A method for preparing a bottlebrush polymer

Abstract

The application discloses a preparation method of bottle brush polymer, comprising the following steps: heating norbornene-terminated polyester macromonomer to a molten state, adding a ROMP catalyst under the condition of containing a ligand to initiate a ring-opening metathesis polymerization reaction, and obtaining the bottle brush polymer; wherein the ligand is used for adjusting the activity of the ROMP catalyst, the polymerization reaction is carried out in a bulk system, and the content of the organic solvent in the bulk system is less than 8 wt%; and the ligand is pyridine. By adding the ligand (such as pyridine) into the reaction system, the initial activity of the Grubbs catalyst (such as G3) is effectively controlled, the catalyst is uniformly dispersed in the melt, then the norbornene-terminated polyester macromonomer is smoothly and controllably subjected to bulk ring-opening metathesis polymerization (ROMP) in a molten state, and the large amount of organic solvent required in traditional solution polymerization and the subsequent cumbersome removal process are avoided.

Description

Technical Field

[0001] This invention relates to the field of bottle brush polymer preparation technology, and more particularly to a method for preparing a bottle brush polymer. Background Technology

[0002] Bottlebrush polymers (BBPs) are a class of special polymers with high-density side chains attached to their main chain. The dense arrangement of these side chains creates strong steric hindrance, causing the main chain to exhibit an extended conformation and effectively reducing chain entanglement, thus giving BBPs a unique cylindrical morphology. Based on its tunable morphology, abundant side chains, and end-group functions, BBPs show broad application prospects in drug carriers, lubricants, ultrasoft elastomers, and photonic crystals.

[0003] Despite their superior performance, synthesizing biopolymers (BBPs) with well-defined chain structures and precisely controllable molecular weight, grafting density, and molecular weight distribution remains challenging. BBP synthesis typically requires two different polymerization mechanisms to construct the side chains and main chain, resulting in complex processes and high organic solvent consumption. Among these, the "grafting-through method" based on ring-opening metathesis polymerization (ROMP) has become a commonly used strategy for BBP preparation due to its mild reaction conditions and good functional group tolerance. However, traditional ROMP grafting requires large amounts of organic solvent to dissolve macromonomers to achieve controlled polymerization; simultaneously, the catalyst concentration in ROMP processes is usually extremely low (below 0.1 mM), imposing stringent requirements on solvent and monomer purity. Furthermore, the high viscosity of BBP solutions makes subsequent solvent removal cumbersome and energy-intensive, limiting the large-scale preparation of BBPs and causing environmental problems. Residual solvents also affect the physical properties of BBPs. Therefore, developing bulk polymerization strategies that do not require organic solvents has become a crucial problem to be solved in this field.

[0004] Currently, there are few reports on the controllable preparation of BBP from ROMP using a grafting method under solvent-free conditions. Obtaining structurally well-defined BBPs through living polymerization requires overcoming several challenges: the high temperatures required for melting macromonomers accelerate polymerization kinetics; the dispersion of catalysts and macromonomers is limited in high-viscosity systems; and the polymerization rate is difficult to effectively control. Among these, good catalyst dispersion in the melt and precise control of the polymerization rate are crucial for the bulk synthesis of BBPs. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for preparing bottle-brush-like polymers.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect is to provide a method for preparing a bottle-brush-like polymer, comprising the following steps: The norbornene-terminated polyester macromonomer was heated to a molten state, and a ROMP catalyst was added under the condition of containing ligands to initiate a ring-opening metathesis polymerization reaction to prepare the bottle brush polymer. The ligand is used to adjust the activity of the ROMP catalyst, the polymerization reaction is carried out in a bulk system, and the content of organic solvent in the bulk system is less than 8 wt%; the ligand is pyridine.

[0007] Furthermore, the ROMP catalyst is Grubbs' third-generation catalyst G3.

[0008] Furthermore, the norbornene-terminated polyester macromonomer is selected from one or more of norbornene-terminated polycaprolactone and norbornene-terminated poly(5-hydroxyoctanoic acid lactone).

[0009] Furthermore, the molar ratio of the ligand to the ROMP catalyst is (5-15):1.

