Preparation method of organic electron transport material P (NDI2OD-T2) single-ended block copolymer

Abstract

The invention discloses a preparation method of an organic electron transport material P (NDI2OD-T2) single-ended block copolymer, which comprises the following three steps: by taking a 4, 9-dibromo derivative (compound 1) as an initial raw material, synthesizing a polymeric monomer (compound 6) containing a boric acid ester group through Stille coupling, NBS bromination and Suzuki coupling reaction; the preparation method comprises the following steps: carrying out Suzuki coupling polymerization and a deprotection reaction to obtain single-terminal hydroxylated P (NDI2OD-T2)-OH; and directionally connecting the carboxyl-terminated polymer to a hydroxyl end through Steglich coupling, so as to prepare the single-ended block copolymer. Through single-ended functional modification, on the basis of retaining high electron mobility of a main chain of P (NDI2OD-T2), an adjustable block polymer is introduced, so that the electron mobility is improved, the thermal stability and the processing performance of the material and the morphology regularity of a device are effectively improved, and the problems of complex process, limited electron transmission efficiency and single function in the prior art are solved. The obtained single-ended block copolymer can be widely applied to high-performance organic photoelectric devices such as organic field effect transistors, organic solar cells and flexible electronic devices.

Description

Technical Field

[0001] The present invention relates to the field of polymer materials, and particularly to a preparation method of a novel organic electron transport material, P(NDI2OD-T2) single-end block copolymer. By precisely performing block chemical modification at one end of the P(NDI2OD-T2) molecule, the electron transport efficiency, device stability, and processability of the material in organic field effect transistors (OFETs), organic solar cells, and other optoelectronic devices are improved. Background Art

[0002] P(NDI2OD-T2), fully known as poly{[N,N′-bis(2-octyldodecyl)-1,4,5,8-naphthalenediimide-2,6-diyl]-alternating-5,5′-(2,2′-bithiophene)}, is a typical n-type conjugated polymer with high electron mobility, excellent thermal stability, and good solution processability. Therefore, it has been widely used in organic solar cells, mainly as an electron transport layer material for efficiently collecting and transporting electrons, reducing recombination losses, and thus improving the photoelectric conversion efficiency and service life of the device.

[0003] However, the traditional methods for preparing P(NDI2OD-T2) have the following deficiencies: First, the preparation process is complex, with many reaction steps and strict requirements for operating conditions, making it difficult to achieve large-scale production; second, the electron transport efficiency is limited. Although P(NDI2OD-T2) itself has a high carrier mobility, the research on its end-group functionalization and block copolymerization is not sufficient, and it is difficult to further break through the performance bottleneck; third, the structure and function are single. For specific device applications, materials often need to have diverse functions, but the current research on single-end block modification of P(NDI2OD-T2) is relatively scarce.

[0004] Although the reported double-end block copolymers can achieve certain results in regulating molecular packing and device morphology, during the device manufacturing and processing process, it is often necessary to retain the original characteristics of the other end and only functionalize one end to achieve more flexible performance regulation. However, there is currently no publicly reported preparation method for P(NDI2OD-T2) single-end block copolymer, which restricts the application of this material in high-end optoelectronic devices. Summary of the Invention

[0005] The object of the present invention is to provide a preparation method of an organic electron transport material P(NDI2OD-T2) single-end block copolymer. Through molecular design and multi-step reaction optimization of the single end of the P(NDI2OD-T2) molecule, the present invention can not only ensure the original high electron mobility of the material but also precisely regulate the end-group function, endowing it with more excellent optoelectronic properties, thermal stability, and device processing controllability.

[0006] The present invention provides a preparation method of an organic electron transport material P(NDI2OD-T2) single-end block copolymer, which has a simple process, controllable molecular weight and is suitable for large-scale production. Through precise single-end functionalization modification, while retaining the high electron mobility of the P(NDI2OD-T2) main chain, a regulable block polymer is introduced, significantly improving the thermal stability, processing performance and device morphology regularity of the material. This method overcomes the defects of the traditional double-end modification process, such as complex process and single function, and provides a new material with both high mobility and functional diversity for high-performance organic optoelectronic devices.

[0007] The present invention provides a preparation method of an organic electron transport material P(NDI2OD-T2) single-end block copolymer, comprising the following steps: Step 1. Intermediate synthesis: Using 4,9-dibromo-2,7-bis(2-octyldodecyl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetrone (Compound 1) as the starting material, with 2-tributylstannylthiophene (Compound 2), N-bromosuccinimide (NBS) and other raw materials, successively through Stille coupling and bromination reactions to synthesize 4,9-bis(2-thienyl) derivative (Compound 4) and 4,9-bis(5-bromo-2-thienyl) derivative (Compound 5); coupling Compound 5 with 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (Compound 3) through Suzuki coupling reaction to synthesize a polymerization monomer Compound 6 containing a borate ester group; synthesizing the key intermediates Compound 4, Compound 5 and the polymerization monomer Compound 6, providing a basis for the construction of the subsequent polymer main chain. The Stille coupling reaction couples Compound 1 with Compound 2 to generate 4,9-bis(2-thienyl) derivative (Compound 4), which introduces a thiophene group and provides an active site for the subsequent bromination reaction; the bromination reaction uses N-bromosuccinimide (NBS) to brominate Compound 4 to generate 4,9-bis(5-bromo-2-thienyl) derivative (Compound 5), providing the necessary bromine atom for the subsequent Suzuki coupling reaction to introduce a borate ester group; the Suzuki coupling reaction couples Compound 5 with Compound 3 to synthesize a polymerization monomer Compound 6 containing a borate ester group, which introduces a borate ester group and provides an active site for the subsequent polymerization reaction.

[0008] Step 2. Modification of polymer backbone: Compound 6 is converted into P(NDI2OD-T2)-OTBS by Suzuki coupling polymerization, and then single-end hydroxylated P(NDI2OD-T2)-OH is obtained by deprotection reaction of TBS; polymerized monomer compound 6 is converted into single-end hydroxylated P(NDI2OD-T2)-OH by Suzuki coupling polymerization and deprotection reaction, providing key intermediates for the subsequent synthesis of single-end block copolymers. Compound 6 is polymerized by Suzuki coupling polymerization to generate P(NDI2OD-T2)-OTBS. This reaction realizes the construction of polymer backbone by coupling borate group with bromine atom; deprotection reaction of TBS is carried out by deprotection reaction of TBS (tri-tert-butylsilyl) to convert P(NDI2OD-T2)-OTBS into single-end hydroxylated P(NDI2OD-T2)-OH. This reaction removes the protecting group and exposes the hydroxyl group, providing active sites for subsequent block copolymerization.

[0009] Step 3. Synthesis of single-end block copolymer: P(NDI2OD-T2)-OH is subjected to Steglich coupling reaction with a carboxyl-terminated polymer to generate the target single-end block copolymer P(NDI2OD-T2)-b-Polymer, the structural formula of which is shown in Figure 1 The Steglich coupling reaction connects P(NDI2OD-T2) with a carboxyl-terminated polymer through an esterification reaction between hydroxyl and carboxyl groups to form a single-end block copolymer. This reaction realizes the block copolymerization of P(NDI2OD-T2) with other polymers, giving the material better performance and functions.

[0010] The present invention avoids the disorder of molecular structure caused by double-end reaction through hydroxyl directional coupling, and ensures the regularity of device morphology; the reaction conditions of each step are mild, the total yield is improved, and it is suitable for large-scale production; the electron mobility of the single-end block copolymer is 10-25 times higher than that of the homopolymer, and the thermal stability and processability are significantly optimized. The single-end block copolymer obtained by the preparation method of the present invention can be widely used in organic field effect transistors (OFETs), organic solar cells (OPVs) and flexible electronic devices, and can be further adapted to different device requirements by adjusting the block type (such as hydrophobic / hydrophilic polymers), breaking through the performance bottleneck of traditional materials.

