Degradable bio-based copolymer pressure-sensitive adhesive with high bonding strength and preparation method thereof

Abstract

The invention discloses a degradable bio-based copolymer pressure-sensitive adhesive with high bonding strength and a preparation method thereof, and belongs to the field of high-performance polymers. According to the method, the copolymer pressure-sensitive adhesive is synthesized through emulsion polymerization, homogeneous polymerization, free radical polymerization and the like, controllable copolymerization of a lactic acid-based monomer and lipoic acid is achieved, meanwhile, the problem that a traditional polymer adhesive is difficult to degrade is solved, a reaction system conforms to the green chemical principle, and the obtained pressure-sensitive adhesive has good biocompatibility and is suitable for large-scale production. The potential influence of residues on the material performance and the environment is avoided. According to the method, a copolymer pressure-sensitive adhesive sample is prepared by adopting two sample preparation modes of hot coating and hot-pressing slicing, an aluminum sheet is taken as a test base material, a lap joint shear test is performed by utilizing a universal material testing machine, and the adhesion strength of the adhesive is obtained by analyzing force and displacement data. Experimental results show that the bio-based copolymer pressure-sensitive adhesive shows good adhesive performance in different sample preparation modes, is excellent in processing compatibility and has diversified application prospects and potential.

Description

Technical Field

[0001] This invention belongs to the field of high-performance polymers, specifically relating to a biodegradable bio-based copolymer pressure-sensitive adhesive with high adhesive strength and its preparation method. Background Technology

[0002] While traditional pressure-sensitive adhesives (PSAs) are widely used due to their simple synthesis process, excellent adhesion, and low production cost, their monomers are mostly derived from petroleum-based chemicals such as acrylates. These raw materials are difficult to degrade in the natural environment and lack necessary biocompatibility, easily causing microplastic pollution and ecological accumulation risks during use and disposal. Therefore, they fail to meet the stringent requirements for green, environmentally friendly, and sustainable materials. To address this issue, bio-based raw materials are increasingly being used in the synthesis of PSAs, and the introduction of functional monomers imparts biodegradability, significantly improving the performance and application range of PSAs.

[0003] Lactic acid is mainly obtained through the microbial fermentation of carbohydrates (such as corn starch and sugarcane), making it an abundant and renewable source. Its polymer, polylactic acid (PLA), is considered one of the most promising alternatives to traditional petroleum-based plastics due to its excellent biocompatibility, biodegradability, good mechanical strength, and thermoplasticity, showing broad application prospects in food packaging, textiles, automotive parts, agricultural mulch films, and biomedical engineering. Starting from lactic acid as a platform compound, the design and synthesis of (methyl)lactic acid acrylate monomers, and subsequently the preparation of functional polymers with well-defined structures and tunable properties, has become an important direction in the current field of bio-based polymer research.

[0004] Lipoic acid is a natural, endogenous small molecule, first isolated from the liver, and widely present in cell membranes, cytoplasm, and mitochondria, thus exhibiting good biocompatibility. Its unique disulfide five-membered ring structure can undergo copolymerization with acrylate monomers via ring-opening free radical polymerization, introducing degradable CS and SS bonds into the polymer chain. The carboxyl groups on the polymer side chains can generate strong intermolecular forces with various substrate surfaces, thereby significantly improving polymer adhesion.

[0005] This invention develops a biodegradable bio-based copolymer pressure-sensitive adhesive with high adhesive strength. Through a mild photolysis-controlled polymerization method and a traditional free radical polymerization method, the controlled copolymerization of lactic acid monomers and thioctic acid is achieved. The reaction system conforms to the principles of green chemistry, and the resulting pressure-sensitive adhesive has good biocompatibility, avoiding the potential impact of residues on material performance and the environment. It is expected to have wide applications in the biomedical field. Summary of the Invention

[0006] The purpose of this invention is to provide a biodegradable bio-based copolymer pressure-sensitive adhesive with high adhesive strength and its preparation method. The aim is to synthesize copolymer pressure-sensitive adhesives with different molecular weights and different thioctic acid contents under mild polymerization conditions, demonstrate their excellent performance as pressure-sensitive adhesives, and reveal the influence of molecular weight and thioctic acid content on the adhesive strength of copolymer pressure-sensitive adhesives, while solving the problem of difficult degradation of traditional polymer adhesives.

[0007] The biodegradable bio-based copolymer pressure-sensitive adhesive with high adhesive strength described in this invention has the following structural formula:

[0008]

[0009] Where R1 represents H, C1~C 18 Alkyl groups or substituents capable of generating primary, secondary, or tertiary carbon radicals (such as -CH2CN, -CH(CH3)CN, -C(CH3)2CN, -CH(C2H5)CN, -C(CH3)(C2H5)CN, -C6H 10 CN, -C(CH3)((CH2)2COOH)CN, -C(CH3)((CH2)2COOC n H 2n+1 )CN, -C(CH3)(CH2)2OH, -CH2Ph, -CH(CH3)Ph, -CH(COOH)Ph, -CH(COOC n H 2n+1 )Ph, -C(CH3)2Ph, -CH2COOH, -CH2COOC n H 2n+1 , -CH(CH3)COOH, -CH(CH3)COOC n H 2n+1 , -C(CH3)2COOH, -C(CH3)2COOC n H 2n+1 (e.g., -C(CH3)2C(NH)(NH2), -C(CH3)2C(NH)N(CH2)2, etc.)

[0010] R2 represents H, C1~C 18 Alkyl group, -C(=S)-S-C1~C 18 Or substituents capable of generating primary, secondary, or tertiary carbon free radicals (such as -C(=S)-S-CH2CN, -C(=S)-S-CH(CH3)CN, -C(=S)-SC(CH3)2CN, -C(=S)-S-CH(C2H5)CN, -C(=S)-SC(CH3)(C2H5)CN, -C(=S)-SC6H 10CN, -C(=S)-SC(CH3)((CH2)2COOH)CN, -C(=S)-SC(CH3)((CH2)2COOC n H 2n+1 )CN, -C(=S)-SC(CH3)(CH2)2OH, -C(=S)-S-CH2Ph, -C(=S)-S-CH(CH3)Ph, -C(=S)-S-CH(COOH)Ph, -C(=S)-S-CH(COOC n H 2n+1 )Ph, -C(=S)-SC(CH3)2Ph, -C(=S)-S-CH2COOH, -C(=S)-S-CH2COOC n H 2n+1 , -C(=S)-S-CH(CH3)COOH, -C(=S)-S-CH(CH3)COOC n H 2n+1 , -C(=S)-SC(CH3)2COOH, -C(=S)-SC(CH3)2COOC n H 2n+1 (e.g., -C(=S)-S-C(CH3)2C(NH)(NH2), -C(=S)-SC(CH3)2C(NH)N(CH2)2, etc.)

