A hyperbranched multi-arm reversibly cross-linked resin and its preparation and application as an adhesive

Abstract

The present invention discloses a hyperbranched multi-arm reversible cross-linked resin, its preparation, and application as an adhesive. The preparation method of the hyperbranched multi-arm reversible cross-linked resin comprises: step 1, using an α-diimine palladium catalyst to catalyze the copolymerization of ethylene and a reversible cross-linking functional monomer A shown in formula I based on a "chain walking" mechanism to obtain a hyperbranched polyethylene reversible cross-linking agent; step 2, using 2-bromoisobutyryl bromide as an initiator, and using ordinary monomers and a reversible cross-linking functional monomer B shown in formula IV as comonomers, and synthesizing a linear reversible cross-linked polymer by atom transfer radical polymerization; step 3, cross-linking the hyperbranched polyethylene reversible cross-linking agent and the linear reversible cross-linked polymer in a solvent to obtain a hyperbranched multi-arm reversible cross-linked resin. The present invention provides the application of the hyperbranched multi-arm reversible cross-linked resin as an adhesive, which has excellent bonding properties and recyclability and is suitable for large-scale application. #imgabs0##imgabs1#

Description

Technical Field

[0001] The present invention relates to a hyperbranched multi-arm reversible cross-linked resin and a preparation method thereof and application thereof as an adhesive Background Art

[0002] Cross-linking is a fundamental approach to improving the performance of resin applications. Traditional thermosetting resins, such as epoxy resins, polyurethanes, acrylic resins, and silicones, can form stable three-dimensional network structures through irreversible covalent cross-linking, significantly improving their mechanical, heat-resistant, solvent-resistant, and dimensional stability properties. These resins, as coatings and adhesives, are widely used in construction, transportation, information technology, high-end equipment, and other fields. However, due to the irreversible nature of these cross-linking systems, recycling them is difficult, resulting in significant resource waste and increasingly serious environmental pollution.

[0003] To promote the recycling of thermosetting resins, a series of reversible crosslinking methods for polymers have been reported to date, including non-covalent reversible crosslinking and covalent reversible crosslinking. The former can be further subdivided into non-covalent crosslinking types such as hydrogen bonding, electrostatic bonding, ionic bonding, lipophilic bonding, coordination, π-π bonding, and cation-π bonding. Due to the generally weak non-covalent bonding, the resulting reversible crosslinked structures are relatively unstable, resulting in poor mechanical, heat, and solvent resistance properties of the crosslinked polymers. The latter utilizes specific reversible chemical reactions such as the Diels-Alder reaction, dynamic disulfide exchange reaction, and dynamic ester exchange reaction to form reversible crosslinked structures. Compared with non-covalent approaches, this type of dynamic reversible crosslinked structure has higher stability and therefore has important application prospects in the recycling of plastics, rubber, coatings, adhesives, and other fields.

[0004] However, to construct such a covalently reversible crosslinking system, a certain proportion of reversibly crosslinking components must often be introduced into the polymer molecular structure. These chemical components are often specialized and expensive, and the polymerization process often involves complex synthesis techniques, making large-scale application very difficult. Therefore, how to achieve efficient covalently reversible crosslinking of polymers using primarily common monomer raw materials with the aid of a small amount of reversibly crosslinking components, in order to prepare recyclable polymer reversibly crosslinked materials that meet the needs of applications such as adhesives, is an urgent application need in this field. Summary of the Invention

[0005] The present invention provides a hyperbranched multi-arm reversibly cross-linked resin, a preparation method thereof, and an application thereof as an adhesive. The resin has excellent bonding properties and recyclability when used as an adhesive, and has the advantages of low preparation cost, suitability for large-scale application, high reversible cross-linking efficiency, simple process, and controllable and adjustable performance.

[0006] The technical solution adopted by the present invention is described in detail below.

[0007] In a first aspect, the present invention provides a method for preparing a hyperbranched multi-arm reversibly cross-linked resin, comprising the following steps:

[0008] In the first step, ethylene and a reversible crosslinking functional monomer A are copolymerized using an α-diimide palladium catalyst based on a "chain walking" mechanism to obtain a hyperbranched polyethylene reversible crosslinker; the reversible crosslinking functional monomer A is an acrylic acid maleimide shown in Formula I, and its structure is shown below:

[0009]

[0010] Step 2: Using 2-bromoisobutyryl bromide as shown in Formula III as an initiator, and common monomers and reversibly crosslinking functional monomer B as comonomers, a linear reversibly crosslinked polymer is synthesized by atom transfer radical polymerization; the common monomer is selected from the following: styrene, methyl methacrylate, methyl acrylate, butyl acrylate, trifluoroethyl acrylate, and ethyl methacrylate; the reversibly crosslinking functional monomer B is furfuryl methacrylate as shown in Formula IV;

[0011]

[0012] In the third step, the hyperbranched polyethylene reversible crosslinking agent and the linear reversible crosslinking polymer are crosslinked in a solvent to obtain a hyperbranched multi-arm reversible crosslinking resin.

