A method for synthesizing acrylate block copolymer based on visible light promoted nickel catalyzed living radical polymerization

Abstract

This invention provides a method for synthesizing acrylate block copolymers based on visible light-promoted nickel-catalyzed radical polymerization. This method utilizes a nickel-bipyridine complex and an organic photosensitizer to construct a photoinduced catalytic system, achieving controlled radical polymerization of polar acrylate monomers under visible light irradiation. During polymerization, the reversible transformation of the nickel complex between different oxidation states enables the regulation of halogen atom transfer equilibrium, thereby effectively controlling the chain growth process. This method exhibits high chain end fidelity and can precisely construct diblock, triblock, and even multiblock copolymers using a sequential feeding method. The resulting polymers possess controllable molecular weight, narrow molecular weight distribution, and well-defined block structures, making them suitable for applications in functional coatings, optical materials, and flexible electronic materials.

Description

Technical Field

[0001] This invention relates to polymer synthesis technology, and more specifically, to a method for synthesizing acrylate block copolymers based on visible light-promoted nickel-catalyzed free radical polymerization. Background Technology

[0002] Acrylic ester copolymers are an important class of polymer compounds in the field of polymer materials. They have outstanding weather resistance and UV aging resistance, water resistance, high transparency, good adhesion and flexibility, good compatibility and processing fluidity. Due to their excellent physicochemical properties, they are widely used in industrial and scientific research fields.

[0003] For narrow molecular weight distribution (molecular weight distribution index) Polymers with a molecular weight typically ≤1.50 have precisely controllable molecular weight, uniform distribution, regular and uniform chain structure, superior rheological properties and processing consistency, and can achieve precise block or multi-block structures. These advantages make narrow molecular weight distribution acrylate copolymers particularly suitable for high-end optical films, biomedical nanocarriers, high-performance coatings, flexible electronic materials and precision functional coatings.

[0004] Traditional acrylate copolymers are mostly produced by free radical polymerization (thermal or photo-initiated). However, this type of traditional free radical polymerization lacks an effective chain growth control mechanism during polymerization, and is prone to chain termination and chain transfer reactions. This results in a wide molecular weight distribution and strong randomness in the chain structure of the obtained polymer, making it difficult to obtain block copolymer systems with controllable molecular weight and regular structure. This, to some extent, limits the development and application of high-performance functional materials.

[0005] To address the aforementioned challenges, controlled radical polymerization using transition metal catalysis systems has attracted widespread attention. Among these, nickel-based catalysts, due to their unique redox properties and reversible multivalent state transformation capabilities, have been used in partial radical polymerization research. Nickel complexes can undergo reversible transitions between different oxidation states, thereby controlling the generation and deactivation of active radicals during polymerization and achieving a dynamic balance between active and dormant species. Furthermore, nickel-based catalysts typically possess advantages such as abundant raw material sources, relatively low cost, and good structural tunability, making them potentially valuable for applications in controlled radical polymerization systems.

[0006] However, current research on nickel-based catalytic systems in the photoinduced controlled radical polymerization of acrylates remains relatively limited, and their catalytic mechanisms, catalytic efficiency, and ability to regulate polymer structure still require further exploration. Therefore, developing novel photoinduced catalytic systems based on nickel complexes to achieve controlled polymerization and block structure construction of acrylate polymers remains of significant research importance and application value. Summary of the Invention

[0007] To overcome the shortcomings of existing technologies, this invention provides a method for synthesizing acrylate block copolymers based on visible light-promoted nickel-catalyzed active radical polymerization. This method uses visible light as an initiator to efficiently achieve the active radical polymerization of polar acrylate monomers under mild conditions, yielding block copolymers with precisely controllable molecular weight, narrow molecular weight distribution, and regular chain structure.

[0008] According to one object of the present invention, an acrylate block copolymer is provided, the block copolymer comprising at least one first polyacrylate segment (A segment) and at least one second polyacrylate segment (B segment), wherein the polyacrylate segments are connected by covalent bonds and form a linearly connected block structure (e.g., AbB, or AbBbC).

