A CABC-type asymmetric block copolymer and its preparation method

Abstract

The present invention discloses a CABC-type asymmetric block copolymer and a preparation method thereof. The in-situ bromine-iodine conversion of a bromine initiator containing double initiation sites and an iodine agent generates a carbon-iodine bond active site, thereby initiating monomers for reversible complex-mediated polymerization. The first monomer is photo-initiated for polymerization through the carbon-iodine bonds at both ends, the second monomer is photo-initiated for chain extension polymerization through the carbon-iodine bonds at both ends, and the third monomer is thermally initiated for polymerization by the carbon-iodine bonds at both ends and the middle azo group simultaneously, finally obtaining a CABC-type asymmetric block copolymer. It overcomes the problems of cumbersome process and unstable controllability in the synthesis of CABC-type asymmetric block copolymers by traditional sequential polymerization, and solves the problems of difficult preparation and storage of iodine catalysts in the reversible complex-mediated polymerization system and easy thermal cleavage of end groups.

Description

Technical Field

[0001] The present invention relates to the field of polymer synthesis and controlled polymerization, and particularly relates to a CABC-type asymmetric block copolymer and a preparation method thereof. Background Art

[0002] A block copolymer is a type of polymer material formed by covalently connecting two or more polymer segments with different chemical properties. Due to the adjustable physical and chemical properties and rich nanostructures of block polymers, they have attracted extensive attention in the fields of biomedicine and materials science. CABC-type asymmetric block copolymers are an interesting type of block copolymer, which can self-assemble to produce non-centrosymmetric nanostructures and have properties different from ordinary block copolymers. Currently, almost all block copolymers are synthesized by living polymerization methods, mainly including anionic polymerization, living radical polymerization, and group transfer polymerization. Among many living polymerization techniques, living radical polymerization has the most promising industrial production technology due to its wide monomer range and mild conditions, and has greater practical significance.

[0003] Living radical polymerization (LRP), also known as reversible deactivation radical polymerization (RDRP), has developed rapidly in the past few decades. Most existing living radical polymerization techniques have inevitable disadvantages. For example, ATRP uses transition metal catalysts, which causes environmental pollution problems and is inconvenient for subsequent treatment. RAFT requires a chain transfer agent, which is expensive and causes polymer products to be colored, which is not conducive to subsequent processing. NMP has a narrow range of applicable monomers and requires a relatively high reaction temperature. Compared with other reversible deactivation radical polymerizations, reversible complex-mediated radical polymerization (RCMP) has the advantages of simple operation, energy saving, spatiotemporal controllability of polymer polydispersity (Mw / Mn), and strong tolerance to functional groups. It is feasible to synthesize CABC asymmetric block copolymers by the method of reversible complex-mediated radical polymerization (RCMP).

[0004] The traditional sequential polymerization for synthesizing CABC-type asymmetric block copolymers requires four steps, and there are problems of cumbersome process and unstable controllability. In recent years, there have been studies on the three-step temperature-controlled synthesis of CABC-type asymmetric block copolymers using a reversible complex-mediated polymerization system, but the problems of expensive iodine catalyst and difficult preparation and storage are still obvious.

[0005] Therefore, it is very necessary to invent a concise and efficient synthesis method for CABC-type asymmetric block copolymers. Summary of the Invention

[0006] The problem to be solved by the present invention is to overcome the problems of cumbersome process and unstable controllability in the traditional sequential polymerization for synthesizing CABC-type asymmetric block copolymers, and to solve the problems of difficult preparation, storage of iodine catalysts and easy thermal cleavage of end groups in the reversible complexation-mediated polymerization system. A synthesis method of a bromine catalyst with both photoinitiating active sites and thermal initiating active sites is provided, and a three-step method of photopolymerization-photopolymerization-thermal polymerization is established based on this initiator.

[0007] The present invention adopts the following technical solutions to achieve the above technical problems:

[0008] A CABC-type asymmetric block copolymer and its preparation method. The in-situ bromine-iodine conversion of a bromine initiator and an iodine agent containing double initiating sites generates carbon-iodine bond active sites, thereby initiating monomers to carry out reversible complexation-mediated polymerization. The first monomer is photopolymerized through the carbon-iodine bonds at both ends, the second monomer is chain-extended by photopolymerization through the carbon-iodine bonds at both ends, and the third monomer is thermally polymerized simultaneously through the carbon-iodine bonds at both ends and the middle azo group, and finally a CABC-type asymmetric block copolymer is obtained.