[0013] The α-diimine palladium catalyst of the present invention adopts the following α-diimine palladium catalyst 1 or 2:

[0014]

[0015] Both of the above can be synthesized in the laboratory according to the following literature:

[0016] [1] Johnson LK, Killian CM, Brookhart MJ Am. Chem. Soc., 1995, 117, 6414; [2] Johnson LK, Mecking S., Brookhart MJ Am. Chem. Soc., 1996, 118, 267.

[0017] The reversible cross-linking functional monomer A of the present invention is acrylic maleimide, which is synthesized by reacting N-hydroxyethyl maleimide shown in formula II with acryloyl chloride.

[0018]

[0019] The N-hydroxyethylmaleimide can be synthesized according to existing literature, such as: Hu Zhongyu, Huang Huashan, Cheng Chuanjie. Journal of Natural Science of Xiangtan University, 2014, 36, 81-84.

[0020] The reversibly crosslinkable monomer A is synthesized by the following process: N-hydroxyethylmaleimide, dichloromethane, and a small amount of triethylamine catalyst are sequentially added to a reaction vessel and stirred thoroughly at room temperature to form a uniform solution. Acryloyl chloride is then dissolved in dichloromethane and gradually added dropwise to the reaction solution. After completion, the mixture is stirred and reacted at 5–10°C for 3–5 hours. After completion of the reaction, the mixture is washed and extracted with distilled water, dried over anhydrous sodium sulfate, and the solvent is further removed using a rotary evaporator, followed by drying to obtain the reversibly crosslinkable monomer A. The molar ratio of N-hydroxyethylmaleimide to acryloyl chloride is 0.5-1:1, preferably 0.7:1.

[0021] The first step of the present invention can be specifically implemented as follows: under the protection of an ethylene atmosphere, an anhydrous grade solvent, acrylic acid maleimide and an α-diimide palladium catalyst are added to a reaction vessel, fully stirred and uniformly reacted for 2-48 hours under the conditions of controlling the temperature at 5-30°C and the ethylene pressure at 0.01-0.5MPa, and then separating and purifying to obtain a hyperbranched polyethylene reversible crosslinker.

[0022] Furthermore, in the above step 1, the anhydrous solvent is one of the following anhydrous solvents: dichloromethane, chloroform, chlorobenzene, preferably dichloromethane.

[0023] Furthermore, in step 1, the initial charging concentration of the reversibly cross-linking functional monomer A is 0.1-2.0 mol / L, preferably 0.5-1.0 mol / L, based on the total volume of the anhydrous solvent; the initial concentration of the α-diimine palladium catalyst is 0.5-50 g / L, preferably 2-20 g / L, based on the total volume of the anhydrous solvent.

[0024] Furthermore, in step 1, the copolymerization reaction temperature is controlled at 15-25°C; the ethylene pressure is controlled at 0.05-0.1 MPa; and the polymerization time is controlled at 12-24 h.

[0025] Furthermore, in step 1, the separation and purification of the hyperbranched polyethylene reversible crosslinker is specifically carried out according to the following steps:

[0026] (a) After the polymerization reaction is completed, the reaction solution is exposed to air to terminate the reaction;

[0027] (b) removing the solvent by blowing with cold air to obtain a preliminary polymerization product;

[0028] (c) dissolving the obtained product in tetrahydrofuran (THF), adding a small amount of hydrogen peroxide and concentrated hydrochloric acid aqueous solution, and stirring for 1 to 5 hours to dissolve the catalyst particles remaining in the polymer product;

[0029] (d) subsequently precipitating with methanol and removing the solvent;

[0030] (e) removing the solvent by blowing with cold air, dissolving the resulting product in tetrahydrofuran, and removing free monomers by polymer precipitation using methanol, repeating this process 2 to 3 times until the upper layer of the solution becomes colorless and transparent;

[0031] (f) The obtained product was vacuum dried at 30-60 °C for 24-48 h to obtain a hyperbranched polyethylene reversible crosslinker.

