High performance, high heterotactic poly(methyl methacrylate) and method of making same

Abstract

This invention discloses a high-performance, high-heterodactyl polymethyl methacrylate and its preparation method. The polymethyl methacrylate is heterodiky, with a heterodiodine sequence content of [missing information]. mr With a purity >99%, a melting point as high as 228℃, and an ultimate tensile strength of 99.1 MPa, its thermal stability and mechanical properties are significantly improved compared to traditional isotactic, syndiotactic, and atactic PMMA. Its preparation method utilizes a neutral semi-sandwich Lu complex and its cationic counterpart Lu. + The synergistic catalytic system initiates MMA polymerization at room temperature under inert gas protection conditions, via neutral Lu sites and cationic Lu. + The synergistic effect of the sites enables the reaction of MMA and cationic Lu at room temperature. + Alternating chain growth of activated MMA. The reaction conditions of this invention are mild and the operation is simple, overcoming the bottleneck of low stereoselectivity of heterotypical PMMA in the prior art. The high-performance heterotypical PMMA prepared can be widely used in high-end fields such as aerospace and precision electronics.

Description

Technical Field

[0001] This invention belongs to the field of polymer synthesis technology, specifically relating to a method for preparing polymethyl methacrylate (PMMA), and more particularly to a polymethyl methacrylate with high heterotacticity, excellent thermal and mechanical properties, and its preparation method. Background Technology

[0002] Polymethyl methacrylate (PMMA), commonly known as plexiglass, is widely used in industrial fields due to its excellent optical transparency, superior insulation properties, and good processing characteristics. The stereoregularity of PMMA plays a decisive role in its mechanical, thermal, and optical properties, thus affecting its applicability in different application scenarios.

[0003] The stereoregularity of PMMA is mainly determined by the stereoselectivity of chain growth of methyl methacrylate (MMA) monomers during polymerization. Based on the arrangement of methyl groups on both sides of the main chain plane, it can be divided into four types: isotactic, syndiotactic, atactic, and heterootactic. Among them, heterootactic PMMA, due to the unique conformation formed by the alternating arrangement of methyl groups in the molecular chain, theoretically possesses superior crystallinity, thermal stability, and mechanical strength, and is expected to break through the performance limits of traditional PMMA.

[0004] However, achieving high heterotactic selectivity in MMA polymerization has always been a core challenge in the field of polymer synthesis. Current technologies for preparing PMMA mainly include radical polymerization, anionic polymerization, group transfer polymerization, and early transition metal-catalyzed coordination addition polymerization. Radical and ionic polymerization techniques can prepare highly isotactic or syndiotactic PMMA, but these methods typically require extremely low temperatures (<-78℃). Pre-transition metal catalysts can mediate MMA polymerization in a more practical temperature range to obtain highly stereoregular PMMA, but due to limitations imposed by ligand structure and catalytic mechanism, it is difficult to precisely control the stereoregular arrangement during chain growth, resulting in PMMA with a heterotacticity typically below 70%, failing to fully utilize the performance advantages of heterotactic structures.

[0005] In recent years, researchers have attempted to improve the stereoregularity of PMMA by optimizing the ligand structure of catalytic systems and controlling polymerization reaction conditions. For example, rare earth metal complexes have been used as catalysts, utilizing the unique coordination ability of rare earth metal ions to regulate the stereoselectivity of chain growth. However, existing rare earth catalytic systems mostly focus on the preparation of isotactic or syndiotactic PMMA, with few reports on highly selective catalytic systems for heterotactic PMMA. Furthermore, existing systems often suffer from low catalytic activity, complex reaction conditions, and insufficient heterotactic regularity of the products. In addition, the mechanisms for regulating the stereoselectivity of PMMA in current technologies are insufficient, making it difficult to guide the design and optimization of catalytic systems at the molecular level, further restricting the development and application of highly heterotactic and high-performance PMMA.