[0011] R3 can be -COOH, -OCH3, or -OCH2CH3;

[0012] R4 is a C1~C4 alkyl group;

[0013] m and n are positive integers.

[0014] The present invention discloses a method for preparing a biodegradable bio-based copolymer pressure-sensitive adhesive with high adhesive strength, the method of which is as follows:

[0015] Method 1: Preparation of copolymer pressure-sensitive adhesives with different molecular weights and similar lipoic acid content

[0016] This method synthesizes bio-based copolymer pressure-sensitive adhesives with different molecular weights and similar lipoic acid content through emulsion polymerization. Specifically, a photoinitiator, transfer terminator, comonomer, surfactant, and solvent are uniformly mixed to prepare a reaction solution, which is then reacted for 5-9 hours under a certain temperature and light source irradiation to obtain a copolymer pressure-sensitive adhesive with controllable dispersion. The resulting structure has R1 as H and C1-C1 as C1. 18 Alkyl groups or substituents capable of generating primary, secondary, or tertiary carbon radicals (such as -CH2CN, -CH(CH3)CN, -C(CH3)2CN, -CH(C2H5)CN, -C(CH3)(C2H5)CN, -C6H 10CN, -C(CH3)((CH2)2COOH)CN, -C(CH3)((CH2)2COOC n H 2n+1 )CN, -C(CH3)(CH2)2OH, -CH2Ph, -CH(CH3)Ph, -CH(COOH)Ph, -CH(COOC n H 2n+1 )Ph, -C(CH3)2Ph, -CH2COOH, -CH2COOC n H 2n+1 , -CH(CH3)COOH, -CH(CH3)COOC n H 2n+1 , -C(CH3)2COOH, -C(CH3)2COOC n H 2n+1 =-C(CH3)2C(NH)(NH2), -C(CH3)2C(NH)N(CH2)2, etc.); R2 is -C(=S)-S-C1~C 18 Or substituents capable of generating primary, secondary, or tertiary carbon free radicals (such as -C(=S)-S-CH2CN, -C(=S)-S-CH(CH3)CN, -C(=S)-SC(CH3)2CN, -C(=S)-S-CH(C2H5)CN, -C(=S)-SC(CH3)(C2H5)CN, -C(=S)-SC6H 10 CN, -C(=S)-SC(CH3)((CH2)2COOH)CN, -C(=S)-SC(CH3)((CH2)2COOC n H 2n+1 )CN, -C(=S)-SC(CH3)(CH2)2OH, -C(=S)-S-CH2Ph, -C(=S)-S-CH(CH3)Ph, -C(=S)-S-CH(COOH)Ph, -C(=S)-S-CH(COOC n H 2n+1 )Ph, -C(=S)-SC(CH3)2Ph, -C(=S)-S-CH2COOH, -C(=S)-S-CH2COOC n H 2n+1 , -C(=S)-S-CH(CH3)COOH, -C(=S)-S-CH(CH3)COOC n H 2n+1 , -C(=S)-SC(CH3)2COOH, -C(=S)-SC(CH3)2COOC n H 2n+1R3 is -COOH, -OCH3, -OCH2CH3; R4 is a C1~C4 alkyl copolymer pressure-sensitive adhesive.

[0017] The photoinitiator transfer terminator is one of dithioester, trithiocarbonate, or xanthate; the comonomer is a combination of one of lactic acid acrylate and one of thioctic acid derivative monomers; and the surfactant is one of cationic surfactant, anionic surfactant, nonionic surfactant, or amphiphilic surfactant.

[0018] Furthermore, the photoinitiator-transfer terminator is one of 4-((((2-carboxyethyl)thio)thiocarbonyl)thio)-4-cyanopentanoic acid, methyl 2-((3-methoxypyrazole-1-carbonylthio)thio)propionate, and 1H-pyrrole-1-carbondithiobenzoate; the comonomer is a combination of one of methyl lactate and ethyl lactate and one of lipoic acid and methyl lipoate; the surfactant is one of sodium dodecyl sulfate, polyoxyethylene octadecyl ether, and hexadecyltrimethylammonium bromide; and the solvent is water.

[0019] The solid content of the reaction solution is 1%–50% by mass; the molar ratio of photoinitiator / transfer terminator to monomer is 1:100–5000; the mass ratio of surfactant to monomer is 1:2–10; the wavelength of the light source is 365–700 nm, and the light intensity is 0.1–100 mW / cm². –2 .

[0020] Method 2: Synthesis of copolymer pressure-sensitive adhesives with similar molecular weights and different thioctic acid contents

[0021] This method synthesizes bio-based copolymer pressure-sensitive adhesives with different thioctic acid contents and similar molecular weights through homogeneous polymerization. Specifically, a photoinitiator, transfer terminator, comonomer, and solvent are uniformly mixed to prepare a reaction solution, which is then reacted for 1-2 hours under a certain temperature and light source irradiation to obtain a copolymer pressure-sensitive adhesive with controllable dispersion. The resulting structure has R1 as H and C1-C1 as C1. 18 Alkyl groups or substituents capable of generating primary, secondary, or tertiary carbon radicals (such as -CH2CN, -CH(CH3)CN, -C(CH3)2CN, -CH(C2H5)CN, -C(CH3)(C2H5)CN, -C6H 10 CN, -C(CH3)((CH2)2COOH)CN, -C(CH3)((CH2)2COOC n H 2n+1)CN, -C(CH3)(CH2)2OH, -CH2Ph, -CH(CH3)Ph, -CH(COOH)Ph, -CH(COOC n H 2n+1 )Ph, -C(CH3)2Ph, -CH2COOH, -CH2COOC n H 2n+1 , -CH(CH3)COOH, -CH(CH3)COOC n H 2n+1 , -C(CH3)2COOH, -C(CH3)2COOC n H 2n+1 =-C(CH3)2C(NH)(NH2), -C(CH3)2C(NH)N(CH2)2, etc.); R2 is -C(=S)-S-C1~C 18 Or substituents capable of generating primary, secondary, or tertiary carbon free radicals (such as -C(=S)-S-CH2CN, -C(=S)-S-CH(CH3)CN, -C(=S)-SC(CH3)2CN, -C(=S)-S-CH(C2H5)CN, -C(=S)-SC(CH3)(C2H5)CN, -C(=S)-SC6H 10 CN, -C(=S)-SC(CH3)((CH2)2COOH)CN, -C(=S)-SC(CH3)((CH2)2COOC n H 2n+1 )CN, -C(=S)-SC(CH3)(CH2)2OH, -C(=S)-S-CH2Ph, -C(=S)-S-CH(CH3)Ph, -C(=S)-S-CH(COOH)Ph, -C(=S)-S-CH(COOC n H 2n+1 )Ph, -C(=S)-SC(CH3)2Ph, -C(=S)-S-CH2COOH, -C(=S)-S-CH2COOC n H 2n+1 , -C(=S)-S-CH(CH3)COOH, -C(=S)-S-CH(CH3)COOC n H 2n+1 , -C(=S)-SC(CH3)2COOH, -C(=S)-SC(CH3)2COOC n H 2n+1 R3 is -C(=S)-S-C(CH3)2C(NH)(NH2), -C(=S)-SC(CH3)2C(NH)N(CH2)2, etc.; R4 is a C1~C4 alkyl copolymer pressure-sensitive adhesive.