[0010] Furthermore, the molar ratio of the ligand to the ROMP catalyst is 10:1.

[0011] Furthermore, the polymerization reaction is carried out at a temperature of 70-80°C.

[0012] Furthermore, when the polymerization reaction is carried out in a system without added organic solvent, the preparation method further includes: pre-dispersing the ligand and the ROMP catalyst in a dispersant before adding the ROMP catalyst; the dispersant is a polymer with a glass transition temperature below room temperature.

[0013] Furthermore, the polymer with a glass transition temperature below room temperature is benzyl alcohol-terminated poly(5-hydroxyoctanoic acid lactone).

[0014] Furthermore, the preparation method further includes adding the polymer to a second norbornene-terminated polyester macromonomer after the first polymerization stage of the ring-opening metathesis polymerization reaction is completed, and continuing the reaction to prepare a block bottle brush copolymer.

[0015] The second aspect is to provide a bottle-brush-like polymer, prepared by the above-described preparation method.

[0016] The present invention adopts the above technical solution and has the following technical effects compared with the prior art: This invention effectively regulates the initial activity of Grubbs catalysts (such as G3) by adding ligands (such as pyridine) to the reaction system, enabling the catalyst to be uniformly dispersed in the melt. This allows the norbornene-terminated polyester macromonomers to undergo stable and controllable bulk ring-opening metathesis polymerization (ROMP) in the molten state, avoiding the large amount of organic solvents and their subsequent cumbersome removal process required by traditional solution polymerization.

[0017] The bottle brush polymer (BBP) obtained by this invention has a molecular weight distribution index (Ð) as low as below 1.2, and the molecular weight can be effectively controlled by the monomer-to-catalyst feed ratio (target degree of polymerization). This method successfully realizes the preparation of block bottle brush copolymers, demonstrating the active / controllable characteristics of the polymerization process. Attached Figure Description

[0018] Figure 1 The macromonomer prepared in Example 1 1 H NMR spectra, of which (a) NBE-PCL 3.4k (b) NBE-PCL 4.2k (c) NBE-PCL 8.6k (d) NBE-PCL 11.0k (e) NBE-PCL 21.3k (f) NBE-POL 6.7k (g) NBE-PLA 3.3k .

[0019] Figure 2 SEC curves of various macromonomers prepared in Example 1; wherein, (a) NBE-PCL; (b) NBE-POL 6.7k (c) NBE-PLA 3.3k .

[0020] Figure 3 The structures of different Grubbs catalysts (a), and the NBE-PCL catalysts catalyzed by (b) G3, (c) G2 and (d) HG-2. 3.4k (DP=100) Perform the SEC curve of BBP obtained from the ontology ROMP.

[0021] Figure 4 For NBE-PCL 3.4k SEC curves of bottle brush polymers prepared by ROMP in DCM solution at a target DP=100.

[0022] Figure 5 BBP obtained for the main body ROMP 1 H NMR spectra, of which (a) NBE-PCL 3.4k , DP=100; (b) NBE-POL6.7k DP=100; (c) NBE-PLA 3.3k DP=50.

[0023] Figure 6 Where, (a) is NBE-PCL 3.4k SEC curves of BBP synthesized under different pyridine equivalents during ROMP under bulk conditions (target DP=100, T=75°C); (b) NBE-PCL 3.4k (c) SEC curves of ROMP under bulk conditions with different target DPs, with or without pyridine; (d) Comparison of Ð in bulk ROMP of different macromonomers; (e) NBE-PCL with target DP=100 monitored by in-situ rheological monitoring. 3.4k Ontology ROMP process.

[0024] Figure 7 The SEC plots are shown for the BBP corresponding to the bulk ROMP of NBE-PCL macromonomers of various lengths under pyridine-containing conditions; where (a) NBE-PCL 8.6k (b) NBE-PCL 11.0k (c) NBE-PCL 21.3k .

[0025] Figure 8 The SEC diagrams are shown for the BBP corresponding to the bulk ROMP of NBE-PCL macromonomers of various lengths under pyridine-free conditions; where (ab)NBE-PCL 3.4k ;(cd)NBE-PCL 8.6k ;(ef)NBE-PCL 11.0k ;(gh)NBE-PCL 21.3k .

