Preparation and application of heterogeneous catalyst for photoinduced reversible addition-fragmentation chain transfer polymerization

Abstract

The application discloses a preparation and application of a heterogeneous catalyst for photoinduced reversible addition-fragmentation chain transfer polymerization, and the method uses conjugated microporous polymer materials B-B, B-CN-B or B-2CN-B as the catalyst for a reversible addition-fragmentation chain transfer (RAFT) polymerization reaction, so that active polymerization with low dispersity (PDI=1.04-1.25) can be obtained. Meanwhile, the conjugated microporous polymer material used as the catalyst in the method has strong stability and can be repeatedly used for many times, has strong applicability, and is suitable for large-scale application.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials, specifically relating to the preparation of a conjugated microporous polymer and its photoinduced reversible addition-fragmentation chain transfer polymerization. Background Technology

[0002] Photoinduced reversible radical polymerization (RDRP) technology can synthesize polymers with precise molecular weights, narrow molecular weight distributions, and controllable sequences using light energy at room temperature. The polymerization process is light-dependent, economical, and environmentally friendly. Catalysts with light absorption properties influence the electron / energy transfer and activation / deactivation equilibrium processes in RDRP, and the tunable photoelectronic properties and recyclability of heterogeneous catalysts are making their application in RDRP increasingly widespread. Photoinduced atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) polymerization are hot topics in the research field of photoinduced RDRP technology.

[0003] In photoinduced electron transfer RAFT (PET-RAFT) polymerization, the heterogeneous catalyst is photoexcited, generating holes in the valence band and electrons in the conduction band. These electrons are transferred to the chain transfer agent (CTA). The reduced CTA can either initiate conventional RAFT polymerization or regenerate the catalyst, participating in the catalytic cycle. Compared to traditional inorganic semiconductor heterogeneous catalysts, organic semiconductors have attracted widespread attention due to their low cost and tunable structure and performance; however, their electron transport capabilities are relatively poor, and their photocatalytic efficiency needs further improvement.

[0004] Conjugated microporous polymer materials (CMPs) possess advantages such as large specific surface area, strong thermal stability, strong chemical stability, and tunable structure and properties, and are widely used in fields such as gas adsorption, heterogeneous photocatalysis, and energy storage and conversion. The designability of the structure of CMPs can affect the migration of photogenerated charge carriers; therefore, CMPs have potential applications in photoinduced electron transfer (RAFT) polymerization. Summary of the Invention

[0005] The purpose of this invention is to provide a heterogeneous catalyst with a well-defined structure-property structure-activity relationship for photoinduced electron transfer (RAFT) polymerization, by introducing electron-withdrawing groups into the CMP material structure to improve the photocatalytic performance of the catalyst.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0007] The preparation and application of a heterogeneous catalyst for photoinduced reversible addition-fragmentation chain transfer polymerization (RAFT) is disclosed. Using covalent organic framework (COF) materials as catalysts, the RAFT catalyst can produce living polymerization with low dispersion (PDI = 1.04 ~ 1.25). Furthermore, the covalent organic framework materials used in this method are highly stable, reusable, highly efficient, and versatile, making them suitable for large-scale applications.

[0008] A heterogeneous catalyst for photoinduced reversible addition-fragmentation chain transfer polymerization, wherein the heterogeneous catalyst for photoinduced reversible addition-fragmentation chain transfer polymerization is one of the conjugated microporous polymers BB, B-CN-B, and B-2CN-B, with the following structure:

[0009] .

[0010] The preparation process of a heterogeneous catalyst for photoinduced reversible addition-fragmentation chain transfer polymerization includes: obtaining an alkynyl monomer through a cross-coupling reaction with a halogenated monomer in the presence of solvent A and catalyst B; wherein solvent A is one or more of N,N-dimethylformamide and triethylamine; catalyst B is one or more of cuprous iodide and palladium dichloride bis(triphenylphosphine); the alkynyl monomer is 1,3,5-triethynylbenzene; the halogenated monomer is one of p-dibromobenzene, 2,5-dibromobenzonitrile, and 2,5-dibromoterephthalonitrile; and the cross-coupling reaction temperature is 80°C.

