阅读说明：本技术 一种功能化石墨烯接枝改性聚乳酸材料及其制法 (Functionalized graphene grafted modified polylactic acid material and preparation method thereof ) 是由 马妮 于 2020-12-30 设计创作，主要内容包括：本发明涉及聚乳酸技术领域,且公开了一种功能化石墨烯接枝改性聚乳酸材料,羧基化石墨烯丰富的羧基与聚乙二醇的单端氨基进行酰胺化反应,得到聚乙二醇共价修饰石墨烯,以辛酸亚锡作为催化剂,聚乙二醇共价修饰石墨烯作为大分子引发剂,聚乙二醇的端羟基作为引发活性位点,引发D,L-丙交酯开环聚合,从而将石墨烯通过聚乙二醇的桥联作用,与聚乳酸分子链有机结合,显著改善了石墨烯与聚乳酸的界面相容性,力学性能优异的石墨烯作为交联位点,显著增强了聚乳酸的拉伸强度,石墨烯纳米粒子可以作为异相结晶成核剂,诱导和促进聚乳酸的结晶过程,提高了聚乳酸材料的热分解温度等热稳定性能。(The invention relates to the technical field of polylactic acid, and discloses a functionalized graphene graft modified polylactic acid material, wherein rich carboxyl of carboxylated graphene and single-end amino of polyethylene glycol are subjected to amidation reaction to obtain polyethylene glycol covalent modified graphene, stannous octoate is used as a catalyst, polyethylene glycol covalently modified graphene is used as a macromolecular initiator, the terminal hydroxyl of the polyethylene glycol is used as an initiation active site to initiate ring-opening polymerization of D, L-lactide, the graphene is organically combined with polylactic acid molecular chains through the bridging effect of polyethylene glycol, the interface compatibility of the graphene and polylactic acid is obviously improved, the graphene with excellent mechanical properties is used as a crosslinking site, the tensile strength of the polylactic acid is obviously enhanced, the graphene nanoparticles can be used as a heterogeneous crystallization nucleating agent to induce and promote the crystallization process of the polylactic acid, and the thermal stability of the polylactic acid material such as thermal decomposition temperature is improved.)

1. A functionalized graphene grafted modified polylactic acid material is characterized in that: the preparation method of the functionalized graphene grafted modified polylactic acid material comprises the following steps:

(1) adding polyethylene glycol, an accelerator triethylamine and p-toluenesulfonyl chloride into a dichloromethane solvent, and reacting to prepare single-ended p-toluenesulfonyl polyethylene glycol;

(2) adding single-ended p-toluenesulfonyl polyethylene glycol and sodium azide in a mass ratio of 100:2-4 into an acetonitrile solvent, placing the mixture in a constant temperature reactor, heating the mixture to 80-100 ℃, and reacting for 24-48h to prepare single-ended azido polyethylene glycol;

(3) adding single-ended azido polyethylene glycol and triphenylphosphine serving as a catalyst into a tetrahydrofuran solvent in a mass ratio of 100:12-25, and reacting at room temperature for 36-72h to prepare single-ended amino polyethylene glycol;

(4) adding carboxylated graphene into a distilled water solvent in a nitrogen atmosphere, adding single-terminal amino polyethylene glycol, a condensing agent 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride and an accelerator N-hydroxysuccinimide after uniformly dispersing by ultrasonic, heating to 50-60 ℃, reacting for 20-30h, filtering, washing and drying to prepare polyethylene glycol covalently modified graphene;

(5) adding D, L-lactide and polyethylene glycol into an anhydrous toluene solvent to covalently modify graphene, uniformly stirring, adding a catalyst stannous octoate, heating to 110-130 ℃, reacting for 20-30h, carrying out reduced pressure distillation, washing and drying, and preparing a solid product into a standard sample strip through a double-screw extruder and an injection molding machine to obtain the functionalized graphene grafted modified polylactic acid material.

2. The functionalized graphene grafted and modified polylactic acid material according to claim 1, wherein: the molecular weight of the polyethylene glycol in the step (1) is 800-1500, and the mass ratio of the polyethylene glycol to the triethylamine to the p-toluenesulfonyl chloride is 100:5-12: 2.5-6.

3. The functionalized graphene grafted and modified polylactic acid material according to claim 1, wherein: the constant temperature reaction instrument in the step (2) comprises a magnetic stirring heater, a screw is fixedly connected above the magnetic stirring heater, a rotating gear is movably connected above the screw, the rotating gear is movably connected with an oil bath heat preservation pot, and a reaction bottle is arranged in the oil bath heat preservation pot.

4. The functionalized graphene grafted and modified polylactic acid material according to claim 1, wherein: the mass ratio of the carboxylated graphene, the single-end amino polyethylene glycol, the 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride and the N-hydroxysuccinimide in the step (4) is 100:75-150:20-30: 20-30.