[0026] Figure 9 To achieve NBE-POL under the following conditions (75°C, DP=50) 6.7k SEC curves of bottle brush polymers prepared by ROMP under pyridine-free conditions.

[0027] Figure 10 This demonstrates NBE-POL with a target DP of 100 achieved via bulk ROMP at room temperature in the presence of pyridine. 6.7k Kinetic tracking of homopolymerization reaction; where (a) is the SEC curve as a function of time; (b) is the relationship between ln(1-p) and reaction time; and (c) is the evolution of Mn and Ð as a function of reaction time.

[0028] Figure 11 For NBE-PLA under different conditions 3.3kThe SEC curves of BBP obtained by bulk ROMP were obtained at DP of 50, with the reaction catalysts being (a) G2 and (b) HG-2.

[0029] Figure 12 For aggregation [(NBE-PCL) 3.4k )-b-(NBE-PCL 8.6k )]of 1 H NMR spectrum.

[0030] Figure 13 (a) is the SEC curve of the block BBP; (b) is the Poly[(NBE-PCL) curve. 3.4k )-b-(NBE-PCL 8.6k )]: First block (NBE-PCL 3.4k (DP=25) and the addition of a second block (NBE-PCL) 8.6k (a) is the SEC curve of the block BBP obtained after DP=20); (b) is Poly[(NBE-PCL 3.4k )-b-(NBE-POL 6.7k )]: First block (NBE-PCL 3.4k (DP=25) and the addition of a second block (NBE-POL) 6.7k The SEC curve of the block BBP obtained after DP=80; the reaction was carried out at 75°C.

[0031] Figure 14 The synthetic route for Bn-POL is shown.

[0032] Figure 15 Among them, (a) is the 1H NMR spectrum of Bn-POL; (b) is the SEC spectrum of BBP synthesized by solvent-free bulk polymerization; and (c) is the 1H NMR spectrum of BBP synthesized by solvent-free bulk polymerization.

[0033] Figure 16 In Example 4, (a) Schematic diagram of the reaction: using norbornene-terminated polycaprolactone (NBE-PCL) macromonomer as raw material, bottle brush polymer was prepared by ROMP polymerization initiated by different catalytic systems under bulk conditions of 75°C; (b) SEC curve: the molecular weight distribution of the products obtained under three different catalytic / dispersion conditions was compared.

[0034] Figure 17 Among them, (a) schematic diagram of the one-pot bulk synthesis route of PCL-type BBP; (b) molecular weight and conversion rate of the products obtained by one-pot bulk synthesis of PCL-type BBP under different DP conditions; (c, d) SEC curves of intermediate macromonomers and final products obtained when the target main chain DP is 50 (c) and 100 (d).

[0035] Figure 18 Among them, (a) the SEC curve of BBP prepared by reactive extrusion using a twin-screw extruder; and (b) the molecular weight and conversion rate of the obtained BBP. Detailed Implementation

[0036] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the invention. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other.

[0037] The main chemical reagents used in the following examples are shown in Table 1 below: Table 1

[0038] Literature [1]: Matson, JB; Grubbs, RH Synthesis of Fluorine-18Functionalized Nanoparticles for Use as in Vivo Molecular Imaging Agents. J.Am. Chem. Soc. 2008, 130 (21), 6731–6733. Literature [2]: Sanford, MS; Love, JA; Grubbs, RH A VersatilePrecursor for the Synthesis of New Ruthenium Olefin Metathesis Catalysts. Organometallics 2001, 20 (25), 5314–5318. Example 1 Synthesis of macromonomers This embodiment provides a method for preparing three polyester macromonomers for bulk ring-opening metathesis polymerization (ROMP): norbornene-terminated polycaprolactone (NBE-PCL), norbornene-terminated poly(5-hydroxyoctanoic acid lactone) (NBE-POL), and norbornene-terminated polylactic acid (NBE-PLA).