[0032] The second step of the present invention can be specifically implemented as follows:

[0033] Under nitrogen protection, 2-bromoisobutyryl bromide is used as an initiator, furfuryl methacrylate and common monomers are used as comonomers, pentamethyldiethylenetriamine (PMDETA) is used as a ligand, and CuBr is used as a catalyst. The reaction is carried out at 80-100°C in an anhydrous organic solvent for 20-30 hours. After the polymerization is completed, a linear reversible cross-linked polymer is obtained through separation and purification.

[0034] The 2-bromoisobutyryl bromide and furfuryl methacrylate described in the present invention are both commercially available analytically pure or chemically pure products.

[0035] Furthermore, in step 2, the anhydrous organic solvent is one of the following anhydrous organic solvents: toluene, cyclohexanone, tetrahydrofuran, preferably toluene.

[0036] Furthermore, in step 2, the molar ratio of the initiator, common monomer, reversible cross-linking functional monomer B, CuBr, and PMDETA is 1:1–300:1–50:0.5–5:0.5–10, preferably 1:1–250:1–30:0.5–2:0.5–5, and more preferably [-Br]:[St]:[FMA]:[CuBr]:[PMDETA]=1:150-250:15-25:0.5–2:0.5–5.

[0037] Furthermore, in step 2, the initial concentration of the common monomer in the reaction system is 2.0-20 mol / L.

[0038] Furthermore, in step 2, the reaction temperature was 90 °C and the reaction time was 24 h.

[0039] Furthermore, in step 2, the separation and purification of the linear reversibly cross-linked polymer is carried out according to the following steps: after the reaction is completed, the reaction solution is transferred to a clean beaker, and the excess solvent is blown away with cold air until it becomes a viscous fluid state, a small amount of THF is added to dissolve the product, and then methanol is added dropwise until no product is precipitated, and the above purification steps are repeated until the upper liquid is colorless and transparent; the obtained polymer is vacuum dried to finally obtain copolymer product I.

[0040] In the third step, the solvent is one of the following analytically pure or chemically pure reagents: THF, chloroform, toluene, petroleum ether, dichloromethane, n-heptane, preferably chloroform or dichloromethane.

[0041] In the third step, the mixing ratio of the hyperbranched polyethylene reversible crosslinker and the linear reversible crosslinked polymer is measured according to the molar ratio of the reversible crosslinking functional groups (i.e., maleimide group and furan group) contained in each, and the ratio is controlled in the range of 1:0.5-1:5, preferably 1:1.

[0042] In step 3, the substrate is one of the following: glass, aluminum plate, wood, polycarbonate, polyester, polytetrafluoroethylene, preferably glass or polycarbonate.

[0043] In the third step, the temperature of the cross-linking reaction is controlled at 30-90°C, preferably 40-70°C; and the cross-linking reaction time is 12-96 h, preferably 12-48 h.

[0044] In a second aspect, the present invention provides a hyperbranched multi-arm reversibly cross-linked resin prepared by the preparation method described in the first aspect.

[0045] In a third aspect, the present invention provides use of the hyperbranched multi-arm reversibly cross-linked resin described in the second aspect as an adhesive.

[0046] The present invention has the following beneficial effects compared to the prior art:

[0047] First, by utilizing the reversible cross-linking of hyperbranched polyethylene and linear polymers, a reversible cross-linked structure composed of approximately spherical hyperbranched polymers and linear polymers is constructed. Compared with a single linear polymer cross-linking system, the above system can achieve higher cross-linking efficiency, thereby effectively reducing the required amount of reversible cross-linking components, and realizing the preparation of reversibly cross-linked polymer materials mainly using ordinary monomer raw materials, reducing production costs, and being more conducive to large-scale applications.

[0048] Second, hyperbranched polymers and linear polymers coexist in the system. Through reversible cross-linking between the two, the performance advantages of the two types of polymers can be brought into play at the same time, so that the system has excellent bonding properties while obtaining excellent toughness, strength, temperature resistance, acid and alkali resistance, and humidity resistance, thereby obtaining high-performance adhesive materials with better comprehensive performance.