[0011] The overall function of step 1 in the present invention is to synthesize the key intermediate compound 6, which provides the necessary precursor for the subsequent polymer main chain construction. Through the three-step reaction of Stille coupling, bromination and Suzuki coupling, compound 1 is used as the starting material, and thiophene groups, bromine atoms and borate groups are gradually introduced to construct a polymer monomer compound 6 containing multiple functionalized sites. This series of reactions lays the foundation for the subsequent polymerization reaction and the synthesis of single-end block copolymers.

[0012] In the preparation method of the present invention, step 1 includes the following operations: Step 1.1: Through the Stille coupling reaction of compound 1 and compound 2, 4,9-bis(2-thienyl)-2,7-bis(2-octyldodecyl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetrone (compound 4) is generated, as shown in Figure 2 . Through the Stille coupling reaction of compound 1 (containing a bromine substituent) and compound 2 (2-tributylstannylthiophene), a thiophene group is introduced onto the phenanthroline backbone to generate compound 4 (a 4,9-bis(2-thienyl) derivative). The thiophene group has good electron transport properties. By introducing it into the backbone of compound 1 through the Stille coupling reaction, it provides a basis for improving the subsequent electron transport characteristics. The thiophene group on the generated compound 4 provides necessary active sites for the subsequent bromination reaction, enabling the smooth introduction of bromine atoms. Step 1.1 forms a carbon-carbon bond, expands the conjugated structure, and provides an active site (the α-position of thiophene) for the subsequent bromination reaction.

[0013] Step 1.2: Through the bromination reaction of NBS and compound 4, 4,9-bis(5-bromo-2-thienyl)-2,7-bis(2-octyldodecyl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetrone (compound 5) is generated, as shown in Figure 3 . The thiophene group of compound 4 is selectively brominated using N-bromosuccinimide (NBS) to generate compound 5 (a 4,9-bis(5-bromo-2-thienyl) derivative). The bromine atom is a necessary precursor for the subsequent Suzuki coupling reaction. Through the bromination reaction, the bromine atom is introduced onto the thiophene group, providing an active site for the subsequent Suzuki coupling reaction. The introduction of the bromine atom makes compound 5 have higher reactivity, facilitating the subsequent coupling reaction. Step 1.2 introduces a bromine atom at the 5-position of the thiophene group, providing a halogen substitution site for the subsequent Suzuki coupling reaction to ensure the directional introduction of the boronic ester group.

[0014] Step 1.3: Through the Suzuki coupling reaction of compound 3 and compound 5, 4-[5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-2-thienyl]-9-(5-bromo-2-thienyl)-2,7-bis(2-octyldodecyl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetrone (compound 6) is generated, as shown in Figure 4。Through the Suzuki coupling reaction of Compound 5 (containing bromo substituents) and Compound 3 (2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane), a boronic ester group is introduced at the bromo substitution site to generate Compound 6 (a polymeric monomer containing a boronic ester group). The boronic ester group is the key reactive site for subsequent polymerization reactions. Through the Suzuki coupling reaction, the boronic ester group is introduced into the backbone of Compound 5, providing the necessary reactive sites for subsequent polymerization reactions. The generated Compound 6 is the monomer for subsequent polymerization reactions, and its structural design ensures the formation and functionalization of the polymer backbone. Step 1.3 replaces the bromine atom with a boronic ester group, endowing the monomer with high reactivity in subsequent polymerization reactions, while retaining the bromine atom at the other end as a polymerization termination site to achieve a single-end functionalization design.

[0015] In Step 1 of the present invention, the polymeric monomer Compound 6 containing a boronic ester group is gradually constructed through Stille coupling, bromination, and Suzuki coupling reactions. This series of reactions not only introduces the necessary functional groups (such as thiophene groups and boronic ester groups), but also provides key intermediates for subsequent polymerization reactions and the synthesis of single-end block copolymers. The synthesis of these intermediates is the basis for the preparation of the high-performance organic electron transport material P(NDI2OD-T2) single-end block copolymer.

[0016] In Step 1.3 of the present invention, through the combination of a low-temperature lithiation reaction and a Suzuki coupling reaction, a boronic ester group (Compound 3) is accurately introduced at the bromo substitution site of Compound 5 to generate the polymeric monomer Compound 6. This step ensures the efficient introduction of the boronic ester group and the high purity of the product by strictly controlling the reaction temperature, reagent addition order, and purification process, laying a key structural foundation for subsequent single-end functionalized polymerization.

[0017] In the preparation method of the present invention, Step 1.3 includes the following operations: Compound 5 (4,9-bis(5-bromo-2-thienyl)-2,7-di(2-octyldodecyl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone) and ether were added to a three-necked flask and replaced with nitrogen to remove oxygen and moisture in the air, ensuring that the reaction was carried out in an oxygen-free and water-free environment. Ether, as a low-polarity solvent, is conducive to the subsequent lithiation reaction; nitrogen replacement removes oxygen and moisture to prevent n-butyl lithium (strong base) from failing to react with oxygen / water, ensuring the inertness of the reaction system. After nitrogen replacement, the reaction system was cooled to -90°C to -70°C and stirred vigorously at this temperature. 1~2 mol / L n-butyl lithium (n-hexane solution) was slowly added dropwise over 20 to 40 minutes. n-Butyl lithium is a strong base used to activate compound 5, capture the α-hydrogen of the thiophene ring in compound 5, and generate an aryl lithium intermediate, which can react with the subsequent compound 3. Low temperature (-90℃ to -70℃) inhibits side reactions (such as decomposition or overreaction of the lithiation reagent) and improves the lithiation selectivity. After the n-butyl lithium is added dropwise, the reaction solution is naturally heated to 5~15℃, stirred for 5~15 minutes, and the reaction solution is cooled to -90℃ to -70℃ again. The heating stage promotes the stabilization of the aryl lithium intermediate to ensure the complete lithiation reaction; the cooling stage provides a low temperature environment for the subsequent nucleophilic substitution reaction of the borate reagent to avoid the decomposition of the intermediate. Then compound 3 (2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane) is added at a low temperature. The borate reagent reacts with the aryl lithium intermediate to generate a borate ester-substituted product; the one-time addition avoids the uneven local concentration caused by the step-by-step addition and ensures the reaction efficiency. After stirring at low temperature for 0.5 to 1.5 hours, the mixture was heated to room temperature and stirred for 20 to 30 hours. The low temperature stage promoted the initial reaction of the borate reagent and reduced the formation of by-products; the room temperature stage ensured that the coupling reaction was completely completed by extending the reaction time to improve the conversion rate. The reaction progress was monitored by thin layer chromatography (TLC), the end point was determined, and whether the raw material (compound 5) was completely converted into the product (compound 6) was confirmed in real time to avoid over-reaction or unreacted residue. After the reaction was completed, the reaction solution was washed and extracted with water for 2 to 4 times, and the oil phase was dried with anhydrous sodium sulfate. Water-soluble by-products (such as LiBr and unreacted borate reagent) were removed by washing with water; anhydrous sodium sulfate adsorbed trace water to improve the purity of the product. The desiccant was removed by filtration, the solvent was removed by rotary evaporation, and the yellow solid compound 6 was separated by column chromatography. By removing the residual solvent, unreacted reagents and by-products, a high-purity yellow solid product compound 6 was obtained; column chromatography achieved fine separation through polarity differences to ensure the uniformity of the product molecular structure.

