Method for continuously preparing star-shaped block copolymer based on organic catalysis atom transfer radical polymerization method

Abstract

The invention discloses a method for continuously preparing a star-shaped block copolymer based on an organocatalytic atom transfer radical polymerization method, which comprises the following steps: mixing and dissolving MMA (methyl methacrylate), an alkyl bromide initiator and an organic catalyst, and carrying out O-ATRP (atom transfer radical polymerization) reaction under the irradiation of blue light to obtain a star-shaped homopolymer; mixing and dissolving PEGMA300 and an organic catalyst, mixing with the star-shaped homopolymer, and carrying out O-ATRP reaction under the irradiation of blue light to obtain the amphiphilic star-shaped block copolymer. The method is based on an O-ATRP reaction, the O-ATRP reaction is introduced into a continuous flow microtube reactor, and efficient and controllable preparation of star-shaped block copolymers with different polymerization degrees and block ratios is achieved by regulating and controlling feeding of reactants, illumination conditions, reactor parameters and the sample injection rate of reaction liquid; the operation process is effectively simplified, the efficiency is improved, and the production scale is favorably expanded; meanwhile, the conditions are mild, no transition metal is used, the components are simple, and the polymerization reaction speed is high.

Description

Technical Field

[0001] The invention relates to the technical field of polymer preparation, and in particular to a method for continuously preparing star-shaped block copolymers based on organic catalytic atom transfer radical polymerization. Background Art

[0002] Star polymers have attracted widespread attention due to their unique structure. By designing a multifunctional macromolecule or small molecule as the core, and using this to initiate monomer polymerization to grow arms, a polymer with a certain number of arms can be obtained. The polymer structure obtained using this strategy is more clear.

[0003] Photo-controlled reversible-deactivation radical polymerization (RDRP) has excellent, unique and powerful capabilities in the precision synthesis of macromolecules and polymer structure design. Among them, atom transfer radical polymerization (ATRP) is widely used in the preparation of star polymers. However, its catalyst is generally a transition metal catalyst. On the one hand, it has poor solubility in organic solvents and is easy to cause blockage, which is not conducive to the flow system; on the other hand, the metal residue will have an adverse effect on the subsequent application of the polymer; at the same time, the existing preparation methods of star polymers still have problems such as harsh conditions, complex components, and cumbersome steps.

[0004] In addition, the preparation of copolymers is generally carried out in intermittent reactors, which have problems such as uneven mass transfer / heat transfer, exponential decay of light intensity with increasing optical path, and many intermittent operations, which are not conducive to the large-scale production of photocontrolled polymerization. Summary of the invention

[0005] The present invention aims at the deficiencies in the prior art and provides a method for continuously preparing a star-shaped block copolymer based on an organic catalytic atom transfer radical polymerization method. The photocontrolled organic catalytic atom transfer radical polymerization (O-ATRP) method is adopted and introduced into a continuous flow microtube reactor to prepare the star-shaped block copolymer, thereby providing a simple and efficient method for the photocontrolled synthesis of the star-shaped polymer, effectively simplifying the operation process, improving the efficiency, and facilitating the expansion of the production scale. At the same time, the conditions are mild, no transition metal is used, and the components are simple.

[0006] In order to solve the above technical problems, the first aspect of the present invention provides a method for continuously preparing a star-shaped block copolymer based on organic catalytic atom transfer radical polymerization, comprising the following steps:

[0007] S1, dissolving a hydrophobic methyl methacrylate monomer (MMA), an alkyl bromide initiator and an organic catalyst in an organic solvent to obtain a reaction solution A, and obtaining a hydrophobic star-shaped homopolymer by O-ATRP reaction under blue light irradiation;

[0008] S2, dissolving a hydrophilic polyethylene glycol monomethyl ether methacrylate monomer (PEGMA300) and an organic catalyst in an organic solvent to obtain a reaction solution B, mixing the reaction solution B with the hydrophobic star-shaped homopolymer, and obtaining an amphiphilic star-shaped block copolymer by O-ATRP reaction under blue light irradiation;

[0009] The structural formulas of the methyl methacrylate monomer, the polyethylene glycol monomethyl ether methacrylate monomer, the alkyl bromide initiator, the hydrophobic star-shaped homopolymer and the amphiphilic star-shaped block copolymer are respectively:

[0010]

[0011]

[0012] in, n and m are independently selected from integers between 80-120.