[0049] Third, based on the principle of dynamic cross-linking chemical reaction, the cross-linked structure formed in the system can be decross-linked through temperature changes, obtaining properties such as self-repair and recyclability, with the advantages of simple process and controllable and adjustable performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 : Preparation process of hyperbranched multi-arm reversibly cross-linked resin;

[0051] Figure 2 :A is the acrylic acid maleimide obtained in step 1 of Example 1 1 H NMR spectrum; B is the hyperbranched polyethylene reversible crosslinker obtained in step 1 of Example 1 1 H NMR spectrum; C is the linear reversible cross-linked polymer obtained in step 2 of Example 1 1 H NMR spectrum; D is the lap shear strength (glass substrate) of the samples obtained in Example 1 and Comparative Example 1;

[0052] Figure 3 :A is the linear reversible cross-linked polymer (Linear PSF) obtained in Comparative Example 2 and Examples 2 and 3 1 H NMR spectrum; B is a GPC curve of the linear reversibly cross-linked polymer obtained in Comparative Example 2 and Examples 2 and 3; C is the lap shear strength of the linear reversibly cross-linked polymer obtained in Comparative Example 2 and Examples 2 and 3;

[0053] Figure 4 : A is a schematic diagram of the recycling process of the hyperbranched multi-arm reversible cross-linked resin; B is the shear stress-strain curve of each sample of Comparative Example 3 and Example 4; C is the lap shear strength corresponding to each sample of Example 3 and Comparative Example 4;

[0054] Figure 5 : A is the adhesion performance of the sample obtained in Example 5 on various material surfaces; B is the comparison of the lap shear strength of Example 5 and Comparative Examples 4-6;

[0055] Figure 6 : A is the lap shear strength of the samples corresponding to Example 6 and Comparative Examples 7-10; B is the lap shear strength retention rate of the samples corresponding to Example 6 and Comparative Examples 7-10. DETAILED DESCRIPTION

[0056] The present invention will be described in further detail below with reference to specific embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0057] Example 1, Comparative Example 1

[0058] 1. Sample preparation

[0059] (1) Example 1

[0060] Step 1: In a 250 mL three-necked flask, add 0.0014 mol N-hydroxyethylmaleimide, 10 mL dichloromethane (analytical grade) and 0.19 mL catalyst triethylamine in sequence, and stir at room temperature for 0.5 h to form a uniform solution. Then, dissolve 0.002 mol acryloyl chloride in 10 mL dichloromethane (analytical grade) and slowly add it dropwise to the above reaction solution. After the reaction, stir and react at 10°C for 4 h. After the reaction, wash and extract with distilled water, dry with anhydrous sodium sulfate, further remove the solvent by rotary evaporator, and dry at 30°C for 2 h to obtain the reversible cross-linking monomer acrylic maleimide. Furthermore, under ethylene protection, 10 mL of anhydrous dichloromethane and 0.41 g of the reversible crosslinking monomer, acrylic maleimide, were added to a 250 mL glass reaction flask and stirred for 30 minutes to form a homogeneous solution. Subsequently, 0.25 g of α-diimine palladium catalyst 1 was dissolved in 10 mL of anhydrous dichloromethane and further injected into the reaction flask. Polymerization was continued at 25°C and an ethylene pressure of 0.1 MPa with stirring for 24 hours. After the polymerization, the reaction solution was exposed to air to terminate the polymerization, and the solvent was removed by air purging to obtain a preliminary product. The product was further dissolved in an appropriate amount of tetrahydrofuran, and a small amount of H₂O₂ and aqueous hydrochloric acid were added dropwise. The product was stirred for 4 hours to dissolve the remaining catalyst particles, and then precipitated with methanol. The resulting product was further dissolved in an appropriate amount of tetrahydrofuran and precipitated with methanol. This process was repeated three times to remove unreacted monomer. The product was then vacuum-dried at 60°C for 48 hours to obtain a hyperbranched polyethylene reversible crosslinker. (Note: The feed concentration of the reversible crosslinking functional monomer acrylic maleimide is 0.10 mol / L based on the total volume of the solvent; the initial concentration of the α-diimine palladium catalyst 1 is 12.5 g / L based on the total volume of the solvent)