[0018] Compound 6 synthesized through this step, with its borate ester group providing an active site for the subsequent Suzuki polymerization reaction, while the remaining bromine atom at the other end serves as a polymerization termination point, ultimately achieving the single-end hydroxylation modification of the P(NDI2OD-T2) main chain (Step 2, see Figure 5 ). This design is the core chemical basis for the controllable synthesis of single-end block copolymers. In this step, through the Suzuki coupling reaction, the borate ester group in Compound 3 is introduced into the backbone of Compound 5 to generate Compound 6; the borate ester group is the key active site for the subsequent polymerization reaction and can undergo a coupling reaction with the bromine atom to achieve the construction of the polymer main chain; Compound 6 is the monomer for the subsequent polymerization reaction, and its structural design ensures the formation and functionalization of the polymer main chain; by precisely controlling the reaction conditions (temperature, stirring time, and reagent dropping rate), the efficient progress of the reaction and the high purity of the product are ensured; by conducting the reaction at low temperature, the reaction rate can be effectively controlled to avoid side reactions and improve the selectivity and yield of the target product; at the same time, by adopting the strategy of gradually increasing and decreasing the temperature, the stability of the reaction system can be better controlled to ensure the smooth progress of the reaction; through operations such as water washing extraction, drying, filtration, and column chromatography separation, impurities and unreacted raw materials in the reaction are effectively removed to obtain the target product Compound 6 with high purity, providing a pure monomer for the subsequent polymerization reaction.

[0019] In Step 2 of the present invention, Compound 6 is converted into single-end hydroxylated P(NDI2OD-T2)-OH through the Suzuki coupling polymerization and deprotection reaction. The core of this step lies in constructing the polymer main chain and introducing a hydroxyl functional group directionally, providing the only reaction site for the subsequent single-end block coupling and ensuring the precise controllability of the molecular structure.

[0020] In the preparation method of the present invention, Step 2 includes the following operations: Step 2.1: Add compound 6 and deoxytoluene into a three-necked flask under nitrogen protection, freeze and degas 2 - 4 times to thoroughly remove dissolved oxygen and moisture, and maintain an inert reaction environment. Then successively add potassium carbonate solution, tetrakis(triphenylphosphine)palladium, and 4-(tert-butyldimethylsilyloxy-ethoxy)-iodobenzene, and react at 85 - 95 °C for 30 - 40 hours. After the reaction, wash with saturated sodium chloride solution (to remove residual catalyst and salts), extract with toluene, dry over anhydrous magnesium sulfate, filter, and rotary evaporate to remove water and impurities in the organic phase. Redissolve in a small amount of toluene and reprecipitate in methanol, then dry under vacuum to obtain P(NDI2OD-T2)-OTMS. Among them, potassium carbonate provides an alkaline environment to promote the activation of borate groups and accelerate the Suzuki coupling reaction. Tetrakis(triphenylphosphine)palladium catalyzes the cross-coupling of borate esters and aryl bromides to drive the extension of the polymer backbone. 4-(tert-butyldimethylsilyloxy-ethoxy)-iodobenzene acts as a capping agent, reacting with the borate ester at the end of the main chain through the iodobenzene group to introduce the TBS (tert-butyldimethylsilyl) protecting group, realizing the single-end functionalization of the polymer. The addition of the capping agent in this step limits the infinite extension of the polymer chain, ensuring a narrow molecular weight distribution (PDI < 1.5); the TBS group is introduced only at one end, and the other end retains the hydroxyl precursor (subsequent deprotection generates -OH), laying the foundation for single-end block copolymerization.

[0021] Step 2.2: Add P(NDI2OD-T2)-OTMS and anhydrous tetrahydrofuran into a reaction flask, and slowly add pyridine hydrogen fluoride as a deprotecting agent under stirring. After stirring at room temperature for 20 - 30 hours, rotary evaporate to remove the solvent. Dissolve the residue in chloroform and reprecipitate in methanol, and dry the filter cake under vacuum to obtain the blue solid P(NDI2OD-T2)-OH. Among them, pyridine hydrogen fluoride (HF·Py) acts as a deprotecting agent to remove the TBS protecting group, selectively cleave the TBS protecting group to generate free hydroxyl groups (-OH), while avoiding the degradation of the main chain or the destruction of other functional groups. Anhydrous tetrahydrofuran acts as a polar solvent to promote the full contact of the deprotecting reagent with the polymer. This step only removes the TBS group at one end, and the other end remains inert, realizing the directional exposure of hydroxyl groups and ensuring the specificity of subsequent block coupling reactions. The reaction at room temperature has mild conditions, avoiding the breakage of the polymer backbone caused by high temperature, and the yield is as high as 94% (example data). Through the synergistic effect of the capping agent and the deprotecting reagent, this step realizes single-end hydroxylation with a narrow molecular weight distribution; reprecipitation with toluene / methanol and purification with chloroform / methanol effectively remove by-products, and the product has high purity; deoxytoluene and nitrogen protection inhibit side reactions, improving the total yield, which is suitable for large-scale production.

[0022] In Step 2, through Suzuki coupling polymerization reaction and de-TBS protection reaction, the polymerization monomer compound 6 was successfully converted into P(NDI2OD-T2)-OH with a single-terminal hydroxyl group. This series of reactions not only constructed the polymer backbone but also, through protection and deprotection strategies, ensured the exposure of the active site of the hydroxyl group, providing a key intermediate for the subsequent synthesis of single-terminal block copolymers. These operations ensured the high efficiency of the reaction and the high purity of the product, laying a solid foundation for the preparation of high-performance single-terminal block copolymers of P(NDI2OD-T2).

[0023] In Step 3 of the present invention, through Steglich coupling reaction, the carboxyl-terminated polymer (Polymer-COOH) was directionally linked to the hydroxyl end of P(NDI2OD-T2)-OH to generate the single-terminal block copolymer P(NDI2OD-T2)-b-Polymer, as shown in Figure 6 . This step, through precise coupling design and efficient purification process, ensured controllable block molecular weight and excellent product purity, while retaining the high electron mobility characteristics of the main chain, providing a core material with optimized performance for optoelectronic devices.

[0024] In the preparation method of the present invention, Step 3 includes the following operations: P(NDI2OD-T2)-OH, Polymer with a carboxyl end group, dicyclohexylcarbodiimide (DCC), and 4-dimethylaminopyridine (DMAP) were placed in a round-bottom flask, and nitrogen replacement was carried out to exclude oxygen and moisture in the air, ensuring that the reaction proceeded in an oxygen-free and water-free environment. Nitrogen protection excluded oxygen and moisture to prevent the hydrolysis and inactivation of DCC or side reactions (such as oxidation); dichloromethane, as an aprotic polar solvent, dissolved the polymer and promoted the full contact of the coupling reagent with the reactants. After nitrogen replacement, dichloromethane was added as a solvent, and the mixture was stirred at room temperature for 20 - 30 hours to ensure full reaction. DCC and DMAP, as dehydrating condensing agents, promoted the esterification reaction between P(NDI2OD-T2)-OH and Polymer. Among them, DCC (dicyclohexylcarbodiimide) acted as a dehydrating agent to activate the carboxyl group to generate an active intermediate (O-acylisourea), promoting the formation of an ester bond between the carboxylic acid and the hydroxyl group; DMAP (4-dimethylaminopyridine) acted as a nucleophilic catalyst to accelerate the nucleophilic substitution reaction of the active intermediate with the hydroxyl group, significantly improving the coupling efficiency; the mild reaction conditions at room temperature avoided the degradation of the polymer backbone or side reactions at the end groups, ensuring the reaction selectivity.

[0025] After the reaction was completed, dichloromethane was evaporated and acetone was added, and the mixture was stirred for 10 - 20 hours to precipitate the product, thereby recovering the product. The solvent evaporation removed unreacted DCC, DMAP, and by-products (such as dicyclohexylurea, DCU); acetone precipitation utilized the low solubility of acetone in the block copolymer to selectively precipitate the target product and preliminarily separate impurities.