[0006] Therefore, developing a method for highly selective polymerization of MMA under mild conditions to prepare PMMA with both high heterotactic structure and excellent thermal and mechanical properties, while elucidating its stereoregulation mechanism, is of significant theoretical and practical value for overcoming existing technological bottlenecks and expanding the high-end application scenarios of PMMA materials. Based on this, this invention proposes a novel synergistic catalytic system and a bimetallic chain growth strategy to address the problems of low stereoselectivity, poor product performance, and harsh reaction conditions in the preparation of heterotactic PMMA in existing technologies. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing technologies in the preparation of heterotypical PMMA, such as low stereoselectivity, insufficient product performance, harsh reaction conditions, and unclear catalytic mechanisms, and to provide a high-performance, highly heterotypical polymethyl methacrylate (PMMA) and its preparation method. By constructing a novel synergistic catalytic system and an innovative chain growth strategy, highly stereoselective polymerization of MMA is achieved under mild conditions, preparing heterotypical PMMA with a heterotacticity greater than 99% and both high melting point and excellent mechanical strength. Simultaneously, the selectivity regulation mechanism is elucidated, laying the foundation for the industrial application of high-performance PMMA materials.

[0008] The present invention solves the above-mentioned technical problems through the following technical means: The first aspect of the present invention provides a synergistic catalytic system for the preparation of highly heteroregulated polymethyl methacrylate, wherein the catalyst is composed of a neutral semi-sandwich rare earth complex and its cationic counterpart. The neutral semi-sandwich rare earth complex includes CP LnBn2, CPLnBn2 and CP TMS One of LnBn2, with the following structural formula:

[0009] Ln-1 corresponds to CP LnBn2 and Ln-2 correspond to CPLnBn2, while Ln-3 corresponds to CP. TMS LnBn2 Ln = Sc, Y, La, Gd or Lu A second aspect of this invention provides a method for preparing high heterotactic, high-performance polymethyl methacrylate (MMA). This method employs a synergistic catalytic system to initiate the polymerization reaction of MMA monomers. The synergistic catalytic system consists of a neutral semi-sandwich rare earth complex and its cationic counterpart. The specific preparation steps are as follows: (1) Preparation of catalytic system: In an inert gas atmosphere, a neutral semi-sandwich rare earth complex and a co-catalyst are mixed in a certain proportion, a small amount of anhydrous organic solvent is added to dissolve them completely, and after stirring evenly, a synergistic catalytic system is obtained. This synergistic catalytic system is the catalyst. (2) Polymerization reaction: MMA monomers were anhydrous and purified, and then added to the above-mentioned synergistic catalytic system for polymerization reaction under normal temperature and inert gas protection conditions; (3) Post-processing of product: After the polymerization reaction is completed, the system is exposed to air and the reaction is quenched by injecting methanol. Then the polymer is redissolved in dichloromethane, the reaction solution is poured into a large amount of methanol to precipitate, the solid product is collected by filtration, and after washing and vacuum drying, high heterotactic, high performance polymethyl methacrylate is obtained.

[0010] Preferably, the inert gas is nitrogen or argon, used to isolate air and moisture, and to avoid affecting the activity of the catalytic system.

[0011] Preferably, the anhydrous organic solvent is selected from one or more of anhydrous toluene, anhydrous dichloromethane, and anhydrous tetrahydrofuran. The preferred amount is 0.5 mL to 5 mL.

[0012] Preferably, the co-catalyst comprises B(C6F5)3, [Ph3C][B(C6F5)4], [PhNHMe2][B(C6F5)4], and Al. i One of Bu3.

[0013]

[0014] Preferably, in step (1), the neutral semi-sandwich rare earth complex and the co-catalyst are mixed in a certain proportion to obtain a synergistic catalytic system of neutral semi-sandwich rare earth complex and cationic semi-sandwich rare earth complex, wherein the molar ratio of neutral semi-sandwich rare earth complex to cationic semi-sandwich rare earth complex is 1:0~1:19; and the molar ratio of neutral semi-sandwich rare earth complex to co-catalyst is 1:0~1:1.

[0015] Preferably, the molar ratio of the MMA monomer to the catalyst is 100:1 to 500:1.

[0016] Preferably, the polymerization reaction temperature is 25±5℃ and the reaction time is 0.5~24 h.