[0039] 1.1 Synthesis of NBE-PCL macromonomer With NBE-PCL 3.4kThe synthesis of [polymer name] is illustrated using an example. Distilled Cl (10.0 g, 87.7 mmol) was mixed with NBE-OH (603 mg, 2.9 mmol) and stirred until the NBE-OH was completely dissolved. Then, 125 μL of a stannous octoate toluene solution (containing 21 mg of stannous octoate in 150 μL of toluene) was added to the mixture to initiate ring-opening polymerization (ROP). The reaction was stirred at 130°C for 40 min, followed by cooling to room temperature. The resulting polymer was dissolved in DCM and precipitated three times with methanol. The product was then dried under vacuum for 12 h to obtain pure polymer (white powder, 8.8 g).

[0040] The synthesis process of other PCL macromonomers is the same, and their feed ratios and reaction conditions are listed in Table 2 below.

[0041] Table 2

[0042] 1.2 Synthesis of NBE-POL macromonomer NBE-POL 6.7k The synthesis involved mixing distilled OL (10 g, 70.4 mmol), NBE-OH (243 mg, 1.2 mmol), and 1-cyclohexyl-3-[4-(trifluoromethyl)phenyl]urea (U1, 672 mg, 2.3 mmol). After the solids were completely dissolved, tBuP2 solution (586 μL, 1.17 mmol) was added to the mixture. The reaction was stirred at room temperature for 3 min, quenched with acetic acid, and the product was precipitated three times with cold methanol. The product was then dried overnight under vacuum to give a transparent oily product in 71% yield.

[0043] 1.3 Synthesis of NBE-PLA macromonomer NBE-PLA 3.3k For the synthesis, recrystallized LA (4.0 g, 27.8 mmol) was dissolved in 28 mL of DCM, followed by the addition of NBE-OH (230 mg, 1.1 mmol) and then DBU (167.5 mg, 1.1 mmol). The reaction was terminated with acetic acid after stirring at room temperature for 2 minutes. The resulting polymer solution was concentrated, precipitated three times with methanol, and dried under vacuum overnight to obtain a white powder product in 91% yield.

[0044] 1.4 Characterization of macromonomers The corresponding macromonomers mentioned above 1 H NMR spectrum see Figure 1 See SEC curve Figure 2 The molecular weight characterization results are summarized in Table 3. (1H NMR spectrum) Figure 1The results show that the NBE functional group has been successfully attached to the macromonomer, and the calculated molecular weight of the macromonomer based on the spectrum is consistent with the theoretical value. (SEC results) Figure 2 As can be seen, all macromonomers exhibited a narrow molecular weight distribution, indicating that the target macromonomers have been successfully prepared.

[0045] Table 3

[0046] a This value is from 1 The H NMR spectrum was obtained through calculation. b This value was measured by the SEC.

[0047] Example 2: Controlled Bulk Ring-Opening Metastasis Polymerization (ROMP) Homopolymerization of Different Polyester Macromonomers This embodiment provides the preparation of brush polymers (BBPs) using the NBE-PCL, NBE-POL, and NBE-PLA series macromonomers prepared in Example 1 via the bulk ROMP method. The influence of ligand addition on polymerization controllability was investigated, and the universality of this method for polyester macromonomers with different chemical compositions was verified.

[0048] 2.1 Catalyst Screening For NBE-PCL 3.4k Solution polymerization of 40 mg NBE-PCL 3.4k Dissolved in 200 μL DCM, followed by the addition of 5.9 μL G3 solution (7.3 mg G3 dissolved in 1000 μL DCM). The reaction was quenched with EVE after 20 min. The purified product was then analyzed by SEC. For NBE-PCL... 3.4k Other catalysts were also tested in this embodiment, and the specific feeding conditions are shown in Table 4.

[0049] Table 4

[0050] Results Reference Figure 3 As shown in Table 5, all catalysts achieved high conversion rates (above 95%), compared to ROMP in solution ( Figure 4 The observed results were similar. However, even with G3 as the catalyst, the molecular weight distribution of bulk ROMP remained above 1.50, which is much wider than the molecular weight distribution of BBP obtained by ROMP in DCM solution. This may be attributed to the rapid initiation of chain growth processes under high-temperature conditions, before the catalyst is uniformly dispersed in the macromolecular monomer melt.