[0022] The photoinitiator transfer terminator is one of dithioester, trithiocarbonate, or xanthate; the comonomer is a combination of one of lactic acid acrylate and one of thioctic acid derivative monomers; and the surfactant is one of cationic surfactant, anionic surfactant, nonionic surfactant, or amphiphilic surfactant.

[0023] Furthermore, the photoinitiator-transfer terminator is one of 4-((((2-carboxyethyl)thio)thiocarbonyl)thio)-4-cyanopentanoic acid, methyl 2-((3-methoxypyrazole-1-carbonylthio)thio)propionate, or methyl 1H-pyrrole-1-carbondithiocarbamate; the comonomer is a combination of one of methyl lactate or ethyl lactate and one of lipoic acid or methyl lipoate; and the solvent is one of organic solvents such as dimethyl sulfoxide, N,N-dimethylformamide, or dichloromethane.

[0024] The solid content of the reaction solution is 1%–100% by mass; the molar ratio of the photoinitiator / transfer terminator to the comonomer is 1:100–50000; the wavelength of the light source is 365–700 nm, and the light intensity is 0.1–100 mW / cm². –2 .

[0025] Method 3: Traditional free radical polymerization

[0026] This method uses traditional free radical polymerization to synthesize bio-based copolymer pressure-sensitive adhesives. Specifically, a thermal initiator, comonomer, and solvent are mixed uniformly to prepare a reaction solution, which is then heated at 30-50°C. The reaction is carried out at ℃ for 10-20 hours to obtain a copolymer pressure-sensitive adhesive, in which R1 is H and C1~C in the above general formula. 18 Alkyl group; R2 is H, C1~C 18 Alkyl groups; R3 is -COOH, -OCH3, -OCH2CH3; R4 is a C1~C4 alkyl copolymer pressure-sensitive adhesive;

[0027] The thermal initiator is one of the following: azo initiators, organic peroxide initiators, or inorganic peroxide initiators;

[0028] The comonomer is a combination of one of the lactic acrylates with different tail-end alkyl chain lengths, such as methyl lactate and ethyl lactate, and one of the thioctic acid derivative monomers, such as thioctic acid or methyl thiocate; the solvent is water; and the azo initiator is azobisisobutyrazoline hydrochloride (VA-044).

[0029] The method and copolymer pressure-sensitive adhesive of the present invention have the following advantages:

[0030] In Method 1, this invention employs a mild aqueous emulsion polymerization system and photoinitiated polymerization to prepare a series of copolymer pressure-sensitive adhesives of lactic acid-derived monomers and thioctic acid with controllable molecular weight and adjustable dispersibility. The number-average molecular weight of the obtained copolymer pressure-sensitive adhesives can reach up to 315 kg mol. –1 The prepared copolymer pressure-sensitive adhesive exhibits significantly higher adhesive strength than commercially available pressure-sensitive adhesives, with a maximum lap shear strength reaching 3.89 MPa. Furthermore, this invention reveals the influence of molecular weight on adhesive properties, providing important insights into elucidating the intrinsic relationship between material structure and properties, and the development of high-performance materials.

[0031] In Method 2, this invention prepares polymers with molecular weights of 43-45 kg mol by changing the feed ratio of thioctic acid in a homogeneous polymerization system. –1 Three copolymer pressure-sensitive adhesives were prepared within the specified range, with thioctic acid content of 10 mol%, 20 mol%, and 30 mol%, respectively. The prepared copolymer pressure-sensitive adhesive exhibited the highest lap shear strength of 1.12 MPa when the thioctic acid content was 20 mol%. The photolysis-controlled polymerization method used allows for flexible adjustment of the proportions of the two co-monomers in the copolymer chain, and the lap shear test revealed the influence of thioctic acid content on adhesion performance.

[0032] In Method 3, this invention uses conventional free radical polymerization to synthesize copolymer pressure-sensitive adhesives. Azobisisobutyrazoline hydrochloride (VA-044), a commonly used thermal initiator, is used as the initiator to synthesize a copolymer pressure-sensitive adhesive of lactic acid-derived monomers and thioctic acid-derived monomers. The thioctic acid content is 17.5 mol%, and the molecular weight is 110 kg mol. –1 The lap shear strength is 1.81 MPa.

[0033] This invention prepares copolymer pressure-sensitive adhesive samples using two methods: hot coating and hot pressing slicing. Using aluminum sheets as the test substrate, lap shear tests are conducted using a universal testing machine. The adhesive strength is obtained by analyzing the force and displacement data. Experimental results show that this bio-based copolymer pressure-sensitive adhesive exhibits good adhesion performance under different sample preparation methods, excellent processing compatibility, and potential for diverse applications. Attached Figure Description

[0034] Figure 1 The particle size and light intensity distribution curve of the polymer emulsion in Example 1;

[0035] Figure 2 The GPC curve of the methyl lactate and thioctic acid copolymer pressure-sensitive adhesive prepared in Example 1 is shown.

[0036] Figure 3The number-average molecular weight was 16.9 kg mol, as obtained in Example 1. –1 Purified pressure-sensitive adhesive of methyl lactate and thioctic acid copolymer 1 H NMR spectrum;

[0037] Figure 4 The number-average molecular weight was 32.7 kg mol, as obtained in Example 1. –1 Purified pressure-sensitive adhesive of methyl lactate and thioctic acid copolymer 1 H NMR spectrum;

[0038] Figure 5 The number-average molecular weight was 75.9 kg mol, as obtained in Example 1. –1 Purified pressure-sensitive adhesive of methyl lactate and thioctic acid copolymer 1 H NMR spectrum;

[0039] Figure 6 The number-average molecular weight was 157 kg mol, as obtained in Example 1. –1 Purified pressure-sensitive adhesive of methyl lactate and thioctic acid copolymer 1 H NMR spectrum;

[0040] Figure 7 The number-average molecular weight was 315 kg mol, as obtained in Example 1. –1 Purified pressure-sensitive adhesive of methyl lactate and thioctic acid copolymer 1 H NMR spectrum;

[0041] Figure 8 The DSC curves are of the methyl lactate acrylate and thioctic acid copolymer pressure-sensitive adhesives with different molecular weights prepared in Example 1.