[0017] The stereoselectivity of polymethyl methacrylate prepared by the above method includes the following four categories:

[0018] Among them, MMA and cationic Lu are alternately performed at neutral Lu sites. +By activating chain growth in MMA, this system yielded PMMA with unprecedented heteroregularity (mr > 99%) at room temperature, with the following structural formula:

[0019] This invention utilizes neutral Lu sites and cationic Lu + The synergistic effect of the sites enables MMA and cation Lu to interact. + Alternating chain growth of activated MMA enabled the formation of an unprecedentedly high heterotactic PMMA. DFT calculations confirmed the cis-selective coordination insertion of free MMA into the neutral Lu catalyst with cationic Lu. + The alternating intermolecular addition of isomers to activated MMA can generate PMMA with a high heteroregular (mr>99%) microstructure.

[0020] A third aspect of this invention discloses a high-performance, highly heterodioretic polymethyl methacrylate prepared by the above-described method, and its application in the preparation of high-temperature resistant, high-strength materials.

[0021] The advantages and beneficial effects of this invention are as follows: 1. This invention utilizes neutral Lu sites and cationic Lu + The synergistic effect of the sites enables the reaction of MMA and cationic Lu at room temperature. + Alternating chain growth of activated MMA enabled the formation of unprecedentedly high heterodyne PMMA (mr>99%).

[0022] 2. The polymerization reaction of this invention can be carried out at room temperature without the need for harsh conditions such as low temperature and high pressure. It is simple to operate and has low energy consumption. Compared with existing technologies such as anionic polymerization, it is more suitable for large-scale industrial production.

[0023] 3. The high heterotactic PMMA prepared by this invention has a high heterotactic structure that gives PMMA better crystallization performance and molecular chain stacking efficiency. Its melting point is as high as 228℃, and its thermal stability is significantly improved compared with traditional isotactic and syndiotactic PMMA. Its ultimate tensile strength reaches 99.1 MPa, and its mechanical strength far exceeds that of existing PMMA materials, which can meet the needs of high-end fields for high-temperature resistant and high-strength materials.

[0024] 4. This invention elucidates, through DFT calculations, the cis-selective coordination insertion of free MMA into a neutral Lu catalyst and the interaction of cationic Lu. + The alternating intermolecular addition of isomerically selective activated MMA elucidates the mechanism of stereoselectivity regulation, providing theoretical guidance for the optimization of subsequent catalytic systems and the design of high-performance heterotactic polymer materials.

[0025] 5. The high heterotactic, high-performance PMMA prepared by this invention significantly improves thermal and mechanical properties while maintaining the excellent light transmittance and weather resistance of PMMA. It can be widely used in high-end fields such as aerospace components, precision electronic packaging materials, high-end optical devices, and high-temperature resistant automotive parts, thus expanding the application boundaries of PMMA materials. Attached Figure Description

[0026] Figure 1 The above is the hydrogen nuclear magnetic resonance spectrum of a high heterotypical PMMA (mr>99%) in Example 10 of this invention.

[0027] Figure 2 This is the carbon NMR spectrum of a high heterodox PMMA (mr>99%) in Example 10 of the present invention.

[0028] Figure 3 The room temperature mechanical properties of the high heterotypical PMMA (mr>99%) prepared in Example 10 of this invention.

[0029] Figure 4 The high-temperature mechanical properties of the high heterotypical PMMA (mr>99%) prepared in Example 10 of this invention are shown in the figure.

[0030] Figure 5 The DSC test pattern of the high heterorgence PMMA (mr>99%) prepared in Example 10 of the present invention.

[0031] Figure 6 The TGA test images of high heterorgence PMMA (mr>99%) prepared in Example 10 of the present invention are shown, where (a) is under a nitrogen atmosphere and (b) is in air.

[0032] Figure 7 The XRD pattern of the high heterorgence PMMA (mr>99%) prepared in Example 10 of this invention.

[0033] Figure 8 This is a flowchart of a method for preparing high heterotactic, high-performance polymethyl methacrylate proposed in this invention.

[0034] In the above figures, it-PMMA is isochronous PMMA, st-PMMA is interstitial PMMA, and ht-PMMA is miscellaneous PMMA. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] The present invention does not limit the source of the above-mentioned compounds. They can be commercially available or monomers that can be prepared by simple methods. The present invention does not limit the source of the compounds.