5. The functionalized graphene grafted and modified polylactic acid material according to claim 1, wherein: the mass ratio of the D, L-lactide, polyethylene glycol covalent modified graphene and stannous octoate in the step (5) is 100:1-3: 0.15-0.3.

Technical Field

The invention relates to the technical field of polylactic acid, in particular to a functionalized graphene grafted modified polylactic acid material and a preparation method thereof.

Background

Along with the increasing severity of the problem of environmental pollution and the popularization of sustainable green development, the application of the bio-based degradable polymer material in the life of people is more and more extensive, polylactic acid is an organic renewable polymer material derived from plants such as corn, sweet potato and the like, is prepared by biological fermentation, refining and dehydration polymerization, has the advantages of excellent biocompatibility, biodegradability and easy processing, is widely applied to the fields such as food, medical treatment, agriculture and the like, and therefore the comprehensive performance of the polylactic acid needs to be further improved to meet the requirement of industrial development.

However, the traditional polylactic acid has a slow crystallization speed, and has a low glass transition temperature and a low thermal decomposition temperature, which results in poor thermal stability, a nucleating agent is usually added to promote the crystallization behavior of the polylactic acid, and graphene, as a novel two-dimensional carbon material, has unique properties of electricity, mechanics, thermology and the like, and is a novel functional nano filler which is extremely effective for polymer materials such as epoxy resin, polyurethane, polylactic acid and the like, but the graphene nanoparticles have poor interface compatibility with the polylactic acid, and are easy to agglomerate, so that the crystallinity and the mechanical strength of the polylactic acid are affected, and therefore, the graphene needs to be functionally modified, and the compatibility and the dispersibility of the graphene and the polylactic acid are improved.

Technical problem to be solved

Aiming at the defects of the prior art, the invention provides a functionalized graphene grafted modified polylactic acid material and a preparation method thereof, solves the problems of poor crystallization and thermal stability of the traditional polylactic acid, and simultaneously solves the problems of low mechanical properties such as tensile strength and the like of the polylactic acid.

(II) technical scheme

In order to achieve the purpose, the invention provides the following technical scheme: a preparation method of a functionalized graphene grafted modified polylactic acid material comprises the following steps:

(1) adding a dichloromethane solvent, polyethylene glycol and an accelerator triethylamine into a reaction bottle, stirring uniformly, adding p-toluenesulfonyl chloride, stirring at a constant speed for reaction, and separating and purifying through column chromatography to prepare the single-ended p-toluenesulfonyl polyethylene glycol.

(2) Adding acetonitrile solvent, single-ended p-toluenesulfonyl polyethylene glycol and sodium azide in a mass ratio of 100:2-4 into a reaction bottle, placing the mixture into a constant temperature reactor, heating the mixture to 80-100 ℃, uniformly stirring the mixture for reaction for 24-48h, adding distilled water and dichloromethane for extraction, removing an organic phase, carrying out reduced pressure distillation, recrystallizing and purifying to prepare the single-ended azido polyethylene glycol.

(3) Adding a tetrahydrofuran solvent, single-ended azido polyethylene glycol with a mass ratio of 100:12-25 and a catalyst triphenylphosphine into a reaction bottle, uniformly stirring and reacting for 36-72h at room temperature, distilling under reduced pressure to remove the solvent, adding dilute hydrochloric acid, uniformly stirring until a large amount of precipitate is separated out, filtering the solvent, washing with diethyl ether and treating with a dilute sodium hydroxide solution to prepare the single-ended amino polyethylene glycol.

(4) Adding a distilled water solvent and carboxylated graphene into a reaction bottle in a nitrogen atmosphere, adding single-terminal amino polyethylene glycol, a condensing agent 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride and an accelerator N-hydroxysuccinimide after ultrasonic dispersion is uniform, heating to 50-60 ℃, stirring at a constant speed for reaction for 20-30h, filtering to remove the solvent, washing with distilled water and ethanol, and drying to prepare the polyethylene glycol covalent modified graphene.

(5) Adding an anhydrous toluene solvent, D, L-lactide and polyethylene glycol to covalently modify graphene into a reaction bottle, uniformly stirring, adding a catalyst stannous octoate, heating to 110-.

Preferably, the molecular weight of the polyethylene glycol in the step (1) is 800-1500, and the mass ratio of the polyethylene glycol to the triethylamine to the p-toluenesulfonyl chloride is 100:5-12: 2.5-6.

Preferably, the constant temperature reactor in the step (2) comprises a magnetic stirring heater, a screw is fixedly connected above the magnetic stirring heater, a rotating gear is movably connected above the screw, the rotating gear is movably connected with an oil bath heat preservation pot, and a reaction bottle is arranged inside the oil bath heat preservation pot.

Preferably, the mass ratio of the carboxylated graphene, the single-ended amino polyethylene glycol, the 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride and the N-hydroxysuccinimide in the step (4) is 100:75-150:20-30: 20-30.

Preferably, the mass ratio of the D, L-lactide, the polyethylene glycol covalently modified graphene and the stannous octoate in the step (5) is 100:1-3: 0.15-0.3.