[0009] The block copolymer is a linear multiblock copolymer (containing at least two different polyacrylate segments) prepared by visible light-promoted atom transfer radical polymerization of polar acrylate monomers catalyzed by a nickel-bipyridine complex.

[0010] The number-average molecular weight (Mn) of the block copolymer is between 30,000 and 85,000 g / mol, and the molecular weight distribution index (Mn) is between 30,000 and 85,000 g / mol. ≤1.40.

[0011] According to a preferred embodiment of the invention, the molecular weight of the acrylate copolymer is between 30,000 and 85,000 g / mol, and the molecular weight distribution index (MBDI) is... ≤1.40. The acrylate in the acrylate block copolymer is selected from methyl acrylate, ethyl acrylate, n-butyl acrylate, tert-butyl acrylate, and phenyl acrylate.

[0012] According to a preferred embodiment of the present invention, the molar content of each polyacrylate segment in the acrylate copolymer is 10% to 90%.

[0013] Typically, but not limited to, the acrylate block copolymer may be one or more of PMA-b-PBA, PMA-b-PtBA, PMA-b-PPA, PMA-b-PEA, PMA-b-PEA-b-PBA, and PMA-b-PBA-b-PMA-b-PBA.

[0014] According to another objective of the present invention, the present invention provides a method for synthesizing acrylate block copolymers based on visible light-promoted nickel-catalyzed free radical polymerization, the method being used to synthesize the aforementioned acrylate block copolymers; the method comprising the following steps:

[0015] Step 1: Under an inert atmosphere, nickel-bipyridine complex catalyst, photosensitizer, acrylate monomer A, and alkyl radical initiator are added to an organic solvent and reacted at a constant temperature under visible light irradiation to obtain polyacrylate segment P. A ;

[0016] Step 2: Stop the light exposure, and under the protection of an inert atmosphere, add acrylate monomer B into the reaction tube and continue the reaction under the same conditions as in Step 1 to form polyacrylate monomer Ab-acrylate monomer B chain segments.

[0017] Step 3: Depending on the number of polyacrylate segments and the type of acrylate in the block copolymer, repeat step 2 or do not repeat step 2 until the desired multiblock structure of the acrylate block copolymer is obtained.

[0018] Step 4: Terminate the reaction and separate and purify to obtain the desired acrylate block copolymer.

[0019] According to a preferred embodiment of the present invention, the organic solvent is selected from one or more of dichloromethane, N,N-dimethylformamide, n-hexane, dimethylthionamide, chloroform, and ethyl acetate.

[0020] According to a preferred embodiment of the present invention, the alkyl radical initiator is selected from one or more of ethyl 2-bromo-2-methylpropionate, ethyl α-bromophenylacetate, trichlorobromomethane, and methyl 2-bromopropionate.

[0021] According to a preferred embodiment of the present invention, the polymerization temperature is 15-60 °C (room temperature). The polymerization time for each monomer is 12-24 h. The stirring rate during polymerization is 700-1500 rpm.

[0022] According to a preferred embodiment of the present invention, the wavelength of the visible light source is selected from one or more of 360-365 nm, 375-380 nm, 450-455 nm, and 455-460 nm.

[0023] According to a preferred embodiment of the present invention, the catalyst is selected from one or more nickel-bispyridine complexes. The nickel-bispyridine complexes have the structure shown in formula (I):

[0024]

[0025] in:

[0026] R 1 , R 2 Selected from hydrogen, methyl, tert-butyl, aryl, or carboxyl, wherein R 1 , R 2 The groups can be the same as or different from each other;

[0027] R 3 Selected from hydrogen, methyl, fluorine, or trifluoromethyl;

[0028] M represents nickel.

[0029] X is selected from halogen atoms Cl, Br, and I.