[0042] Figure 9 The GPC curve of the methyl lactate and thioctic acid copolymer pressure-sensitive adhesive prepared in Example 2 is shown.

[0043] Figure 10 The purified pressure-sensitive adhesive of the copolymer of methyl lactate and thioctic acid with a thioctic acid feed ratio of 10 mol% in Example 2. 1 H NMR spectrum;

[0044] Figure 11 The purified pressure-sensitive adhesive of the copolymer of methyl lactate and thioctic acid with a thioctic acid feed ratio of 20 mol% in Example 2. 1 H NMR spectrum;

[0045] Figure 12 The purified pressure-sensitive adhesive of the copolymer of methyl lactate and thioctic acid with a thioctic acid feed ratio of 30 mol% in Example 2.1 H NMR spectrum;

[0046] Figure 13 The DSC curves of the pressure-sensitive adhesives of methyl lactate and thioctic acid copolymers with different thioctic acid contents prepared in Example 2 are shown.

[0047] Figure 14 The GPC curve of the methyl lactate and thioctic acid copolymer pressure-sensitive adhesive prepared in Example 3 is shown.

[0048] Figure 15 The purified product of the methyl lactate and thioctic acid copolymer pressure-sensitive adhesive prepared in Example 3 1 H NMR spectrum;

[0049] Figure 16 The DSC curve of the purified methyl lactate and thioctic acid copolymer pressure-sensitive adhesive prepared in Example 3 is shown below.

[0050] Figure 17 The images show the failure of the pressure-sensitive adhesives of different molecular weights of methyl lactate and thioctic acid copolymers prepared in Example 4 during the lap shear test.

[0051] Figure 18 The displacement-load curves of the methyl lactate acrylate and thioctic acid copolymer pressure-sensitive adhesives with different molecular weights prepared in Example 4 are shown.

[0052] Figure 19 The bar chart shows the lap shear strength of the pressure-sensitive adhesives of different molecular weights of methyl acrylate lactate and thioctic acid copolymers prepared in Example 4.

[0053] Figure 20 The images show the failure of the pressure-sensitive adhesives of different molecular weights of methyl lactate and thioctic acid copolymers prepared in Example 5 during the lap shear test.

[0054] Figure 21 Displacement-load curves of pressure-sensitive adhesives of methyl lactate and methyl thioctic acid copolymers with different thioctic acid contents prepared in Example 5;

[0055] Figure 22 The bar chart shows the lap shear strength of the pressure-sensitive adhesives of methyl lactate and thioctic acid copolymers with different thioctic acid contents prepared in Example 5.

[0056] Figure 23 The image shows the failure of the pressure-sensitive adhesive of methyl lactate and thioctic acid copolymer prepared by conventional free radical polymerization in Example 5 during the lap shear test.

[0057] Figure 24The displacement-load curve of the methyl lactate-acrylate and thioctic acid copolymer pressure-sensitive adhesive prepared by conventional free radical polymerization in Example 5 is shown.

[0058] Figure 25 This is a bar chart showing the lap shear strength of the pressure-sensitive adhesive obtained by conventional free radical polymerization of methyl lactate and thioctic acid in Example 5.

[0059] Figure 26 The images show the GPC curves of the copolymer pressure-sensitive adhesive before and after degradation in Example 6. Detailed Implementation

[0060] To make the objectives and technical solutions of this invention clearer, the substantive content of this invention will be described below in conjunction with specific embodiments; the embodiments listed in this invention are only used to illustrate this invention and are not intended to limit the scope of this invention.

[0061] Example 1: Preparation of copolymer pressure-sensitive adhesives with different molecular weights and similar lipoic acid content by emulsion polymerization

[0062] Polymerization reaction of the copolymer pressure-sensitive adhesive with a target degree of polymerization of 100: 0.0111 g of 4-((((2-carboxyethyl)thio)thiocarbonyl)thio)-4-cyanopentanoic acid photoinitiator / transfer terminator, 0.5143 g of methyl lactate acrylate (MLA) comonomer, 0.0750 g of lipoic acid (LA) comonomer, 0.0900 g of sodium dodecyl sulfate (SDS) surfactant, and 1.486 mL of ultrapure water were added to a 4 mL reaction flask. The mixture was thoroughly mixed to prepare the reaction solution. Oxygen was removed by argon displacement for 30 minutes, and then the mixture was placed in a light source at a wavelength of 365 nm and an intensity of 2 mW / cm². –2 The reaction was carried out under a light source at 35 ℃ and 800 rpm for 5 hours; through 1 ¹H NMR spectroscopy analysis showed that the MLA conversion rate was 98% and the LA conversion rate was 99%. DLS analysis revealed that the particle size and distribution fraction of the polymer emulsion were 238 nm and 0.16, respectively. (See attached diagram). Figure 1 GPC measurements showed that the obtained copolymer pressure-sensitive adhesive P(MLA) 88 -co-LA 10 The number-average molecular weight and dispersity were 16.9 kg mol. –1 And 1.24, see 1.24. Figure 2 The copolymer pressure-sensitive adhesive was washed three times with ultrapure water and once with methanol, then dried in a vacuum drying oven at 60°C for at least 24 hours. 1 ¹H NMR spectroscopy confirmed the copolymer pressure-sensitive adhesive to be pure and free of impurities, and the actual thioctic acid content was calculated to be 9.1 mol%. (See [reference needed]). Figure 3 The structure of the copolymer pressure-sensitive adhesive is shown in structural formula I.

