylene skeletons. Example 3 has been successfully synthesized, and the obtained meta-amino-substituted pentylene skeleton monomer was confirmed to have the correct structure by ¹H NMR. Thermogravimetric analysis showed that its Td5% was not lower than 255℃, and the ultra-long pentylene rigid core endowed the monomer with excellent thermal stability. Due to the meta-substitution causing the molecule to adopt a "zigzag" nonlinear configuration, intermolecular stacking was suppressed, and the solubility of this monomer in DMAc and NMP was improved compared to the para-substituted structure, making it easier to prepare a uniform coating solution. UV irradiation tests showed that the photocrosslinking activity of the coumarin fragment remained intact. The above results verified the feasibility of controlling the molecular spatial configuration by changing the amino substitution site, thereby balancing heat resistance and processability, achieving the design goal of "combining rigidity and flexibility."

[0061] Example 4: Synthesis of a photosensitive diamine monomer with a heteroatom-containing flexible chain and a tetraphenyl backbone This embodiment aims to verify the adaptability of the modular strategy to flexible chains containing heteroatoms (ether bonds) and the effectiveness of constructing ultra-long rigid cores of tetraphenyl.

[0062] The specific module assembly reaction equation for this embodiment is as follows:

[0063] The specific synthesis steps are as follows: Step 1. Synthesis of the pivot module (diaminotetraphenol intermediate): The method is the same as step 1 of Example 1, except that the core polyphenylene raw material is replaced.

[0064] In a 250 mL double-necked flask, 3,5-dibromo-[1,1'-biphenyl]-4-phenol (1.00 g, 3.05 mmol), 4-aminophenylborate (1.06 g, 6.10 mmol), tetra(triphenylphosphine)palladium (0.18 g, 0.15 mmol, 5 mol%), and potassium carbonate (2.52 g, 18.3 mmol) were added sequentially, followed by tetrahydrofuran (30 mL) and water (8 mL). The mixture was stirred under nitrogen protection in the dark. The temperature was raised to 80 °C, and the reaction was allowed to proceed for 12 hours. After the reaction was complete as monitored by TLC, the mixture was cooled to room temperature. The reaction mixture was filtered, and the filter cake was washed 3–4 times with tetrahydrofuran. The filtrates were combined and extracted with saturated brine (40 mL × 3) and ethyl acetate (40 mL × 3). The organic phase was dried over anhydrous sodium sulfate, concentrated under reduced pressure, and purified by silica gel column chromatography to give 0.99 g of a light yellow solid product (diaminotetraphenylphenol intermediate), with a yield of 92%.

[0065] Step 2. Preparation of the functional module (precursor containing a heteroatom-containing brominated flexible chain): The synthesis steps are the same as in Example 1, except that the dihalogenated flexible chain is replaced.

[0066] In a 250 mL two-necked flask, 7-hydroxy-4-(trifluoromethyl)coumarin (1.00 g, 4.35 mmol), bis(2-bromoethyl) ether (1.90 g, 8.20 mmol), cesium carbonate (2.24 g, 6.87 mmol), and tetrabutylammonium iodide (0.21 g, 0.57 mmol) were added, followed by 18 mL of anhydrous tetrahydrofuran under nitrogen protection. The mixture was heated to 80 °C and reacted for 12 hours. After the reaction was complete as monitored by TLC, it was cooled to room temperature. The reaction mixture was filtered, and the filtrate was concentrated by rotary evaporation under reduced pressure at 35 °C to obtain the crude product. The crude product was washed three times with anhydrous diethyl ether and dried under vacuum at 60 °C for 12 hours to obtain 1.51 g of a terminally brominated flexible chain precursor containing heteroatoms (ether bonds), with a yield of 93%.

[0067] Step 3. Module Assembly (Target Tetraphenyl Monomer): In a 100 mL double-necked flask, the prepared diaminotetraphenyl intermediate (0.50 g, 1.40 mmol), the heteroatom-containing brominated flexible chain precursor (0.54 g, 1.40 mmol), and potassium carbonate (0.58 g, 4.20 mmol) were added and dissolved in anhydrous N,N-dimethylformamide (DMF, 15 mL) under nitrogen protection. The mixture was heated to 80 °C and reacted in the dark for 12 hours. After filtration and washing with ethyl acetate, the crude product was purified by silica gel column chromatography and dried under vacuum for 12 hours to obtain 0.84 g of the tetraphenyl target photosensitive diamine monomer with a heteroatom-containing flexible chain, with a yield of 91%.

