A method for preparing star-shaped block copolymer based on photo-controlled in-situ bromine-iodine conversion reversible-inactivation free radical polymerization

Abstract

The application discloses a method for preparing star-shaped block copolymer based on light-controlled in-situ bromine-iodine conversion reversible-deactivation radical polymerization, which comprises the following steps: mixing and dissolving MMA, alkyl bromide initiator, iodide and amine catalyst, and obtaining star-shaped homopolymer through BIT-RDRP reaction under blue light irradiation; mixing and dissolving PEGMA300, iodide and amine catalyst, mixing with the star-shaped homopolymer, and obtaining amphiphilic star-shaped block copolymer through BIT-RDRP reaction under blue light irradiation. The BIT-RDRP reaction is adopted, and the BIT-RDRP reaction is introduced into a continuous flow micro-tube reactor to prepare amphiphilic star-shaped block copolymer with controllable block ratio; the method has the advantages of mild conditions, simple components and high efficiency, can realize continuous preparation, and provides a simple and efficient method for controllable large-scale preparation of star-shaped block copolymer.

Description

TECHNICAL FIELD

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

[0002] Star-shaped polymers have a unique three-dimensional snowflake-like structure, containing a core and several polymer "arms". There are mainly two strategies for synthesizing star-shaped polymers: "core-first" and "arm-first". In the "core-first" strategy, a multifunctional macromolecule or small molecule is designed as the core to initiate the polymerization of monomers to grow arms. In the "arm-first" strategy, polymer arms are first synthesized and then chemically crosslinked to the core. The "arm-first" strategy usually has the following disadvantages: the number of polymer arms is difficult to control accurately and is not easy to characterize. In the "core-first" 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] Reversible-deactivation radical polymerization, also known as reversible-deactivation radical polymerization (RDRP), combines the advantages of traditional radical polymerization and living anionic polymerization, and can accurately control the molecular weight, molecular weight distribution, sequence structure, etc. of the polymer under relatively mild reaction conditions, and is widely used in the design and synthesis of various polymer materials with complex structure and rich function. Among them, atom transfer radical polymerization (ATRP), reversible addition-fragmentation chain transfer (RAFT) polymerization and iodine-regulated reversible-deactivation radical polymerization are widely used due to their mild polymerization conditions, wide range of monomers, etc. Among them, iodine-regulated reversible-deactivation radical polymerization mainly uses alkyl iodide as an initiator, and uses organic amine, quaternary ammonium salt, alkali metal salt as a catalyst to activate the carbon-iodine bond through halogen and build a reversible balance, and has the advantages of good controllability and wide range of monomers. However, its inherent disadvantage is that the iodine-containing initiator has poor stability in normal environment, making it difficult to store, transport and mass produce; at the same time, the iodine end is highly active, which leads to its loss during polymerization and post-processing; in addition, the alkali metal salt catalyst has poor solubility in organic solvents, which can easily 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.

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

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

[0006] To solve the above technical problems, the present application provides a method for preparing star-shaped block copolymer based on light-controlled in-situ bromine-iodine conversion reversible-deactivation radical polymerization, which comprises 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 reaction liquid A, and a hydrophobic star-shaped homopolymer is obtained through BIT-RDRP reaction under blue light irradiation;

[0008] S2, hydrophilic polyethylene glycol monomethyl ether methacrylate monomer (PEGMA300), iodide and amine 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, and an amphiphilic star-shaped block copolymer is obtained through BIT-RDRP reaction under blue light irradiation;

[0009] 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 as follows:

[0010]

[0011] Among them, n is an integer selected from 40-80, and m is an integer selected from 60-100.

[0012] The present application adopts the light-controlled in-situ bromine-iodine conversion reversible-deactivation radical polymerization (BIT-RDRP) method to prepare an intermediate hydrophobic star-shaped homopolymer, and based on this, the active groups at the chain ends of the polymer are used to expand the chain through BIT-RDRP reaction to obtain an amphiphilic star-shaped block copolymer with controllable block ratio; the conditions are mild, the components are simple, no alkali metal salt and alkyl iodide are added, the problems of poor solubility of alkali metal salt and poor stability of alkyl iodide initiator in iodine-regulated RDRP are overcome; the initial feeding of reactants and light irradiation conditions are designed to prepare the block copolymer with the target block ratio, which has precise control effect on the polymer structure, and provides a simple and efficient method for controllable large-scale preparation of star-shaped block copolymer.