[0013] The invention adopts a light-controlled organic catalytic atom transfer radical polymerization (O-ATRP) method to prepare an intermediate hydrophobic star-shaped homopolymer, and based on this, utilizes the active group at the end of the polymer chain to obtain an amphiphilic star-shaped block copolymer with controllable block ratio through O-ATRP reaction chain extension; the conditions are mild, the catalyst does not use transition metals, and the components are simple; the block copolymer with the target block ratio is prepared by designing the initial feed of reactants and light stimulation conditions, which has a precise control effect on the polymer structure, and realizes the efficient and controllable preparation of star-shaped block copolymers with different polymerization degrees and block ratios.

[0014] Furthermore, the organic catalyst is 1,2,3,5-tetrakis(carbazole-9-yl)-4,6-dicyanobenzene (4CzIPN), and its structural formula is: in, 4CzIPN itself has the characteristics of a wide visible light absorption region, a reversible cyclic voltammetry (CV) curve, and a high excited state reduction potential. It has excellent catalytic effect when applied to "living" free radical polymerization reactions.

[0015] Furthermore, in S1, the molar ratio of the methyl methacrylate monomer, the alkyl bromide initiator and the organic catalyst is (80-120):1:(0.001-0.3).

[0016] Furthermore, in S2, the molar ratio of the polyethylene glycol monomethyl ether methacrylate monomer, the hydrophobic star-shaped homopolymer, and the organic catalyst is (80-120):1:(0.001-0.3).

[0017] Furthermore, the O-ATRP reaction is carried out in an inert atmosphere.

[0018] Furthermore, the organic solvent is selected from one or more of 1,3-dimethyl-2-imidazolidinone (DMI), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), 1,1,3,3-tetramethylurea (TMU), anisole, dioxane, and acetone.

[0019] Furthermore, the reaction liquid A is uniformly injected into the reactor I for O-ATRP reaction, the reaction liquid B is uniformly injected and merged with the hydrophobic star-shaped homopolymer in the mixer before entering the reactor II for O-ATRP reaction, and the reactor I and reactor II are continuous flow microtubule reactors. Microtubule reactors have the characteristics of large specific surface area, high mass transfer / heat transfer efficiency, high light radiation efficiency, and continuous process, which can achieve continuous preparation of polymers while improving polymerization rate and controllability. In addition, after the reaction in reactor I, the reaction liquid A does not need purification and separation steps, and directly enters the reactor II after merging with the reaction liquid B in the mixer to continue the reaction, chain extension, grafting or intramolecular crosslinking, and obtains a star-shaped block copolymer at the outlet of reactor II.

[0020] Furthermore, the reaction solution A and the reaction solution B are respectively driven for injection by metering pumps.

[0021] Furthermore, the continuous flow micro-tube reactor comprises a spiral tube for liquid flow, and a blue light LED tube passing through the center of the spiral tube;

[0022] And / or, the diameter of the liquid flow in the spiral tube (the inner diameter of the tube) is 1±0.5 mm, the outer diameter of the tube is 3±0.5 mm, and the length of the tube is 10-50 m.

[0023] Furthermore, the overall outer diameter of the spiral tube (spiral outer diameter) is 40 mm.

[0024] Furthermore, the spiral tube is made of polytetrafluoroethylene.

[0025] Furthermore, the injection rate of the reaction solution A is 0.06-0.2 mL / min, and the injection rate of the reaction solution B is 0.09-0.3 mL / min.

[0026] Furthermore, the wavelength of the blue light is 420-460nm and the power is 3-4mW / cm 2 .