[0063]

[0064] Ⅰ

[0065] Polymerization reaction of the copolymer pressure-sensitive adhesive with a target degree of polymerization of 200: 0.0056 g of 4-((((2-carboxyethyl)thio)thiocarbonyl)thio)-4-cyanopentanoic acid photoinitiator / transfer terminator, 0.5191 g of methyl lactate (MLA), 0.0753 g of lipoic acid (LA), 0.0900 g of sodium dodecyl sulfate (SDS) surfactant, and 1.480 mL of ultrapure water were added to a 4 mL reaction flask. The mixture was thoroughly mixed to prepare the reaction solution. Oxygen was removed by argon purging for 30 minutes, and then the mixture was placed in a light source at a wavelength of 365 nm and an intensity of 2 mW / cm². –2 The reaction was carried out under a light source at 35 °C and 800 rpm for 5 hours; through... 1 ¹H NMR spectroscopy analysis showed that the MLA conversion rate was 98% and the LA conversion rate was 98%. DLS analysis revealed that the particle size and distribution fraction of the polymer emulsion were 256 nm and 0.15, respectively. (See [reference needed]). Figure 1 GPC measurements showed that the obtained copolymer pressure-sensitive adhesive P(MLA) 176 -co-LA 20 The number-average molecular weight and dispersity were 32.7 kg mol. –1 And 1.26, see 1.26. Figure 2 The copolymer pressure-sensitive adhesive was washed three times with ultrapure water and once with methanol, then dried in a vacuum drying oven at 60°C for at least 24 hours. 1 ¹H NMR spectroscopy confirmed the copolymer pressure-sensitive adhesive to be pure and free of impurities, and the actual thioctic acid content was calculated to be 10.2 mol%. (See [reference needed]). Figure 4 The structure of the copolymer pressure-sensitive adhesive is shown in structural formula II.

[0066]

[0067] II

[0068] Polymerization reaction of a copolymer pressure-sensitive adhesive with a target degree of polymerization of 500: 0.0023 g of 4-((((2-carboxyethyl)thio)thiocarbonyl)thio)-4-cyanopentanoic acid photoinitiator / transfer terminator, 0.5220 g of methyl lactate (MLA), 0.0758 g of lipoic acid (LA), 0.0900 g of sodium dodecyl sulfate (SDS) surfactant, and 1.478 mL of ultrapure water were added to a 4 mL reaction flask. The mixture was thoroughly mixed to prepare the reaction solution. Oxygen was removed by argon displacement for 30 minutes, and then the mixture was placed in a light source at a wavelength of 365 nm and an intensity of 2 mW / cm². –2The reaction was carried out under a light source at 35 °C and 800 rpm for 6 hours; through... 1 ¹H NMR spectroscopy analysis showed that the MLA conversion rate was 96% and the LA conversion rate was 99%. DLS analysis revealed that the particle size and distribution fraction of the polymer emulsion were 289 nm and 0.23, respectively. (See [reference needed]). Figure 1 GPC measurements showed that the obtained copolymer pressure-sensitive adhesive P(MLA) 432 -co-LA 49 The number-average molecular weight and dispersity were 75.9 kg mol. –1 And 1.25, see Figure 2 The copolymer pressure-sensitive adhesive was washed three times with ultrapure water and once with methanol, then dried in a vacuum drying oven at 60°C for at least 24 hours. 1 ¹H NMR spectroscopy confirmed the copolymer pressure-sensitive adhesive to be pure and free of impurities, and the actual thioctic acid content was calculated to be 9.7 mol%. (See [reference needed]). Figure 5 The structure of the copolymer pressure-sensitive adhesive is shown in structural formula III.

[0069]

[0070] Structural Form III

[0071] The polymerization reaction of the copolymer pressure-sensitive adhesive with a target degree of polymerization of 1000: 0.0011 g of 4-((((2-carboxyethyl)thio)thiocarbonyl)thio)-4-cyanopentanoic acid photoinitiator / transfer terminator, 0.5229 g of methyl lactate (MLA), 0.0762 g of lipoic acid (LA), 0.0900 g of sodium dodecyl sulfate (SDS) surfactant, and 1.479 mL of ultrapure water were added to a 4 mL reaction flask. The mixture was thoroughly mixed to prepare the reaction solution. Oxygen was removed by argon purging for 30 minutes, and then the mixture was placed in a light source at a wavelength of 365 nm and an intensity of 2 mW / cm². –2 The reaction was carried out under a light source at 35 °C and 800 rpm for 7 hours; through... 1 ¹H NMR spectroscopy analysis showed that the MLA conversion rate was 93% and the LA conversion rate was 95%. DLS analysis revealed that the particle size and distribution fraction of the polymer emulsion were 269 nm and 0.21, respectively. (See [reference needed]). Figure 1 GPC measurements showed that the obtained copolymer pressure-sensitive adhesive P(MLA) 837 -co-LA 95 The number-average molecular weight and dispersity were 157 kg mol. –1 And 1.32, see 1.32. Figure 2 The copolymer pressure-sensitive adhesive was washed three times with ultrapure water and once with methanol, then dried in a vacuum drying oven at 60°C for at least 24 hours. 1¹H NMR spectroscopy confirmed the copolymer pressure-sensitive adhesive to be pure and free of impurities, and the actual thioctic acid content was calculated to be 9.8 mol%. (See [reference needed]). Figure 6 The structure of the copolymer pressure-sensitive adhesive is shown in structural formula IV.

[0072]

[0073] Structural Form IV

[0074] The polymerization reaction of the copolymer pressure-sensitive adhesive with a target degree of polymerization of 2000: 0.0056 g of 4-((((2-carboxyethyl)thio)thiocarbonyl)thio)-4-cyanopentanoic acid photoinitiator / transfer terminator, 0.5191 g of methyl lactate (MLA), 0.0753 g of lipoic acid (LA), 0.0900 g of sodium dodecyl sulfate (SDS) surfactant, and 1.480 mL of ultrapure water were added to a 4 mL reaction flask. The mixture was thoroughly mixed to prepare the reaction solution. Oxygen was removed by argon purging for 30 minutes, and then the mixture was placed in a light source at a wavelength of 365 nm and an intensity of 2 mW / cm². –2 The reaction was carried out under a light source at 35 °C and 800 rpm for 9 hours; through... 1 ¹H NMR spectroscopy analysis showed that the MLA conversion rate was 92% and the LA conversion rate was 96%. DLS analysis revealed that the particle size and distribution fraction of the polymer emulsion were 287 nm and 0.18, respectively. (See [reference needed]). Figure 1 GPC measurements showed that the obtained copolymer pressure-sensitive adhesive P(MLA) 1656 -co-LA 192 The number-average molecular weight and dispersity were 315 kg mol. –1 And 1.36, see figure; the copolymer pressure-sensitive adhesive was washed three times with ultrapure water and once with methanol, and then dried in a vacuum drying oven at 60 ℃ for at least 24 hours. 1 ¹H NMR spectroscopy confirmed the copolymer pressure-sensitive adhesive to be pure and free of impurities, and the actual thioctic acid content was calculated to be 10.3 mol%. (See [reference needed]) Figure 7 The structure of the copolymer pressure-sensitive adhesive is shown in structural formula V.