[0030] According to a preferred embodiment of the present invention, the photosensitizer is selected from one or more of 2,4,5,6-tetra(9-carbazolyl)isophthalonitrile (4CzIPN), tetraphenylporphyrin (TPP), disodium decatungstate, 10-phenyl-10H-phenthiazide (PTH), 2,4,6-tris(4-methoxyphenyl)pyranium tetrafluoroborate (TMPP+BF4⁻), tris(2-phenylpyridinium)iridium(III) (Ir(ppy)3), tris(2-phenylquinoline)iridium (Ir(pq)3), and cuprous bromide-tris(2-pyridylmethyl)amine complex (CuBr / TPMA).

[0031] Compared with the prior art, the present invention has the following outstanding advantages:

[0032] (1) The present invention constructs a visible light-promoted active radical polymerization catalytic system based on nickel-bipyridine complex, which can realize the controlled polymerization of acrylate monomers under visible light irradiation conditions. The reaction conditions are mild (15-60℃), and no high temperature and high pressure conditions are required. It has good operational safety and applicability.

[0033] (2) The method of this invention has high chain end fidelity. Different types of acrylate monomers can be introduced sequentially through a sequential feeding method, successfully preparing diblock (PMA-b-PBA), triblock (PMA-b-PEA-b-PBA), and even tetrablock (PMA-b-PBA-b-PMA-b-PBA) copolymers. GPC characterization showed that the molecular weight of each segment shifted towards higher molecular weights after polymerization, and the distribution curve maintained a single peak, confirming the active characteristics of the polymer chain ends and the successful construction of the block structure. The acrylate copolymers obtained by this invention have been proven to be block copolymers.

[0034] (3) The number-average molecular weight of the acrylate block copolymer prepared by the method of the present invention can be precisely controlled within the range of 30,000-85,000 g / mol, and the molecular weight distribution index is [not specified]. ≤ 1.40 (measured 1.31-1.38), significantly better than traditional free radical polymerization (comparative example). > 2.10). NMR analysis confirmed the characteristic signals of different monomer units, and DSC testing showed that the copolymer had multiple glass transition temperatures, indicating the existence of a clear microphase separation structure in the system, further proving that the product is a block structure rather than a random copolymer or homopolymer mixture.

[0035] (4) The polymerization system provided by this invention can realize the sequential polymerization of acrylate monomers, thereby preparing well-structured block copolymers or multi-block copolymers, providing a new method for constructing functional polymer materials with fine structures. The acrylate block copolymers prepared by the method of this invention have controllable molecular structures and narrow molecular weight distributions, and the resulting materials have potential application value in the fields of coatings, functional coatings, optical materials and flexible electronic materials. Attached Figure Description

[0036] Figure 1 This is the 1H NMR spectrum of PMA-b-PBA obtained in Example 1.

[0037] Figure 2 This is the DSC diagram of PMA-b-PBA obtained in Example 1.

[0038] Figure 3 This is the GPC diagram of PMA-b-PBA obtained in Example 1.

[0039] Figure 4 This is the DSC plot of P(MA-co-BA) obtained from Comparative Example 1. Detailed Implementation

[0040] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0041] The following methods were used to test the structure or properties of the acrylate copolymers synthesized in the examples described:

[0042] High-temperature gel permeation chromatography (GPC) is used to test the weight-average molecular weight and molecular weight distribution of acrylate copolymers.

[0043] Differential scanning calorimetry (DSC) is used to test the glass transition temperature of acrylate copolymers.

[0044] Nuclear magnetic resonance (NMR) spectrometry is used to calculate the content of each monomer in acrylate copolymers.

[0045] This invention relates to an atom transfer radical polymerization method catalyzed by a nickel-bipyridine complex, used to achieve the living radical copolymerization of polar acrylate monomers to prepare acrylate block copolymers. The method utilizes a photoinduced catalytic system constructed from a nickel-bipyridine complex and an organic photosensitizer to achieve controlled radical polymerization of polar acrylate monomers under visible light irradiation. During polymerization, the reversible transformation of the nickel complex between different oxidation states allows for the regulation of halogen atom transfer equilibrium, thereby effectively controlling the chain growth process.