[0026] The filtered solid was purified by Soxhlet extraction with acetone for 40 - 50 hours to remove unreacted starting materials and by-products, yielding the single-end block copolymer P(NDI2OD-T2)-b-Polymer. Through continuous reflux extraction, residual small-molecule impurities (such as DCU and uncoupled Polymer-COOH) were thoroughly removed; the high-polarity solvent (acetone) preferentially dissolved low-molecular-weight by-products, retaining the high-molecular-weight block copolymer and ensuring a narrow molecular weight distribution of the product (PDI < 1.5).

[0027] In Step 3, P(NDI2OD-T2)-OH was linked to the carboxyl-terminated Polymer through an esterification reaction to form the single-end block copolymer P(NDI2OD-T2)-b-Polymer. This reaction not only achieved the block copolymerization of P(NDI2OD-T2) with other polymers but also endowed the material with more excellent properties and functions; through block copolymerization, the electron transport characteristics of P(NDI2OD-T2) were combined with the physical and chemical properties of the Polymer to form a composite material with unique properties; for example, block copolymerization with polystyrene (PSt) could improve the solubility and processability of the material; block copolymerization with polymethyl methacrylate (PMMA) could improve the mechanical properties of the material; through operations such as solvent evaporation, addition of acetone precipitation, filtration, and Soxhlet extraction, impurities and unreacted starting materials in the reaction were removed to obtain a high-purity single-end block copolymer, ensuring the quality and performance of the final product.

[0028] In the preparation method of the present invention, the carboxyl-terminated polymer is selected from one of polystyrene (PSt), polymethyl methacrylate (PMMA), polyethylene oxide (PEO), and polythiophene-based conjugated polymers. The selection of these polymers is of great significance for the properties and applications of the final single-end block copolymer P(NDI2OD-T2)-b-Polymer.

[0029] Polystyrene (PSt) is a common thermoplastic polymer with good mechanical properties, transparency, and processability; Carboxyl-terminated polystyrene (PSt-COOH) can introduce carboxyl groups at the end of the polymer chain through chemical methods, enabling it to undergo an esterification reaction with P(NDI2OD-T2)-OH. The PSt segment can enhance the hydrophobic interfacial properties of the material and is suitable for the insulating layer or encapsulation layer of organic field-effect transistors (OFETs); it is easy to form a film by solution method and has high compatibility with the P(NDI2OD-T2) backbone; by regulating the length of the PSt block, the regularity of the device morphology can be optimized and interface defects can be reduced. The introduction of polystyrene can significantly improve the solubility of the single-end block copolymer in organic solvents, facilitating subsequent processing and applications; the rigidity and mechanical strength of polystyrene can enhance the mechanical properties of the final copolymer, making it more suitable for optoelectronic devices that require high mechanical stability; the thermoplastic properties of polystyrene enable the single-end block copolymer to have better plasticity and moldability during processing.

[0030] Poly(methyl methacrylate) (PMMA) is a transparent thermoplastic polymer with good optical properties, weather resistance, and mechanical properties; Carboxyl-terminated poly(methyl methacrylate) (PMMA-COOH) can also introduce carboxyl groups at the end of the polymer chain through chemical methods. The PMMA block can inhibit excessive crystallization of the P(NDI2OD-T2) backbone and balance the flexibility and electron transport efficiency of the device. The high transparency of PMMA can improve the application performance of the single-end block copolymer in optical devices, such as in organic solar cells and organic light-emitting diodes (OLEDs); the weather resistance of PMMA can enhance the stability and service life of the single-end block copolymer in outdoor environments; the toughness and mechanical strength of PMMA can improve the impact resistance and wear resistance of the final copolymer.

[0031] Poly(ethylene oxide) (PEO) is a polymer with good water solubility and biocompatibility, commonly used in the fields of biomedicine and drug delivery; Carboxyl-terminated poly(ethylene oxide) (PEO-COOH) can introduce carboxyl groups at the end of the polymer chain through chemical methods. The PEO block can introduce hydrogen bonding interactions and enhance the adhesion of the material to polar substrates; its hydrophilicity and ionic conductivity are suitable for devices that require interface wetting or ion transport (such as the hole transport layer of perovskite solar cells); the chain segment flexibility improves the interface contact between the material and the electrode. The introduction of PEO can significantly improve the solubility of the single-end block copolymer in water, making it suitable for aqueous processing and biomedical applications; the biocompatibility of PEO can increase the application potential of the single-end block copolymer in biomedical devices, such as in drug delivery and tissue engineering; the flexibility of PEO can enhance the flexibility and elasticity of the final copolymer, making it more suitable for flexible optoelectronic devices.

[0032] Polythiophene-based conjugated polymers (such as poly(3-hexylthiophene) P3HT) are a class of polymers with excellent electrical conductivity and optoelectronic properties, which are widely used in organic optoelectronic devices; carboxyl-terminated polythiophene-based conjugated polymers can introduce carboxyl groups at the end of the polymer chain through chemical methods. The intrinsic conductivity of polythiophene-based conjugated polymers forms a p-n heterojunction with P(NDI2OD-T2), promoting exciton separation; the thiophene block can provide a hole transport channel, which is complementary to the electron transport characteristics of P(NDI2OD-T2); optimize the energy level alignment of optoelectronic devices (such as the donor-acceptor interface of organic solar cells). The high electrical conductivity of polythiophene-based conjugated polymers can significantly improve the electrical conductivity of single-end block copolymers, making them perform better in organic solar cells and organic field-effect transistors (OFETs); the optoelectronic properties of polythiophene-based conjugated polymers can enhance the light absorption and charge transport capabilities of single-end block copolymers in optoelectronic devices; the chemical stability of polythiophene-based conjugated polymers can improve the stability and reliability of single-end block copolymers during long-term use.

[0033] By selecting different carboxyl-terminated polymers, different physical and chemical properties and functions are imparted to the P(NDI2OD-T2) single-end block copolymer. The present invention selects polystyrene, poly(methyl methacrylate), polyethylene oxide and polythiophene-based conjugated polymers as carboxyl-terminated blocks, not only based on their chemical properties and functional complementarity, but also verifies their significant effects in improving electron mobility, thermal stability and device efficiency through experiments. Therefore, according to specific application requirements, suitable polymers can be selected for block copolymerization to achieve optimal performance and functions.

