Method for preparing star-shaped block copolymer based on light-operated in-situ bromine-iodine conversion reversible-inactivation free radical polymerization method

Abstract

The invention discloses a method for preparing a star-shaped block copolymer based on a light-operated in-situ bromine-iodine conversion reversible-inactivation free radical polymerization method, which comprises the following steps: mixing and dissolving MMA (methyl methacrylate), an alkyl bromide initiator, iodide and an amine catalyst, and carrying out BIT-RDRP reaction under the irradiation of blue light to obtain a star-shaped homopolymer; and mixing and dissolving PEGMA300, iodide and an amine catalyst, mixing with the star-shaped homopolymer, and carrying out a BIT-RDRP reaction under the irradiation of blue light to obtain the amphiphilic star-shaped block copolymer. According to the invention, a BIT-RDRP reaction is adopted, and the BIT-RDRP reaction is introduced into a continuous flow microtube reactor to prepare an amphiphilic star-shaped block copolymer with a controllable block ratio; the method is mild in condition, simple in component, high in efficiency and capable of realizing continuous preparation, and a simple and efficient method is provided for controllable large-scale preparation of the star-shaped block copolymer.

Description

Technical Field

[0001] The invention relates to the technical field of polymer preparation, and in particular to a method for preparing a star-shaped block copolymer based on a light-controlled in-situ bromine-iodine conversion reversible-deactivation free radical polymerization method. Background Art

[0002] Star polymers have a unique three-dimensional snowflake-like structure, consisting of a core and several polymer "arms". There are two main strategies for synthesizing star polymers: "core first, arms later" and "arms first, core later". The "core first, arms later" strategy first designs a multifunctional macromolecule or small molecule as the core to trigger monomer polymerization to grow arms; the "arms first, core later" strategy first synthesizes polymer arms and then joins them to the core by chemical cross-linking. The "arms first, core later" strategy usually has the following disadvantages: the number of polymer arms is difficult to accurately control and difficult to characterize. In the "core first, arms later" strategy, the number of arms is relatively easier to determine, and the focus is on how to control the length of each arm to be relatively uniform.

[0003] Living / controlled free radical polymerization, also known as reversible-deactivation free radical polymerization (RDRP), combines the advantages of traditional free radical polymerization and living anionic polymerization. It can precisely control the molecular weight, molecular weight distribution, sequence structure, etc. of the polymer under relatively mild reaction conditions. It is widely used to design and synthesize a variety of complex and functional polymer materials. Among them, atom transfer radical polymerization (ATRP), reversible addition-fragmentation chain transfer (RAFT) polymerization and iodine-regulated reversible-deactivation free radical polymerization are widely used due to their mild polymerization conditions and wide range of monomer applications. Among them, iodine-regulated reversible-deactivation free radical polymerization mainly uses alkyl iodide as initiator, organic amine, quaternary ammonium salt, alkali metal salt as catalyst, activates carbon-iodine bond through halogen bond and constructs reversible equilibrium, and has the advantages of good controllability and wide range of monomer applications. However, its inherent disadvantage is that iodine-containing initiators have poor stability under normal conditions, making their storage, transportation and large-scale production difficult; at the same time, the iodine end is highly active, which makes it easy to be lost during polymerization and post-processing; in addition, alkali metal salt catalysts have poor solubility in organic solvents, which can easily cause blockage and is not conducive to operation in a flow system; on the other hand, metal residues will have an adverse effect on the subsequent application of the polymer.

[0004] In addition, the preparation of existing copolymers is usually 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 photo-controlled polymerization. Summary of the invention

[0005] The invention aims at the deficiencies in the prior art and provides a method for preparing a star-shaped block copolymer based on a light-controlled in-situ bromine-iodine conversion reversible-deactivation free radical polymerization method. The light-controlled in-situ bromine-iodine conversion reversible-deactivation free radical polymerization (BIT-RDRP) method is adopted and introduced into a continuous flow micro-tube reactor to prepare the star-shaped block copolymer, thereby overcoming the problem of poor stability of an alkyl iodide initiator in iodine-regulated RDRP, and providing a simple and efficient method for the controllable large-scale preparation of the star-shaped block copolymer.