[0011] Application: At room temperature, conjugated microporous polymers BB, B-CN-B, or B-2CN-B are used as catalysts, mixed with monomers, chain transfer agents, electron sacrificial agents, and solvents in a certain proportion. Under a nitrogen atmosphere, the mixture is irradiated by LED strips to carry out a reversible addition-fragmentation chain transfer polymerization reaction. By controlling the reaction time of the light irradiation, polymers with controllable molecular weight and uniform molecular weight distribution can be obtained.

[0012] Preferably, when carrying out a reversible addition-fragmentation chain transfer polymerization reaction, the monomer is methyl methacrylate (MMA).

[0013] Preferably, when carrying out the reversible addition-fracture chain transfer polymerization reaction, the chain transfer agent is dithiocarbonate (4-cyano-4-(thiobenzoyl)valerate CPADB, CAS: 201611-92-9).

[0014] Preferably, when carrying out a reversible addition-fragmentation chain transfer polymerization reaction, the electron sacrificial agent is triethylamine (TEA).

[0015] Preferably, when carrying out the reversible addition-fragmentation chain transfer polymerization reaction, the solvent is dimethylacetamide (DMAc).

[0016] Preferably, when carrying out a reversible addition-fragmentation chain transfer polymerization reaction, controlled free radical polymerization can be achieved under nitrogen conditions.

[0017] Preferably, the catalyst maintains good catalytic activity during reversible addition-fragmentation chain transfer polymerization.

[0018] Preferably, when carrying out the reversible addition-fragmentation chain transfer polymerization reaction, the light source is 13W / m or 15mW / cm. 2 LED light strips in various colors.

[0019] The beneficial effects and outstanding advantages of this invention are as follows:

[0020] 1. Introducing electron-withdrawing groups into the structure of CMPs materials can significantly improve photocatalytic performance.

[0021] 2. It has a metal-free catalytic system and the catalyst is simple to synthesize.

[0022] 3. It can maintain considerable catalytic activity even after multiple cycles. Attached Figure Description

[0023] Figure 1 The nuclear magnetic resonance carbon spectra of the polymers described in Examples 1, 2, and 3 demonstrate the successful preparation of BB, B-CN-B, and B-2CN-B.

[0024] Figure 2 Scanning electron microscope (SEM) images of catalysts BB, B-CN-B, and B-2CN-B.

[0025] Figure 3 The nitrogen adsorption-desorption curves (a, b, c) and pore size distribution diagrams (d, e, f) of catalysts BB, B-CN-B, and B-2CN-B are shown. Polymer BB has a high specific surface area of ​​673 m². 2 g -1 The pore size is mainly distributed at 3.64 nm, and the specific surface area of ​​polymer B-CNB is reduced to 563 m². 2 g -1 The pore size is mainly distributed at 3.90 nm, and the specific surface area of ​​polymer B-2CN-B is significantly reduced to 362 m². 2 g -1 The pore size is mainly distributed at 4.24 nm.

[0026] Figure 4 The electrochemical impedance spectroscopy (EIS) plots for catalysts BB, B-CN-B, and B-2CN-B show that the resistance arc radii of polymers BB, B-CN-B, and B-2CN-B decrease, indicating that the introduction of cyano groups helps reduce the resistance to charge transfer.

[0027] Figure 5 The polymerization kinetics curves (a) and the relationship between experimental molecular weight and monomer conversion (b) of catalysts BB, B-CN-B, and B-2CN-B are shown. M ]0 / [ M ] t The curves showing the change of reaction time exhibit first-order kinetic traces, and the experimental molecular weight and monomer conversion rate also show a linear relationship, which is consistent with the characteristics of reversible-deactivation polymerization. Among them, the catalyst with the fastest polymerization rate and the best effect is B-2CN-B.