[0034] In summary, the present invention has the following beneficial effects: 1. Through the single-end directed modification strategy, the present invention optimizes the complex process of traditional double-end reactions, synthesizes key intermediates by using a three-step method of Stille coupling, bromination and Suzuki coupling, and combines deprotection and Steglich coupling reactions, significantly shortening the reaction steps. The conditions of each step are mild (such as room temperature reaction, low-temperature lithiation to control side reactions), the total yield is increased, and it is suitable for industrial scale-up production; 2. During the preparation process, the present invention can precisely control the molecular weight, uses a capping agent (such as 4-(tert-butyldimethylsilyloxy-ethoxy)-iodobenzene) to limit the infinite extension of the polymer chain, and combines low-temperature lithiation and directed coupling technologies to achieve a narrow molecular weight distribution (PDI < 1.5), ensuring batch consistency of the material, making the material have more stable performance and predictable behavior during application, and providing guarantee for the stability and repeatability of device performance; 3. The polymers introduced into the block copolymer (such as PMMA) can inhibit the excessive crystallization of the main chain, balancing the rigidity and flexibility of the material; the hydrophobic block (such as PSt) enhances the film-forming uniformity; the material exhibits excellent solubility in solution processing (such as solvents like dichloromethane and toluene), and the thermal decomposition temperature is increased, significantly improving the stability of the device in a high-temperature environment; the electron mobility of the single-end block copolymer is significantly improved. Through the precise design of the single-end block copolymer, while retaining the high electron mobility of the P(NDI2OD-T2) main chain, a functionalized block polymer (such as a polythiophene-based conjugated polymer) is introduced to form a p-n heterojunction, promoting exciton separation and charge transport; at the same time, the thermal stability and processing performance are also significantly optimized, breaking through the performance bottleneck of traditional double-end modified P(NDI2OD-T2) materials, better meeting the strict requirements of high-performance organic optoelectronic devices for material properties, and showing broad application prospects in fields such as organic field-effect transistors (OFETs), organic solar cells (OPVs), and flexible electronic devices; 4. The single-end block copolymer prepared by the present invention can flexibly select a carboxyl-terminated block polymer and perform block copolymerization with various polymers such as polystyrene, polymethyl methacrylate, polyethylene oxide, and polythiophene-based conjugated polymers according to needs. By regulating the block types, such as hydrophobic / hydrophilic polymers, it can further adapt to different device requirements, realize the diversification of material functions, and thus expand its application scope in various fields; 5. The present invention adopts the method of hydroxyl-directed coupling, avoiding the molecular structure chaos caused by double-end reactions, ensuring the regularity of the device morphology, being beneficial to improving the performance and stability of optoelectronic devices, reducing interface defects, and improving the charge transport efficiency, which is of great significance for enhancing the photoelectric conversion efficiency and service life of organic optoelectronic devices. Brief Description of the Drawings

[0035] Figure 1 is a schematic structural diagram of the single-end block copolymer P(NDI2OD-T2)-b-Polymer; Figure 2 is a schematic diagram of the synthesis route of 4,9-bis(2-thienyl)-2,7-bis(2-octyldodecyl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetrone (Compound 4); Figure 3 is a schematic diagram of the synthesis route of 4,9-bis(5-bromo-2-thienyl)-2,7-bis(2-octyldodecyl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetrone (Compound 5); Figure 4It is a schematic diagram of the synthetic route of 4-[5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-2-thienyl]-9-(5-bromo-2-thienyl)-2,7-di(2-octyldodecyl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone (Compound 6); Figure 5 It is a schematic diagram of the synthetic route of P(NDI2OD-T2)-OH; Figure 6 It is a schematic diagram of the synthetic route of P(NDI2OD-T2)-b-Polymer. Detailed implementation manners

[0036] This specific embodiment is only an explanation of the present invention and is not a limitation thereof. Those skilled in the art can make modifications without creative contributions to this embodiment according to needs after reading this specification, but as long as it is within the scope of the claims of the present invention, it is protected by the patent law.

[0037] Example 1 Synthesis of the single-end block copolymer P(NDI2OD-T2)-b-PSt: Polymer is polystyrene (PSt), and the number-average molecular weight (Mn) is 18000; Step 1. Intermediate synthesis: Step 1.1: Through the Stille coupling reaction of Compound 1 and Compound 2, 4,9-bis(2-thienyl)-2,7-di(2-octyldodecyl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone (Compound 4) is generated; Step 1.2: Through the bromination reaction of NBS and Compound 4, 4,9-bis(5-bromo-2-thienyl)-2,7-di(2-octyldodecyl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone (Compound 5) is generated; Step 1.3: Add compound 5 (11.50 g, 10.0 mmol) and diethyl ether (90 mL) into a three-necked flask. After purging with nitrogen, stir vigorously at -78 °C. Slowly add n-butyllithium (1.6 mol / L n-hexane solution, 6.25 mL) dropwise within 30 minutes. Then let the reaction solution warm up to 10 °C naturally, stir for 10 minutes, and then cool down to -78 °C. Next, add compound 3 (2.26 mL, 11.0 mmol) all at once. Stir at -78 °C for 1 hour, then warm the reaction solution to room temperature and stir for 24 hours. After judging the completion of the reaction by thin-layer chromatography, wash the reaction solution with water and extract it 3 times (30 mL each time). Dry the organic phase with anhydrous sodium sulfate, then filter, rotary evaporate, and separate by column chromatography to obtain the red solid product compound 6 (7.33 g, yield 64%); Step 2. Modification of the polymer main chain: Add compound 6 (5.98 g, 5.0 mmol) and deoxytoluene (30 mL) into a three-necked flask under nitrogen protection. Freeze and degas 2 - 4 times. Then add potassium carbonate solution (2 mol / L, 45 mL), tetrakis(triphenylphosphine)palladium (56 mg), and 4-(tert-butyldimethylsilyloxy-ethoxy)-iodobenzene (55 mg) in sequence. React at 90 °C for 36 hours. After the reaction is completed, wash with saturated sodium chloride solution, extract with toluene, dry with anhydrous magnesium sulfate, filter, rotary evaporate, dissolve in a small amount of toluene and then reprecipitate in methanol, and dry in vacuo to obtain dark blue polymer P(NDI2OD-T2)-OTMS (3.91 g, yield 80%); Add P(NDI2OD-T2)-OTMS (3.20 g, 0.4 mmol) and anhydrous tetrahydrofuran (100 mL) into the reaction flask. Slowly add pyridine hydrogen fluoride (0.72 mL) with stirring at room temperature. After stirring for 24 hours, rotary evaporate. Dissolve in chloroform and then reprecipitate in methanol, and dry in vacuo to obtain blue solid P(NDI2OD-T2)-OH (Mn is 8000) (3.02 g, yield 94%); Step 3. Synthesis of single-end block copolymer P(NDI2OD-T2)-b-PSt Place P(NDI2OD-T2)-OH (0.80 g, 0.1 mmol), PSt with carboxyl end groups (1.0 g, 1.0 mmol), DCC (0.3 g), and DMAP (0.177 g) in a round-bottom flask and purge with nitrogen; then add dichloromethane (30 mL) and stir the mixture at room temperature for 24 h; after the reaction is completed, add a few drops of water, continue to stir for 5 minutes, then add 30 mL of dichloromethane and filter. Evaporate the solvent from the filtrate. Add acetone to the residual solid and stir overnight; filter, and purify the obtained solid by Soxhlet extraction with acetone for 48 hours to obtain the blue single-end block copolymer product P(NDI2OD-T2)-b-PSt (0.81 g, yield 90%).

[0038] Example 2

[0039] Synthesis of single-end block copolymer P(NDI2OD-T2)-b-PMMA: Polymer is poly(methyl methacrylate) (PMMA), Mn is 22000; Steps 1 and 2: The same as in Example 1; Step 3. Synthesis of single-end block copolymer P(NDI2OD-T2)-b-PMMA: Put P(NDI2OD-T2)-OH (0.80 g, 0.1 mmol), PMMA with carboxyl end groups (2.0 g, 1.0 mmol), DCC (0.3 g) and DMAP (0.177 g) into a round-bottom flask, and displace with nitrogen; then add dichloromethane (30 mL), and stir the mixture at room temperature for 24 h; after the reaction is completed, add a few drops of water, continue to stir for 5 minutes, then add 30 mL of dichloromethane and filter, evaporate the solvent from the filtrate, add acetone to the residual solid and stir overnight; filter, and purify the obtained solid by Soxhlet extraction with acetone for 48 hours to obtain blue single-end block copolymer product P(NDI2OD-T2)-b-PMMA (0.88 g, yield 88%).

