CN114163374A

CN114163374A - Dendritic macromolecule and preparation method and application thereof

Info

Publication number: CN114163374A
Application number: CN202111558677.3A
Authority: CN
Inventors: 张国颖; 刘国钦; 刘固寰
Original assignee: University of Science and Technology of China USTC
Current assignee: University of Science and Technology of China USTC
Priority date: 2021-12-17
Filing date: 2021-12-17
Publication date: 2022-03-11

Abstract

The invention provides a dendritic macromolecule. The dendrimer is useful for adjusting the viscosity of a lubricant. The invention also provides a preparation method of the dendritic macromolecule.

Description

Dendritic macromolecule and preparation method and application thereof

Technical Field

The invention relates to the field of macromolecular materials, in particular to a dendritic structure molecule and a preparation method and application thereof.

Background

Dendrimers include high-generation dendrimers and low-generation dendrimers, both of which are highly branched and structurally precise molecules synthesized by repeated propagation reactions. It includes main structure (kernel, branching unit, peripheral group) and microenvironment (cavity). Dendritic macromolecules are synthetic macromolecular structures with low dispersibility and controllable surface functions. The number of dendritic polymer surface groups increases exponentially with the amount of dendritic polymer produced, compared to linear polymer/copolymer. Dendritic polymers, because of their extremely high shear stability, have a great role in the preparation of lubricants with excellent shear stability. For example, dendritic polymers have been reported to be useful as viscosity index improvers for lubricant formulations. Since the high molecular weight polymer can increase the thickening ability while causing a problem of a sharp decrease in molecular weight due to irreversible chain scission under high shear conditions. Therefore, high molecular weight linear polymers have poor shear stability, and thus it is necessary to reduce the molecular weight of dendrimers.

Disclosure of Invention

It is a first object of the present invention to provide a dendrimer having an extremely high shear stability which can be used over a wide temperature range.

A second object of the invention is to provide a use of said dendrimer.

The third purpose of the invention is to provide a preparation method of the dendritic macromolecule.

In order to achieve the purpose, the invention adopts the following technical means:

a dendrimer which is

Or the dendrimer is

Wherein R is₁Is H or CH₃；R₂Is H or an amino group; r₃Is H or an amine group.

The application of the dendritic molecules is applied to adjusting the viscosity of the lubricant.

The lubricant comprises a paraffinic lubricating oil.

The preparation method of the dendritic molecule comprises the following steps:

s1, dissolving butanethiol in chloroform and triethylamine solution, adding carbon disulfide, dropwise adding benzyl bromide or 1-bromoethylbenzene, and purifying to obtain an RAFT reagent;

s2, mixing the RAFT reagent and the bismaleimide compound in an organic solvent, and under the photocatalytic condition, performing addition reaction on double bonds on two amide rings in the RAFT reagent and the bismaleimide compound to insert the bismaleimide compound into the RAFT reagent to obtain a compound I;

s3, mixing the RAFT reagent and the bismaleimide compound in an organic solvent, and under the photocatalytic condition, carrying out addition reaction on a double bond on one amide ring in the RAFT reagent and the bismaleimide compound to insert the bismaleimide compound into the RAFT reagent to obtain a compound II;

s4, mixing the compound I and indene or an indene derivative in an organic solvent, and carrying out addition reaction on the compound I and the indene or the indene derivative under a photocatalytic condition to insert the indene or the indene derivative into the compound II to obtain a compound III;

s5, mixing the compound II and the compound III in an organic solvent, and performing addition reaction on the compound II and the compound III under the photocatalytic condition to insert the compound II into the compound III to obtain a compound IV;

s6, mixing the compound IV and indene or an indene derivative in an organic solvent, and carrying out addition reaction on the compound IV and the indene or the indene derivative under a photocatalytic condition to insert the indene or the indene derivative into the compound IV to obtain the dendrimer;

the RAFT agent is

The bismaleimide compound is

The compound I is

The compound II is

The compound III is

The compound IV is

The catalyst adopted by the photocatalysis is as follows:

and S1 is that 0.3mol of butyl mercaptan is added into a solution containing 300ml of chloroform and 0.3mol of triethylamine, then 0.3mol of carbon disulfide is dripped, 0.2mol of 1-bromoethyl benzene or benzyl bromide is dripped, suction filtration is carried out, then ethyl acetate and water are added into the filtrate, ethyl acetate is used for extraction for three times, saturated potassium carbonate aqueous solution is used for washing the organic phase once, the organic phase is collected, anhydrous sodium sulfate is added for drying, the organic phase is concentrated, petroleum ether is used as an eluent, and a 200-mesh 300-mesh silica gel column is used for carrying out column chromatography separation on the organic phase, thus obtaining the RAFT reagent.