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

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

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

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

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

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

[0019] Further, the reaction liquid A is uniformly fed into the reactor I by a metering pump I to carry out the BIT-RDRP reaction, the reaction liquid B is uniformly fed by a metering pump II and then mixed with the hydrophobic star-shaped homopolymer in a mixer before entering the reactor II to carry out the BIT-RDRP 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, which can improve the polymerization rate and control while realizing the continuous preparation of the polymer. In the secondary continuous micro-tube reactor, the target block copolymer with a block ratio is prepared, the reaction liquid A is directly mixed with the reaction liquid B in the mixer after reaction in the reactor I without a purification and separation step, and then enters the reactor II for further reaction, chain extension, grafting or intramolecular crosslinking, so that the star-shaped block copolymer is obtained at the outlet of the reactor II, thereby simplifying the operation steps.

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

[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] Further, the diameter of the liquid flow in the spiral tube (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] And / or, the wavelength of the blue light is 420-460nm, and the power is 3-4mW / cm 2 .

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

[0025] Further, the material of the spiral tube is polytetrafluoroethylene.

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

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

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

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

[0030] The present application adopts the light-controlled in-situ bromine-iodine conversion reversible-deactivation radical polymerization (BIT-RDRP) method, and introduces it into the continuous flow micro-tube reactor to prepare the amphiphilic star-shaped block copolymer with controllable block ratio; the conditions are mild, the components are simple, and the efficiency is high, and the continuous preparation can be realized; and no alkali metal salt and alkyl radical are added, which overcomes the problems of poor solubility of alkali metal salt and poor stability of alkyl iodine initiator in the iodine-controlled RDRP.

[0031] The present application prepares the block copolymer with target block ratio by designing the initial feeding of reactants, light stimulation conditions, reactor parameters and injection rate of reaction liquid, has precise control effect on polymer structure, and provides a simple and efficient method for controllable large-scale preparation of star-shaped block copolymer. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the present application, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings in the following description are only embodiments of the present application, and other drawings can also be obtained according to these drawings without creative labor for those skilled in the art.

[0033] Figure 1 is the H NMR chart of the alkyl bromide initiator prepared in example 1 of the present application 1 H NMR chart

[0034] Figure 2 is the method flow chart schematic diagram of preparing star-shaped block copolymer in example 4 of the present application

[0035] Figure 3 Figure 3 is a GPC chart of the hydrophobic star-shaped homopolymer and amphiphilic star-shaped block copolymer prepared in Example 4 of the present application. DETAILED DESCRIPTION

[0036] The technical solutions of the present application will be described clearly and completely below in combination with specific examples of the present application. Obviously, the described examples are only some of the examples of the present application, but not all the examples. Based on the examples in the present application, all the other examples obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

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

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

[0039] 2. Polymer number average molecular weight (Mn) and molecular weight distribution The polymer number average molecular weight (Mn) and molecular weight distribution were determined by a TOSOH HLC-8320 gel permeation chromatograph equipped with a refractive index detector (TOSOH), using a TSK gel Super MP-N (4.6x20mm) as a guard column. A TSK gel Super HZ-N (4.6x150mm) was used as a detection column, and THF was used as an eluent, the test temperature was 40°C, the flow rate was 0.35mL / min, and the molecular weight range was 5x10 2-5 g / mol. The gel permeation chromatograph sample was injected using a TOSOH plus automatic sampler, and the results of the measured polymer were calibrated using standard PMMA samples purchased from TOSOH.

[0040] 3. Light intensity of light source The light intensity of light source was determined using an 0820FD18T-TS15 laser power meter purchased from Changchun Xin industry Optoelectronic Technology Co., Ltd., the environmental temperature of the polymerization system was 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 250mL round-bottom flask, 0.54g (4mmol) of pentaerythritol, 5.16g (24mmol) of α-bromophenylacetic acid and 75mg (0.4mmol) of p-toluenesulfonic acid were sequentially added, then 35mL of toluene was added, heated to 110°C and condensed to reflux, and reacted for 12 hours.