[0027] Furthermore, in S2, the O-ATRP reaction time is 1-6 h.

[0028] The second aspect of the present invention provides a star-shaped block copolymer prepared by the preparation method described in the first aspect.

[0029] Beneficial effects of the present invention:

[0030] The present invention adopts a light-controlled organic catalytic atom transfer radical polymerization method and introduces it into a continuous flow microtube reactor to prepare a star-shaped block copolymer, thereby providing a simple and efficient method for the light-controlled synthesis of the star-shaped block copolymer, effectively simplifying the operation process, improving efficiency, and facilitating the expansion of production scale. At the same time, the conditions are mild, no transition metal is used, the components are simple, and the polymerization reaction rate is fast.

[0031] The invention realizes efficient and controllable preparation of star-shaped block copolymers with different polymerization degrees and block ratios by regulating the feeding of reactants, light stimulation conditions, reactor parameters and the injection rate of the reaction solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solution of the present invention, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 is the alkyl bromide initiator prepared in Example 1 of the present invention 1 H NMR spectra;

[0034] Figure 2 is a schematic flow chart of the preparation method of the star-shaped block copolymer of Example 5 of the present invention;

[0035] Figure 3 It is the GPC chart of the hydrophobic star-shaped homopolymer and star-shaped block copolymer prepared by the specific example No. 2 in Example 5 of the present invention. DETAILED DESCRIPTION

[0036] The technical solution of the present invention will be described clearly and completely below in conjunction with the specific embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] In the following embodiments of the present invention, the characterization conditions involved are as follows:

[0038] 1. The monomer conversion rate and polymer nuclear magnetic resonance spectrum were measured by Bruker 300 MHz nuclear magnetic resonance (NMR), and CDCl3 or DMSO-d6 was selected as the deuterated reagent for measurement.

[0039] 2. Polymer number average molecular weight (Mn) and molecular weight distribution The results were determined by TOSOH HLC-8320 gel permeation chromatograph (GPC) equipped with a refractive index detector (TOSOH), using a TSK gel Super MP-N (4.6×20 mm) guard column. The detection column was TSK gel Super HZ-N (4.6×150 mm) as the eluent, the test temperature was 40°C, the flow rate was 0.35 mL / min, and the molecular weight range was 5×10 2-5 The gel permeation chromatography samples were injected using a TOSOH plus autosampler and the results for the measured polymers were calibrated using standard PMMA samples purchased from TOSOH.

[0040] 3. The light intensity of the light source was determined using a 0820FD18T-TS15 laser power meter purchased from Changchun New Industry Optoelectronics Technology Co., Ltd., and the ambient temperature of the polymerization system was measured using an infrared thermal imager purchased from Dongguan Xintai Instrument Co., Ltd.

[0041] Example 1

[0042] This embodiment relates to a method for preparing an alkyl bromide initiator (PE-4BPA), comprising the following steps:

[0043] To a 250 mL round-bottom flask, 0.54 g (4 mmol) of pentaerythritol, 5.16 g (24 mmol) of α-bromophenylacetic acid and 75 mg (0.4 mmol) of p-toluenesulfonic acid were added in sequence, and then 35 mL of toluene was added. The mixture was heated to 110° C. and condensed under reflux, and reacted for 12 hours.

[0044] After the reaction is completed, the reaction solution is cooled to room temperature, and toluene is removed by rotary evaporation to obtain a dark yellow oil, which is dissolved in a saturated sodium bicarbonate solution. The solution is extracted with 150 mL of ethyl acetate, and the organic phase is taken. It is then washed with 50 mL of a 10% mass fraction hydrochloric acid solution and then with 50 mL of saturated brine. The organic phase is dried overnight using anhydrous magnesium sulfate.