[0009] The initiator Br-EPhAzo-Br used in the present invention has the following specific general formula:

[0010]

[0011] The preparation method of the initiator used in the present invention includes the following synthesis steps:

[0012] 1) Add 2.0 g of 4,4'-azobis(4-cyanopentanol), 3.784 g of α-bromophenylacetic acid, 0.185 g of 4-dimethylaminopyridine and 50 ml of dichloromethane to a round-bottom flask and mix evenly.

[0013] 2) Add N,N'-dicyclohexylcarbodiimide (3.955 g) dissolved in 15 ml of dichloromethane at 0 °C and stir for one hour.

[0014] 3) Then, transfer the reaction system to room temperature and continue the reaction for 24 hours.

[0015] 4) After the reaction is completed, filter the reaction mixture, concentrate the obtained filtrate by rotary evaporation, and purify it by silica gel column chromatography to obtain the target product Br-EPhAzo-Br.

[0016] The CABC-type asymmetric block copolymer described in the present invention has the following specific general formula:

[0017]

[0018] m ∈ (0, 50); n ∈ (0, 100); p ∈ (0, 200)

[0019] A preparation method of a CABC-type asymmetric block copolymer according to the present invention, the synthesis steps thereof include:

[0020] (1) Methyl methacrylate, initiator Br-EPhAzo-Br, sodium iodide, and pentamethyldiethylenetriamine were successively added to a glass bottle, and the bottle mouth was directly sealed with a rubber stopper to remove excess air. The glass bottle containing the reaction mixture was placed on a stirring table and irradiated with a white LED lamp. Samples were taken with a syringe at the expected time points. The remaining samples were precipitated in n-hexane and dried under vacuum to obtain the macroinitiator I-PMMA-N=N-PMMA-I.

[0021] (2) Benzyl methacrylate, I-PMMA-N=N-PMMA-I, and pentamethyldiethylenetriamine were successively added to a glass bottle, and the bottle mouth was directly sealed with a rubber stopper to remove excess air. The glass bottle containing the reaction mixture was placed on a stirring table and irradiated with a white LED lamp. Samples were taken with a syringe at the expected time points. The remaining samples were precipitated in n-hexane and dried under vacuum to obtain the macroinitiator I-PBzMA- b -PMMA-N=N-PMMA- b -PBzMA-I.

[0022] (3) Butyl methacrylate, I-PBzMA- b -PMMA-N=N-PMMA- b -PBzMA-I, elemental iodine, and tetrabutylammonium iodide were successively added to a 25 mL Schlenk tube, and a liquid nitrogen freezing-pumping-thawing cycle was carried out three times for deoxygenation, and a polymerization reaction was carried out at a certain temperature. Samples were taken with a sampling needle at the expected time points. The remaining samples were precipitated in n-hexane and dried under vacuum to obtain the target product I-PBMA- b -PBzMA- b -PMMA- b -PBMA-I.

[0023] The light source conditions in the synthesis step (1) are 13 Wm -1 , 15 mW cm -2 , and the polymerization time of the macroinitiator I-PMMA-N=N-PMMA-I for the next polymerization is 60 min, and the sampling times are 45 min, 90 min, 135 min, and 180 min respectively.

[0024] The light source conditions in the synthesis step (2) are 13 Wm -1 , 15 mW cm -2 , and the macroinitiator I-PBzMA- b -PMMA-N=N-PMMA-b The polymerization time of -PBzMA-I was 60 min, and the sampling times were 15 min, 30 min, 45 min, and 60 min, respectively.

[0025] The reaction temperature in step (3) of its synthesis was 90 °C, and the final product was I-PBMA- b -PBzMA- b -PMMA- b The polymerization time of -PBMA-I was 80 min, and the sampling times were 20 min, 40 min, 60 min, and 80 min, respectively.

[0026] In step (1) of its synthesis, the molar ratio of methyl methacrylate: Br-EPhAzo-Br: sodium iodide: pentamethyldiethylenetriamine was 100:1:2.4:0.5.

