A method for continuously preparing star block copolymers based on organocatalytic atom transfer radical polymerization

Abstract

The application discloses a method for continuously preparing star-shaped block copolymer based on organic catalytic atom transfer radical polymerization, which comprises the following steps: mixing and dissolving MMA, alkyl bromide initiator and organic catalyst, and obtaining star-shaped homopolymer through O-ATRP reaction under blue light irradiation; mixing and dissolving PEGMA300 and organic catalyst, mixing with the star-shaped homopolymer, and obtaining amphiphilic star-shaped block copolymer through O-ATRP reaction under blue light irradiation. The application introduces O-ATRP reaction into a continuous flow micro-tube reactor, and realizes efficient and controllable preparation of star-shaped block copolymer with different polymerization degrees and block ratios by adjusting the feeding of reactants, light irradiation conditions, reactor parameters and the sampling rate of reaction solution; the operation process is effectively simplified, the efficiency is improved, and the production scale is expanded; meanwhile, the conditions are mild, no transition metal is used, the components are simple, and the polymerization reaction rate is fast.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polymer preparation, in particular to a method for continuously preparing star block copolymer based on organic catalytic atom transfer radical polymerization. BACKGROUND

[0002] Star polymers have been widely concerned due to their unique structure, and the strategy of using a multifunctional macromolecule or small molecule as a core to initiate monomer polymerization to grow arms can obtain polymers with a certain number of arms, and the structure of the polymers obtained by the strategy is more explicit.

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

[0004] In addition, the preparation of copolymer is generally carried out in a batch reactor at present, which has problems such as uneven mass transfer / heat transfer, exponential decay of light intensity with increasing light path, and batch operation, which is not conducive to the large-scale production of photo-controlled polymerization. SUMMARY

[0005] The present application provides a method for continuously preparing star block copolymer based on organic catalytic atom transfer radical polymerization, which adopts photo-controlled organic catalytic atom transfer radical polymerization (O-ATRP) method and introduces it into a continuous flow micro-tube reactor to prepare star block copolymer, provides a simple and efficient method for photo-controlled synthesis of star polymers, effectively simplifies the operation process, improves the efficiency, and is conducive to expanding the production scale, and 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 application provides a method for continuously preparing star block copolymer based on organic catalytic atom transfer radical polymerization, which comprises the following steps:

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

[0008] S2, hydrophilic methacrylic acid polyethylene glycol monomethyl ether ester monomer (PEGMA300), organic catalyst mixed and dissolved in an organic solvent to obtain a reaction liquid B, the reaction liquid B and the hydrophobic star-shaped homopolymer are mixed, and under blue light irradiation, an amphiphilic star-shaped block copolymer is obtained by O-ATRP reaction;

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

[0010]

[0011]

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

[0013] The present application adopts light-controlled organic catalytic atom transfer radical polymerization (O-ATRP) method to prepare intermediate hydrophobic star-shaped homopolymer, and based on this, the active group at the end of the polymer chain is used to expand the chain to obtain an amphiphilic star-shaped block copolymer with controllable block ratio by O-ATRP reaction; The condition is mild, the catalyst does not use transition metal, and the components are simple; By designing the initial feeding of the reactants and the light stimulation conditions to prepare the block copolymer with the target block ratio, the polymer structure has precise control effect, and the star-shaped block copolymer with different polymerization degrees and block ratios is efficiently and controllably prepared.

[0014] Further, the organic catalyst is 1,2,3,5-tetrakis(carbazole-9-yl)-4,6-dicyano benzene (4CzIPN), and its structural formula is: Among them, 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, and when applied to the "active" radical polymerization reaction, it has excellent catalytic effect.

[0015] Further, 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] Further, in S2, the molar ratio of the methacrylic acid polyethylene glycol monomethyl ether ester monomer, the hydrophobic star-shaped homopolymer and the organic catalyst is (80-120):1:(0.001-0.3).

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

[0018] Further, 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-tetramethyl urea (TMU), anisole, dioxane, acetone.