[0044] After the reaction was completed, the reaction solution was cooled to room temperature, toluene was removed by rotary evaporation, a dark yellow oil was obtained, which was dissolved in saturated sodium bicarbonate solution, the solution was extracted with 150 mL of ethyl acetate, the organic phase was taken, 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 the 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 preparing star-shaped homopolymer based on light-controlled in-situ bromine-iodine conversion reversible-inactivation radical polymerization, comprising the following steps:

[0050] According to the molar ratio of MMA: PE-4BPA (prepared in Example 1): NaI: TEA = 60:1:10:2, 3 times the volume of DMSO solvent of MMA monomer was mixed to prepare reaction solution A, which was added to the ampoule. The reaction mixture was bubbled for 30 min to remove oxygen, then it was transferred to the metering pump, and the flow rate was 0.15 mL / min through the micro-tube reactor I with an outer diameter of 40 mm and an inner diameter of 1 mm. The reaction mixture in the micro-tube was irradiated with blue light with a wavelength of 460 nm and a power of 3.6 mW / cm 2 , 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 of 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, Mn and The results are shown in Table 1. It can be seen that under the same flow rate, the tube length is proportional to the time, and the conversion rate is positively correlated with the reaction time. Under the condition of prolonging the tube length, the conversion rate is improved to different degrees.

[0051] Table 1

[0052]

[0053] Example 3

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

[0055] MMA monomer was mixed with PE-4BPA (prepared in Example 1), NaI and TEA in a molar ratio of MMA:PE-4BPA:NaI:TEA = 60:1:10:2, and 3 times the volume of DMSO solvent was added to prepare reaction liquid A, which was added to the ampoule. The reaction mixture was bubbled for 30 min to remove oxygen, and then transferred to the metering pump. The reaction mixture was irradiated with blue light with a wavelength of 460 nm and a power of 3.6 mW / cm 2 at a flow rate of 0.117-0.583 mL / min through a micro-tube reactor I with an outer diameter of 40 mm, an inner diameter of 1 mm, and a length of 44.56 m. The light source was a blue light with a wavelength of 460 nm and a power of 3.6 mW / cm 1 The light source was a blue light with a wavelength of 460 nm and a power of 3.6 mW / cm 1 The conversion rate of monomer was measured by n,GPC 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 product was dissolved in THF to prepare a 2-5 mg / mL solution, which was tested by GPC to determine the M n,GPC and The results are shown in Table 2. Under the same tube length, the flow rate is inversely proportional to the time, where 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 example relates to a method for preparing amphiphilic star-shaped block copolymer based on photo-controlled in-situ bromine-iodine conversion reversible-deactivation radical polymerization, the flow chart is shown in Figure 2 , comprising the following steps:

[0061] MMA:PE-4BPA (prepared in Example 1): NaI:TEA = 60:1:10:2 by mole ratio, and then MMA monomer was dissolved in 3 times volume of DMSO to prepare reaction liquid A which was added into the ampoule. The reaction mixture was bubbled for 30 min to remove oxygen, and then was transferred to metering pump I. PEGMA300: NaI:TEA = 80:10:2 by mole ratio, and then PEGMA300 monomer was dissolved in 3 times volume of DMSO to prepare reaction liquid B which was added into the ampoule. The reaction mixture was bubbled for 30 min to remove oxygen, and then was transferred to metering pump II. The flow rate of metering pump I was set to 0.05 mL / min, and reaction liquid A was pumped into reactor I. The spiral outer diameter of reactor I was 40 mm, the tube inner diameter was 1 mm, and the tube length was 44.56 m. The reaction mixture in the microtube was irradiated by blue light with a wavelength of 460 nm and a power of 3.6 mW / cm2to obtain a hydrophobic star-shaped homopolymer. The flow rate of metering pump I was kept unchanged, and the flow rate of metering pump II was set to 0.135 mL / min. Reaction liquid B was mixed with the product from reactor I to enter reactor II through the mixer. The spiral outer diameter of reactor II was 40 mm, the tube inner diameter was 1 mm, and the tube length was 22.92 m. The reaction mixture in the microtube was irradiated by blue light with a wavelength of 460 nm and a power of 3.6 mW / cm2to carry out chain extension polymerization for 70 min. After the reaction was completed, an amphiphilic star-shaped block copolymer was obtained. 2 2 1 n,GPC 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 Figure 3