[0027] In step (2) of its synthesis, the molar ratio of benzyl methacrylate: I-PMMA-N=N-PMMA-I: pentamethyldiethylenetriamine was 200:1:0.5.

[0028] In step (3) of its synthesis, the molar ratio of butyl methacrylate: I-PBzMA- b -PMMA-N=N-PMMA- b -PBzMA-I: iodine: tetrabutylammonium iodide was 800:1:1:4.

[0029] The initiator Br-EPhAzo-Br has two active initiation sites, namely the halogen bond at both ends and the azo bond structure in the middle.

[0030] In the first step, the initiator Br-EPhAzo-Br undergoes in-situ bromo-iodine conversion with sodium iodide to obtain a carbon-iodine bond, which initiates the monomer for photoinduced reversible complex-mediated polymerization.

[0031] For a CABC-type asymmetric block copolymer and its preparation method according to the present invention, the monomers used are methacrylate monomers, including one of methyl methacrylate, benzyl methacrylate, and butyl methacrylate.

[0032] The prominent features of the present invention:

[0033] 1. In the present invention, a carbon-iodine bond is generated through in-situ bromo-iodine conversion of a carbon-bromine bond and an iodinating agent, serving as an active initiation site for photoinitiated reversible complex-mediated polymerization.

[0034] 2. The initiator prepared in the present invention has the advantages of simple synthesis, low price, and convenient transportation and storage compared with iodine initiators.

[0035] 3. The synthesis method of the CABC-type asymmetric block copolymer established in the present invention is simpler than the traditional four-step sequential polymerization method, and the efficiency is improved.

[0036] 4. The synthesis method of the CABC-type asymmetric block copolymer established in the present invention is widely applicable to a variety of methacrylate monomers.

[0037] 5. The synthesis process of the CABC-type asymmetric block copolymer established in the present invention is controllable, and a CABC-type asymmetric block copolymer with precise molecular weight and low polydispersity can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is the structural diagram of Br-EPhAzo-Br in Example 1;

[0039] Figure 2 It is the 1H NMR spectrum of Br-EPhAzo-Br in Example 1;

[0040] Figure 3 It is the 13C NMR spectrum of Br-EPhAzo-Br in Example 1;

[0041] Figure 4 It is the time-of-flight mass spectrum of Br-EPhAzo-Br in Example 1;

[0042] Figure 5 It is the group of kinetic curves in Example 2;

[0043] Figure 6 It is for I-PMMA-N=N-PMMA-I, I-PBzMA- b -PMMA-N=N-PMMA- b -PBzMA-I, I-PBMA- b -PBzMA- b -PMMA- b -PBMA-I in Example 3;

[0044] Figure 7 It is for I-PMMA-N=N-PMMA-I, I-PBzMA- b -PMMA-N=N-PMMA- b -PBzMA-I, I-PBMA- b -PBzMA- b -PMMA- b -PBMA-I in Example 3; DETAILED DESCRIPTION OF THE INVENTION

[0045] To make the content of the present invention more understandable, the technical solutions of the present invention will be further described below in conjunction with specific embodiments. However, the present invention is not limited thereto.

[0046] Example 1

[0047] 2.0 g of 4,4'-azobis(4-cyanopentanol), 3.784 g of α-bromophenylacetic acid, 0.185 g of 4-dimethylaminopyridine and 50 ml of dichloromethane were added to a 100 ml round-bottom flask and mixed evenly. N,N'-Dicyclohexylcarbodiimide (3.955 g) dissolved in 15 ml of dichloromethane was slowly added dropwise at 0 °C, and the mixture was stirred for one hour. Then, the reaction system was transferred to room temperature and reacted for another 24 hours. After the reaction was completed, the reaction mixture was filtered, and the obtained filtrate was concentrated by rotary evaporation and purified by silica gel column chromatography, where the volume ratio of the eluent was dichloromethane:n-hexane = 4:1. Finally, the target product Br-EPhAzo-Br was obtained with a yield of 63%. The target product Br-EPhAzo-Br was characterized by 1H NMR, 13C NMR and mass spectrometry.