[0019] Further, the reaction liquid A is uniformly fed into the reactor I to perform O-ATRP reaction, the reaction liquid B is uniformly fed and mixed with the hydrophobic star-shaped homopolymer in the mixer and then enters the reactor II to perform O-ATRP reaction, and the reactor I and the reactor II are continuous flow micro-tube reactors. The micro-tube reactor has the characteristics of large specific surface area, high mass transfer / heat transfer efficiency, high light radiation efficiency, and continuous process, so that the polymerization rate and controllability can be improved, and the continuous preparation of the polymer can be realized. In addition, the reaction liquid A does not need a purification and separation step after the reaction in the reactor I, and is directly mixed with the reaction liquid B in the mixer and then enters the reactor II to continue the reaction, chain extension, grafting or intramolecular crosslinking, so that the star-shaped block copolymer is obtained at the outlet of the reactor II.

[0020] Further, the reaction liquid A and the reaction liquid B are respectively fed by a metering pump.

[0021] Further, the continuous flow micro-tube reactor comprises a spiral tube for liquid flow, and a blue light LED lamp tube penetrating 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±0.5mm, the outer diameter of the tube is 3±0.5mm, and the length of the tube is 10-50m.

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

[0024] Further, the material of the spiral tube is polytetrafluoroethylene.

[0025] Further, the feeding rate of the reaction liquid A is 0.06-0.2mL / min, and the feeding rate of the reaction liquid B is 0.09-0.3mL / min.

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

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

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

[0029] The beneficial effects of the present application are as follows:

[0030] The present application adopts the light-controlled organic catalytic atom transfer radical polymerization method, and introduces it into a continuous flow micro-tube reactor to prepare star block copolymers, thereby providing a simple and efficient method for the light-controlled synthesis of star block copolymers, effectively simplifying the operation process, improving the efficiency, facilitating the expansion of the production scale, and 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 present application realizes the efficient and controllable preparation of star block copolymers with different polymerization degrees and block ratios by adjusting the feeding of reactants, light stimulation conditions, reactor parameters and the sampling rate of the reaction solution. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the present application, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0033] Figure 1 is the alkyl bromide initiator prepared in Example 1 of the present application 1 HNMR chart

[0034] Figure 2 is a preparation method flow chart of the star block copolymer in Example 5 of the present application

[0035] Figure 3 is the GPC chart of the hydrophobic star homopolymer and star block copolymer prepared in Example 5 of the present application. DETAILED DESCRIPTION

[0036] The technical solutions of the present application will be described in detail below with reference to specific embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

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

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

[0039] 2. Number average molecular weight (Mn) and molecular weight distribution of the polymer Determined by TOSOH HLC-8320 gel permeation chromatograph (GPC) equipped with refractive index detector (TOSOH), using TSK gel Super MP-N (4.6 x 20 mm) as guard column. The detection column is TSK gel Super HZ-N (4.6 x 150 mm), using eluent, the test temperature is 40℃, the flow rate is 0.35 mL / min, the molecular weight range is 5 x 10 2-5 g / mol. The gel permeation chromatography sample is injected using TOSOH plus automatic sampler, and the results of the measured polymer are calibrated using standard PMMA samples purchased from TOSOH.

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

[0041] Example 1

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

[0043] Into 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 sequentially added, followed by the addition of 35 mL of toluene, heating to 110℃ and condensing reflux, and reacting for 12 hours.

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

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

[0046] The reaction route of this example is as follows:

[0047]

[0048] Example 2

[0049] This example relates to a method for continuous preparation of star-shaped homopolymer based on organic catalytic atom transfer radical polymerization, comprising the following steps:

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

[0051] Table 1

[0052]