[0040] Example 3

[0041] Synthesis of single-end block copolymer P(NDI2OD-T2)-b-PEO: Polymer is polyethylene oxide (PEO), Mn is 24000; Steps 1 and 2: The same as in Example 1; Step 3. Synthesis of single-end block copolymer P(NDI2OD-T2)-b-PEO: Put P(NDI2OD-T2)-OH (0.80 g, 0.1 mmol), PEO with carboxyl end groups (4.0 g, 1.0 mmol), DCC (0.3 g) and DMAP (0.177 g) into a round-bottom flask, and displace with nitrogen; then add dichloromethane (30 mL), and stir the mixture at room temperature for 24 h; after the reaction is completed, add a few drops of water, continue to stir for 5 minutes, then add 30 mL of dichloromethane and filter, evaporate the solvent from the filtrate, add acetone to the residual solid and stir overnight; filter, and purify the obtained solid by Soxhlet extraction with acetone for 48 hours to obtain blue single-end block copolymer product P(NDI2OD-T2)-b-PEO (0.96 g, yield 80%).

[0042] Comparative Example 1 Synthesis of double-end block copolymer P(NDI2OD-T2)-b-PSt-b-P(NDI2OD-T2): Step 1. Synthesis of double-end intermediate: Compound 1 (10.0 g, 8.7 mmol) and an excess of Compound 2 (2-tributylstannylthiophene, 24.0 g, 26.1 mmol) were reacted in toluene with tetrakis(triphenylphosphine)palladium(0) (0.5 mol%) as a catalyst at 110 °C for 48 hours to form a dithienyl derivative (Compound 4, yield 68%, Mn = 1250); Compound 4 (8.0 g, 5.5 mmol) and NBS (4.0 g, 22.0 mmol) were reacted in THF at 0 °C for 4 hours to form a dibromo derivative (Compound 5, yield 75%, Mn = 1400); Compound 5 (7.0 g, 4.2 mmol) and an excess of Compound 3 (2-isopropoxyboronic ester, 3.8 g, 12.6 mmol) were reacted in toluene with palladium acetate (1 mol%) as a catalyst at 90 °C for 36 hours to obtain a diboronated monomer (Compound 6, yield 62%, Mn = 1600); Step 2. Double-end polymerization and protection: Compound 6-D (5.0 g, 2.5 mmol) was reacted with potassium carbonate (3.0 g) and tetrakis(triphenylphosphine)palladium(0) (0.3 mol%) in toluene at 90 °C for 48 hours to obtain a double-end active polymer (Mn = 15,000, PDI = 2.3); the polymer was deprotected with pyridine hydrogen fluoride (5 mL) at room temperature for 24 hours to obtain a double-end hydroxylated product (P(NDI2OD-T2)-OH2 (yield 50%, Mn = 14,500, PDI = 2.5)); Step 3. Synthesis of double-end block copolymer: P(NDI2OD-T2)-OH2 (1.0 g, 0.07 mmol) and PSt-COOH (2.0 g, 2.0 mmol) were reacted in dichloromethane at room temperature for 48 hours under the catalysis of DCC (0.5 g) and DMAP (0.2 g) to obtain a double-end block copolymer P(NDI2OD-T2)-b-PSt-b-P(NDI2OD-T2) (yield 40%, Mn = 28,000, PDI = 2.5).

[0043] Comparative Example 2 Synthesis of block copolymer P(NDI2OD-T2)-b-PMMA: Step 1. Intermediate synthesis: Compound 5 (10.0 g, 6.8 mmol) and magnesium powder (2.0 g, 83.3 mmol) were refluxed in anhydrous ether for 6 hours to form a thienyl Grignard reagent (Compound 5, yield 55%); Compound 5r (5.0 g, 2.5 mmol) and Compound 3 (0.8 g, 2.7 mmol) were reacted at 80 °C for 24 hours to obtain a monomer containing a boronic ester group (Compound 6, yield 35%, Mn = 1300); Step 2. Aggregation and Blocking: Compound 6 (3.0 g, 1.5 mmol) was polymerized in toluene without using a capping agent to obtain P(NDI2OD-T2)-OH (Mn = 8,000, PDI = 1.9); P(NDI2OD-T2)-OH (1.0 g, 0.13 mmol) and PMMA-COOH (2.5 g, 1.25 mmol) were reacted under the catalysis of DCC (0.4 g) to obtain the block copolymer P(NDI2OD-T2)-b-PMMA (yield 50%, Mn = 18,000, PDI = 2.0) Performance Detection The block copolymer samples prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to performance detection, including: optoelectronic performance test, thermal performance test, structural characterization, mechanical performance test, and environmental stability test.

[0044] 1. Optoelectronic Performance Test 1.1 Electron Mobility Detection Method: Electron mobility is an important indicator to measure the ability of electrons to move in a material under the action of an electric field, which directly affects the performance of devices such as organic field effect transistors (OFETs). Using the organic field effect transistor test method, the single-ended block copolymer to be tested was made into a semiconductor layer, and an OFET device with a bottom-gate top-contact structure was constructed. The relationship curve between the source-drain current and the gate voltage was measured using a semiconductor parameter tester under a nitrogen atmosphere.

[0045] Specific Operation: Spin-coat an insulating gate dielectric layer of silicon dioxide on a glass or silicon wafer substrate, and then spin-coat the single-ended block copolymer solution on the dielectric layer to form a semiconductor layer; evaporate and deposit source and drain electrode gold electrodes on the semiconductor layer to form an OFET device structure; place the device on a probe station, connect a semiconductor parameter tester, apply different gate voltages and source-drain voltages, and measure the source-drain current; according to the measurement data, calculate the electron mobility using the field effect model.

[0046] 1.2 Luminescence Efficiency Detection Method: Luminescence efficiency is an important indicator to measure the ability of light-emitting devices such as organic light-emitting diodes (OLEDs) to convert electrical energy into visible light, which represents the light intensity emitted when a unit current passes through the device, and directly reflects the luminescence performance and energy utilization efficiency of the device. Using the photoluminescence method, the material to be tested was made into an OLED device structure. Under specific current conditions, the light intensity emitted by the device was measured using a luminance meter, and the current value flowing through the device was recorded at the same time, and the luminescence efficiency was calculated.

[0047] Specific operation: Spin-coat a hole injection layer (PEDOT:PSS) on a transparent conductive substrate (ITO glass), then spin-coat a light-emitting layer (block copolymer), and then evaporate and deposit an electron injection layer (LiF) and a metal electrode (Al) to form an OLED device structure; Place the device in a vacuum environment and measure it using a luminance meter with an accuracy of ±0.1 cd / m² and a source meter with an accuracy of ±0.1 mA; At room temperature, apply different currents to the device, gradually increasing from 0.1 mA to 10 mA. After each current stabilizes, use the luminance meter to measure the light intensity emitted by the device (unit: cd / m²), and record the corresponding current value (unit: A) at the same time; According to the formula: luminous efficiency (cd / A) = light intensity (cd / m²) / current (A), calculate the luminous efficiency at different currents.

[0048] 1.3 Photovoltaic conversion efficiency Detection method: Photovoltaic conversion efficiency is an important indicator for evaluating the ability of optoelectronic devices such as organic solar cells (OPV) to convert light energy into electrical energy. Using a solar cell test system, fabricate the material to be tested into an organic solar cell device, irradiate it with simulated sunlight, and measure its output photocurrent and photovoltage.

[0049] Specific operation: Spin-coat an electron transport layer (the block copolymer prepared in the example or comparative example) on a transparent conductive substrate (ITO glass), then spin-coat a donor-acceptor blend layer (a blend of a donor polymer and a fullerene derivative) on it, and finally evaporate and deposit a metal electrode (aluminum electrode) to form an organic solar cell device structure; Place the device in a solar cell test system and, under standard simulated sunlight (AM1.5G) irradiation, use a source meter to measure the current-voltage (I-V) curve of the device and calculate the photovoltaic conversion efficiency (PCE).