[0006] In order to solve the above technical problems, the first aspect of the present invention provides a method for preparing a star-shaped block copolymer based on a photo-controlled in-situ bromine-iodine conversion reversible-deactivation free radical polymerization method, comprising the following steps:

[0007] S1, methyl methacrylate monomer (MMA), alkyl bromide initiator, iodide and amine catalyst are mixed and dissolved in an organic solvent to obtain a reaction solution A, and a hydrophobic star-shaped homopolymer is obtained by BIT-RDRP reaction under blue light irradiation;

[0008] S2, dissolving a hydrophilic polyethylene glycol monomethyl ether methacrylate monomer (PEGMA300), an iodide and an amine 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 through a BIT-RDRP 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] in, n is selected from an integer between 40-80, and m is selected from an integer between 60-100.

[0012] The invention adopts a light-controlled in-situ bromine-iodine conversion reversible-deactivation free radical polymerization (BIT-RDRP) 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 BIT-RDRP reaction chain extension; the conditions are mild, the components are simple, and no alkali metal salt and alkyl iodide are added, thereby overcoming the problems of poor solubility of alkali metal salts and poor stability of alkyl iodide initiators in iodine-controlled RDRP; the block copolymer with a 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 provides a simple and efficient method for controllable large-scale preparation of star-shaped block copolymers.

[0013] Furthermore, in S1, the molar ratio of the methyl methacrylate monomer, the alkyl bromide initiator, the iodide and the amine catalyst is (40-80):1:(8-12):(2-4).

[0014] Furthermore, in S2, the molar ratio of the polyethylene glycol monomethyl ether methacrylate monomer, the iodide and the amine catalyst is (60-100):1:(8-12):(2-4).

[0015] Furthermore, the amine catalyst is selected from one or more of triethylamine (TEA), diethanolamine (DEA), ethylamine (EA), and tetramethylethylenediamine (TMEDA).

[0016] Furthermore, the iodide is sodium iodide (NaI).

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

[0018] Furthermore, the solvent is selected from one or more of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), 1,3-dimethyl-2-imidazolidinone (DMI), and N-methylpyrrolidone (NMP).

[0019] Furthermore, the reaction solution A is uniformly injected into the reactor I through metering pump I for BIT-RDRP reaction, and the reaction solution B is uniformly injected into the reactor II through metering pump II and merged with the hydrophobic star-shaped homopolymer through a mixer for BIT-RDRP reaction. 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. They can achieve continuous preparation of polymers while improving polymerization rate and controllability. Block copolymers with target block ratios are prepared in a two-stage series of continuous microtubule reactors. After the reaction in reactor I, the reaction solution A does not need purification and separation steps. It directly merges with the reaction solution B in the mixer and enters the reactor II to continue the reaction, chain extension, grafting or intramolecular crosslinking, and a star-shaped block copolymer is obtained at the outlet of reactor II, simplifying the operation steps.

[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 (tube inner diameter) is 1±0.5 mm, the outer diameter of the tube is 3±0.5 mm, and the tube length is 10-50 m;

[0023] And / or, the wavelength of the blue light is 420-460nm, and the power is 3-4mW / cm 2 .

[0024] Furthermore, the overall outer diameter of the spiral tube (spiral outer diameter) is 40 mm.

[0025] Furthermore, the spiral tube is made of polytetrafluoroethylene.

[0026] Furthermore, the injection rate of the reaction solution A is 0.05-0.3 mL / min, and the injection rate of the reaction solution B is 0.1-0.2 mL / min.

[0027] Furthermore, in S2, the BIT-RDRP reaction time is 2-6 hours.

[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 invention adopts a light-controlled in-situ bromine-iodine conversion reversible-deactivation free radical polymerization (BIT-RDRP) method, and introduces it into a continuous flow microtube reactor to prepare an amphiphilic star block copolymer with controllable block ratio; the conditions are mild, the components are simple, the efficiency is high, and continuous preparation can be achieved; and no alkali metal salts and alkyl iodides are added, thereby overcoming the problems of poor solubility of alkali metal salts and poor stability of alkyl iodide initiators in iodine-controlled RDRP.