[0048] Example 2

[0049] (1) 2 mL of methyl methacrylate MMA, 122.0 mg of initiator Br-EPhAzo-Br, 68.0 mg of NaI and 4.08 mg of pentamethyldiethylenetriamine PMDETA were successively added to a 3 ml glass bottle, and the bottle mouth was directly sealed with a rubber stopper. The excess air was removed from the vial by purging with nitrogen. The glass bottle containing the reaction mixture was placed on a stirring table and irradiated with an LED lamp. Samples were taken with a syringe at the expected time points for GPC and 1 1H NMR detection.

[0050] (2) 1.60 mL of benzyl methacrylate BzMA, 122.72 mg of I-PMMA-N=N-PMMA-I and 4.08 mg of pentamethyldiethylenetriamine PMDETA were successively added to a 3 ml glass bottle, and the bottle mouth was directly sealed with a rubber stopper. The excess air was removed from the vial by purging with nitrogen. The glass bottle containing the reaction mixture was placed on a stirring table and irradiated with an LED lamp. Samples were taken with a syringe at the expected time points for GPC and 1 1H NMR detection.

[0051] (3) 1.49 ml of butyl methacrylate BMA, 116.82 mg of I-PBzMA- b -PMMA-N=N-PMMA- b-PMBzMA-I, 3.00 mg of I2, and 17.4 mg of tetrabutylammonium iodide (BNI) were successively added into a 25 mL Schlenk tube, and the tube opening was directly sealed with a rubber stopper. The Schlenk tube containing the reaction mixture was subjected to three freeze-pump-thaw cycles with liquid nitrogen for deoxygenation and then reacted at 90 °C. Samples were taken with a sampling needle at the expected time points for GPC and 1H NMR detection respectively.

[0052] Example 3

[0053] (1) 2 mL of MMA, 122.0 mg of Br-EPhAzo-Br, 68.0 mg of NaI, and 4.08 mg of PMDETA were successively added into a 3 mL glass bottle, and the bottle opening was directly sealed with a rubber stopper. The excess air was removed from the vial by bubbling nitrogen. The glass bottle containing the reaction mixture was placed on a stirring table and irradiated with an LED lamp for 60 min. After the reaction, the mixture was reprecipitated in n-hexane and dried to obtain a macroinitiator (I-PMMA-N=N-PMMA-I, M n = 2600, M w / M n = 1.25).

[0054] (2) 1.60 mL of BzMA, 122.72 mg of I-PMMA-N=N-PMMA-I, and 4.08 mg of PMDETA were successively added into a 3 mL glass bottle, and the bottle opening was directly sealed with a rubber stopper. The excess air was removed from the vial by bubbling nitrogen. The glass bottle containing the reaction mixture was placed on a stirring table and irradiated with an LED lamp for 60 min. After the reaction, the mixture was reprecipitated in n-hexane and dried to obtain a macroinitiator (I-PBzMA- b -PMMA-N=N-PMMA- b -PBzMA-I, M n = 10200, M w / M n = 1.22).

[0055] (3) 1.49 ml of BMA, 116.82 mg of I-PBzMA- b -PMMA-N=N-PMMA- b-PMBzMA-I, 3.00 mg of I2, and 17.4 mg of BNI were successively added into a 25 mL Schlenk tube, and the tube mouth was directly sealed with a rubber stopper. The Schlenk tube containing the reaction mixture was subjected to three cycles of liquid nitrogen freezing - evacuation - thawing for deoxidation, and the reaction was carried out at 90 °C for 80 min. After the reaction, the mixture was reprecipitated in n - hexane, and after drying, an asymmetric block copolymer of the CABC type (I - PBMA - b -PBzMA- b -PMMA- b -PBMA-I, M n = 27700, M w / M n = 1.26).

[0056] Appendix Figure 2 , 3 , and the results in Figure 4 demonstrated the successful synthesis of the initiator Br - EPhAzo - Br.

[0057] Appendix Figure 5 The results indicated that the three - step synthesis process was strictly controlled, and all polymers had a low polydispersity, reflecting the reliability of this method.

[0058] Appendix Figure 6 In the results of b -PBzMA- b -PMMA- b -PBMA-I, the characteristic peaks of each block monomer all existed, indicating the successful synthesis of the asymmetric block copolymer of the CABC type I - PBMA - b -PBzMA- b -PMMA- b -PBMA-I.

[0059] Appendix Figure 7 The results reflected the chain - extension process of each block monomer in the three - step synthesis process, and the molecular weight data was determined by gel permeation chromatography.