[0051] Table 5 Polymerization of NBE-PCL with Different Catalysts 3.4kCharacterization information of the product

[0052] a The additives are added in different equivalents relative to the catalyst. b M n and M w Determined by the SEC. c The conversion rate is calculated based on the integral area ratio of each peak in the SEC curve.

[0053] 2.2 Effect of Pyridine Addition on the Controllability of Bulk ROMP For the polymerization of NBE-PCL macromonomers, using NBE-PCL 8.6k The polymerization of macromonomers using a pyridine-containing G3 catalyst at DP=100 is illustrated using an example. 10 mg (13.8 μmol) of G3 and 10.9 mg (138 μmol) of pyridine were added to 200 μL of THF (THF organic solvent content is extremely low (0.6~8% wt), which will not affect the polymerization behavior of the macromonomer) to prepare a G3 / pyridine solution. For the control group polymerization reaction, pyridine was not added in this step, and all other reaction parameters remained consistent with the polymerization conditions in this section. NBE-PCL... 8.6k (450 mg, 52.3 μmol) was heated to 75°C and maintained for 15 min. Subsequently, 7.6 μL of G3 / pyridine solution was added to the PCL melt while the reaction system was mechanically stirred. After reacting for 30 min, the reaction was quenched by adding THF / EVE (v / v = 1:1). The product was precipitated with methanol, dried under vacuum, and samples were taken for further analysis. 1 ¹H NMR and SEC analyses. Bulk polymerization feed conditions for other NBE-PCL and NBE-POL macromonomers are shown in Table 6.

[0054] Table 6

[0055] Tables 7 and 8 summarize the molecular weight and conversion rate of each NBE-PCL and NBE-POL macromonomer bulk ROMP under conditions of adding pyridine and not adding pyridine.

[0056] Table 7. Molar mass and conversion rate of BBP obtained from bulk ROMP of NBE-PCL and NBE-POL macromonomers under G3 catalysis with pyridine additive.

[0057] Table 8. Molar mass and conversion rate of BBP obtained from the bulk ROMP of NBE-PCL macromonomers under G3 catalysis without pyridine addition.

[0058] Furthermore, the amount of pyridine used was optimized in this embodiment. For NBE-PCL 3.4k Different equivalents (relative to G3) of pyridine were added to the bulk ROMP. The results are as follows: Figure 6 As shown in (a), pyridine can be used to achieve NBE-PCL 3.4k The polymerization is controllable, and the molecular weight distribution gradually decreases with increasing pyridine dosage. Meanwhile, when the pyridine dosage exceeds ten times the equivalent of G3, Ð remains almost unchanged. Figure 6 As shown in (b), for NBE-PCL 3.4k The polymerization was carried out with and without pyridine (target DP = 50 and 100, respectively). The BBPs synthesized in the presence of pyridine exhibited a narrower dispersion, while the conversion and M... n The similarity remains. This indicates that adding pyridine allows for controlled polymerization without affecting the conversion rate of macromonomers.

[0059] The SEC curves of NBE-PCL macromonomers with different molecular weights and target DPs, polymerized under conditions with and without pyridine are shown in the figure. Figure 7-9 . Figure 6 (c) summarizes the different side chains M n Polymerization of NBE-PCL macromonomers with target DP and DP values. In all cases, polymerization with the addition of pyridine achieved a narrower molecular weight distribution. Notably, the viscosity of the reaction system increases with the increase of side chains and target DP, making polymerization more difficult. Even for M n Even with a large monomer with a value of 21.3 kDa, the reaction can still maintain controllable behavior (Ð = 1.39).

[0060] In addition, this embodiment also used in-situ rheological monitoring of the polymerization process: 300 mg (88.2 μmol) of NBE-PCL was used. 3.4k The sample was pressed into discs with a diameter of 20 mm and a thickness of 1 mm. The reaction was carried out at 75°C. After melting, the sample was subjected to oscillatory rheological testing at a strain of 1% and a frequency of 1 Hz. Subsequently, 13 μL of a G3 / pyridine solution (containing 0.64 mg G3 and 0.70 mg pyridine) was added to the melt and immediately mixed with a spatula to ensure rapid and uniform dispersion of the catalyst. Results Figure 6 As shown in (d), G3 catalyst is added to molten NBE-PCL 3.4k Subsequently, the storage modulus (G') and viscosity (|η*|) increased significantly, indicating that the polymerization of the macromonomer proceeded smoothly.