[0061] Step 2: Under nitrogen, 0.1 g of the initiator 2-bromoisobutyryl bromide (containing 0.52 mmol Br), 11.4 mL of styrene (St, 98.8 mmol), 0.8 mL of the reversible crosslinking functional monomer furfuryl methacrylate 6 (FMA, analytical grade, 5.2 mmol), 0.22 mL of PMDETA (1.04 mmol), and 12.4 mL of anhydrous toluene were sequentially added to a 250 mL reaction flask. The flask was then subjected to three cycles of liquid nitrogen freeze-evacuation-thaw and nitrogen purging to remove residual oxygen from the solvent. Finally, 0.075 g of CuBr (0.52 mmol) was rapidly added under nitrogen, and the reaction was stirred at a constant temperature of 90°C for 24 h. Upon completion, the reaction solution was transferred to a 250 mL beaker, and excess solvent was removed with cold air until a viscous liquid was obtained. The product was dissolved in 10 mL of THF, and methanol was then added dropwise until no product precipitated. The purification steps were repeated until the supernatant was colorless and transparent. The resulting polymer was dried in a vacuum oven at 30°C for 72 h to obtain a linear reversibly cross-linked polymer (approximately 3.2 g). (The molar ratio of [-Br]:[St]:[FMA]:[CuBr]:[PMDETA] was 1:190:10:1:2, and the initial styrene concentration was 4.1 mol / L.)

[0062] Step 3: The linear reversibly cross-linked polymer obtained in step 2 and the hyperbranched polyethylene reversible cross-linker obtained in step 1 were added to chloroform at a reversible cross-linking group molar ratio of 1:1, mixed under stirring for 0.5 h, and then cast on a glass substrate. Cross-linked at 45°C for 48 h to obtain a hyperbranched multi-arm reversibly cross-linked resin.

[0063] (2) Comparative Example 1

[0064] Step 1: Prepare a linear reversible cross-linked polymer by referring to step 2 in Example 1.

[0065] Step 2: The linear reversibly cross-linked polymer obtained in step 1 above and the small molecule cross-linker N-phenylmaleimide (BMI) were added to chloroform at a reversible cross-linking group molar ratio of 1:1, mixed under stirring for 0.5 h, and then cast on a glass substrate. Cross-linked at 45 °C for 48 h to obtain a reversibly cross-linked resin.

[0066] 2. Characterization and testing

[0067] (1) 1 H NMR spectroscopy analysis

[0068] The measurements were performed using a 500 MHz ANANCE III NMR spectrometer (Bruker, Switzerland) with deuterated chloroform as the solvent and room temperature as the test temperature.

[0069] (2) Lap shear strength test

[0070] Standard lap shear specimens were prepared. The substrate dimensions and lap area were determined according to GB / T 7124-2008. Lap shear performance of the polyadhesive was tested using an electronic universal testing machine. The tensile rate was 5 mm / min and the test temperature was room temperature. Five specimens were tested per group, and the average value was calculated.

[0071] 3. Comparison and analysis of test results

[0072] Figure 2 A shows the acrylic acid maleimide prepared in step 1 of Example 1 1 The H NMR spectrum shows that the characteristic peaks together confirm that its structure is consistent with the expectation. Figure 2 B shows the hyperbranched polyethylene reversible crosslinker prepared in Example 1. 1 The H NMR spectrum shows peaks a–d corresponding to reversible crosslinking groups formed by copolymerization of acrylic maleimide and ethylene. Peaks corresponding to methyl, methylene, and methine hydrogen atoms in the hyperbranched polyethylene backbone can also be identified. Based on the characteristic peak areas, the grafting ratio of the reversible crosslinking groups is 0.6 mol%, and the branch density of the hyperbranched polyethylene backbone is 85 branches / 1000C. This confirms that the hyperbranched polyethylene reversible crosslinker can be successfully synthesized according to the method described in Step 1 of Example 1. Furthermore, Figure 2 C gives the linear reversibly cross-linked polymer obtained in Example 1 1 The H NMR spectrum confirmed that the polymer was composed of monomer styrene and reversible cross-linking monomer, wherein the proportion of reversible cross-linking monomer was 2 mol%. Figure 2 As shown by D, the reversibly cross-linked resin obtained in Example 1 exhibited a lap shear strength of 2.65 MPa on a glass substrate, while the sample obtained in Comparative Example 1 exhibited a lap shear strength of only 0.32 MPa. This is because the cross-linked resin in Example 1 is composed of hyperbranched polyethylene and a linear polymer, while the resin obtained in Comparative Example 1 is composed of a linear polymer and a small molecule cross-linker. Therefore, these results demonstrate that the process described in Example 1 can produce a hyperbranched, multi-arm, reversibly cross-linked resin with superior bonding properties.

[0073] Examples 2, 3, Comparative Example 2

[0074] 1. Sample preparation

[0075] (1) Example 2

[0076] Step 1: Prepare a linear reversibly cross-linked polymer by referring to the process described in Step 2 of Example 1; the only difference is that the initial molar ratio of the components is adjusted from [-Br]:[St]:[FMA]:[CuBr]:[PMDETA]=1:190:10:1:2 to [-Br]:[St]:[FMA]:[CuBr]:[PMDETA]=1:190:20:1:2.