[0037] Preparation of neutral Lu catalysts: (1) Lu(CH2C6H4NMe2- o The preparation process of )3 is as follows:

[0038] Anhydrous LuCl3 (2.251 g, 8 mmol) was weighed into a 100 mL round-bottom flask and dissolved in 20 mL of tetrahydrofuran. LiCH2C6H4NMe2-o (2.287 g, 24 mmol) was weighed into a sample vial and dissolved in 20 mL of tetrahydrofuran, then slowly added dropwise to the round-bottom flask. After stirring at room temperature for 30 minutes, the solvent was removed by evaporation under reduced pressure. The residue was dissolved in 30 mL of toluene and filtered to remove the lithium salt. The filtrate was concentrated and recrystallized at -30 °C to obtain yellow crystalline Lu(CH2C6H4NMe2-o)3 (3.234 g, 70% yield).

[0039] (2) (C5Me5)Lu(CH2C6H4NMe2- o The preparation process of )2 is as follows:

[0040] Weigh the Lu(CH2C6H4NMe2-) prepared in Example 1 into the glove box. o 0.866 g (1.5 mmol) was dissolved in 10 mL of tetrahydrofuran in a 50 mL pressure-resistant flask. Then, 0.204 mg (1.5 mmol) of pentamethylcyclopentadiene was weighed, dissolved in 5 mL of tetrahydrofuran, and slowly added dropwise to the pressure-resistant flask. The stopper was tightened, and the flask was taken out of the glove box and heated in a 70ºC oil bath for 12 hours. After cooling to room temperature, the solvent was removed under reduced pressure in a glove box. The residue was washed with diethyl ether and dissolved in toluene. The solution was concentrated and cooled to -30 °C to give yellow crystals (0.494 g, yield 57%).

[0041] Example 1: A method for preparing polymethyl methacrylate includes the following steps: In an inert gas atmosphere, the prepared semi-sandwich (C5Me5)Lu(CH2C6H4NMe2- o )2. The complex was dissolved in 2 mL of anhydrous toluene and stirred until homogeneous to obtain a synergistic catalytic system (the molar ratio of the neutral semi-sandwich rare earth complex to the cationic semi-sandwich rare earth complex was 1:0, i.e., [Ln] / [Ln] + The ratio of the monomers in the reaction mixture was 1:0. The MMA monomers, after anhydrous purification (distillation after stirring with calcium hydride), were added to the aforementioned synergistic catalytic system, and polymerization was carried out at room temperature. After polymerization, the system was exposed to air and the reaction was quenched by injecting 5 mL of methanol. The polymer was then redissolved in dichloromethane, and the reaction solution was poured into a large amount of methanol to precipitate the product. The solid product was collected by filtration, washed, and vacuum dried to obtain polymethyl methacrylate (PMMA). PMMA Sample 1 was then obtained.

[0042] Example 2: The difference between this embodiment and Embodiment 1 is that [Ln] / [Ln] is used. + ]=1:0 changed to [Ln] / [Ln + The ratio of polymethyl methacrylate to polymethyl methacrylate (PMMA) was 0:1, and the other steps were the same as in Example 1. The resulting PMMA is Sample 2.

[0043] Example 3: The difference between this embodiment and Embodiment 1 is that [Ln] / [Ln] is used. + ]=1:0 changed to [Ln] / [Ln + The ratio of polymethyl methacrylate to polymethyl methacrylate (PMMA) was 1:1, and the other steps were the same as in Example 1. The resulting PMMA was Sample 3.

[0044] Example 4: The difference between this embodiment and Embodiment 1 is that [Ln] / [Ln] is used. + ]=1:0 changed to [Ln] / [Ln + The ratio of polymethyl methacrylate to polymethyl methacrylate (PMMA) was 4:1, and the other steps were the same as in Example 1. The resulting PMMA was Sample 4.

[0045] Example 5: The difference between this embodiment and Embodiment 1 is that [Ln] / [Ln] is used. + ]=1:0 changed to [Ln] / [Ln + The ratio of polymethyl methacrylate to polymethyl methacrylate (PMMA) was 2:1, and the other steps were the same as in Example 1. The obtained PMMA is Sample 5.