[0046] The nickel-bipyridine complex catalyst described in this invention and its embodiments is selected from the following structures:

[0047]

[0048] The 12 nickel-bispyridine complexes mentioned above, or other nickel-bispyridine complexes with similar structures, can all be prepared by the following steps:

[0049] Step 1: Bipyridine compound The intermediate was obtained by reacting with bis(1,5-cyclooctadiene)nickel(0);

[0050] Step 2: Intermediate and aryl halogenated compound The reaction occurs to produce the nickel-bispyridine complex shown in formula (I);

[0051] .

[0052] In this invention, under visible light irradiation, photosensitizer molecules absorb light energy and transition to an excited state, activating a nickel-bispyridine complex catalyst through an energy transfer process. An additional alkyl radical initiator promotes homolytic cleavage of the Ni(II)-X bond, generating a low-valence Ni(I) complex. Simultaneously, the released halogen atom (X•) is rapidly captured by the alkyl radical to form a dormant species. This system maintains a dynamic balance between the active and dormant species through reversible halogen atom transfer. Each monomer addition and chain growth cycle reverts the active species back to a dormant species, thus achieving a controllable chain growth process.

[0053] The present invention will be described below with reference to specific embodiments and comparative examples.

[0054] Example 1

[0055] Under an inert atmosphere, 5.5 mmol of methyl acrylate monomer, 0.00275 mmol of nickel-bispyridine complex catalyst Cat-1, 0.001375 mmol of photosensitizer 4CzIPN, and 0.006875 mmol of alkyl radical initiator trichlorobromomethane were added sequentially to the reaction tube, along with 1.5 mL of dichloromethane as the reaction solvent. The reaction tube was sealed to ensure the polymerization system was under anaerobic conditions. The reaction tube was then placed in the sample position of a photoreaction parallel instrument, the rotation speed was adjusted to 1000 rpm, the polymerization temperature was maintained at 25 °C by a cooling device, and an LED lamp of 450-455 nm was used for irradiation for 24 h to obtain polymethyl acrylate segments. After turning off the light source, the reaction tube was transferred back to an inert atmosphere, 5.5 mmol of butyl acrylate monomer was added to the system, the reaction tube was resealed, and the reaction was continued for another 24 h under the same illumination conditions. After the reaction was completed, an acidified ethanol solution was added to the system to terminate the reaction. The resulting product was filtered, washed several times with ethanol, and dried to obtain polymethyl acrylate-butyl acrylate block copolymer (PMA-b-PBA).

[0056] like Figures 1-3 The figures shown are the 1H NMR spectrum, DSC spectrum, and GPC spectrum of the PMA-b-PBA obtained in Example 1. The copolymer obtained in Example 1, after GPC and NMR characterization, showed Mn=35200, PDI=1.36, and the copolymer contained 86.7% methyl acrylate and 13.3% butyl acrylate.

[0057] ¹H NMR (400 MHz, CDCl3) δ 3.65 (s, 3H, –OCH3, PMA), 0.93 (d, 3H, –CH3,PBA).

[0058] GPC analysis of the polymer obtained in Example 1 showed that after the second monomer polymerization, the number-average molecular weight of the polymer shifted significantly towards higher molecular weights, while the molecular weight distribution curve still maintained a single peak distribution, indicating that the polymer chain ends of the first stage remained active and successfully initiated the second monomer polymerization.

[0059] NMR analysis of the polymer obtained in Example 1 revealed characteristic signal peaks of methyl acrylate and butyl acrylate, further demonstrating that the polymer contains both monomeric structural units.

[0060] DSC analysis of the polymer obtained in Example 1 showed that the copolymer had two glass transition temperatures Tg, located at approximately -51°C and 13°C, respectively, which correspond to the glass transition temperatures of the polybutyl acrylate segment and the polymethyl acrylate segment. This indicates that there is a microphase separation structure of different segments in the system, thus proving that the obtained polymer is a block copolymer.