[0028] Figure 6 The monomer conversion and molecular weight distribution of catalyst B-2CN-B in three-cycle polymerization experiments were shown. The monomer conversion rates for the three cycles were 48.3%, 44.2%, and 42.3%, respectively. The decrease in monomer conversion rate was very small, which proves the stability of the catalyst. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0030] Example 1

[0031] Synthesis of polymer BB-CMP:

[0032] p-Dibromobenzene (354 mg, 1.5 mmol), 1,3,5-triethynylbenzene (150 mg, 1.0 mmol), bis(triphenylphosphine) palladium dichloride (20 mg), cuprous iodide (3.0 mg), N,N-dimethylformamide (50 ml), and triethylamine (50 ml) were added to a 250 ml single-necked flask. The mixture was purged with nitrogen for 15 min, heated to 80 °C, and stirred for 24 h. After cooling to room temperature, the mixture was filtered under reduced pressure. The solid was washed with dichloromethane and methanol, respectively, and then subjected to Soxhlet extraction and washing with methanol solution for 48 h. The solid was then placed in a 60 °C forced-air drying oven and dried for 12 h to obtain polymer BB (211 mg, yield: 81%).

[0033] Example 2

[0034] Synthesis of polymer B-CN-B-CMP:

[0035] 2,5-Dibromobenzonitrile (392 mg, 1.5 mmol, CAS: 57381-41-6), 1,3,5-triethynylbenzene (150 mg, 1.0 mmol), palladium dichloride of bis(triphenylphosphine) (20 mg), cuprous iodide (3.0 mg), N,N-dimethylformamide (50 ml), and triethylamine (50 ml) were added to a 250 ml single-necked flask. The mixture was purged with nitrogen for 15 min, heated to 80 °C, and stirred for 24 h. After cooling to room temperature, the mixture was filtered under reduced pressure. The solid was washed with dichloromethane and methanol, respectively, and then subjected to Soxhlet extraction and washing with methanol solution for 48 h. The solid was then placed in a 60 °C forced-air drying oven and dried for 12 h to obtain polymer B-CN-B (235 mg, yield: 79%).

[0036] Example 3

[0037] Synthesis of polymer B-2CN-B-CMP:

[0038] 2,5-Dibromoterephthalonitrile (429 mg, 1.5 mmol, CAS: 18870-11-6), 1,3,5-triethynylbenzene (150 mg, 1.0 mmol), bis(triphenylphosphine) palladium dichloride (20 mg), cuprous iodide (3.0 mg), N,N-dimethylformamide (50 ml), and triethylamine (50 ml) were added to a 250 ml single-necked flask. The mixture was purged with nitrogen for 15 min, heated to 80 °C, and stirred for 24 h. After cooling to room temperature, the mixture was filtered under reduced pressure. The solid was washed with dichloromethane and methanol, respectively, and then subjected to Soxhlet extraction and washing with methanol solution for 48 h. The solid was then placed in a 60 °C forced-air drying oven and dried for 12 h to obtain polymer B-2CN-B (289 mg, yield: 88%).

[0039] Application Example 1

[0040] MMA (2 mL, 18.6 mmol), CPADB (26.3 mg, 0.093 mmol), DMAc (0.5 mL), BB-CMP (20 mg), and TEA (268 μL, 1.86 mmol, 20 eq) were added to a 4 mL glass vial. The vial was sealed tightly with a rubber stopper and degassed with a nitrogen balloon for 30 min. The mixture was then incubated under a 400 nm white LED (13 W m²). -1 15 mW cm -2 The polymer was irradiated at room temperature, and samples were collected at regular intervals. GPC analysis was used to characterize its molecular weight (Mn) and molecular weight dispersibility (Mw / Mn). After 36 hours of reaction, the resulting polymer had a molecular weight of 10700 g / mol, a monomer conversion rate of 45.2%, and a polydispersity index (PDI) of 1.11.