[0045] The filtrate was collected by suction filtration and rotary evaporation to obtain a crude product, which was separated and purified by column chromatography (developing solvent: petroleum ether: ethyl acetate = 4:1 (volume ratio)) to obtain 2.88 g of the target product alkyl bromide initiator (PE-4BPA) (yield: 77.9%). 1 H NMR images Figure 1 shown.

[0046] The reaction scheme of this embodiment is as follows:

[0047]

[0048] Example 2

[0049] This embodiment relates to a method for continuously preparing a star-shaped homopolymer based on organic catalytic atom transfer radical polymerization, comprising the following steps:

[0050] The mixture was mixed at a molar ratio of MMA:PE-4BPA (prepared in Example 1):4CzIPN=100:1:0.003, and a DMI solvent twice the volume of the MMA monomer was added to prepare a reaction solution A, which was added to an ampoule bottle. The reaction mixture was deoxygenated by bubbling for 30 minutes, and then transferred to a metering pump and passed through a micro-tube reactor I with a spiral outer diameter of 40 mm, a tube inner diameter of 1 mm, and a tube length of 22.92 m at a flow rate of 0.08 mL / min. The wavelength was 460 nm and the power was 3.6 mW / cm 2 The reaction mixture in the microtube was irradiated with blue light, and a light yellow polymer solution was obtained at the outlet. 1 H NMR test, by 1 The monomer conversion rate was measured by H NMR. The collected polymer solution was dissolved in 20 mL THF, precipitated in petroleum ether, filtered and vacuum dried to obtain a light yellow solid. A small amount of the product was dissolved in THF to prepare a 2-5 mg / mL solution and subjected to GPC testing. The monomer conversion rate, Mn and The results are shown in Table 1. It can be seen that under the same microtube reactor and lighting conditions, polymers with different molecular weights can be obtained by controlling the polymerization time.

[0051] Table 1

[0052]

[0053] Example 3

[0054] This embodiment relates to a method for continuously preparing a star-shaped homopolymer based on organic catalytic atom transfer radical polymerization, comprising the following steps:

[0055] MMA:PE-4BPA (prepared in Example 1):4CzIPN=100:1:0.003 were mixed in a molar ratio, and 3 volumes of DMI solvent of MMA monomer were added to prepare reaction solution A, which was added to an ampoule bottle. The reaction mixture was bubbled for deoxygenation for 30 min, and then transferred to a metering pump and passed through a microtube reactor I with different axial lengths, with a spiral outer diameter of 40 mm and a tube inner diameter of 1 mm, at different flow rates. The wavelength was 460 nm and the power was 3.6 mW / cm 2 The reaction mixture in the microtube was irradiated with blue light, and a light yellow polymer solution was obtained at the outlet. 1 H NMR test, by 1The monomer conversion rate was measured by H NMR. The collected polymer solution was dissolved in 20 mL THF, precipitated in petroleum ether, filtered and vacuum dried to obtain a light yellow solid. A small amount of the product was dissolved in THF to prepare a 2-5 mg / mL solution for GPC testing. The monomer conversion rate, Mn and The results are shown in Table 2. It can be seen that under the same reaction time (80 min) and light conditions, polymers with different molecular weights can be obtained by adjusting the inner diameter and length of the spiral tube, and a better polymerization effect is obtained when the flow rate is 0.12 mL / min and the tube length is 22.92 m. While the conversion rate is improved, the dispersibility is also better than other conditions.

[0056] Table 2

[0057]

[0058] Example 4

[0059] This embodiment relates to a method for continuously preparing a star-shaped homopolymer based on organic catalytic atom transfer radical polymerization, comprising the following steps:

[0060] MMA:PE-4BPA (prepared in Example 1):4CzIPN=100:1:0.003 were mixed in a molar ratio, and 3 volumes of DMI solvent of MMA monomer were added to prepare reaction solution A, which was added to an ampoule bottle. The reaction mixture was bubbled for deoxygenation for 30 min, and then transferred to a metering pump and passed through a micro-tube reactor I with a spiral outer diameter of 40 mm, a tube inner diameter of 1 mm, and a tube length of 22.92 m at different flow rates. The wavelength was 460 nm and the power was 3.6 mW / cm 2 The reaction mixture in the microtube was irradiated with blue light, and a light yellow polymer solution was obtained at the outlet. 1 H NMR test, by 1 The monomer conversion rate was measured by H NMR. The collected polymer solution was dissolved in 20 mL THF, precipitated in petroleum ether, filtered and vacuum dried to obtain a light yellow solid. A small amount of the product was dissolved in THF to prepare a 2-5 mg / mL solution for GPC testing. The monomer conversion rate, Mn and The results are shown in Table 3. It can be seen that under the same tube length and lighting conditions, polymers with different molecular weights can be obtained by regulating the inner diameter of the spiral tube and the reaction time. Under the same tube length and lighting conditions, the flow rate is inversely proportional to the time. The effect of the O-ATRP reaction is mainly positively correlated with the time. A higher polymerization time should be preferred. At the same time, a lower flow rate makes the reaction solution tend to a laminar steady state. When the flow rate is 0.072 mL / min and the time is 250 min, a higher conversion rate, polymerization degree and better dispersibility can be obtained.

[0061] Table 3

[0062]

[0063] Example 5

[0064] This embodiment relates to a method for continuously preparing a star-shaped block copolymer based on organic catalytic atom transfer radical polymerization. The flow chart is as follows: Figure 2 As shown, the following steps are included:

[0065] Mix according to the molar ratio R1 of MMA:PE-4BPA (prepared in Example 1):4CzIPN=(80-120):1:0.003, add 3 times the volume of DMI solvent of MMA monomer to prepare reaction solution A, add it to an ampoule, bubble and deoxygenate the reaction mixture for 30 minutes, and then transfer it to metering pump I. Mix according to the molar ratio R2 of PEGMA300:4CzIPN=(80-120):0.003, add 1 times the volume of DMI solvent of PEGMA300 monomer to prepare reaction solution B, add it to an ampoule, bubble and deoxygenate the reaction mixture for 30 minutes, and then transfer it to metering pump II. Set the flow rate of metering pump I to 0.072mL / min, and pump reaction solution A into reactor I. The spiral outer diameter of reactor I is 40mm, the inner diameter of the tube is 1mm, and the length of the tube is 22.92m. The wavelength is 460nm and the power is 3.6mW / cm 2 The reaction mixture in the microtube was irradiated with blue light to obtain a hydrophobic star-shaped homopolymer. The flow rate of metering pump I was kept constant, and the flow rate of metering pump II was set to 0.3 mL / min. The reaction liquid B and the product flowing out of reactor I were combined into reactor II through a mixer. The spiral outer diameter of reactor II was 40 mm, the inner diameter of the tube was 1 mm, and the length of the tube was 22.92 m. The wavelength was 460 nm and the power was 3.6 mW / cm 2 The reaction mixture in the microtube was irradiated with blue light to carry out chain extension polymerization for 250 min. After the reaction, an amphiphilic star-shaped block copolymer was obtained. 1 H NMR and GPC were used to measure the monomer conversion rate and product Mn of O-ATRP reaction in two reactors. The results are shown in Table 4 and Table 5. The GPC graphs of the star-shaped homopolymer (Before Chain Extension) and star-shaped block copolymer (After Chain Extension) prepared in Example No. 2 are shown in Table 4 and Table 5. Figure 3 As shown in Tables 4 and 5, by presetting different feed ratios, star-shaped block copolymers with different block ratios can be obtained in the micro-tube reactor.

[0066] Table 4

[0067]

[0068]

[0069] Table 5

[0070]

[0071] In summary, the present invention adopts a light-controlled organic catalytic atom transfer radical polymerization method and introduces it into a continuous flow microtube reactor to prepare a star-shaped block copolymer, which provides a simple and efficient method for the light-controlled synthesis of star-shaped block copolymers, effectively simplifies the operation process, improves efficiency, and is conducive to expanding the production scale. At the same time, the conditions are mild, no transition metal is used, the components are simple, and the polymerization reaction rate is fast; by regulating the feeding of reactants, light stimulation conditions, reactor parameters, and the injection rate of the reaction solution, efficient and controllable preparation of star-shaped block copolymers with different polymerization degrees and block ratios is achieved.