[0075]

[0076] Structural V

[0077] DSC testing revealed that the glass transition temperatures of the purified copolymers of methyl acrylate lactate and thioctic acid with different molecular weights were 6–7 °C. (See [reference needed]). Figure 8 .

[0078] Example 2

[0079] Homogeneous polymerization was used to prepare copolymer pressure-sensitive adhesives with different thioctic acid contents and similar molecular weights.

[0080] The polymerization reaction of a copolymer pressure-sensitive adhesive with a 10 mol% thioctic acid feed ratio: 0.0026 g of methyl 2-((3-methoxypyrazole-1-carbonylthio)thio)propionate photoinitiator / transfer terminator, 0.3416 g of methyl lactate (MLA) comonomer, 0.0496 g of thioctic acid (LA) comonomer, and 1.058 mL of dimethyl sulfoxide solvent were added to a 4 mL reaction flask and mixed thoroughly to prepare a reaction solution. The solution was deoxygenated using argon purging for 30 minutes, and then placed under light at a wavelength of 462 nm and an intensity of 20 mW / cm². –2 The reaction was carried out under a light source at 30 °C and 300 rpm for 1 hour; through... 1 ¹H NMR spectroscopy analysis showed that the MLA conversion rate was 98% and the LA conversion rate was 99%; GPC analysis showed that the obtained copolymer pressure-sensitive adhesive P(MLA) was... 212 -co-LA 24 The number-average molecular weight and dispersity were 43 kg mol. –1 And 1.09, see Figure 9 The copolymer pressure-sensitive adhesive was washed three times with ultrapure water and once with methanol, then dried in a vacuum drying oven at 60°C for at least 24 hours. 1 ¹H NMR spectroscopy confirmed the copolymer pressure-sensitive adhesive to be pure and free of impurities, and the actual thioctic acid content was calculated to be 9.8 mol%. (See [reference needed]) Figure 10 The structure of the copolymer pressure-sensitive adhesive is shown in structural formula VI.

[0081]

[0082] Structural Formula VI

[0083] The polymerization reaction of a copolymer pressure-sensitive adhesive with a 20 mol% thioctic acid feed ratio: 0.0026 g of methyl 2-((3-methoxypyrazole-1-carbonylthio)thio)propionate photoinitiator / transfer terminator, 0.3036 g of methyl lactate (MLA), 0.099 g of thioctic acid (LA), and 0.696 mL of dimethyl sulfoxide were added to a 4 mL reaction flask and mixed thoroughly to prepare a reaction solution. The solution was deoxygenated using argon purging for 30 minutes, and then placed in a light source at a wavelength of 462 nm and an intensity of 20 mW / cm². –2 The reaction was carried out under a light source at 30 °C and 300 rpm for 1 hour; through... 1 ¹H NMR spectroscopy analysis showed that the MLA conversion rate was 99% and the LA conversion rate was 99%; GPC analysis showed that the obtained copolymer pressure-sensitive adhesive P(MLA) was... 191 -co-LA 48 The number-average molecular weight and dispersity were 45 kg mol.–1 And 1.05, see Figure 9 The copolymer pressure-sensitive adhesive was washed three times with ultrapure water and once with methanol, then dried in a vacuum drying oven at 60°C for at least 24 hours. 1 ¹H NMR spectroscopy confirmed the copolymer pressure-sensitive adhesive to be pure and free of impurities, and the actual thioctic acid content was calculated to be 19.2 mol%. (See [reference needed]) Figure 11 The structure of the copolymer pressure-sensitive adhesive is shown in structural formula VII.

[0084]

[0085] Structural VII

[0086] The polymerization reaction of a copolymer pressure-sensitive adhesive with a thioctic acid feed ratio of 30 mol% was carried out as follows: 0.0026 g of methyl 2-((3-methoxypyrazole-1-carbonylthio)thio)propionate photoinitiator / transfer terminator, 0.2656 g of methyl lactate (MLA), 0.1486 g of thioctic acid (LA), and 0.334 mL of dimethyl sulfoxide were added to a 4 mL reaction flask and mixed thoroughly to prepare a reaction solution. The solution was deoxygenated using argon purging for 30 minutes, and then placed under light at a wavelength of 462 nm and an intensity of 20 mW / cm². –2 The reaction was carried out under a light source at 30 °C and 300 rpm for 2 hours; through... 1 ¹H NMR spectroscopy analysis showed that the MLA conversion rate was 98% and the LA conversion rate was 99%; GPC analysis showed that the obtained copolymer pressure-sensitive adhesive P(MLA) was... 167 -co-LA 72 The number-average molecular weight and dispersity were 43 kg mol. –1 And 1.16, see 1.16 Figure 9 The copolymer pressure-sensitive adhesive was washed three times with ultrapure water and once with methanol, then dried in a vacuum drying oven at 60°C for at least 24 hours. 1 ¹H NMR spectroscopy confirmed the copolymer pressure-sensitive adhesive to be pure and free of impurities, and the actual thioctic acid content was calculated to be 29.3 mol%. (See [reference needed]) Figure 12 The structure of the copolymer pressure-sensitive adhesive is shown in structural formula VIII.

[0087]

[0088] Structural VIII

[0089] The glass transition temperatures of the purified copolymer pressure-sensitive adhesives of methyl acrylate and lipoic acid with different lipoic acid contents were obtained by DSC testing. The glass transition temperature of the copolymer pressure-sensitive adhesive with a lipoic acid content of 9.8 mol% was 11. oC; The glass transition temperature of the copolymer pressure-sensitive adhesive with a thioctic acid content of 19.2 mol% is 3 ℃, and the glass transition temperature of the copolymer pressure-sensitive adhesive with a thioctic acid content of 29.3 mol% is -2 ℃. o C, see also Figure 13 .

[0090] Example 3

[0091] Add 0.6326 g of methyl lactate acrylate (MLA) comonomer, 0.1619 g of lipoic acid (LA) comonomer, 0.0016 g of VA-044 thermal initiator, and 1.867 mL of ultrapure water to a 10 mL reaction flask, mix thoroughly to prepare a reaction solution, deoxygenate using argon displacement for 30 minutes, and then react at 40 ℃ and 300 rpm for 12 hours; 1 ¹H NMR spectroscopy analysis showed that the MLA conversion rate was 98% and the LA conversion rate was 99%. GPC analysis determined that the number-average molecular weight of the obtained copolymer pressure-sensitive adhesive P(MLA-co-LA) was 110 kg / mol. –1 See Figure 14 The copolymer pressure-sensitive adhesive was washed three times with ultrapure water and once with methanol, then dried in a vacuum drying oven at 60°C for at least 24 hours. 1 ¹H NMR spectroscopy analysis showed that the copolymer pressure-sensitive adhesive was pure and free of impurities. (See also...) Figure 15 The structure of the copolymer pressure-sensitive adhesive is shown in structural formula IX.