[0050] 2. Thermal performance test 2.1 Thermal decomposition temperature Detection method: Thermal decomposition temperature is a key indicator for measuring the stability of materials under high-temperature conditions and is of great significance for evaluating the thermal stability of materials during processing and use. Using thermogravimetric analysis (TGA), place the sample in a TGA sample crucible and heat it at a certain heating rate in a nitrogen or air atmosphere, and record the relationship curve between the mass loss of the sample and temperature.

[0051] Specific operation: Accurately weigh about 10 mg of the sample and place it in a TGA sample crucible; In a nitrogen atmosphere, heat it from room temperature to 800 °C at a heating rate of 10 °C / min; Record the mass change curve of the sample, and use the temperature corresponding to a 5% mass loss as the thermal decomposition temperature (Td).

[0052] 2.2 Glass transition temperature Detection method: The glass transition temperature (Tg) is the temperature at which a material changes from a glassy state to a rubbery state, reflecting the activity of the molecular chain segments of the material and having an important impact on the mechanical properties, thermal stability, and processing properties of the material. Using differential scanning calorimetry (DSC), the sample is placed in a DSC sample pan and heated at a certain heating rate under a nitrogen atmosphere, and the relationship curve between the heat flow and temperature of the sample is recorded.

[0053] Specific operation: Accurately weigh about 5 - 10 mg of the sample and place it in a DSC sample pan; under a nitrogen atmosphere, heat from room temperature to 300 °C at a heating rate of 20 °C / min; record the DSC curve and determine the baseline turning point corresponding to the glass transition temperature (Tg).

[0054] 3. Structural characterization Molecular weight and molecular weight distribution Detection method: The molecular weight and its distribution (PDI) are important characteristic parameters of polymer materials, affecting the physical properties, processing properties, and performance stability of the materials. Using gel permeation chromatography (GPC), the sample is dissolved and injected into the GPC instrument, and the molecular weight and its distribution information are obtained by comparing with a standard sample.

[0055] Specific operation: Accurately weigh an appropriate amount of the sample, dissolve it with a suitable solvent (tetrahydrofuran or chloroform), and prepare a solution with a certain concentration; inject the solution into the GPC instrument and calibrate it using a polystyrene standard sample; record the chromatogram and calculate the number-average molecular weight (Mn) and polydispersity index (PDI) of the sample by comparing with the retention time of the standard sample.

[0056] 4. Mechanical property testing Tensile strength and elongation at break Detection method: Tensile strength and elongation at break are important indicators for evaluating the mechanical properties of materials, respectively reflecting the maximum stress that the material can withstand during the tensile process and the elongation ability at the time of fracture, and are of great significance for the preparation and application of flexible optoelectronic devices. Using a universal material testing machine for tensile testing, the sample is made into a standard tensile specimen and stretched at a certain tensile rate, and the stress-strain curve during the tensile process is recorded.

[0057] Specific operation: Spin-coat the single-end block copolymer solution on a flexible substrate (polyimide film) to form a film; use laser cutting or die molding methods to prepare a standard tensile specimen (dumbbell-shaped specimen); clamp the specimen between the upper and lower fixtures of the universal material testing machine, set the tensile rate to 5 - 50 mm / min, and conduct tensile testing at room temperature; record the stress and strain data of the specimen during the tensile process, plot the stress-strain curve, and calculate the tensile strength and elongation at break.

[0058] 5. Environmental stability testing 5.1 Bending Durability Detection method: Evaluating the performance stability of flexible devices under repeated bending conditions is of great significance for the practicality and lifespan of flexible optoelectronic devices. The prepared flexible devices (organic field-effect transistors or organic solar cells based on single-end block copolymers) are subjected to bending cycle tests, and the performance changes of the devices are measured under certain bending radii and cycle numbers.

[0059] Specific operation: Fix the flexible device on the bending test device, set the bending radius to 3 mm and the bending rate to 60 times per minute; conduct 1000 bending cycle tests at room temperature; during the test, pause the test regularly to measure the performance parameters of the device (electron mobility, photoelectric conversion efficiency, etc.), record the performance change curve, and obtain the efficiency retention rate of the comprehensive performance.

[0060] 5.2 Long-term Storage Stability Detection method: Evaluating the performance stability of materials during long-term storage to predict the service life and storage conditions of materials. Place the samples under normal temperature / dark environmental conditions and conduct performance tests after different storage times, compare with the initial performance, and calculate the performance retention rate.

[0061] Specific operation: Seal and store the block copolymer samples in a normal temperature (about 25 °C), dark, and dry environment; during storage, take out the samples regularly once a month for performance tests, such as measuring electron mobility, thermal decomposition temperature, etc.; compare the test results after 6 months of storage with the initial performance data and calculate the performance retention rate.

[0062] 6. Test Results Summary of Performance Test Results of Each Group of Samples in Table 1

[0063] Result Analysis: The electron mobility of Examples 1-3 is significantly better than that of Comparative Examples 1-2, indicating that on the basis of retaining the high electron mobility of the P(NDI2OD-T2) main chain, the single-end block copolymer effectively improves the electron transport efficiency through precise single-end functionalization modification. The electron mobility of Example 1 is 7.93×10-5 cm² / Vs, which is much higher than 3.25×10-6 cm² / Vs of Comparative Example 1 and 3.10×10-6 cm² / Vs of Comparative Example 2, indicating that the single-end directed modification strategy optimizes the main chain conjugated structure, reduces interface defects, and significantly improves the electron transport efficiency. The electron mobilities of Example 2 and Example 3 are 3.81×10-5 cm² / Vs and 1.27×10-5 cm² / Vs respectively, still significantly better than the comparative examples, reflecting the advantages of single-end functionalization.

[0064] The luminous efficiencies of Examples 1-3 are also better than those of the comparative examples. The luminous efficiency of Example 2 is the highest, reaching 15.3 cd / A. Thanks to the high transparency, uniform film-forming properties of the PMMA block, and the promotion of exciton separation, it helps to improve the luminous performance and reduce light scattering loss. While the luminous efficiency of Comparative Example 1 is only 9.2 cd / A, the disordered double-end structure leads to rough device interfaces and increased light loss.

[0065] The power conversion efficiency (PCE) of Example 1 is the highest, reaching 8.7%. The PCEs of Examples 2 and 3 are 7.9% and 6.5% respectively, all better than 5.3% of Comparative Example 1 and 4.1% of Comparative Example 2, indicating that the application of single-end block copolymers in organic solar cells has higher power conversion efficiency. Among them, the PCE of Example 1 is 64% higher than 5.3% of Comparative Example 1, indicating that the hydrophobic PSt block optimizes the device interface morphology, reduces charge recombination, and improves exciton separation efficiency. The PCE of Example 3 is 6.5%, although lower than that of the PSt block, its hydrophilicity is suitable for flexible devices and the comprehensive performance is balanced.

[0066] The thermal decomposition temperatures of Examples 1-3 are all higher than those of Comparative Examples 1-2. Among them, the thermal decomposition temperature (Td) of Example 1 is 385 °C, which is 45 °C higher than 340 °C of Comparative Example 1, indicating that the PSt block enhances the intermolecular interaction and improves the thermal stability of the material. The Td values of Examples 2 and 3 are 372 °C and 360 °C respectively, still significantly higher than those of the comparative examples, verifying that the single-end block copolymer has better thermal stability and can remain stable at higher temperatures.

[0067] The glass transition temperatures of Examples 1-3 are 105 °C, 90 °C, and 75 °C respectively, that of Comparative Example 1 is 120 °C, and that of Comparative Example 2 is 80 °C. The difference in glass transition temperature is related to the introduction of different polymer blocks. The glass transition temperature (Tg) of Example 3 is the lowest, reflecting the flexibility of the PEO block and being suitable for flexible optoelectronic devices. While the Tg of Comparative Example 1 is as high as 120 °C, the double-end rigid structure leads to limited processing performance.