[0061] The above results indicate that the polymer obtained in this invention is a PMA-b-PBA block copolymer, rather than a mixture of two homopolymers or a random copolymer.

[0062] Example 2

[0063] Under an inert atmosphere, 5.5 mmol of methyl acrylate monomer, 0.00275 mmol of nickel-bispyridine complex catalyst Cat-3, 0.001375 mmol of photosensitizer 4CzIPN, and 0.006875 mmol of alkyl radical initiator trichlorobromomethane were added sequentially to the reaction tube, along with 1.5 mL of dichloromethane as the reaction solvent. The reaction tube was sealed to ensure the polymerization system was under anaerobic conditions. The reaction tube was then placed in the sample position of a photoreaction parallel instrument, the rotation speed was adjusted to 1500 rpm, the polymerization temperature was maintained at 25 °C by a cooling device, and an LED lamp of 455-460 nm was selected. The reaction was irradiated for 24 h to obtain polymethyl acrylate segments. After the light source was turned off, the reaction tube was transferred back to an inert atmosphere, 5.5 mmol of tert-butyl acrylate monomer was added to the system, the reaction tube was resealed, and the reaction was continued for another 24 h under the same illumination conditions. After the reaction was completed, an acidified ethanol solution was added to the system to terminate the reaction. The resulting product was filtered, washed several times with ethanol, and dried to obtain polymethyl acrylate-butyl acrylate block copolymer (PMA-b-PtBA).

[0064] The copolymer obtained in Example 2 was characterized by GPC and NMR and showed that Mn=50600, PDI=1.31, the methyl acrylate content in the copolymer was 79.9%, and the tert-butyl acrylate content was 20.1%.

[0065] Example 3

[0066] Under an inert atmosphere, 5.5 mmol of methyl acrylate monomer, 0.00275 mmol of nickel-bispyridine complex catalyst Cat-4, 0.001375 mmol of photosensitizer 4CzIPN, and 0.006875 mmol of alkyl radical initiator methyl 2-bromopropionate were added sequentially to the reaction tube, along with 1.5 mL of n-hexane as the reaction solvent. The reaction tube was sealed to ensure the polymerization system was under anaerobic conditions. The reaction tube was then placed in the sample position of a photoreaction parallel instrument, the rotation speed was adjusted to 1000 rpm, and the polymerization temperature was maintained at 25 °C by a cooling device. A 455-460 nm LED lamp was selected, and the reaction was irradiated for 24 h to obtain polymethyl acrylate segments. After turning off the light source, the reaction tube was transferred back to an inert atmosphere, 5.5 mmol of tert-butyl acrylate monomer was added to the system, the reaction tube was resealed, and the reaction was continued for another 24 h under the same illumination conditions. After the reaction was completed, an acidified ethanol solution was added to the system to terminate the reaction. The resulting product was filtered, washed several times with ethanol, and dried to obtain polymethyl acrylate-tert-butyl acrylate block copolymer (PMA-b-PtBA).

[0067] The copolymer obtained in Example 3 was characterized by GPC and NMR and showed that Mn=42000, PDI=1.35, methyl acrylate content was 85.2%, and tert-butyl acrylate content was 14.8%.