S2 is that 20mmol RAFT reagent is mixed with 10mmol bismaleimide compound, 0.1mmol of photocatalyst ZnTPP is added, 30ml of dimethyl sulfoxide is added, nitrogen is introduced for 20 minutes after dissolution, and then the mixture is subjected to illumination reaction for about 4 hours in red light; after the reaction is finished, diluting the reaction system with ethyl acetate, washing with saturated saline water, collecting an organic phase, and drying with anhydrous sodium sulfate; after drying, concentrating the solution, adopting petroleum ether and ethyl acetate as eluent, and separating by using 200-and 300-mesh silica gel column chromatography to obtain a compound I; the volume ratio of the petroleum ether to the ethyl acetate is 8: 1.

S3 is prepared by weighing 5mmol RAFT reagent, 25mmol bismaleimide compound and 0.025mmol photocatalyst ZnTPP, adding 40ml dimethyl sulfoxide, dissolving, introducing nitrogen, and carrying out light irradiation reaction in red light for about 2 hours; after the reaction is finished, diluting the reaction system by using ethyl acetate, and then washing by using saturated saline solution; collecting the organic phase, and drying with anhydrous sodium sulfate; after drying, concentrating the solution, adopting petroleum ether and ethyl acetate as eluent, and separating by using 200-and 300-mesh silica gel column chromatography to obtain a compound II; the volume ratio of the petroleum ether to the ethyl acetate is 6: 1.

S4 is that 1mmol of compound I, 10mmol of indene or indene derivatives and 5umol of photocatalyst are weighed and subjected to red light illumination reaction in a nitrogen environment; after the reaction is finished, diluting the reaction system by using ethyl acetate, and then washing by using saturated saline solution; finally, collecting an organic phase, and drying the organic phase by using anhydrous sodium sulfate; after drying, concentrating the solution, and separating by using 200-300-mesh silica gel column chromatography, wherein an eluent is a mixture of petroleum ether and ethyl acetate, and the volume ratio of the petroleum ether to the ethyl acetate is 6: 1, and finally obtaining the compound III.

Weighing 0.6mmol of compound III, 1.2mmol of compound II and 3.2umol of photocatalyst by the aid of S5, and carrying out red light illumination reaction in a nitrogen environment; after the reaction is finished, diluting the reaction system by using ethyl acetate, and then washing by using saturated saline solution; collecting the organic phase, and drying with anhydrous sodium sulfate; after drying, concentrating the solution, and separating by using a preparative silica gel plate, wherein an eluent is a mixture of petroleum ether and ethyl acetate, and the volume ratio of the eluent to the mixture of the petroleum ether and the ethyl acetate is 4: 1, so as to finally obtain a compound IV;

s6 is that 0.042mmol of compound IV, 1.67mmol of indene or indene derivative and 0.21umol of photocatalyst are weighed and subjected to red light illumination reaction in a nitrogen environment; after the reaction is finished, diluting the reaction system by using ethyl acetate, and then washing by using saturated saline solution; finally, collecting an organic phase, and drying the organic phase by using anhydrous sodium sulfate; after drying, concentrating the solution, and separating with a preparative silica gel plate, wherein the eluent is a mixture of petroleum ether and ethyl acetate, and the volume ratio of the eluent to the mixture of petroleum ether and ethyl acetate is 4: 1 to finally obtain a compound IV; and finally obtaining the dendritic macromolecule.