[0031] The present invention prepares a block copolymer with a target block ratio by designing the initial charge of reactants, light stimulation conditions, reactor parameters and the injection rate of the reaction solution, has a precise control effect on the polymer structure, and provides a simple and efficient method for the controllable large-scale preparation of star-shaped block copolymers. 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 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 a method for preparing a star-shaped block copolymer according to Example 4 of the present invention;

[0035] Figure 3 3 is a GPC chart of the hydrophobic star-shaped homopolymer and the amphiphilic star-shaped block copolymer prepared in Example 4 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 examples of the present invention, the characterization conditions 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 equipped with a refractive index detector (TOSOH), using a TSK gel Super MP-N (4.6×20 mm) guard column and a TSK gel Super HZ-N (4.6×150 mm) detection column as the eluent, at a test temperature of 40°C, a flow rate of 0.35 mL / min, and a molecular weight range of 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 preparing a star-shaped homopolymer based on a photo-controlled in-situ bromine-iodine conversion reversible-deactivation free radical polymerization method, comprising the following steps:

[0050] MMA:PE-4BPA (prepared in Example 1):NaI:TEA=60:1:10:2 were mixed in a molar ratio, 3 volumes of DMSO solvent were added to the MMA monomer to prepare reaction solution A, and the reaction mixture was bubbled for deoxygenation for 30 min, then transferred to a metering pump, and passed through a micro-tube reactor I with a spiral outer diameter of 40 mm and a tube inner diameter of 1 mm at a flow rate of 0.15 mL / min, using a wavelength of 460 nm and a power of 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, passed 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 at the same flow rate, the tube length is proportional to the time, the conversion rate is positively correlated with the reaction time, and the conversion rate is improved to varying degrees when the tube length is extended.

[0051] Table 1

[0052]

[0053] Example 3

[0054] This embodiment relates to a method for preparing a star-shaped homopolymer based on a photo-controlled in-situ bromine-iodine conversion reversible-deactivation free radical polymerization method, comprising the following steps:

[0055] MMA:PE-4BPA (prepared in Example 1):NaI:TEA=60:1:10:2 were mixed in a molar ratio, 3 volumes of DMSO solvent of MMA monomer were added to prepare reaction solution A, and 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 44.56 m at a flow rate of 0.117-0.583 mL / min, using a wavelength of 460 nm and a power of 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, passed 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 its M was tested by GPC. n,GPC and The results are shown in Table 2. Under the condition of the same tube length, the flow rate is inversely proportional to the time. When the flow rate is 0.146 mL / min and the time is 240 min, the conversion rate is the highest and the best polymerization effect is achieved.

[0056] Table 2

[0057]

[0058]

[0059] Example 4

[0060] This embodiment relates to a method for preparing an amphiphilic star-shaped block copolymer based on a photo-controlled in-situ bromine-iodine conversion reversible-deactivation free radical polymerization method, as shown in the flow chart. Figure 2 As shown, the following steps are included:

[0061] Mix according to the molar ratio of MMA:PE-4BPA (prepared in Example 1):NaI:TEA=60:1:10:2, add 3 times the volume of DMSO solvent of MMA monomer to prepare reaction solution A, add it to the ampoule, bubble the reaction mixture for deoxygenation for 30 minutes, and then transfer it to metering pump I. Mix according to the molar ratio of PEGMA300:NaI:TEA=80:10:2, add 3 times the volume of DMSO solvent of PEGMA300 monomer to prepare reaction solution B, add it to the ampoule, bubble the reaction mixture for deoxygenation for 30 minutes, and then transfer it to metering pump II. Set the flow rate of metering pump I to 0.05mL / 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 44.56m. 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 0.135 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 70 minutes. After the reaction, an amphiphilic star-shaped block copolymer was obtained. 1 HNMR and GPC measurements of monomer conversion and product M in BIT-RDRP reactions in two reactors n,GPC and The results are shown in Table 3. The GPC graphs of the star-shaped homopolymer (before chain extension) and the star-shaped block copolymer (after chain extension) are shown in Table 3. Figure 3 As shown. It can be seen that this method successfully prepared star-shaped block copolymers.