[0068] Example 4

[0069] Under an inert atmosphere, 5.5 mmol of methyl acrylate monomer, 0.00275 mmol of nickel-bispyridine complex catalyst Cat-10, 0.001375 mmol of photosensitizer TPP, and 0.006875 mmol of alkyl radical initiator methyl 2-bromopropionate were added sequentially to the reaction tube, along with 1.5 mL of ethyl acetate as the reaction solvent. The reaction tube was sealed to ensure the polymerization system was under anaerobic conditions. The reaction tube was then placed in the sample position of a photoreaction parallel instrument, the rotation speed was adjusted to 1500 rpm, the polymerization temperature was maintained at 25 °C by a cooling device, and a 375-380 nm LED lamp was selected and turned on for 24 h of irradiation to obtain polymethyl acrylate segments. After turning off the light source, the reaction tube was transferred back to an inert atmosphere, 5.5 mmol of phenyl acrylate monomer was added to the system, the reaction tube was resealed, and the reaction was continued for another 24 h under the same light conditions. After the reaction was completed, an acidified ethanol solution was added to the system to terminate the reaction. The resulting product was filtered, washed several times with ethanol, and dried to obtain polymethyl acrylate-phenyl acrylate block copolymer (PMA-b-PPA).

[0070] The copolymer obtained in Example 4 was characterized by GPC and NMR and showed that Mn=60800, PDI=1.33, and the copolymer contained 69.5% methyl acrylate and 30.5% phenyl acrylate.

[0071] Example 5

[0072] Under an inert atmosphere, 5.5 mmol of methyl acrylate monomer, 0.00275 mmol of nickel-bispyridine complex catalyst Cat-12, 0.001375 mmol of photosensitizer TPP, and 0.006875 mmol of alkyl radical initiator methyl 2-bromopropionate were added sequentially to the reaction tube, along with 1.5 mL of ethyl acetate as the reaction solvent. The reaction tube was sealed to ensure the polymerization system was under anaerobic conditions. The reaction tube was then placed in the sample position of a photoreaction parallel instrument, the rotation speed was adjusted to 1500 rpm, and the polymerization temperature was maintained at 25 °C by a cooling device. A 375-380 nm LED lamp was selected, and the reaction was irradiated for 24 h to obtain polymethyl acrylate segments. After turning off the light source, the reaction tube was transferred back to an inert atmosphere, and 5.5 mmol of ethyl acrylate monomer was added to the system. The reaction tube was resealed, and the reaction was continued for 24 h under the same illumination conditions to obtain polymethyl acrylate-ethyl acrylate segments. After turning off the light source, the reaction tube was transferred back to an inert atmosphere. 5.5 mmol of butyl acrylate monomer was added to the system, the reaction tube was resealed, and the reaction continued for 24 h under the same illumination conditions. After the reaction was complete, acidified ethanol solution was added to the system to terminate the reaction. The resulting product was filtered, washed several times with ethanol, and dried to obtain a polymethyl acrylate-ethyl acrylate-butyl acrylate multiblock copolymer (PMA-b-PEA-b-PBA).

[0073] The copolymer obtained in Example 5 was characterized by GPC and NMR and showed that Mn=69800, PDI=1.36, and the copolymer contained 79.3% methyl acrylate, 10.2% ethyl acrylate, and 10.5% butyl acrylate.

[0074] Example 6

[0075] Under an inert atmosphere, 5.5 mmol of methyl acrylate monomer, 0.00275 mmol of nickel-bispyridine complex catalyst Cat-12, and 0.001375 mmol of photosensitizer TMPP were added sequentially to the reaction tube. +BF4⁻ and 0.006875 mmol of methyl 2-bromopropionate, an alkyl radical initiator, were added, along with 1.5 mL of dichloromethane as the reaction solvent. The reaction tube was sealed to ensure an oxygen-free environment for polymerization. The tube was then placed in the sample position of a photoreaction parallel instrument, the rotation speed was adjusted to 1500 rpm, and the polymerization temperature was maintained at 25 °C by a cooling device. A 375-380 nm LED lamp was selected, and the reaction was carried out under irradiation for 24 h to obtain polymethyl acrylate segments. After turning off the light source, the reaction tube was transferred back to an inert atmosphere, and 5.5 mmol of butyl acrylate monomer was added to the system. The reaction tube was resealed, and the reaction was continued under the same light conditions for 24 h to obtain polymethyl acrylate-butyl acrylate segments. (This process was repeated three times in the original text.) After turning off the light source, the reaction tube was transferred back to an inert atmosphere. 5.5 mmol of butyl acrylate monomer was added to the system, and the reaction tube was resealed. The reaction was continued for 24 h under the same light conditions. After the reaction was completed, acidified ethanol solution was added to the system to terminate the reaction. The resulting product was filtered, washed several times with ethanol, and dried to obtain a polymethyl acrylate-butyl acrylate-methyl acrylate-butyl acrylate multiblock copolymer (PMA-b-PBA-b-PMA-b-PBA).