[0060] The above - mentioned are only the preferred embodiments of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope covered by the present invention.

Claims

1. An asymmetric block copolymer of the CABC type, characterized in that, The CABC-type asymmetric block copolymer has the following structure: m ∈ (0, 50); n ∈ (0, 100); p ∈ (0, 200).

2. The preparation method of a CABC-type asymmetric block copolymer according to claim 1, characterized in that, It includes the following steps: (1) Methyl methacrylate, initiator Br-EPhAzo-Br, sodium iodide, and pentamethyldiethylenetriamine were successively added to a glass bottle, and the bottle mouth was directly sealed with a rubber stopper to remove excess air; the glass bottle containing the reaction mixture was placed on a stirring table and irradiated with a white LED lamp. Samples were taken with a syringe at the expected time points, and the remaining samples were precipitated in n-hexane and dried under vacuum to obtain the macroinitiator I-PMMA-N=N-PMMA-I; (2) Benzyl methacrylate, I-PMMA-N=N-PMMA-I, and pentamethyldiethylenetriamine were successively added to a glass bottle, and the bottle mouth was directly sealed with a rubber stopper to remove excess air. The glass bottle containing the reaction mixture was placed on a stirring table and irradiated with white LED lights. Samples were taken with a syringe at the expected time points, and the remaining samples were precipitated in n-hexane and dried under vacuum to obtain the macroinitiator I-PBzMA- b -PMMA-N=N-PMMA- b -PBzMA-I; (3) Add butyl methacrylate, I-PBzMA- b -PMMA-N=N-PMMA- b -PBzMA-I, elemental iodine, and tetrabutylammonium iodide into a 25 mL Schlenk tube in sequence, conduct three cycles of liquid nitrogen freezing - evacuation - thawing for deoxygenation, carry out a polymerization reaction at a certain temperature, sample with a sampling needle at the expected time points, precipitate the remaining sample in n-hexane, and obtain the target product I-PBMA- b -PBzMA- b -PMMA- b -PBMA-I; The structure of the initiator Br-EPhAzo-Br is as follows: 。 3. The preparation method according to claim 2, characterized in that: The light source conditions in copolymer synthesis steps (1) and (2) are 13 Wm -1 , 15 mW cm -2 .

4. The preparation method according to claim 2, characterized in that: The reaction temperature condition in step (3) of copolymer synthesis is 90 °C.

5. The preparation method according to claim 2, wherein In step (1) of copolymer synthesis, the reactant ratio is: the molar ratio of methyl methacrylate: Br-EPhAzo-Br: sodium iodide: pentamethyldiethylenetriamine is 100:1:2.4:0.

5.

6. The preparation method according to claim 2, wherein In step (2) of copolymer synthesis, the reactant ratio is: the molar ratio of benzyl methacrylate: I-PMMA-N=N-PMMA-I: pentamethyldiethylenetriamine is 200:1:0.

5.

7. The preparation method according to claim 2, wherein In the copolymer synthesis step (3), the ratio of reactants is: butyl methacrylate: I-PBzMA- b -PMMA-N=N-PMMA- b -PBzMA-I: iodine: tetrabutylammonium iodide is 800:1:1:4 in molar ratio.

8. The preparation method according to claim 2, wherein In the first step, the initiator Br-EPhAzo-Br undergoes an in-situ bromo-iodine exchange reaction with sodium iodide to obtain a carbon-iodine bond to initiate monomers for photoinduced reversible complex-mediated polymerization.

9. The preparation method according to claim 2, characterized in that, The synthesis steps of the initiator Br-EPhAzo-Br include: 1) Add 2.0 g of 4,4'-azobis(4-cyanopentanol), 3.784 g of α-bromophenylacetic acid, 0.185 g of 4-dimethylaminopyridine, and 50 ml of dichloromethane to a round-bottom flask and mix well; 2) Add N,N'-dicyclohexylcarbodiimide dissolved in 15 ml of dichloromethane at 0 °C and stir for one hour; 3) Then, transfer the reaction system to room temperature and continue the reaction for 24 hours; 4) After the reaction is completed, filter the reaction mixture, concentrate the obtained filtrate by rotary evaporation, and purify it by silica gel column chromatography to obtain the target product Br-EPhAzo-Br.

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