[0061] Comparative Example 1 This comparative example demonstrates the use of the same body ROMP operating conditions as in Example 2, but specifically for NBE-PLA. 3.3k The results of polymerization of macromonomers are used to illustrate that the method of the present invention is not universally applicable to PLA-type polyester macromonomers.

[0062] For NBE-PLA 3.3k Bulk polymerization was carried out at DP=50 with mechanical stirring at 150°C for 10 min. Different catalysts were tested; the remaining operational steps were the same as for the polymerization of PCL macromonomers. NBE-PLA 3.3k Table 9 shows the feed ratios of macromonomers under different catalytic conditions. The SEC curves of the polymerization products are shown below. Figure 11 The molecular weight and conversion rate data are summarized in Table 10.

[0063] Table 9

[0064] Table 10 NBE-PLA 3.3k Molecular weight and conversion rate of BBP prepared by bulk ROMP under target DP = 50 conditions.

[0065] It is evident that although POL is an amorphous polymer with a glass transition temperature below room temperature, its volumetric polymerization rate is relatively slow at room temperature. Figure 10 ).like Figure 9 As shown, at 75°C, NBE-POL 6.7k Bulk polymerization was performed with and without pyridine. Similar to the observations of PCL macromonomers, the addition of pyridine effectively reduced the molecular weight distribution index (from 1.28 to 1.14). Unlike PCL and POL macromonomers, PLA requires much higher processing temperatures (approximately 130-150°C). NBE-PLA 3.3k The macromonomers were polymerized at 150°C using different catalysts. Due to the poor thermal stability of G3 at this temperature, the G3 / pyridine strategy was no longer applicable. In this case, the G2 catalyst with P(O) was used. n Bu)3 ligand mixing was used to suppress polymerization. Although the introduction of phosphonate ligands narrowed the molecular weight distribution (Ð = 1.47), it also limited the conversion (65.5%). On the other hand, the HG-2 catalyst achieved the highest conversion of macromonomers (91.5%), but still failed to provide a narrow distribution ( Figure 11 (Table 10).

[0066] Example 3 Synthesis and Characterization of Block Brush Polymers 3.1 Polymerization [(NBE-PCL)]3.4k )-b-(NBE-PCL 8.6k Synthesis of )] 50 mg (14.7 μmol) of NBE-PCL 3.4k With 50 mg (5.8 μmol) of NBE-PCL 8.6k The solutions were melted separately at 75°C. Subsequently, 9 μL of a G3 / pyridine solution (dissolved in THF, containing 0.43 mg (0.59 μmol) G3 and 0.47 mg (5.9 μmol) pyridine) was added to NBE-PCL. 3.4k In the melt. After mechanical stirring for 4 min, approximately 1 mg of the obtained BBP was collected and quenched for SEC analysis. Simultaneously, approximately 25 mg of BBP (containing approximately 0.22 mg (0.30 μmol) of G3) was taken from the reaction mixture and immediately added with 50 mg (5.8 μmol) of NBE-PCL under mechanical stirring. 8.6k The polymerization reaction was initiated in the melt. After 10 minutes of reaction, a sample was taken, quenched, and subjected to SEC analysis.

[0067] 3.2 Poly[(NBE-PCL)] 3.4k )-b-(NBE-POL 6.7k Synthesis of )] 50 mg (14.7 μmol) of NBE-PCL 3.4k With 50 mg (7.5 μmol) of NBE-POL 6.7k The solutions were melted separately at 75°C. Subsequently, 9 μL of a G3 / pyridine solution (dissolved in THF, containing 0.43 mg (0.59 μmol) G3 and 0.47 mg (5.9 μmol) pyridine) was added to NBE-PCL. 3.4k In the melt. After mechanical stirring for 4 min, approximately 1 mg of the obtained BBP was collected and quenched for SEC analysis. Simultaneously, 7.5 mg of BBP (containing approximately 0.07 mg (0.09 μmol) G3) was taken from the reaction mixture and immediately added to 50 mg (7.5 μmol) NBE-POL under mechanical stirring. 6.7k The chain extension step is initiated in the melt. After reacting for 10 minutes, the reaction is quenched and subjected to SEC and... 1 1H NMR analysis. The corresponding 1H NMR spectrum is shown below. Figure 12 .