[0077] Step 2: Prepare a hyperbranched multi-arm reversibly cross-linked resin by combining the hyperbranched polyethylene reversible cross-linker prepared in Example 1 with the linear reversibly cross-linked polymer obtained in Step 1 above, with reference to the process described in Step 3 of Example 1.

[0078] (2) Example 3

[0079] Step 1: Prepare a linear reversibly cross-linked polymer by referring to the process described in Step 2 of Example 1; the only difference is that the initial molar ratio of the components is adjusted from [-Br]:[St]:[FMA]:[CuBr]:[PMDETA]=1:190:10:1:2 to [-Br]:[St]:[FMA]:[CuBr]:[PMDETA]=1:190:30:1:2.

[0080] Step 2: Prepare a hyperbranched multi-arm reversibly cross-linked resin by combining the hyperbranched polyethylene reversible cross-linker prepared in Example 1 with the linear reversibly cross-linked polymer obtained in Step 1 above, with reference to the process described in Step 3 of Example 1.

[0081] (3) Comparative Example 2

[0082] The hyperbranched multi-arm reversibly cross-linked resin was prepared by steps 1-3 according to Example 1.

[0083] 2. Characterization and testing

[0084] (1) 1 H NMR spectroscopy analysis: refer to Example 1.

[0085] (2) Gel permeation chromatography (GPC) analysis

[0086] Analyses were performed on a 1525 / 2414 gel permeation chromatograph (Waters, USA) at 35°C with THF as the mobile phase, using PS as the standard. A small amount of polymer sample was dissolved in THF and filtered three times through a PTFE filter membrane (average pore size 0.2 µm) to a sample concentration of 2–5 mg / mL.

[0087] (3) Lap shear strength test: refer to Example 1.

[0088] 3. Comparison and analysis of test results

[0089] Figure 3 A shows the linear reversible cross-linked polymers obtained in Comparative Example 2 and Examples 2 and 3. 1 H NMR spectrum, Examples 2 and 3 are obtained on the basis of Comparative Example 2 only by changing the initial charging ratio of the reversible cross-linking monomer. As shown in the figure, although the initial charging ratio of each reaction component changes, the structure of the resulting polymer product remains consistent, and both are composed of ordinary monomer styrene and reversible cross-linking monomer, showing the characteristics of a linear reversible cross-linked polymer. It is inferred by the characteristic peak area in the spectrum that the proportion of the reversible cross-linking component in the resulting polymer product increases with the increase of the initial concentration of the reversible cross-linking monomer, respectively, from 0.20 mol% in Comparative Example 2 to 0.47 mol% in Example 2, and further to 0.99 mol% in Example 3. Figure 3 B shows the GPC elution curve of the sample. Each sample presents a regular single peak shape, indicating that the molecular weight distribution is narrow. Figure 3 Figure C compares the lap shear strength of Examples 2 and 3 with that of Comparative Example 2. As shown in the figure, increasing the proportion of reversibly crosslinked components in the system significantly increases the lap shear strength of the resulting samples. These results demonstrate that adjusting the proportion of reversibly crosslinked components within the linear reversibly crosslinked polymer structure can effectively adjust the interfacial adhesion properties of the resulting hyperbranched multi-arm reversibly crosslinked resin.

[0090] Example 4, Comparative Example 3

[0091] 1. Sample preparation

[0092] (1) Example 4

[0093] Step 1: Prepare a hyperbranched multi-arm reversibly cross-linked resin by referring to steps 1-3 of Example 1.

[0094] Step 2: Weigh 120 mg of the sample obtained in step 1 above and place it in an oven at 130°C for decrosslinking treatment for 0.5 h. The obtained sample is dissolved in chloroform by stirring at room temperature for 0.5 h, then cast on a glass substrate and crosslinked at 40°C for 48 h to obtain a hyperbranched multi-arm reversibly cross-linked resin.

[0095] Step 3: Repeat the above steps 1 and 2 in sequence to obtain a reversible cross-linked resin after multiple recycling.

[0096] (2) Comparative Example 3

[0097] The hyperbranched multi-arm reversibly cross-linked resin was prepared by steps 1-3 according to Example 1.

[0098] 2. Characterization and testing

[0099] Lap shear strength test: carry out as in Example 1.