[0046] Example 6: The difference between this embodiment and Embodiment 1 is that [Ln] / [Ln] is used. + ]=1:0 changed to [Ln] / [Ln + The ratio of polymethyl methacrylate to polymethyl methacrylate (PMMA) was 1:2, and the other steps were the same as in Example 1. The resulting PMMA was Sample 6.

[0047] Example 7: The difference between this embodiment and Embodiment 1 is that [Ln] / [Ln] is used. + ]=1:0 changed to [Ln] / [Ln + The ratio of polymethyl methacrylate to polymethyl methacrylate (PMMA) was 1:5, and the other steps were the same as in Example 1. The resulting PMMA was Sample 7.

[0048] Example 8: The difference between this embodiment and Embodiment 1 is that [Ln] / [Ln] is used. + ]=1:0 changed to [Ln] / [Ln + The ratio of polymethyl methacrylate to polymethyl methacrylate (PMMA) was 1:10, and the other steps were the same as in Example 1. The resulting PMMA was Sample 8.

[0049] Example 9: The difference between this embodiment and Embodiment 1 is that [Ln] / [Ln] is used. + ]=1:0 changed to [Ln] / [Ln + The ratio was 1:19, and other steps were the same as in Example 1. The resulting polymethyl methacrylate was Sample 9. mr >99%.

[0050] Example 10: The difference between this embodiment and Example 9 is that the total volume of toluene is changed from 2 mL to 0.5 mL; the other steps are the same as in Example 9. The resulting polymethyl methacrylate is Sample 10. mr >99%.

[0051] Figure 1 The above is the hydrogen nuclear magnetic resonance spectrum of a high heterotypical PMMA (mr>99%) in Example 10 of this invention.

[0052] Figure 2 This is the carbon NMR spectrum of a high heterodox PMMA (mr>99%) in Example 10 of the present invention.

[0053] The stereoselectivity, glass transition temperature, melting point, and other parameters of the polymethyl methacrylate (PMMA) samples 1-10 prepared in Examples 1-10 are shown in Table 1 below: Table 1: MMA polymerization reaction catalyzed by semi-layered rare earth catalysts a

[0054] In the toluene system, when the monomer to catalyst feed ratio [MMA] / [Ln] = 100 / 1, the Lu complex exhibits high activity at room temperature, with a conversion rate exceeding 95% within 30 minutes (Table 1, Sample 1). The resulting polymer has a high molecular weight (Mn = 38 kDa) and rr =73%. When 1 equivalent of [Ph3C][B(C6F5)4] is present, its cationic rare earth catalyst Cp Lu + The MMA polymerization reaction could not be initiated. Therefore, we further investigated the performance of the combination of neutral and cationic rare earth catalysts in the MMA polymerization reaction. In the toluene system, when [Lu] / [Lu] + ] = 1 / 1 and [Ln tol When [[MMA]] = 1 / 100, high molecular weight polymethyl acrylate (Mn = 116 kDa) can be generated at room temperature. = 1.70, Table 1, Sample 3). Notably, the stereoregularity of the polymer changed from moderate syndiotactic (mm: mr: rr = 2: 25: 73) to moderate heterodiotactic (mm: mr: rr = 3: 57: 40), a change caused by the neutral catalyst Lu and the neutral / cationic bicomponent catalyst Lu-Lu, respectively. + Implementation. By [Ln] / [Ln] + When the ratio was adjusted from 1:0 to 4:1, 2:1, 1:1, 1:2, 1:5, 1:10, and 1:19, the molecular weight of PMMA significantly increased from 38 kDa to 187 kDa, while maintaining a stable molecular weight distribution. = 1.4–1.7); meanwhile, the heterorgence regularity (mr) also gradually increased from 25% to 99% (Table 1, Sample 3–9). When the solvent volume was reduced to 0.5 mL, a PMMA yield of 91% could be obtained within 10 minutes, and the polymer still maintained high molecular weight and perfect heterorgence regularity (Mn = 202 kDa, mr>99%, Table 1, Sample 10).

[0055] Example 11: Room temperature mechanical testing of high-performance, highly heterodioretic polymethyl methacrylate materials According to the standard test method ASTM 638, dumbbell-shaped specimens with a length of 28 mm, a width of 2 mm (at the narrowest point), and a thickness of 1 mm were used. Stress-strain tests were conducted at room temperature at a speed of 10 mm / min, and at least three specimens of each type were tested.