[0076] The copolymer obtained in Example 6 was characterized by GPC and NMR and showed that Mn=78800, PDI=1.38, and the copolymer contained 82.5% methyl acrylate and 17.5% phenyl acrylate.

[0077] Comparative Example 1

[0078] Under nitrogen protection, 0.01 mol of methyl acrylate and 0.011 mol of butyl acrylate were added to a 100 mL three-necked flask containing 20 mL of toluene and stirred until completely dissolved. Then, 0.10 g of azobisisobutyronitrile (AIBN) was added as an initiator. The reaction system was controlled to react in an oil bath at 70 °C for 12 h. After the reaction was completed, acidified ethanol solution was added to terminate the reaction. The resulting product was filtered, washed several times with ethanol, and dried to obtain the random copolymer of methyl acrylate / butyl acrylate, P(MA-co-BA).

[0079] Figure 4 This is the DSC diagram of P(MA-co-BA) obtained in Comparative Example 1. The copolymer obtained in Comparative Example 1, after characterization by GPC and DSC, showed the following: Mn = 40800, PDI = 2.12, Tg = -20. o C.

[0080] Comparative Example 2

[0081] Under nitrogen protection, 0.078 mol of butyl acrylate was added to a 100 mL three-necked flask containing 20 mL of toluene and stirred until completely dissolved. Then, 0.10 g of azobisisobutyronitrile (AIBN) was added as a free radical initiator. The reaction system was controlled to react in an oil bath at 70 °C for 12 h. After the reaction was completed, acidified ethanol solution was added to terminate the reaction. The resulting product was filtered, washed several times with ethanol, and dried to obtain butyl acrylate homopolymer PBA.

[0082] The homopolymer obtained in Comparative Example 2 was characterized by GPC and NMR, yielding Mn = 38300 and PDI = 2.20. ¹H NMR (400 MHz, CDCl3) δ 4.02 (t, J = 6.6 Hz, 2H, –OCH2–), 2.35–2.10 (br m, 1H, mainchain –CH–), 1.65–1.25 (m, 6H, –CH2–), 0.92 (t, J = 7.4 Hz, 3H, –CH3).

[0083] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. Those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. An acrylate block copolymer, characterized in that, The block copolymer comprises at least one first polyacrylate segment and at least one second polyacrylate segment, wherein the polyacrylate segments are connected by covalent bonds and form a linearly connected block structure. The block copolymer is a linear multiblock copolymer, which is prepared by visible light-promoted atom transfer radical polymerization of polar acrylate monomers catalyzed by nickel-bipyridine complexes. The number-average molecular weight Mn of the block copolymer is between 30,000 and 85,000 g / mol, and the molecular weight distribution index is ≤1.

40.

2. The acrylate block copolymer according to claim 1, characterized in that, The block copolymer comprises two or more linearly linked polyacrylate segments, wherein the acrylates in the polyacrylate segments are selected from methyl acrylate, ethyl acrylate, n-butyl acrylate, tert-butyl acrylate, and phenyl acrylate, and the types of acrylates in adjacent polyacrylate segments are different, and the molar content of each polyacrylate segment in the acrylate block copolymer is 10% to 90%.