[0068] Technical effect analysis: The synthesis of the tetraphenylene skeleton monomer containing ether-bonded heteroatoms in Example 4 has been completed. The structure of the obtained monomer with a flexible chain and ether-bonded heteroatoms was confirmed to be correct by ¹H NMR. Thermogravimetric analysis showed that its Td5% was not lower than 252 °C, indicating good thermal stability. The introduction of ether bonds increased the polarity and flexibility of the flexible chain. This monomer exhibited superior solubility in DMAc and NMP compared to the pure carbon chain structure, allowing for the preparation of homogeneous solutions that meet processing requirements. Under 365 nm UV irradiation, the characteristic absorption peak of coumarin also showed a significant attenuation, indicating that the photocrosslinking activity was not affected by the tetraphenylene skeleton and the ether-bonded flexible chain structure. These results demonstrate that Example 4 further verifies the universal applicability of the modular strategy to flexible chains containing ether-bonded heteroatoms and longer polyphenylene skeletons. The obtained monomer also meets the design requirement of "balancing rigidity and flexibility" while maintaining heat resistance and improving solubility and processability.

[0069] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and various changes or modifications can be made to these embodiments without departing from the principles and essence of the present invention. The scope of protection of the present invention is defined only by the appended claims.

Claims

1. A photosensitive diamine monomer containing a polyphenylene backbone and a flexible bridging chain, characterized in that, The photosensitive diamine monomer has the molecular structure shown in general formula (I): (I), where: Ar represents the phenyl unit, and the Ar units are connected by carbon-carbon single bonds to form a polyphenyl aromatic skeleton; the curved bond represents the connection site, which is independently selected from the ortho, meta or para position of the corresponding Ar unit; m and n are each independently selected from 1, 2 or 3, and I is selected from 1 or 2; the two –NH2 are each independently located in the adjacent, meta, or anti-position of the corresponding terminal Ar unit; –O–(CH2) p –Z–(CH2)q–O– is a flexible bridging chain, where p and q are each independently selected from integers from 1 to 6, and Z is selected from single bonds, –O–, –S–, or –NH–.

2. The photosensitive diamine monomer containing a polyphenylene backbone and a flexible bridging chain according to claim 1, characterized in that, In general formula (I): p and q are each independently selected from integers from 2 to 4; Z is selected from single bond, –O– or –NH–; both –NH2 are located at the anti or meta position of the corresponding terminal Ar unit.

3. The photosensitive diamine monomer containing a polyphenylene backbone and a flexible bridging chain according to claim 1, characterized in that, The aromatic skeleton of the polyphenylene is a terphenyl, tetraphenyl, or pentphenyl skeleton.

4. The photosensitive diamine monomer containing a polyphenylene backbone and a flexible bridging chain according to claim 1, characterized in that, The photosensitive diamine monomer is selected from any one of the following compounds (a) to (d): (a) is 7-[4-(3,5-bis(4-aminophenyl)phenoxy)butoxy]-4-(trifluoromethyl)-2H-chromen-2-one, with the structural formula shown below: ； (b) is 7-{3-[(3-(3,5-bis(4-aminophenyl)phenoxy)propyl)amino]propoxy}-4-(trifluoromethyl)-2H-chromen-2-one, with the structural formula shown below: ； (c) is 7-{4-[3,5-bis(3′-amino-[1,1′-biphenyl]-4-yl)phenoxy]butoxy}-4-(trifluoromethyl)-2H-chromen-2-one, with the structural formula shown below: ； (d) is 7-(2-{2-[(4,4″-diamino-5′-phenyl-[1,1′:3′,1″-terphenyl]-2′-yl)oxy]ethoxy}ethoxy)-4-(trifluoromethyl)-2H-chromen-2-one, with the structural formula shown below: 。 5. The method for preparing a photosensitive diamine monomer containing a polyphenylene backbone and a flexible bridging chain according to any one of claims 1-4, characterized in that, Includes the following steps: (1) Preparation of hub module: Dihalopolyphenols are coupled with amino-containing arylboronic acids or their derivatives in an organic solvent under the presence of a palladium catalyst and a base to obtain a diaminopolyphenol intermediate with phenolic hydroxyl groups, which serves as the hub module. (2) Preparation of functional module: 7-hydroxy-4-(trifluoromethyl)coumarin is reacted with the dihalogenated flexible bridging chain shown in the following general formula (a) in an organic solvent under the presence of a phase transfer catalyst and a base to obtain a terminal halogenated coumarin flexible ether chain precursor, which serves as the functional module. (a) Wherein: X and Y are each independently selected from chlorine, bromine or iodine, p and q are each independently selected from integers from 1 to 6, and Z is selected from single bond, –O–, –S– or –NH–; (3) Module assembly: In the presence of a Lewis base and in an organic solvent, the phenolic hydroxyl group of the hub module obtained in step (1) undergoes a nucleophilic substitution reaction with the terminal halogen of the functional module obtained in step (2) to form an ether, thereby obtaining the photosensitive diamine monomer compound shown in general formula (I).