Compared with the prior art, the invention has the following technical effects:

the invention provides a dendritic macromolecule, the main chain of which is not connected by polar groups, the intermolecular or mechanical non-covalent action is weak, and the dendritic macromolecule is suitable for being used as a viscosity index improver and solves the problem of poor shear stability at different temperatures.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

FIG. 1 shows the scheme for the synthesis of dendrimers with R1 as CH₃Dendrimers for which R2 and R3 are H are examples;

FIG. 2 is a NMR spectrum of the compound prepared in example 2;

FIG. 3 is a NMR spectrum of the compound prepared in example 3;

FIG. 4 is a NMR spectrum of the compound prepared in example 4;

FIG. 5 is a NMR chart of the compound prepared in example 5;

FIG. 6 is a NMR spectrum of a compound prepared in example 6;

fig. 7 is a summary of gel permeation chromatograms of the compounds prepared in examples 2, 4, 5, 6.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.

Will be described below

Abbreviated as formula (1), when R in formula (1)₁Is methyl, R₂Is H, R₃When the formula is H, the formula (1) is abbreviated as formula (1-1); when R in the formula (1)₁Is H, R₂Is H, R₃When the formula is H, the formula (1) is abbreviated as formula (1-2); when R in the formula (1)₁Is methyl, R₂Is amino, R₃When the amino group is used, the formula (1) is abbreviated as formula (1-3); when R in the formula (1)₁Is H, R₂When R3 is an amino group, the formula (1) is abbreviated as formula (1-4).

Will be described below

Abbreviated as formula (2), when R in formula (2)₁Is methyl, R₂Is H, R₃When the formula is H, the formula (2) is abbreviated as formula (2-1); when R in the formula (2)₁Is H, R₂Is H, R₃When the formula is H, the formula (2) is abbreviated as formula (2-2); when R in the formula (2)₁Is methyl, R₂Is amino, R₃When the amino group is used, the formula (2) is abbreviated as a formula (2-3); when R in the formula (2)₁Is H, R₂Is amino, R₃When the amino group is used, the formula (2) is abbreviated as the formula (2-4).

The present invention is further illustrated by the following examples.

Examples 1 to 6 show the synthesis methods of the dendrimers represented by the formula (1-1).

Example 1

Synthesis of RAFT agent BETC

Butyl mercaptan (27g, 0.3mol) was weighed into a solution containing 300ml chloroform and TEA (30.3g, 0.3mol), stirred at room temperature for about 20 minutes, then carbon disulfide (22.8g, 0.3mol) was slowly added dropwise and reacted for about 20 minutes, at which time the reaction solution turned yellow, then 1-bromoethylbenzene (37g, 0.2mol) was added dropwise and, after completion of the addition, reacted at room temperature overnight.

After the reaction is finished, filtering to remove solid impurities. Ethyl acetate and water were then added to the filtrate and extracted three times with ethyl acetate (3 x 30 ml). The organic phase was then washed once with saturated aqueous potassium carbonate solution. The organic phase was collected and dried by adding anhydrous sodium sulfate. After drying for a period of time, the solution was concentrated and separated by 200-mesh 300-mesh silica gel column chromatography. Petroleum ether was used as eluent. Finally, a reddish brown liquid product is obtained.

Example 1 relates to the following chemical reaction equation:

example 2

Synthesis of BETC-BM-BETC

The BETC (5.4g, 20mmol) prepared in example 1, the monomer BM (3.58g, 10mmol) and the photocatalyst ZnTPP (67.8mg, 0.1mm0l) were weighed into a reaction flask, 30ml of dimethyl sulfoxide was added thereto, dissolved, and then a small magneton was added thereto to plug the stopper. Introducing nitrogen into the mixed solution by using a steel needle for 20 minutes, and then placing the mixed solution into red light to perform a light irradiation reaction for about 4 hours.

After completion of the reaction, the reaction system was diluted with a large amount of ethyl acetate and washed with saturated brine several times. Finally, the organic phase was collected and dried over anhydrous sodium sulfate. After drying, the solution is concentrated and separated by 200-300 mesh silica gel column chromatography, and the eluent petroleum ether and ethyl acetate are 8: 1. Finally obtaining a reddish brown solid product.

The chemical reaction scheme involved in example 2 is as follows:

example 3

Synthesis of BETC-BM

The BETC (1.35g, 5mmol) prepared in example 1, the monomer BM (9g, 25mmol) and the photocatalyst ZnTPP (17mg, 0.025mmol) were weighed into a reaction flask, 40ml of dimethyl sulfoxide was added thereto, and after dissolution, a small magneton was added thereto and the stopper was closed. Introducing nitrogen into the mixed solution by using a steel needle for 20 minutes, and then placing the mixed solution into red light to perform a light irradiation reaction for about 2 hours.