[0092]

[0093] Structural IX

[0094] DSC testing revealed that the glass transition temperatures of the purified methyl lactate / thioctic acid copolymer pressure-sensitive adhesive were 44°C and 44°C, respectively. o C, see also Figure 16 .

[0095] Example 4

[0096] Samples were prepared using the coating method for overlap shear testing and to obtain test results.

[0097] 60 mg of purified copolymer pressure-sensitive adhesives with different molecular weights and similar thioctic acid content prepared in Example 1 were accurately weighed. An aluminum sheet was placed on a heating stage preheated to 70 °C, and the 60 mg copolymer pressure-sensitive adhesive sample was placed on the surface of the aluminum sheet. After the sample melted upon heating, it was uniformly coated onto the aluminum sheet, with a coating area controlled at 2.5 cm × 1 cm. After coating, the aluminum sheet was removed from the heating stage and cooled to room temperature. The lap shear test was performed on a universal testing machine (5944) using a 2 kN load cell and adhesive surface clamps, with a tensile rate set to 50 mm / min.–1 The test substrate was an aluminum sheet (GB / T 7124). Before testing, another blank aluminum sheet was overlapped with the aluminum sheet coated with copolymer pressure-sensitive adhesive. The overlap length was 1 cm, and the overlap area was 2.5 cm × 1 cm. Dovetail clips were used to hold the overlapped aluminum sheet in place for 2 minutes to ensure a tight interface. The overlapped aluminum sheet was then mounted on a universal testing machine, ensuring the overlapped sample was positioned at the center line of force. Testing then began until adhesion failure occurred in the overlapped area. (See [link to relevant documentation]). Figure 17 The instrument automatically records force and displacement data. See below. Figure 18 For each sample with a different molecular weight, three parallel samples were set up for parallel testing.

[0098] The lap shear adhesion strength of the copolymer pressure-sensitive adhesive was obtained by processing the force and displacement data. At a similar thioctic acid content, the molecular weight was 16.9 kg mol. –1 The average adhesion strength of the copolymer pressure-sensitive adhesive is 0.68 MPa; the molecular weight is 32.7 kg mol. –1 The average adhesion strength of the copolymer pressure-sensitive adhesive is 1.15 MPa; the molecular weight is 78.8 kg mol. –1 The average adhesion strength of the copolymer pressure-sensitive adhesive is 1.96 MPa; the molecular weight is 157 kg mol. –1 The average adhesion strength of the copolymer pressure-sensitive adhesive is 2.96 MPa; the molecular weight is 315 kg mol. –1 The average adhesion strength of the copolymer pressure-sensitive adhesive is 3.89 MPa. (See [reference needed]) Figure 19 .

[0099] Example 5

[0100] Samples were prepared using the hot-press slicing method for lap shear testing and to obtain test results.

[0101] All purified copolymer pressure-sensitive adhesives with similar molecular weights and different thioctic acid contents prepared in Example 2 were transferred onto a PDMS film, and then completely covered with another PDMS film. The film was then hot-pressed for 1 minute using a preheated hot press to 60 °C to form a film with a thickness of approximately 0.5 mm. After cooling to room temperature, the film was cut into square sample pieces with an area of ​​1 cm × 1 cm, with PDMS film retained on both sides for protection. Overlap shear tests were performed on a universal testing machine (5944) using a 2 kN load cell and adhesive surface clamps, with a tensile rate set to 50 mm / min. –1The test substrate was an aluminum sheet (GB / T 7124). Before testing, the PDMS film on one side of the sample sheet was peeled off and adhered to an aluminum sheet. Then, the PDMS film on the other side of the sample sheet was peeled off and overlapped with another aluminum sheet. The overlap length was 1 cm, and the overlap area was 1 cm × 1 cm. Dovetail clips were used to hold and fix the sample for 2 minutes to ensure a tight fit. The overlapped aluminum sheet was then mounted on a universal testing machine, ensuring the overlapped sample was positioned at the center line of force. Testing then began until adhesion failure occurred in the overlap area. (See [link to relevant documentation]). Figure 20 The instrument automatically records force and displacement data. See below. Figure 21 For each sample with different lipoic acid content, three parallel samples were set up for parallel testing.

[0102] The lap shear adhesion strength of the copolymer pressure-sensitive adhesive was obtained by processing the force and displacement data. At similar molecular weights, the average adhesion strength of the copolymer pressure-sensitive adhesive was 0.96 MPa when the thioctic acid content was 9.8 mol%; 1.12 MPa when the thioctic acid content was 19.2 mol%; and 0.59 MPa when the thioctic acid content was 29.3 mol%. (See [reference needed]). Figure 22 .

[0103] The bio-based copolymer pressure-sensitive adhesive obtained by conventional free radical polymerization in Example 3 was subjected to an overlap shear test using the same sample preparation method. Adhesion failure occurred in the overlap area (see [reference needed]). Figure 23 The instrument automatically records force and displacement data. See below. Figure 24 The sample was tested in parallel with three parallel samples. The average adhesion strength was 1.81 MPa. See [link to relevant documentation]. Figure 25 .

[0104] Example 6: Degradation of copolymer pressure-sensitive adhesive using a reductive degradation method

[0105] The number-average molecular weight obtained in Example 1 was 75.9 kg mol. –1 Degradation of a copolymer pressure-sensitive adhesive with a dispersion of 1.25 and a thioctic acid content of 9.1 mol%: 150 mg of the copolymer pressure-sensitive adhesive was dissolved in 1 mL of N,N-dimethylformamide, and 0.0142 mg of dithiothreitol (DTT) (molar ratio to copolymer pressure-sensitive adhesive 1:50) was added. The mixture was stirred at room temperature in the dark for 12 hours. After 12 hours of degradation, GPC analysis showed that the number average molecular weight of the copolymer pressure-sensitive adhesive decreased to 14.9 kg mol. –1 See Figure 26 .

[0106] The raw materials and equipment used in this invention are all commonly used in the field; the methods used in this invention, unless otherwise specified, are all conventional methods in the field.

[0107] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A biodegradable bio-based copolymer pressure-sensitive adhesive with high adhesive strength, the structural formula of which is shown below: ； R1 is H, C1~C 18 Alkyl groups or substituents capable of generating primary, secondary, or tertiary carbon free radicals; R2 is H, C1~C 18 Alkyl group, -C(=S)-S-C1~C 18 Or one of the substituents that can generate primary, secondary, or tertiary carbon free radicals; R3 is one of -COOH, -OCH3, or -OCH2CH3; R4 is one of the C1~C4 alkyl groups; m and n are positive integers.