6. The method for preparing a photosensitive diamine monomer containing a polyphenylene backbone and a flexible bridging chain according to claim 5, characterized in that, The hub module has a structure as shown in general formula (b): （b） Wherein: Ar represents a phenyl unit, and each Ar unit is connected by a carbon-carbon single bond to form a polyphenyl aromatic skeleton; the curved bond represents a linking site, which is independently selected from the ortho, meta or para position of the corresponding Ar unit; m and n are independently selected from 1, 2 or 3, and I is selected from 1 or 2; the two -NH2 are independently located at the ortho, meta or para position of the corresponding terminal Ar unit; the phenolic hydroxyl group connected by the curved bond is -OH, which is used as the active site for the nucleophilic substitution reaction in step (3).

7. The method for preparing a photosensitive diamine monomer containing a polyphenylene backbone and a flexible bridging chain according to claim 5, characterized in that, The dihalogenated polyphenol is selected from any one of 3,5-dibromophenol, 3,5-bis(4-bromophenyl)phenol, and 3,5-dibromo-[1,1′-biphenyl]-4-phenol; and / or, the amino-containing arylboronic acid or its derivative is selected from any one of 2-aminophenylboronic acid, 3-aminophenylboronic acid, 4-aminophenylboronic acid, 4-aminophenylboronic acid pinacol ester, and 3-aminophenylboronic acid pinacol ester; and / or, the dihalogenated flexible bridging chain is selected from any one of 1,4-dibromobutane and bis(2-bromoethyl) ether.

8. The method for preparing a photosensitive diamine monomer containing a polyphenylene backbone and a flexible bridging chain according to claim 5, characterized in that, The palladium catalyst in step (1) is selected from any one of tetra(triphenylphosphine)palladium, dichlorobis(triphenylphosphine)palladium, palladium acetate, and palladium on carbon; the base is selected from at least one of potassium carbonate, sodium carbonate, and cesium carbonate. And / or, the phase transfer catalyst in step (2) is selected from any one of tetrabutylammonium iodide, tetraethylammonium bromide, octadecanoic acid, and benzyltriethylammonium chloride; the base is selected from at least one of potassium carbonate, sodium carbonate, and cesium carbonate; And / or, the Lewis base in step (3) is selected from any one of sodium hydride, potassium carbonate, sodium carbonate, and cesium carbonate; And / or, the organic solvents in steps (1) to (3) are each independently selected from any one or a mixture of two or more of the following solvents: methanol, ethanol, acetone, tetrahydrofuran, acetonitrile, chloroform, ethyl acetate, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, and 1,4-dioxane.

9. The method for preparing a photosensitive diamine monomer containing a polyphenylene backbone and a flexible bridging chain according to claim 5, characterized in that, Steps (1) to (3) are all performed under inert gas protection and satisfy the following conditions: The Suzuki coupling reaction in step (1) is carried out at a temperature of 70–100 °C for 8–24 hours, and the molar ratio of the dihalopolyphenol to the aminoarylboronic acid or its derivative is 1:2.0–1:2.

5. The Williamson etherification reaction in step (2) is carried out at a temperature of 60–90 °C for 8–24 hours, and the molar ratio of 7-hydroxy-4-(trifluoromethyl)coumarin to the dihalogenated flexible bridging chain is 1:2.0–1:3.

0. The nucleophilic substitution reaction in step (3) is carried out at a temperature of 70–95 °C for 8–24 hours, and the molar ratio of the hub module to the functional module is 1:1.0 to 1:1.

2.

10. The application of the photosensitive diamine monomer containing a polyphenylene backbone and a flexible bridging chain as described in any one of claims 1-4, or the photosensitive diamine monomer containing a polyphenylene backbone and a flexible bridging chain prepared by the preparation method described in any one of claims 5-9, in the preparation of photosensitive polyimides.

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