After completion of the reaction, the reaction system was diluted with a large amount of ethyl acetate and washed with saturated brine several times. Finally, the organic phase was collected and dried over anhydrous sodium sulfate. After drying, the solution was concentrated and separated by 200-mesh 300-mesh silica gel column chromatography eluting with petroleum ether/ethyl acetate 6: 1. The product was finally obtained as a bright yellow solid.

Example 3 relates to the following chemical reaction equation:

example 4

Synthesis of BETC-IND-BM-IND-BETC

The BETC-BM-BETC (0.89g, 1mmol) prepared in example 2, the monomer IND (1.16g, 10mmol) and the photocatalyst ZnTPP (3.4mg, 5. mu. mol, 1mg/ml in dimethyl sulfoxide) were weighed into a reaction flask, 0.1ml of dimethyl sulfoxide was added thereto, dissolved, and then a small magneton was added to plug the stopper. Introducing nitrogen into the mixed solution by using a steel needle for 20 minutes, and then putting the mixed solution into red light for illumination reaction for 24 hours.

After completion of the reaction, the reaction system was diluted with a large amount of ethyl acetate and washed with saturated brine several times. Finally, the organic phase was collected and dried over anhydrous sodium sulfate. After drying, the solution was concentrated and separated by 200-mesh 300-mesh silica gel column chromatography eluting with petroleum ether/ethyl acetate 6: 1. Finally, a green solid product is obtained.

Example 4 relates to the following chemical reaction scheme:

example 5

Synthesis of BETC-BM-IND-BM-IND-BM-BETC

The BETC-IND-BM-IND-BETC (0.728g, 0.6mmol) prepared in example 4, the monomer BETC-BM (0.81g, 1.2mmol), the photocatalyst ZnTPP (2.18mg, 3.2. mu. mol, 1mg/ml in dimethyl sulfoxide) were weighed out and added to a reaction flask, 1ml of dimethyl sulfoxide was added thereto, and after dissolution, a small magneton was added and the stopper was closed. Introducing nitrogen into the mixed solution by using a steel needle for 20 minutes, and then putting the mixed solution into red light for illumination reaction for 24 hours.

After completion of the reaction, the reaction system was diluted with a large amount of ethyl acetate and washed with saturated brine several times. Finally, the organic phase was collected and dried over anhydrous sodium sulfate. After drying, the solution was concentrated and separated on preparative silica gel plates eluting with petroleum ether/ethyl acetate 4: 1. Finally, a green solid product is obtained.

The chemical reaction scheme involved in example 5 is as follows:

example 6

Synthesis of BETC-IND-BM-IND-BM-IND-BM-IND-BETC

The BETC-BM-IND-BM-IND-BM-BETC (0.1g, 0.042mmol) prepared in example 5, the monomer IND (0.194g, 1.67mmol), the photocatalyst ZnTPP (0.142mg, 0.21. mu. mol, 1mg/ml in dimethyl sulfoxide) were weighed and added to a reaction flask, 0.2ml of dimethyl sulfoxide was added thereto, and after dissolution, a small magneton was added to the flask and the stopper was closed. Introducing nitrogen into the mixed solution by using a steel needle for 20 minutes, and then putting the mixed solution into red light for illumination reaction for 24 hours.

After completion of the reaction, the reaction system was diluted with ethyl acetate and washed with saturated brine several times. Finally, the organic phase was collected and dried over anhydrous sodium sulfate. After drying, the solution was concentrated and separated on preparative silica gel plates eluting with petroleum ether/ethyl acetate 4: 1. Finally, a green solid product is obtained.

Example 6 relates to the following chemical reaction scheme:

examples 7 to 12 show the synthesis methods of the dendrimers represented by the formula (1-2).

Example 7

Synthesis of RAFT agent BBTC

Butyl mercaptan (27g, 0.3mol) was weighed into a solution containing 300ml of chloroform and triethylamine (30.3g, 0.3mol), stirred at room temperature for about 20 minutes, carbon disulfide (22.8g, 0.3mol) was slowly added dropwise and reacted for about 20 minutes, at which time the reaction solution turned yellow, then benzyl bromide (34g, 0.2mol) was added dropwise and reacted at room temperature overnight after the addition was completed.