[0041] Application Example 2

[0042] MMA (2 mL, 18.6 mmol), CPADB (26.3 mg, 0.093 mmol), DMAc (0.5 mL), B-CN-B-CMP (20 mg), and TEA (268 μL, 1.86 mmol, 20 eq) were added to a 4 mL glass vial. The vial was sealed tightly with a rubber stopper and degassed with a nitrogen balloon for 30 min. The mixture was then incubated under a 400 nm white LED (13 W m²). -1 15 mW cm -2 Irradiated at room temperature, samples were collected at regular intervals, and their molecular weight (M) was characterized by GPC analysis. n ) and molecular weight dispersibility (M w / M n After 36 hours of reaction, the resulting polymer had a molecular weight of 17,000 g / mol, a monomer conversion rate of 67.9%, and a polydispersity index (PDI) of 1.11.

[0043] Application Example 3

[0044] MMA (2 mL, 18.6 mmol), CPADB (26.3 mg, 0.093 mmol), DMAc (0.5 mL), B-2CN-B-CMP (20 mg), and TEA (268 μL, 1.86 mmol, 20 eq) were added to a 4 mL glass vial. The vial was sealed tightly with a rubber stopper and degassed with a nitrogen balloon for 30 min. The mixture was then incubated under a 400 nm white LED (13 W m²). -1 15 mW cm -2 Irradiated at room temperature, samples were collected at regular intervals, and their molecular weight (M) was characterized by GPC analysis. n ) and molecular weight dispersibility (M w / M n After 22 hours of reaction, the resulting polymer had a molecular weight of 12400 g / mol, a monomer conversion rate of 68.8%, and a polydispersity index (PDI) of 1.15.

[0045] Application Example 4

[0046] B-2CN-B-CMP (20 mg), MMA (2 mL, 18.6 mmol), CPADB (26.3 mg, 0.093 mmol), TEA (268 μL, 1.86 mmol, 20 eq), and DMAc (0.5 mL) were added to a 4 mL glass vial. The vial was sealed tightly with a rubber stopper and degassed with a nitrogen balloon for 30 min. The mixture was then incubated under a 400 nm white LED (13 W m²).-1 15 mW cm -2 The sample was irradiated for 18 hours while maintaining the temperature at room temperature. After the reaction was complete, the sample was analyzed by GPC. THF solution was added to the remaining solvent, and the catalyst was recovered by centrifugation. The obtained catalyst was then subjected to Soxhlet extraction with THF solution, dried in a vacuum drying oven, and subjected to catalytic experiments again. The monomer conversion rates for the three cycles were 48.3%, 44.2%, and 42.3%, respectively.

[0047] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention are within the scope of the present invention.

Claims

1. The application of a heterogeneous catalyst for photoinduced reversible addition-fragmentation chain transfer polymerization, characterized in that: At room temperature, using conjugated microporous polymers BB, B-CN-B, or B-2CN-B as catalysts, and mixing them with monomers, chain transfer agents, electron sacrificial agents, and solvents in a certain proportion, a reversible addition-fragmentation chain transfer polymerization reaction is carried out under a nitrogen atmosphere and irradiated by an LED strip. By controlling the reaction time under light irradiation, a polymer with controllable molecular weight and uniform molecular weight distribution is obtained; the monomer is methyl methacrylate, the chain transfer agent is dithiocarbonate, and the electron sacrificial agent is triethylamine. The heterogeneous catalyst for the photoinduced reversible addition-fragmentation chain transfer polymerization is one of the conjugated microporous polymers BB, B-CN-B, and B-2CN-B, with the following structure: 。 2. The application as described in claim 1, characterized in that, The preparation process of the heterogeneous catalyst for photoinduced reversible addition-fragmentation chain transfer polymerization includes: obtaining an alkynyl monomer by cross-coupling with a halogenated monomer in the presence of solvent A and catalyst B; the cross-coupling reaction temperature is 80℃.

3. The application as described in claim 2, characterized in that, Solvent A is one or more of N,N-dimethylformamide and triethylamine.

4. The application as described in claim 2, characterized in that, Catalyst B is one or more of cuprous iodide and palladium dichloride bis(triphenylphosphine) chloride.

5. The application as described in claim 2, characterized in that, The alkynyl monomer is 1,3,5-triethynylbenzene.

6. The application as described in claim 2, characterized in that, The halogenated monomer is one of p-dibromobenzene, 2,5-dibromobenzonitrile, or 2,5-dibromoterephthalonitrile.

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