2. The biodegradable bio-based copolymer pressure-sensitive adhesive with high adhesive strength as described in claim 1, characterized in that: The substituents in R1 that can generate primary, secondary, and tertiary carbon radicals are -CH2CN, -CH(CH3)CN, -C(CH3)2CN, -CH(C2H5)CN, -C(CH3)(C2H5)CN, and -C6H. 10 CN, -C(CH3)((CH2)2COOH)CN, -C(CH3)((CH2)2COOC n H 2n+1 )CN, -C(CH3)(CH2)2OH, -CH2Ph, -CH(CH3)Ph, -CH(COOH)Ph, -CH(COOC n H 2n+1 )Ph, -C(CH3)2Ph, -CH2COOH, -CH2COOC n H 2n+1 , -CH(CH3)COOH, -CH(CH3)COOC n H 2n+1 , -C(CH3)2COOH, -C(CH3)2COOC n H 2n+1 One of -C(CH3)2C(NH)(NH2) or -C(CH3)2C(NH)N(CH2)2; The substituents in R2 that can generate primary, secondary, and tertiary carbon radicals are -C(=S)-S-CH2CN, -C(=S)-S-CH(CH3)CN, -C(=S)-SC(CH3)2CN, -C(=S)-S-CH(C2H5)CN, -C(=S)-SC(CH3)(C2H5)CN, and -C(=S)-SC6H 10 CN, -C(=S)-SC(CH3)((CH2)2COOH)CN, -C(=S)-SC(CH3)((CH2)2COOC n H 2n+1 )CN, -C(=S)-SC(CH3)(CH2)2OH, -C(=S)-S-CH2Ph, -C(=S)-S-CH(CH3)Ph, -C(=S)-S-CH(COOH)Ph, -C(=S)-S-CH(COOC n H 2n+1 )Ph, -C(=S)-SC(CH3)2Ph, -C(=S)-S-CH2COOH, -C(=S)-S-CH2COOC n H 2n+1 , -C(=S)-S-CH(CH3)COOH, -C(=S)-S-CH(CH3)COOC n H 2n+1 , -C(=S)-SC(CH3)2COOH, -C(=S)-SC(CH3)2COOC n H 2n+1 One of -C(=S)-S-C(CH3)2C(NH)(NH2) and -C(=S)-SC(CH3)2C(NH)N(CH2)2.

3. A method for preparing a biodegradable bio-based copolymer pressure-sensitive adhesive with high adhesive strength as described in claim 1 or 2, characterized in that: A photoinitiator, transfer terminator, comonomer, surfactant, and solvent are mixed uniformly to prepare a reaction solution. The solution is then reacted for 5-9 hours under a certain temperature and light source to obtain a copolymer pressure-sensitive adhesive with controllable dispersion. The photoinitiator is one of dithioester, trithiocarbonate, or xanthate. The comonomer is a combination of one of lactic acrylate and one of thioctic acid derivative monomers. The surfactant is one of cationic surfactant, anionic surfactant, nonionic surfactant, or amphiphilic surfactant.

4. The method for preparing a biodegradable bio-based copolymer pressure-sensitive adhesive with high adhesive strength as described in claim 3, characterized in that: The solid content of the reaction solution is 1%–50% by mass; the molar ratio of photoinitiator / transfer terminator to monomer is 1:100–5000; the mass ratio of surfactant to monomer is 1:2–10; the wavelength of the light source is 365–700 nm, and the light intensity is 0.1–100 mW / cm². –2 The photoinitiator and transfer terminator is one of 4-((((2-carboxyethyl)thio)thiocarbonyl)thio)-4-cyanopentanoic acid, methyl 2-((3-methoxypyrazole-1-carbonylthio)thio)propionate, and 1H-pyrrole-1-carbondithiobenzoate; the comonomer is a combination of one of methyl lactate, ethyl lactate, and thioctic acid, and methyl thiocate; the surfactant is one of sodium dodecyl sulfate, polyoxyethylene octadecyl ether, and hexadecyltrimethylammonium bromide; and the solvent is water.

5. A method for preparing a biodegradable bio-based copolymer pressure-sensitive adhesive with high adhesive strength as described in claim 1 or 2, characterized in that: A photoinitiator, transfer terminator, comonomer, and solvent are mixed uniformly to prepare a reaction solution. The solution is then reacted for 1-2 hours under a certain temperature and light source to obtain a copolymer pressure-sensitive adhesive with controllable dispersion. The photoinitiator is one of dithioester, trithiocarbonate, or xanthate. The comonomer is a combination of one of lactic acrylate and one of thioctic acid derivative monomers. The surfactant is one of cationic surfactant, anionic surfactant, nonionic surfactant, or amphiphilic surfactant.

6. The method for preparing a biodegradable bio-based copolymer pressure-sensitive adhesive with high adhesive strength as described in claim 5, characterized in that: The photoinitiator-transfer terminator is one of 4-((((2-carboxyethyl)thio)thiocarbonyl)thio)-4-cyanopentanoic acid, methyl 2-((3-methoxypyrazole-1-carbonylthio)thio)propionate, or methyl 1H-pyrrole-1-carbodithiocarbamate; the comonomer is a combination of one of methyl lactate or ethyl lactate and one of thioctic acid or methyl thiocate; the solvent is one of dimethyl sulfoxide, N,N-dimethylformamide, or dichloromethane; the solid content of the reaction solution is 1%–100% by mass; the molar ratio of the photoinitiator-transfer terminator to the comonomer is 1:100–50000; the light source wavelength is 365–700 nm, and the light intensity is 0.1–100 mW / cm². –2 .

7. A method for preparing a biodegradable bio-based copolymer pressure-sensitive adhesive with high adhesive strength as described in claim 1 or 2, characterized in that: A reaction solution is prepared by uniformly mixing a thermal initiator, comonomer, and solvent, and then reacting at 30-50°C for 10-20 hours to obtain a copolymer pressure-sensitive adhesive. The thermal initiator is one of azo initiators, organic peroxide initiators, or inorganic peroxide initiators, and the comonomer is a combination of one of lactic acid acrylates and one of thioctic acid derivative monomers.

8. The method for preparing a biodegradable bio-based copolymer pressure-sensitive adhesive with high adhesive strength as described in claim 7, characterized in that: The comonomer is a combination of one of methyl lactate and ethyl lactate and one of thioctic acid and methyl thiocate, and the solvent is water.

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