[0053] Example 3

[0054] This example relates to a method for continuous preparation of 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 by mole ratio, MMA monomer 2 times the volume of DMI solvent was prepared into reaction liquid A added to the ampoule, the reaction mixture was bubbled for 30 min, then it was transferred to the metering pump, at a flow rate of 0.08 mL / min through the spiral outer diameter of 40 mm, tube inner diameter of 1 mm, tube length of 22.92 m micro tube reactor I, using blue light with wavelength of 460 nm, power of 3.6 mW / cm 2 The light irradiated the reaction mixture in the micro tube, and a light yellow polymer solution was obtained at the outlet, and 1 H NMR test was carried out, and the monomer conversion rate was measured by 1Monomer conversion was determined by ¹H NMR. The collected polymer solution was dissolved in 20 mL THF, precipitated in petroleum ether, filtered, and dried under vacuum to obtain a pale yellow solid. A small amount of product was dissolved in THF to prepare a 2-5 mg / mL solution for GPC analysis. Monomer conversion, Mn, and [other parameters] of the product were determined under different flow rates and reactor axial lengths. The results are shown in Table 2. It can be seen that, under the same reaction time (80 min) and light conditions, polymers of different molecular weights can be obtained by adjusting the inner diameter and length of the spiral tube. The best polymerization effect was obtained when the flow rate was 0.12 mL / min and the tube length was 22.92 m. The conversion rate was improved and the dispersibility was better than that under other conditions.

[0056] Table 2

[0057]

[0058] Example 4

[0059] This embodiment relates to a method for the continuous preparation of star-shaped homopolymers based on organocatalytic atom transfer radical polymerization, comprising the following steps:

[0060] Mix MMA:PE-4BPA (prepared in Example 1):4CzIPN in a molar ratio of 100:1:0.003, add 3 times the volume of DMI solvent to prepare reaction solution A, and add it to an ampoule. Bubble the reaction mixture to remove oxygen for 30 min, then transfer it to a metering pump and pass it at different flow rates through a microtube reactor I with a spiral outer diameter of 40 mm, an inner diameter of 1 mm, and a length of 22.92 m. The reaction is carried out at a wavelength of 460 nm and a power of 3.6 mW / cm². 2 The reaction mixture in the microtube was irradiated with blue light, resulting in a pale yellow polymer solution at the outlet, and then subjected to... 1 H NMR testing, through 1 Monomer conversion was determined by ¹H NMR. The collected polymer solution was dissolved in 20 mL THF, precipitated in petroleum ether, filtered, and dried under vacuum to obtain a pale yellow solid. A small amount of product was dissolved in THF to prepare a 2-5 mg / mL solution for GPC analysis. Monomer conversion, Mn content of the product, and other parameters were determined under different flow rates and reaction times. The results are shown in Table 3. Under the same pipe length and light conditions, by adjusting the inner diameter of the spiral pipe and the reaction time, polymers with different molecular weights can be obtained. Under the same pipe length and light conditions, the flow rate is inversely proportional to the time. The effect of O-ATRP reaction is mainly positively correlated with time. Higher polymerization time should be selected preferentially. Meanwhile, lower flow rate makes the reaction liquid tend to be a steady state of laminar flow. Under the conditions of a flow rate of 0.072 mL / min and a time of 250 min, a higher conversion rate, a higher polymerization degree, and better dispersity can be obtained.

[0061] Table 3

[0062]

[0063] Example 5

[0064] This example relates to a method for continuously preparing star-shaped block copolymers based on organic catalytic atom transfer radical polymerization, a flow chart is shown as Figure 2 , comprising the following steps:

[0065] R1 is mixed according to the molar ratio of MMA: PE-4BPA (prepared in Example 1): 4CzIPN = (80-120): 1:0.003, MMA monomer is added to 3 times the volume of DMI solvent to prepare reaction liquid A, which is added to the ampoule. The reaction mixture is bubbled for 30 min to remove oxygen, and then transferred to the metering pump I. R2 is mixed according to the molar ratio of PEGMA300: 4CzIPN = (80-120): 0.003, PEGMA300 monomer is added to 1 times the volume of DMI solvent to prepare reaction liquid B, which is added to the ampoule. The reaction mixture is bubbled for 30 min to remove oxygen, and then transferred to the metering pump II. The flow rate of the metering pump I is set to 0.072 mL / min, and the reaction liquid A is pumped into the reactor I. The spiral outer diameter of the reactor I is 40 mm, the inner diameter of the pipe is 1 mm, and the pipe length is 22.92 m. Blue light with a wavelength of 460 nm and a power of 3.6 mW / cm 2 is used to irradiate the reaction mixture in the micro-pipe to obtain a hydrophobic star-shaped homopolymer. The flow rate of the metering pump I is kept unchanged, and the flow rate of the metering pump II is set to 0.3 mL / min. The reaction liquid B is mixed with the product from the reactor I through the mixer and then enters the reactor II. The spiral outer diameter of the reactor II is 40 mm, the inner diameter of the pipe is 1 mm, and the pipe length is 22.92 m. Blue light with a wavelength of 460 nm and a power of 3.6 mW / cm 2 is used to irradiate the reaction mixture in the micro-pipe to perform chain extension polymerization for 250 min. After the reaction is completed, an amphiphilic star-shaped block copolymer is obtained. The monomer conversion rate and the Mn of the product of the O-ATRP reaction in the two reactors are measured by 1 H NMR and GPC. The results are shown in Table 4 and Table 5. Among them, the GPC chart of the star-shaped homopolymer (Before Chain Extention) and the star-shaped block copolymer (After Chain Extention) prepared in Example No. 2 is shown in Figure 3 As can be seen from Table 4 and 5, by presetting different feeding 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 application adopts the light-controlled organic catalytic atom transfer radical polymerization method and introduces it into the continuous flow micro-tube reactor to prepare the 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 the efficiency, facilitating the expansion of the production scale, and at the same time, the conditions are mild, no transition metal is used, the components are simple, the polymerization reaction rate is fast; by adjusting the feeding of the reactants, the light stimulation conditions, the reactor parameters and the sampling rate of the reaction solution, the star-shaped block copolymer with different polymerization degrees and block ratios can be efficiently and controllably prepared.

[0072] The above detailed description of the present application is made in combination with the specific implementation manners and exemplary examples, but these descriptions cannot be understood as limitations of the present application. Those skilled in the art understand that the technical solutions and implementation manners of the present application can be variously replaced, modified or improved without deviating from the spirit and scope of the present application, and these all fall within the scope of the present application. The protection scope of the present application is subject to the appended claims.

Claims

1. A method for continuous production of star-shaped block copolymer based on organocatalytic atom transfer radical polymerization, characterized by, The method comprises the following steps: S1, hydrophobic methyl methacrylate monomer, alkyl bromide initiator and organic catalyst are mixed and dissolved in an organic solvent to obtain reaction liquid A, and a hydrophobic star-shaped homopolymer is obtained by O-ATRP reaction under blue light irradiation; S2, hydrophilic polyethylene glycol monomethyl ether methacrylate monomer and organic catalyst are mixed and dissolved in an organic solvent to obtain reaction liquid B, and the reaction liquid B is mixed with the hydrophobic star-shaped homopolymer to obtain an amphiphilic star-shaped block copolymer by O-ATRP reaction under blue light irradiation; wherein 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); The structural formulae 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: wherein, n and m are independently selected from integers between 80 and 120; The organic catalyst is 1,2,3,5-tetra(carbazol-9-yl)-4,6-dicyanobenzene, and its structural formula is: wherein, The reaction liquid A is uniformly fed into reactor I at a speed of 0.06-0.2 mL / min to perform O-ATRP reaction, and the reaction liquid B is uniformly fed at a speed of 0.09-0.3 mL / min and then merged with the hydrophobic star-shaped homopolymer in a mixer to enter reactor II to perform O-ATRP reaction, and the reactor I and the reactor II are continuous flow micro-tube reactors; The wavelength of the blue light is 460 nm and the power is 3-4 mW / cm 2 .

2. The method for continuous production of star-shaped block copolymer based on organocatalytic atom transfer radical polymerization according to claim 1, wherein, The continuous flow micro-tube reactor comprises a spiral tube for liquid flow, and a blue light LED lamp tube penetrating the center of the spiral tube; And / or, the diameter of the liquid flow in the spiral tube is 1±0.5 mm.

3. The method for continuous production of star-shaped block copolymer based on organocatalytic atom transfer radical polymerization according to claim 1, wherein, In S2, the O-ATRP reaction time is 1-6 h.

4. A star-shaped block copolymer prepared by the method of any one of claims 1-3.

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