[0100] 3. Comparison and analysis of test results

[0101] Figure 4 Figure A illustrates the recycling process for the resulting hyperbranched, multi-arm, reversibly cross-linked resin. The sample is first dissolved and mixed in a solvent, then coated on a substrate. The solvent evaporates, and the test sample is reversibly cross-linked. Further heat treatment decouples the cross-linking to produce a new resin solution, and the process repeats. Figure 4 B compares the overlap stress-strain curves of the samples obtained in Comparative Example 3 and Example 4, wherein the sample in Example 4 is based on Comparative Example 3 and is subjected to Figure 4 The process shown in A is obtained by recycling 1-5 times. Figure 4 The lap shear strength of each sample is also given by C. As shown in the figure, the prepared hyperbranched multi-arm reversibly cross-linked resin exhibits excellent reversible cycling performance. After multiple cycles, its bonding performance is essentially similar to that of the original sample. These results demonstrate that the hyperbranched multi-arm reversibly cross-linked resin obtained in Example 4 has excellent recyclability.

[0102] Example 5, Comparative Examples 4-6

[0103] 1. Sample preparation

[0104] (1) Example 5

[0105] Step 1: Prepare a hyperbranched polyethylene reversible crosslinker according to step 1 of Example 1.

[0106] Step 2: Prepare a linear reversibly cross-linked polymer by referring to step 2 of Example 1, except that the comonomer styrene is changed to methyl methacrylate, and other process adjustments remain unchanged.

[0107] Step 3: Prepare a hyperbranched multi-arm reversibly cross-linked resin using the hyperbranched polyethylene reversible cross-linker obtained in step 1 and the linear reversibly cross-linked polymer obtained in step 2, referring to the process described in step 3 of Example 1.

[0108] (2) Comparative Examples 4–6

[0109] The method described in Example 5 is referred to for preparation, except that the substrate material used in step 3 is replaced by metal aluminum, plastic film (PC) and wood respectively instead of glass.

[0110] 2. Characterization and testing

[0111] Lap shear strength test: carry out as in Example 1.

[0112] 3. Comparison and analysis of test results

[0113] Figure 5 Figure A shows the adhesion performance of the reversibly cross-linked resin obtained in Example 5 on various substrate surfaces. As shown in the figure, the sample can exhibit certain adhesion performance on surfaces such as glass, rubber, steel, aluminum sheets, various plastic materials, and ceramics. Figure 5 B compared the adhesion performance of this sample on glass (corresponding to Example 5), aluminum (corresponding to Comparative Example 4), plastic film (PC, corresponding to Comparative Example 5), and wood (corresponding to Comparative Example 6). As shown in the figure, this sample exhibited good adhesion to all of these different substrates, with glass and PC showing superior performance. These results demonstrate that hyperbranched multi-arm reversibly cross-linked resins can be prepared using other common monomers in accordance with the method described herein, exhibiting excellent adhesion to a variety of surfaces.

[0114] Example 6, Comparative Examples 7-10

[0115] 1. Sample preparation

[0116] (1) Example 6

[0117] Step 1: Prepare a hyperbranched polyethylene reversible crosslinker according to step 1 of Example 1.

[0118] Step 2: Prepare a linear reversibly cross-linked polymer by referring to step 2 of Example 1, except that the comonomer styrene is changed to trifluoroethyl acrylate, and other process adjustments remain unchanged.

[0119] Step 3: Prepare a hyperbranched multi-arm reversibly cross-linked resin using the hyperbranched polyethylene reversible cross-linker obtained in step 1 and the linear reversibly cross-linked polymer obtained in step 2, referring to the process described in step 3 of Example 1.

[0120] (2) Comparative Examples 7–10

[0121] The resin was prepared according to the method described in Example 6, except that the resin was further treated in pH = 1 (hydrochloric acid solution, Comparative Example 7), 0.1 M Na2SO4 (Comparative Example 8), pH = 13 (NaOH solution, Comparative Example 9) and H2O medium (Comparative Example 10) for 24 hours to obtain samples.

[0122] 2. Characterization and testing

[0123] Lap shear strength test: carry out as in Example 1.

[0124] 3. Comparison and analysis of test results

[0125] Figure 6A compares the lap shear strength of the corresponding samples of Example 6 and Comparative Examples 7-10, wherein Comparative Examples 7-10 are samples obtained by treating the sample of Example 6 in various media. As shown in the figure, the corresponding samples of Example 6 still maintain certain bonding properties after being treated with different pH values or alkaline media, showing good bonding stability. For example, Figure 6 As shown in Figure B, after treatment in pH 1 and 13, the sample's lap shear strength retention rates reached 59.9% and 67.4%, respectively. After treatment in 0.1M Na₂SO₄, the retention rate reached 79.1%, and after treatment in water, the retention rate reached 84.7%. These results demonstrate that the described process can successfully produce a hyperbranched, multi-arm, reversibly cross-linked resin exhibiting excellent resistance to acid, alkali, and humidity.