[0072] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

Claims

1. A method for continuously preparing star-shaped block copolymers based on organic catalytic atom transfer radical polymerization, characterized in that: The steps include: S1, mixing and dissolving a hydrophobic methyl methacrylate monomer, an alkyl bromide initiator and an organic catalyst in an organic solvent to obtain a reaction solution A, and performing an O-ATRP reaction under blue light irradiation to obtain a hydrophobic star-shaped homopolymer; S2, dissolving a hydrophilic methacrylate polyethylene glycol monomethyl ether ester monomer and an organic catalyst in an organic solvent to obtain a reaction solution B, mixing the reaction solution B with the hydrophobic star-shaped homopolymer, and obtaining an amphiphilic star-shaped block copolymer by O-ATRP reaction under blue light irradiation; The structural formulas of the methyl methacrylate monomer, the polyethylene glycol monomethyl ether methacrylate monomer, the alkyl bromide initiator, the hydrophobic star-shaped homopolymer and the amphiphilic star-shaped block copolymer are respectively: in, n and m are independently selected from integers between 80-120.

2. The method for continuously preparing star-shaped block copolymers based on organic catalytic atom transfer radical polymerization as claimed in claim 1, characterized in that: The organic catalyst is 1,2,3,5-tetrakis(carbazole-9-yl)-4,6-dicyanobenzene, and its structural formula is: in, 3. The method for continuously preparing star-shaped block copolymers based on organic catalytic atom transfer radical polymerization as claimed in claim 1, characterized in that: In S1, the molar ratio of the methyl methacrylate monomer, the alkyl bromide initiator and the organic catalyst is (80-120):1:(0.001-0.3).

4. The method for continuously preparing star-shaped block copolymers based on organic catalytic atom transfer radical polymerization as claimed in claim 1, characterized in that: In S2, the molar ratio of the polyethylene glycol monomethyl ether methacrylate monomer, the hydrophobic star-shaped homopolymer, and the organic catalyst is (80-120):1:(0.001-0.3).

5. The method for continuously preparing star-shaped block copolymers based on organic catalytic atom transfer radical polymerization as claimed in claim 1, characterized in that: The reaction solution A is uniformly injected into reactor I for O-ATRP reaction, and the reaction solution B is uniformly injected and merged with the hydrophobic star-shaped homopolymer through a mixer before entering reactor II for O-ATRP reaction. Reactor I and reactor II are continuous flow microtubule reactors.

6. The method for continuously preparing star-shaped block copolymers based on organic catalytic atom transfer radical polymerization as claimed in claim 5, characterized in that: The continuous flow micro-tube reactor comprises a spiral tube for liquid flow, and a blue light LED lamp tube passing through the center of the spiral tube; And / or, the diameter of the liquid flow in the spiral tube is 1±0.5 mm.

7. The method for continuously preparing star-shaped block copolymers based on organic catalytic atom transfer radical polymerization as claimed in claim 5, characterized in that: The injection rate of the reaction solution A is 0.06-0.2 mL / min, and the injection rate of the reaction solution B is 0.09-0.3 mL / min.

8. The method for continuously preparing star-shaped block copolymers based on organic catalytic atom transfer radical polymerization as claimed in claim 1, characterized in that: The wavelength of the blue light is 420-460nm, and the power is 3-4mW / cm 2 .

9. The method for continuously preparing star-shaped block copolymers based on organic catalytic atom transfer radical polymerization as claimed in claim 1, characterized in that: In S2, the O-ATRP reaction time is 1-6 hours.

10. A star-shaped block copolymer prepared by the preparation method according to any one of claims 1 to 9.

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