[0068] The polydispersity index (PDI) values of Examples 1-3 are all less than 1.5, indicating a narrow molecular weight distribution. While the PDI values of Comparative Examples 1 and 2 are 2.5 and 2.0 respectively, indicating that the molecular weight distribution of the single-end block copolymer is more uniform, which helps to improve the performance stability of the material.

[0069] The number-average molecular weights of Examples 1-3 are between 18,000 and 24,000 g / mol, that of Comparative Example 1 is 28,000 g / mol, and that of Comparative Example 2 is 18,000 g / mol, indicating that the molecular weight of the single-end block copolymer can be effectively controlled by the preparation method.

[0070] The tensile strength of Examples 1-3 was between 33-42 MPa, that of Comparative Example 1 was 25 MPa, and that of Comparative Example 2 was 20 MPa, indicating that the single-ended block copolymer had better mechanical strength and could withstand greater tensile stress. Among them, the tensile strength of Example 2 was 42 MPa, which was 110% higher than that of Comparative Example 2, indicating that the rigid segment of PMMA enhanced the tensile properties of the material and was suitable for devices requiring high mechanical strength.

[0071] The elongation at break of Example 3 reached 25%, higher than 15% of Example 1 and 20% of Example 2. Those of Comparative Examples 1 and 2 were 8% and 10% respectively. This indicated that introducing different polymer segments could adjust the flexibility of the material, and the polyethylene oxide (PEO) segment contributed to improving the elongation at break of the material.

[0072] In the 1000-time bending durability test, the efficiency retention rates of Examples 1-3 were between 92%-95%, that of Comparative Example 1 was 75%, and that of Comparative Example 2 was 80%, indicating that the single-ended block copolymer could still maintain high performance stability under repeated bending conditions and was suitable for flexible optoelectronic devices.

[0073] The 6-month storage performance retention rates of Examples 1-3 were between 95%-98%, that of Comparative Example 1 was 70%, and that of Comparative Example 2 was 85%, indicating that the single-ended block copolymer had better performance retention ability during long-term storage and longer service life. Among them, the 6-month storage performance retention rate of Example 3 was 98%, which was 40% higher than that of Comparative Example 1, indicating that the single-ended functionalization design inhibited the degradation of molecular chains and had excellent long-term stability.

[0074] Comparing the data of the examples and comparative examples, the P(NDI2OD-T2) single-ended block copolymer prepared by single-ended functionalization modification in the present invention was superior to the comparative examples in terms of optoelectronic properties, thermal stability, molecular weight control, mechanical properties and environmental stability. The selection of different block polymers played an important role in optimizing the properties of the material and could be flexibly adjusted according to specific application requirements to achieve the best performance and functions. The preparation method of an organic electron transport material P(NDI2OD-T2) single-ended block copolymer provided by the present invention effectively improved the material properties through precise single-ended functionalization modification and appropriate selection of block polymers, overcame the deficiencies of traditional materials, and had broad application prospects in the field of high-performance organic optoelectronic devices.

Claims

1. A method for preparing a single-end block copolymer of an organic electron transport material P (NDI2OD-T2), characterized in that: The following steps are involved: Step 1. Synthesis of intermediates: 4,9-dibromo-2,7-di(2-octyldodecyl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraketone (compound 1) is used as a starting material, and 2-tributylstannylthiophene (compound 2), N-bromosuccinimide (NBS) and other raw materials are sequentially reacted through Stille coupling and bromination reaction to synthesize 4,9-bis(2-thienyl) derivatives (compound 4) and 4,9-bis(5-bromo-2-thienyl) derivatives (compound 5); Compound 5 is reacted with 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (compound 3) through Suzuki coupling reaction to synthesize borate-containing polymer monomer compound 6; Step 2. Polymer main chain modification: Compound 6 was converted into P(NDI2OD-T2)-OTBS by Suzuki coupling polymerization, and then deprotected by TBS to obtain single-end hydroxylated P(NDI2OD-T2)-OH; Step 3. Synthesis of single-end block copolymer: P(NDI2OD-T2)-OH is subjected to a Steglich coupling reaction with a carboxyl-terminated polymer to generate the target single-end block copolymer P(NDI2OD-T2)-b-Polymer.

2. The preparation method according to claim 1, characterized in that: Step 1 includes the following operations: Step 1.1: Compound 1 is reacted with compound 2 for Stille coupling reaction to generate 4,9-bis(2-thienyl)-2,7-di(2-octyldodecyl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone (compound 4); Step 1.2: Compound 4 is subjected to bromination reaction by NBS to generate 4,9-bis(5-bromo-2-thienyl)-2,7-di(2-octyldodecyl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone (compound 5); Step 1.3: Compound 3 and compound 5 are subjected to Suzuki coupling reaction to generate a polymer monomer 4-[5-(4,4,5,5-tetramethyl-1,3,2-dioxaboryl)-2-thienyl]-9-(5-bromo-2-thienyl)-2,7-di(2-octyldodecyl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone (compound 6).

3. The preparation method according to claim 2, characterized in that: Step 1.3 includes the following operations: Compound 5 and ether are added to a three-necked flask, and after nitrogen replacement, the temperature is vigorously stirred at -90°C to -70°C, and n-butyl lithium (1~2 mol / L n-hexane solution) is slowly added dropwise within 20~40 minutes, and then the reaction solution is naturally heated to 5~15°C, stirred for 5~15 minutes, and then cooled to -90°C to -70°C, and then compound 3 is added all at once, and stirred at -90°C to -70°C for 0.5~1.5 hours, and then the reaction solution is heated to room temperature, stirred and reacted for 20~30 hours. After the reaction is completed by thin layer chromatography, the reaction solution is washed and extracted with water 2~4 times, and the oil phase is dried with anhydrous sodium sulfate, and then filtered, spin-dried, and separated by column to obtain a yellow solid product compound 6.

4. The preparation method according to claim 1, characterized in that: Step 2 includes the following operations: Step 2.1: Add compound 6 and deoxygenated toluene into a three-necked flask protected by nitrogen, freeze and degas for 2 to 4 times, then add potassium carbonate solution, tetrakis(triphenylphosphine)palladium and 4-(tert-butyldimethylsilyloxy-ethoxy)-iodobenzene in sequence, react at 85-95°C for 30-40 hours, wash with saturated sodium chloride solution after the reaction, extract with toluene, dry with anhydrous magnesium sulfate, filter, spin dry, dissolve a small amount of toluene in methanol and reprecipitate, vacuum dry to obtain P(NDI2OD-T2)-OTMS; Step 2.2: Add P(NDI2OD-T2)-OTMS and anhydrous tetrahydrofuran into a reaction bottle, slowly add pyridine hydrofluoride as a deprotecting agent under stirring, stir at room temperature for 20 to 30 hours and then spin dry, dissolve a small amount of chloroform and reprecipitate in methanol, and vacuum dry the filter cake to obtain P(NDI2OD-T2)-OH.

5. The preparation method according to claim 1, characterized in that: Step 3 includes the following operations: P(NDI2OD-T2)-OH, carboxyl-terminated Polymer, dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP) are placed in a round-bottom flask, dichloromethane is added after nitrogen replacement, and the mixture is stirred at room temperature for 20 to 30 hours; after evaporating the solvent, acetone is added and stirred for 10 to 20 hours to recover the product; the filtered solid is purified by acetone Soxhlet extraction for 40 to 50 hours to obtain a single-end block copolymer product P(NDI2OD-T2)-b-Polymer.

6. The preparation method according to claim 1, characterized in that: The carboxyl-terminated polymer is selected from one of polystyrene, polymethyl methacrylate, polyethylene oxide, and polythiophene conjugated polymers.

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