[0068] Poly[(NBE-PCL) 3.4k )-b-(NBE-PCL 8.6k )]、Poly[(NBE-PCL 3.4k )-b-(NBE-POL 6.7k The SEC curve of [] is shown in [reference]. Figure 13The results showed that the SEC peak of the block copolymer shifted significantly towards higher molecular weight compared to the first block, while maintaining a single peak distribution and a narrow molecular weight distribution (Ð < 1.3), indicating that the bulk polymerization was active.

[0069] Example 4: Bulk polymerization of macromonomers under solvent-free conditions This embodiment provides a bulk ring-opening metathesis polymerization (ROMP) method for polyester macromonomers that is completely free of small molecule organic solvents. By using a polymer with a low glass transition temperature as a dispersant, a catalyst and ligands are introduced into the reaction system instead of trace amounts of organic solvent.

[0070] First, according to Figure 14 The synthesis of Bn-POL was carried out using a method similar to that used in the preparation of the NBE-POL macromonomer in Example 1. 1 The H NMR spectrum and SEC characterization results are shown in […]. Figure 15 (a) and (b). Subsequently, 100 mg of NBE-PCL was added. 3.4k (29.4 μmol) was heated to 75°C and held for 10 min. 21.4 mg G3 and 23.3 mg pyridine were dispersed in 455 mg Bn-POL. After the solid was fully dispersed in the polymer, 5 mg of the mixture (containing 0.294 μmol G3 and 2.94 μmol pyridine) was added to the PCL macromonomer melt. The reaction was carried out under mechanical stirring for 15 min, followed by quenching with a THF / EVE (v / v = 1:1) solution. The product was precipitated with methanol and then dried under vacuum. The obtained sample... 1 The H NMR spectrum and SEC characterization results are shown in […]. Figure 15 (c) and (b).

[0071] like Figure 16 As shown, the direct addition of G3 powder and pyridine resulted in non-uniform polymerization behavior (Ð = 2.12) and a wide molecular weight distribution. To address this issue, a polymer with a low glass transition temperature was used as a dispersant instead of the organic solvent. In the examples, benzyl alcohol-terminated POL (Bn-POL, Mn = 7.0 kDa, derived from...) was used. 1 (H NMR determination) replaced trace amounts of THF. G3 and pyridine were first dispersed in Bn-POL, and then the mixture was added to the macromonomer melt to initiate the polymerization reaction. Bn-POL accounted for 5 wt% of the macromonomer melt. With the aid of Bn-POL, the Ð value of the BBPs generated by the polymerization catalyzed by G3 and pyridine was 1.33 (Ð = 1.78 for polymerization without pyridine), slightly higher than the result obtained using trace amounts of THF.

[0072] Example 5: Bulk polymerization of macromonomers in a one-pot process This example uses a bottle brush polymer with a target side chain DP of 30 and a target main chain DP of 50 as an example. 6.05 mg (29.2 μmol) of NBE-OH was dissolved in 100 mg (877.2 μmol) of CL, and the mixture was kept at 130°C for 10 min. Then, 2.5 μL of stannous octoate solution (21 mg / 300 μL toluene, 172.8 mM) was added to the system. After stirring at 130°C for 40 min, the mixture was cooled to room temperature, and a sample was taken for further characterization. Next, the mixture was heated to 75°C, and 8.4 μL of G3 solution (containing 5 mg G3 (6.8 μmol) and 5.39 mg pyridine (68.2 μmol) in 100 μL THF) was added to the reaction system with mechanical stirring. After reacting for 30 min, the reaction was quenched with THF / EVE solution. The product was purified by precipitation three times and then dried under vacuum overnight.