[0056] Specific test results are as follows: Figure 3As shown.

[0057] from Figure 3 As can be seen, stress-strain curves were obtained after tensile testing of dumbbell-shaped polymethyl methacrylate (PMMA) specimens with different stereoregularities. The results show that the ultimate tensile strength (σ0) of isotactic and heteroregular PMMA differs. B =90.9±0.2 MPa; heterogeneous PMMA: σ B =5 99.1±0.2 MPa) was significantly higher than that of the synergistic (σ B =25.8±0.3 MPa) and random (σ B =14.9±0.1 MPa). As a glassy material, heterotactic PMMA has an elongation at break (ε =9.5±1.2%) that is about 50% higher than that of isotactic PMMA (6.2±0.8%).

[0058] Example 12: High-Temperature Mechanical Testing of High-Performance, High-Hyperregularity Polymethyl Methacrylate Materials According to the standard test method ASTM 638, dumbbell-shaped specimens with a length of 28 mm, a width of 2 mm (at the narrowest point), and a thickness of 1 mm were used. Stress-strain tests were conducted at room temperature at a speed of 10 mm / min, and at least three specimens of each type were tested.

[0059] Specific test results are as follows: Figure 4 As shown.

[0060] from Figure 4 As can be seen, the tensile strength of isotactic PMMA decreases sharply at 100℃ and 150℃ (σ B =7.6±0.2 MPa, 0.1±0.02 MPa), and exhibits stretchable plastic and viscoelastic behavior. In contrast, heterodox PMMA still maintains a higher ultimate tensile strength (σ = 7.6±0.2 MPa, 0.1±0.02 MPa). B =78.0±0.2 MPa, 35.3±0.6 MPa), which may be related to its higher glass transition temperature and melting point. Overall, heterotactic PMMA has better thermal and mechanical properties than isotactic and syndiotactic PMMA.

[0061] Example 13: Thermal testing of high-performance, highly heterodioretic polymethyl methacrylate materials Differential scanning calorimetry (DSC) was used to measure the samples using a Mettler Toledo DSC 3 instrument with a scan rate set at 10 °C / min and a nitrogen flow rate of 50 mL / min. Polymer samples were weighed (typically in the range of 3-5 mg) and then sealed in a sealed aluminum pan using a DSC press. Any thermal history differences between polymers were eliminated by first heating the sample to 260 °C at a rate of 10 °C / min, equilibrating at this temperature for 5 minutes, and then cooling it to 25 °C at a rate of 10 °C / min and holding it at this temperature for 5 minutes before performing a second DSC measurement.

[0062] The results are as follows Figure 5 As shown, from Figure 5 As can be seen, the prepared heterotactic PMMA exhibits an extremely high melting point of 228℃, which is significantly higher than that of isotactic PMMA. T m =160℃) and interstitial PMMA ( T m Its melting point is 164℃, even exceeding that of isotactic and syndiotactic PMMA stereocomposites. T m =217℃).

[0063] Example 14: Thermal testing of high-performance, highly heterodioretic polymethyl methacrylate materials Thermogravimetric analysis (TGA) was used to determine the thermal degradation temperatures of different stereoregular polymethyl methacrylates in nitrogen and air environments. T d The tests were conducted. In a nitrogen atmosphere, PMMA with different selectivities exhibited similar thermal stability. T d The value is approximately 306-337℃. Figure 6 (a)). Conversely, heterogeneous PMMA in the air T d The value (326℃) is significantly higher than that of isotactic, syndiotactic, and atactic PMMA (approximately 293℃), indicating that heterodactic PMMA possesses unique thermal stability against oxygen-mediated thermal degradation. Figure 6 (b) in the middle.

[0064] Example 15: XRD Testing of High-Performance, High-Hyperregularity Polymethyl Methacrylate Materials The X-ray powder diffraction pattern of this heterogeneous PMMA is as follows: Figure 7 As shown in the figure, the sample is at 2 θDiffraction peaks were observed at 8.0°, 14.2°, and 15.8°, which is consistent with the values ​​reported in the literature (Christofferson AJ, Yiapanis G, Ren JM, et al. Molecular mapping of poly (methylmethacrylate) super-helixstereocomplexes[J]. Chemical Science, 2015, 6(2): 1370-1378.).