The chemical reaction scheme involved in example 7 is as follows:

example 8

Synthesis of BBTC-BM

The difference from example 2 is that the reaction was carried out using RAFT agent BBTC prepared in example 1.

The chemical reaction scheme involved in example 8 is as follows:

example 9

Synthesis of BBTC-BM-BBTC

The difference from example 3 is that BBTC prepared in example 8 is used for the reaction.

Example 9 relates to the following chemical reaction scheme:

example 10

Synthesis of BBTC-IND-BM-IND-BBTC

The difference from example 4 is that BBTC-BM-BBTC prepared in example 9 is used for the reaction.

The chemical reaction scheme involved in example 10 is as follows:

example 11

Synthesis of BBTC-BM-IND-BM-IND-BM-BBTC

The difference from example 5 is that BBTC-IND-BM-IND-BBTC prepared in example 10 was reacted with BBTC-BM obtained in example 8.

Example 11 relates to a chemical reaction scheme as follows:

example 12

Synthesis of BBTC-IND-BM-IND-BM-IND-BM-IND-BBTC

The difference from example 6 is that BBTC-BM-IND-BM-IND-BM-BBTC prepared in example 11 was used for the reaction.

Example 12 relates to a chemical reaction scheme as follows:

the following examples illustrate the preparation of the formulae (1-3) and (1-4).

Example 13

The starting material 5-aminoindan-1-one (1g, 6.8mmol) was charged into a round bottom flask, magneton and rubber stopper were added. The nitrogen was replaced by vacuum evacuation using a syringe needle, and then 30ml of anhydrous tetrahydrofuran was added, and then a tetrahydrofuran solution of lithium aluminum hydride (1mol/L, 6.8ml, 6.8mmol) was added dropwise in an ice bath. After the completion of the dropwise addition, the reaction was carried out for two more hours. After it slowly returned to room temperature.

After the reaction is finished, the reaction solution is dripped into 1M sodium hydroxide aqueous solution, stirred for half an hour, filtered, washed by tetrahydrofuran, and then the filtrate is extracted by ethyl acetate. The organic phase was collected, dried over anhydrous sodium sulfate and concentrated to give the crude product.

The crude product from the above step was taken, 20ml of dilute hydrochloric acid and 20ml of methanol were added, and heated at 40 ℃ for two hours. After the reaction was completed, ethyl acetate and a saturated potassium carbonate solution were added. Extraction was then carried out with ethyl acetate and the organic phase was concentrated. Separating by 200-mesh 300-mesh silica gel column chromatography. The eluent petroleum ether and ethyl acetate are 6: 1. 5-aminoindene is obtained.

Example 13 relates to the following chemical reaction scheme:

the indenes in the example 4 and the example 6 are replaced by the 5-aminoindene prepared in the example 13, and then the synthesis is carried out according to the synthetic routes of the examples 1 to 6, so as to obtain the dendrimer corresponding to the formula (1-3).

The indenes in the example 10 and the example 12 are replaced by the 5-aminoindene prepared in the example 13, and then the synthesis is carried out according to the synthetic route of the example 10 to 12, so as to obtain the dendrimer corresponding to the formula (1-4).

The following examples are provided to illustrate the preparation of formula (2-1), formula (2-2), formula (2-3) and formula (2-4).

Example 14

Preparation of bismaleimide

Maleic anhydride (9.8g, 100mmol) was dissolved in 30ml of N, N-dimethylformamide under ice-bath, and a solution of 1, 8-diamino-3, 6-dioxaoctane (6.66g, 45mmol) dissolved in 20ml of N, N-dimethylformamide was added thereto. After returning to room temperature, the reaction mixture was put in an oil bath at 80 ℃ for 20 minutes. Acetic anhydride (18.3g, 18.3mmol), nickel acetate (0.063g, 0.36mmol) and triethylamine (1.8g, 18mmol) were then added and the reaction was continued at 80 ℃ for 1 h.

After the reaction was complete, the black solution was added to water and extracted three times with DCM (3 × 50ml), then the organic phase was collected, dried over anhydrous sodium sulfate and the solvent was concentrated to dryness. Then separated by 200-300 mesh silica gel column chromatography, and the eluent is pure dichloromethane.