[0073] The results are as follows Figure 17 As shown in (b)-(d), under different target DP values, the molecular weight of the synthesized BBP is close to that obtained by two-step polymerization, while achieving a relatively ideal monomer conversion rate. The SEC spectrum shows a significant shift in the peak corresponding to BBP, indicating that BBP was successfully synthesized from the macromonomer at DP=50 and DP=100, and the molecular weight distribution is relatively narrow.

[0074] Example 6: Twin-screw reactive extrusion First, the HAAKE MiniLab 3 micro mixer was heated to 75°C and maintained for 5 minutes until the temperature stabilized, with the screw speed set to 120 rpm. For the control group without pyridine additive, 5000 mg of NBE-PCL was added. 4.2k (1.19 mmol) and 17.3 mg (0.024 mmol) of G3 catalyst and Bn-POL were thoroughly mixed and added to a twin-screw extruder. After cyclic mixing for 15 min, the product was extruded and quenched for further characterization. For the experimental group with pyridine as an additive, 5000 mg of NBE-PCL was added. 4.2k The mixture was added to a mixer and heated for 10 min. Subsequently, a G3 / pyridine solution (containing 17.3 mg G3 and 18.8 mg pyridine in THF) was added to the system. After cyclic mixing for 10 min, the product was extruded and quenched for further characterization.

[0075] The results are as follows Figure 18 As shown, BBPs were synthesized using pyridine at a scale of 5g, with a target DP of 50. Polymerization proceeded smoothly with high conversion, but the molecular weight distribution was also broad (Ð=3.72 for the product without pyridine, Ð=2.08 for the product with pyridine). The molecular weight of the BBPs was also higher than expected (ROMP of the solution was M). n=190.6kDa, using a twin-screw extruder to add pyridine to the bulk ROMP as M n =259.8 kDa). This indicates that the stability of G3 is somewhat affected under air and heating conditions, and the presence of oxygen may lead to chain termination. However, the successful polymerization in a twin-screw extruder suggests that bulk ROMP has potential for large-scale production of BBPs.

[0076] The above description is merely a preferred embodiment of the present invention and does not limit the implementation and protection scope of the present invention. Those skilled in the art should realize that any equivalent substitutions and obvious changes made based on the content and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a bottle-brush-like polymer, characterized in that, Includes the following steps: The norbornene-terminated polyester macromonomer was heated to a molten state, and a ROMP catalyst was added under the condition of containing ligands to initiate a ring-opening metathesis polymerization reaction to prepare the bottle brush polymer. The ligand is used to adjust the activity of the ROMP catalyst, the polymerization reaction is carried out in a bulk system, and the content of organic solvent in the bulk system is less than 8 wt%; the ligand is pyridine.

2. The preparation method according to claim 1, characterized in that, The ROMP catalyst is Grubbs' third-generation catalyst G3.

3. The preparation method according to claim 1, characterized in that, The norbornene-terminated polyester macromonomer is selected from one or more of norbornene-terminated polycaprolactone and norbornene-terminated poly(5-hydroxyoctanoic acid lactone).

4. The preparation method according to claim 1, characterized in that, The molar ratio of the ligand to the ROMP catalyst is (5-15):

1.

5. The preparation method according to claim 4, characterized in that, The molar ratio of the ligand to the ROMP catalyst is 10:

1.

6. The preparation method according to claim 1, characterized in that, The polymerization reaction is carried out at a temperature of 70-80°C.

7. The preparation method according to claim 1, characterized in that, When the polymerization reaction is carried out in a system without added organic solvent, the preparation method further includes: pre-dispersing the ligand and the ROMP catalyst in a dispersant before adding the ROMP catalyst; the dispersant is a polymer with a glass transition temperature below room temperature.

8. The preparation method according to claim 7, characterized in that, The polymer with a glass transition temperature below room temperature is benzyl alcohol-terminated poly(5-hydroxyoctanoic acid lactone).

9. The preparation method according to claim 1, characterized in that, The preparation method further includes, after the first polymerization stage of the ring-opening metathesis polymerization reaction is completed, adding the polymer to a second norbornene-terminated polyester macromonomer and continuing the reaction to prepare a block bottle brush copolymer.

10. A bottle-brush-like polymer, characterized in that, It is prepared by the preparation method according to any one of claims 1-9.

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