[0062] Table 3

[0063]

[0064] In summary, the present invention adopts a light-controlled in-situ bromine-iodine conversion reversible-deactivation free radical polymerization (BIT-RDRP) method, and introduces it into a continuous flow microtube reactor to prepare an amphiphilic star-shaped block copolymer with a controllable block ratio; the conditions are mild, the components are simple, the efficiency is high, and continuous preparation can be achieved; and no alkali metal salts and alkyl iodides are added, thereby overcoming the problems of poor solubility of alkali metal salts and poor stability of alkyl iodide initiators in iodine-controlled RDRP; block copolymers with a target block ratio are prepared by designing the initial feed of reactants, light stimulation conditions, reactor parameters, and the injection rate of the reaction solution, which has a precise control effect on the polymer structure, and provides a simple and efficient method for the controllable large-scale preparation of star-shaped block copolymers.

[0065] 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 preparing a star-shaped block copolymer based on a photo-controlled in-situ bromine-iodine conversion reversible-deactivation free radical polymerization method, characterized in that: The steps include: S1, dissolving methyl methacrylate monomer, alkyl bromide initiator, iodide and amine catalyst in an organic solvent to obtain a reaction solution A, and obtaining a hydrophobic star-shaped homopolymer through a BIT-RDRP reaction under blue light irradiation; S2, dissolving a hydrophilic polyethylene glycol monomethyl ether methacrylate monomer, an iodide and an amine 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 through a BIT-RDRP 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 is selected from an integer between 40-80, and m is selected from an integer between 60-100.

2. The method for preparing a star-shaped block copolymer based on a photo-controlled in-situ bromine-iodine conversion reversible-deactivation free radical polymerization method according to claim 1, characterized in that: In S1, the molar ratio of the methyl methacrylate monomer, the alkyl bromide initiator, the iodide and the amine catalyst is (40-80):1:(8-12):(2-4).

3. The method for preparing a star-shaped block copolymer based on a photo-controlled in-situ bromine-iodine conversion reversible-deactivation free radical polymerization method according to claim 1, characterized in that: In S2, the molar ratio of the polyethylene glycol monomethyl ether methacrylate monomer, the iodide and the amine catalyst is (60-100):1:(8-12):(2-4).

4. The method for preparing a star-shaped block copolymer based on a photo-controlled in-situ bromine-iodine conversion reversible-deactivation free radical polymerization method according to claim 1, characterized in that: The amine catalyst is selected from one or more of triethylamine, diethanolamine, ethylamine and tetramethylethylenediamine.

5. The method for preparing a star-shaped block copolymer based on photo-controlled in-situ bromine-iodine conversion reversible-deactivation free radical polymerization as claimed in claim 1, characterized in that: The iodide is sodium iodide.

6. The method for preparing a star-shaped block copolymer based on photo-controlled in-situ bromine-iodine conversion reversible-deactivation free radical polymerization as claimed in claim 1, characterized in that: The reaction solution A is uniformly injected into reactor I through metering pump I for BIT-RDRP reaction, and the reaction solution B is uniformly injected into reactor II through metering pump II and then merged with the hydrophobic star-shaped homopolymer through a mixer for BIT-RDRP reaction. Reactor I and reactor II are continuous flow microtubule reactors.

7. The method for preparing a star-shaped block copolymer based on photo-controlled in-situ bromine-iodine conversion reversible-deactivation free radical polymerization as claimed in claim 6, 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; And / or, the wavelength of the blue light is 420-460nm, and the power is 3-4mW / cm 2 .

8. The method for preparing a star-shaped block copolymer based on photo-controlled in-situ bromine-iodine conversion reversible-deactivation free radical polymerization as claimed in claim 1, characterized in that: The injection rate of the reaction solution A is 0.05-0.3 mL / min, and the injection rate of the reaction solution B is 0.1-0.2 mL / min.

9. The method for preparing a star-shaped block copolymer based on photo-controlled in-situ bromine-iodine conversion reversible-deactivation free radical polymerization as claimed in claim 1, characterized in that: In S2, the BIT-RDRP reaction time is 2-6 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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