[0062] Table 3

[0063]

[0064] In summary, the BIT-RDRP method controlled by light in situ bromine-iodine conversion is introduced into a continuous flow microtube reactor to prepare an amphiphilic star-shaped block copolymer with a controllable block ratio. The method has mild conditions, simple components, and high efficiency, and can realize continuous preparation. Moreover, no alkali metal salt and alkyl iodide are added, which overcomes the problems of poor solubility of alkali metal salt and poor stability of alkyl iodide initiator in the iodine-controlled RDRP. The initial feeding of reactants, light stimulation conditions, reactor parameters, and the feeding rate of the reaction liquid are designed to prepare a block copolymer with a target block ratio, which has 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 application has been described in detail by reference to particular embodiments and illustrative examples. These particular embodiments are, however, merely examples of the present application and do not limit the present application. It should be understood by those skilled in the art that in the scope of the rights sought by the present application, various equivalent substitutions, modifications or improvements based on the technical solutions and embodiments of the present application can be made without departing from the spirit and scope of the present application, and these all fall within the scope of the present application. The scope of protection of the present application is defined by the appended claims.

Claims

1. A method for preparing star-shaped block copolymer by photoinitiating in-situ bromine-iodine exchange reversible-deactivation radical polymerization, characterized in that, It comprises the following steps: S1, mixing and dissolving methyl methacrylate monomer, alkyl bromide initiator, iodide and amine catalyst in a molar ratio of 60:1:10:2 in an organic solvent to obtain reaction liquid A, and obtaining a hydrophobic star-shaped homopolymer by BIT-RDRP reaction under blue light irradiation; S2, mixing and dissolving hydrophilic polyethylene glycol monomethyl ether methacrylate monomer, iodide and amine catalyst in a molar ratio of 80:10:2 in an organic solvent to obtain reaction liquid B, mixing reaction liquid B with the hydrophobic star-shaped homopolymer, and obtaining an amphiphilic star-shaped block copolymer by BIT-RDRP reaction under blue light irradiation; The reaction liquid A is uniformly fed into the reactor I at a speed of 0.05-0.3 mL / min by a metering pump I to carry out BIT-RDRP reaction, and the reaction liquid B is uniformly fed at a speed of 0.1-0.2 mL / min by a metering pump II and then merged with the hydrophobic star-shaped homopolymer through a mixer to enter the reactor II to carry out BIT-RDRP reaction, and the reactor I and the reactor II are continuous flow micro-tube reactors; 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 the spiral tube has a length of 10-50 m. 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 as follows: , , , , ; wherein, , n is selected from an integer between 40 and 80, and m is selected from an integer between 60 and 100.

2. The method for preparing star-shaped block copolymer by photoiniferter reversible-deactivation radical polymerization in situ Br-I exchange according to claim 1, wherein the monomer mixture comprises a monomer having a bromine atom and a monomer having an iodine atom. The amine catalyst is selected from one or more of triethylamine, diethanolamine, ethylamine and tetramethyl ethylenediamine.

3. The method for preparing star-shaped block copolymer by photoiniferter reversible-deactivation radical polymerization in situ Br-I exchange according to claim 1, wherein the monomer mixture comprises a monomer having a bromine atom and a monomer having an iodine atom. The iodide is sodium iodide.

4. The method for preparing star-shaped block copolymer by photoiniferter reversible-deactivation radical polymerization in situ Br-I exchange according to claim 1, wherein the monomer mixture comprises a monomer having a bromine atom and a monomer having an iodine atom. The diameter of the liquid flow in the spiral tube is 1±0.5 mm; and / or the blue light has a wavelength of 420-460 nm and a power of 3-4 mW / cm2 2 .

5. The method for preparing star-shaped block copolymer by photoiniferter reversible-deactivation radical polymerization in situ Br-I exchange according to claim 1, wherein the monomer mixture comprises a monomer having a bromine atom and a monomer having an iodine atom. In S2, the BIT-RDRP reaction time is 2-6 h.

6. A star-shaped block copolymer prepared by the method of claim 1-5.

Images