[0065] Figure 8 This is a flowchart illustrating a method for preparing high heterotactic, high-performance polymethyl methacrylate (PMMA) proposed in this invention. This invention utilizes neutral Lu sites and cationic Lu... + The synergistic effect of the sites enables MMA and cation Lu to interact. + Alternating chain growth of activated MMA enabled the formation of an unprecedentedly high heterotactic PMMA. DFT calculations confirmed the cis-selective coordination insertion of free MMA into the neutral Lu catalyst with cationic Lu. + The alternating intermolecular addition of isomers to activated MMA can generate PMMA with a high heteroregular (mr>99%) microstructure.

[0066] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high heterotricar polymethyl methacrylate, characterized in that, The polymethyl methacrylate described is heterodioretic, and the heterodioretic sequence content is... mr >99%, the methyl groups in its molecular chain are arranged in an alternating conformation on both sides of the main chain plane; the high heteroregular polymethyl methacrylate is obtained by polymerizing MMA monomers through a synergistic catalytic system composed of a neutral semi-sandwich rare earth complex and its cationic counterpart.

2. The high heterotactic polymethyl methacrylate according to claim 1, characterized in that, The synergistic catalytic system is composed of a neutral semi-sandwich rare earth complex and its cationic counterpart; The neutral semi-sandwich rare earth complex includes CP LnBn2, CPLnBn2 and CP TMS One of LnBn2, with the following structural formula: Ln-1 corresponds to CP LnBn2, Ln-2 corresponds to CPLnBn2, Ln-3 corresponds to CP TMS LnBn2.

3. The method for preparing high heterotricar polymethyl methacrylate according to claim 1, characterized in that, The specific steps are as follows: (1) Preparation of catalytic system: In an inert gas atmosphere, the neutral semi-sandwich rare earth complex and the co-catalyst are mixed, dissolved in an anhydrous organic solvent, and stirred evenly to obtain a synergistic catalytic system; (2) Polymerization reaction: MMA monomers were anhydrous and purified, and then added to the above-mentioned synergistic catalytic system for polymerization reaction under normal temperature and inert gas protection conditions; (3) Post-processing of product: After the polymerization reaction is completed, the system is exposed to air and the reaction is quenched by injecting methanol. Then the polymer is redissolved in dichloromethane, the reaction solution is precipitated and filtered, the solid product is collected, and after washing and vacuum drying, high heterotactic polymethyl methacrylate is obtained.

4. The preparation method according to claim 3, characterized in that, In step (1), the inert gas is nitrogen or argon; the anhydrous organic solvent is selected from one or more of anhydrous toluene, anhydrous dichloromethane, and anhydrous tetrahydrofuran.

5. The preparation method according to claim 3, characterized in that, In step (1), the co-catalyst includes B(C6F5)3, [Ph3C][B(C6F5)4], [PhNHMe2][B(C6F5)4], and Al. i One of Bu3.

6. The preparation method according to claim 3, characterized in that, In step (1), the neutral semi-sandwich rare earth complex and the co-catalyst are mixed to obtain a synergistic catalytic system of neutral semi-sandwich rare earth complex and cationic semi-sandwich rare earth complex, wherein the molar ratio of neutral semi-sandwich rare earth complex to cationic semi-sandwich rare earth complex is 1:0~1:19; and the molar ratio of neutral semi-sandwich rare earth complex to co-catalyst is 1:0~1:

1.

7. The preparation method according to claim 3, characterized in that, In step (2), the molar ratio of the MMA monomer to the catalyst is 100:1 to 500:

1.

8. The preparation method according to claim 3, characterized in that, In step (2), the polymerization reaction temperature is 25±5℃ and the reaction time is 0.5~24 h.

9. The preparation method according to claim 3, characterized in that, The stereoselectivity of polymethyl methacrylate prepared by the method includes the following four categories: The preparation of heterodyne sequence content mr >99% high heterotricar polymethyl methacrylate, with the following structural formula: 。 10. The application of the high heterotactic polymethyl methacrylate of claim 1 in the preparation of high-temperature resistant and high-strength materials.

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