Claims

1. A method for preparing a hyperbranched multi-arm reversibly cross-linked resin, characterized in that: The preparation method comprises the following steps: In the first step, ethylene and a reversible crosslinking functional monomer A are copolymerized using an α-diimide palladium catalyst based on a "chain walking" mechanism to obtain a hyperbranched polyethylene reversible crosslinker; the reversible crosslinking functional monomer A is an acrylic acid maleimide represented by formula I, and its structure is shown below: I Step 2: Using 2-bromoisobutyryl bromide as shown in Formula III as an initiator, and common monomers and reversibly crosslinking functional monomer B as comonomers, a linear reversibly crosslinked polymer is synthesized by atom transfer radical polymerization; the common monomer is selected from the following: styrene, methyl methacrylate, methyl acrylate, butyl acrylate, trifluoroethyl acrylate, and ethyl methacrylate; the reversibly crosslinking functional monomer B is furfuryl methacrylate as shown in Formula IV; In the third step, the hyperbranched polyethylene reversible crosslinking agent and the linear reversible crosslinking polymer are crosslinked in a solvent to obtain a hyperbranched multi-arm reversible crosslinking resin.

2. The preparation method according to claim 1, wherein: The α-diimine palladium catalyst is the following α-diimine palladium catalyst 1 or 2: .

3. The preparation method according to claim 1 or 2, wherein: The first step is specifically carried out as follows: under the protection of an ethylene atmosphere, an anhydrous solvent, acrylic acid maleimide and an α-diimide palladium catalyst are added to a reaction vessel, fully stirred and reacted for 2-48 hours under the conditions of controlling the temperature at 5-30°C and the ethylene pressure at 0.01-0.5MPa, and then separating and purifying to obtain a hyperbranched polyethylene reversible crosslinker.

4. The preparation method according to claim 3, wherein: In step 1, the anhydrous solvent is one of the following anhydrous solvents: dichloromethane, chloroform, and chlorobenzene; the initial charging concentration of the reversible crosslinking functional monomer A is 0.1-2.0 mol / L based on the total volume of the anhydrous solvent; the initial concentration of the α-diimine palladium catalyst is 0.5-50 g / L based on the total volume of the anhydrous solvent; the copolymerization reaction temperature is controlled at 15-25°C; the ethylene pressure is controlled at 0.05-0.1 MPa; and the reaction time is controlled at 12-24 h.

5. The preparation method according to claim 1, wherein: The second step is specifically implemented as follows: Under nitrogen protection, 2-bromoisobutyryl bromide is used as an initiator, furfuryl methacrylate and common monomers are used as comonomers, pentamethyldiethylenetriamine is used as a ligand, and CuBr is used as a catalyst. The reaction is carried out at 80-100 °C in an anhydrous organic solvent for 20-30 hours. After the polymerization is completed, a linear reversible cross-linked polymer is obtained through separation and purification.

6. The preparation method according to claim 5, wherein: In step 2, the anhydrous organic solvent is one of the following anhydrous organic solvents: toluene, cyclohexanone, and tetrahydrofuran; the molar ratio of the initiator, common monomer, reversible crosslinking functional monomer B, CuBr, and PMDETA is 1:1–300:1–50:0.5–5:0.5–10; and the initial concentration of the common monomer in the reaction system is 2.0–20 mol / L.

7. The preparation method according to claim 1, wherein: In the third step, the solvent is one of the following analytically pure or chemically pure reagents: THF, chloroform, toluene, petroleum ether, dichloromethane, and n-heptane; the mixing ratio of the hyperbranched polyethylene reversible crosslinker and the linear reversibly crosslinked polymer is measured according to the molar ratio of the reversibly crosslinked functional groups contained in each, and the ratio is controlled within a range of 1:0.5-1:

5.

8. The preparation method according to claim 1, wherein: In the third step, the temperature of the cross-linking reaction is controlled at 30-90°C; and the cross-linking reaction time is 12-96 h.

9. A hyperbranched multi-arm reversibly cross-linked resin prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the hyperbranched multi-arm reversibly cross-linked resin as claimed in claim 9 as an adhesive.

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