Example 13 relates to the following chemical reaction scheme:

after BM from example 2 and example 3 was replaced by the bismaleimide prepared in example 14, the synthesis was carried out according to the synthetic route of examples 1 to 6, and the dendrimer corresponding to formula (2-1) was obtained.

After BM from example 8 and example 9 was replaced by the bismaleimide prepared in example 14, the synthesis was carried out according to the synthetic route of examples 7 to 12 to obtain a dendrimer corresponding to formula (2-1).

The corresponding dendrimer of formula (2-3) was synthesized by substituting BM in example 2 and example 3 for the bismaleimide prepared in example 14, and substituting indene in example 4 and example 6 for the 5-aminoindene prepared in example 13, followed by the synthetic routes of examples 1-6.

The synthesis of 5-aminoindene prepared in example 1-6 was carried out by replacing BM in example 8 and example 9 with bismaleimide prepared in example 14 and replacing indene in example 10 and example 12 with indene prepared in example 13, and then the corresponding dendrimer of formula (2-4) was obtained.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.

Claims

1. A dendrimer characterized by:

the dendritic macromolecule is

Or the dendrimer is

2. Use of a dendrimer according to claim 1, wherein:

the method is applied to adjusting the viscosity of the lubricant.

3. Use of a dendrimer according to claim 2, wherein:

the lubricant comprises a paraffinic lubricating oil.

4. A method of producing a dendrimer according to claim 1, comprising the steps of:

the RAFT agent is

The bismaleimide compound is

The compound I is:

the compound II is

The compound III is:

the compound IV is:

5. a method of producing a dendrimer according to claim 4, wherein:

the catalyst adopted by the photocatalysis is

6. A method of producing a dendrimer according to claim 4, wherein:

7. A method of producing a dendrimer according to claim 4, wherein:

s2 is that 20mmol RAFT reagent and 10mmol bismaleimide compound are mixed, 0.1mmol of photocatalyst ZnTPP is added, 30ml of dimethyl sulfoxide is added, nitrogen is introduced for 20 minutes after dissolution, and then the mixture is subjected to illumination reaction for about 4 hours in red light; after the reaction is finished, diluting the reaction system with ethyl acetate, washing with saturated saline water, collecting an organic phase, and drying with anhydrous sodium sulfate; after drying, concentrating the solution, adopting petroleum ether and ethyl acetate as eluent, and separating by using 200-and 300-mesh silica gel column chromatography to obtain a compound I; the volume ratio of the petroleum ether to the ethyl acetate is 8: 1.

8. A method of producing a dendrimer according to claim 4, wherein:

s3 is prepared by weighing 5mmol RAFT reagent, 25mmol bismaleimide compound and 0.025mmol photocatalyst ZnTPP, adding 40ml dimethyl sulfoxide, dissolving, introducing nitrogen, and carrying out light irradiation reaction in red light for about 2 h; after the reaction is finished, diluting the reaction system by using ethyl acetate, and then washing by using saturated saline solution; collecting the organic phase, and drying with anhydrous sodium sulfate; after drying, concentrating the solution, adopting petroleum ether and ethyl acetate as eluent, and separating by using 200-and 300-mesh silica gel column chromatography to obtain a compound II; the volume ratio of the petroleum ether to the ethyl acetate is 6: 1.

9. A method of producing a dendrimer according to claim 4, wherein:

10. A method of producing a dendrimer according to claim 4, wherein:

s6 is that 0.042mmol of compound IV, 1.67mmol of indene or indene derivative and 0.21umol of photocatalyst are weighed and subjected to red light illumination reaction in a nitrogen environment; after the reaction is finished, diluting the reaction system by using ethyl acetate, and then washing by using saturated saline solution; finally, collecting an organic phase, and drying the organic phase by using anhydrous sodium sulfate; after drying, concentrating the solution, and separating by using a preparative silica gel plate, wherein an eluent is a mixture of petroleum ether and ethyl acetate, and the volume ratio of the eluent to the mixture of the petroleum ether and the ethyl acetate is 4: 1, so as to finally obtain a compound IV; and finally obtaining the dendritic macromolecule.