3. A method for synthesizing acrylate block copolymers based on visible light-promoted nickel-catalyzed free radical polymerization, used to prepare the acrylate block copolymers according to claim 1 or 2, characterized in that, The method includes the following steps: Step 1: Under an inert atmosphere, nickel-bipyridine complex catalyst, photosensitizer, acrylate monomer A, and alkyl radical initiator are added to an organic solvent and reacted at a constant temperature under visible light irradiation to obtain polyacrylate segment P. A ; Step 2: Stop the light exposure, and under the protection of an inert atmosphere, add acrylate monomer B into the reaction tube and continue the reaction under the same conditions as in Step 1 to form polyacrylate monomer Ab-acrylate monomer B chain segments. Step 3: Depending on the number of polyacrylate segments and the type of acrylate in the block copolymer, repeat step 2 or do not repeat step 2 until the desired multiblock structure of the acrylate block copolymer is obtained. Step 4: Terminate the reaction and separate and purify to obtain the desired acrylate block copolymer.

4. The synthesis method according to claim 3, characterized in that, The organic solvent is selected from one or more of dichloromethane, N,N-dimethylformamide, n-hexane, dimethylthionamide, chloroform, and ethyl acetate.

5. The synthesis method according to claim 3, characterized in that, The alkyl radical initiator is selected from one or more of ethyl 2-bromo-2-methylpropionate, ethyl α-bromophenylacetate, trichlorobromomethane, and methyl 2-bromopropionate; the amount of the alkyl radical initiator added is based on the molar amount of the monomer and is 0.1–10 mol of the molar amount of the monomer.

6. The synthesis method according to claim 3, characterized in that, The polymerization temperature is 15-60 °C, and the polymerization time for each polyacrylate segment is 12-24 h.

7. The synthesis method according to claim 3, characterized in that, The wavelength of the visible light source is selected from one or more of 360-365 nm, 375-380 nm, 450-455 nm, and 455-460 nm.

8. The synthesis method according to claim 3, characterized in that, The acrylate monomers A and B are of different types; in the acrylate block copolymer, the acrylates in adjacent polyacrylate segments are of different types; the acrylate monomers are selected from one or more of methyl acrylate, ethyl acrylate, n-butyl acrylate, tert-butyl acrylate, and phenyl acrylate.

9. The synthesis method according to claim 3, characterized in that, The selected catalyst is a nickel-bipyridine complex with the structure shown in formula (I): ； in: R 1 R 2 Selected from hydrogen, methyl, tert-butyl, aryl, or carboxyl groups; R 3 Selected from hydrogen, methyl, fluorine, or trifluoromethyl; M represents nickel. X is selected from halogen atoms Cl, Br, and I.

10. The synthesis method according to claim 9, characterized in that, The preparation steps of the nickel-bipyridine complex are as follows: Step 1: Bipyridine compound The intermediate was obtained by reacting with bis(1,5-cyclooctadiene)nickel(0); Step 2: Intermediate and aryl halogenated compound The reaction occurs to produce the nickel-bispyridine complex shown in formula (I); 。 11. The synthesis method according to claim 9, characterized in that, The nickel-bipyridine complex catalyst is selected from the following structures: ； The amount of the nickel-bipyridine complex catalyst added is based on the molar amount of the monomer, which is 0.05–0.5 mol of the monomer molar amount.

12. The synthesis method according to claim 3, characterized in that, The selected photosensitizer is an organic molecular catalyst, selected from 2,4,5,6-tetra(9-carbazolyl)isophthalonitrile (4CzIPN), tetraphenylporphyrin (TPP), disodium decatungstate, 10-phenyl-10H-phenthiazine (PTH), and 2,4,6-tris(4-methoxyphenyl)pyranium tetrafluoroborate (TMPP). + One or more of the following photosensitizers: BF4⁻, tri(2-phenylpyridinium)iridium(III) (Ir(ppy)3), tri(2-phenylquinoline)iridium(Ir(pq)3), and cuprous bromide-tris(2-pyridinylmethyl)amine complex (CuBr / TPMA); the amount of photosensitizer added is based on the molar amount of the monomer and is 0.025–0.25 mol of the molar amount of the monomer.

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