(III) advantageous technical effects

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

the functionalized graphene graft modified polylactic acid material has the advantages that under the promoting action of triethylamine, p-toluenesulfonyl chloride reacts with one terminal hydroxyl group of polyethylene glycol to realize single-terminal p-toluenesulfonyl polyethylene glycol, p-toluenesulfonyl further reacts with sodium azide to obtain single-terminal azido polyethylene glycol, further under the catalytic reduction action of triphenylphosphine, the single-terminal amino polyethylene glycol is obtained, and the rich carboxyl of carboxylated graphene and the single-terminal amino group of polyethylene glycol carry out amidation reaction under the synergistic activation action of 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide to obtain polyethylene glycol covalent modified graphene.

The functionalized graphene grafted modified polylactic acid material takes stannous octoate as a catalyst, polyethylene glycol covalently modified graphene as a macroinitiator, and terminal hydroxyl of the polyethylene glycol as an initiation active site to initiate D, L-lactide ring-opening polymerization, so that the graphene is organically combined with a polylactic acid molecular chain through the bridging effect of the polyethylene glycol, the interface compatibility of the graphene and the polylactic acid is remarkably improved, uniformly dispersed graphene nanoparticles are difficult to agglomerate and aggregate under the bridging effect of the polyethylene glycol, the graphene with excellent mechanical properties is taken as a crosslinking site, the mechanical properties such as tensile strength and the like of the polylactic acid are remarkably enhanced, meanwhile, the polyethylene glycol grafted by the polylactic acid molecular chain can be taken as a plasticizer to promote the chain segment motion of the polylactic acid, and the graphene nanoparticles can be taken as a heterogeneous crystallization nucleating agent to improve the nucleation density, the crystallization behavior of the polylactic acid is improved, the effect of inducing and promoting the crystallization process of the polylactic acid is achieved, and the thermal stability of the polylactic acid material, such as the glass transition temperature, the thermal decomposition temperature and the like, is obviously improved.

Drawings

FIG. 1 is a schematic front view of an isothermal reactor;

FIG. 2 is a schematic top view of an oil bath insulated pan;

FIG. 3 is a schematic view showing the adjustment of the oil bath pot.

1-magnetic stirring heater; 2-a screw; 3-a rotating gear; 4-oil bath of the heat preservation pot; 5-reaction flask.

Detailed Description

To achieve the above object, the present invention provides the following embodiments and examples: a preparation method of a functionalized graphene grafted modified polylactic acid material comprises the following steps:

(1) adding a dichloromethane solvent, polyethylene glycol with the molecular weight of 800-1500 and an accelerant triethylamine into a reaction bottle, uniformly stirring, adding p-toluenesulfonyl chloride, reacting with uniform stirring at the mass ratio of 100:5-12:2.5-6, and separating and purifying by column chromatography to obtain the single-ended p-toluenesulfonyl polyethylene glycol.

(2) Adding an acetonitrile solvent, single-ended p-toluenesulfonyl polyethylene glycol and sodium azide with the mass ratio of 100:2-4 into a reaction bottle, placing the reaction bottle in a constant temperature reactor, wherein the constant temperature reactor comprises a magnetic stirring heater, a screw is fixedly connected above the magnetic stirring heater, a rotating gear is movably connected above the screw and is movably connected with an oil bath heat preservation pot, a reaction bottle is arranged inside the oil bath heat preservation pot, heating the reaction bottle to 80-100 ℃, stirring at a constant speed for reaction for 24-48h, adding distilled water and dichloromethane for extraction, removing an organic phase, carrying out reduced pressure distillation, recrystallization and purification, and preparing the single-ended azido polyethylene glycol.

(3) Adding a tetrahydrofuran solvent, single-ended azido polyethylene glycol with a mass ratio of 100:12-25 and a catalyst triphenylphosphine into a reaction bottle, uniformly stirring and reacting for 36-72h at room temperature, distilling under reduced pressure to remove the solvent, adding dilute hydrochloric acid, uniformly stirring until a large amount of precipitate is separated out, filtering the solvent, washing with diethyl ether and treating with a dilute sodium hydroxide solution to prepare the single-ended amino polyethylene glycol.

(4) Adding a distilled water solvent and carboxylated graphene into a reaction bottle in a nitrogen atmosphere, adding single-terminal amino polyethylene glycol, a condensing agent 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride and an accelerator N-hydroxysuccinimide in a mass ratio of 100:75-150:20-30:20-30 after uniformly dispersing by ultrasound, heating to 50-60 ℃, uniformly stirring for reaction for 20-30h, filtering to remove the solvent, washing with distilled water and ethanol, and drying to prepare the polyethylene glycol covalently modified graphene.

(5) Adding an anhydrous toluene solvent, D, L-lactide and polyethylene glycol to covalently modify graphene into a reaction bottle, uniformly stirring, adding a catalyst stannous octoate, heating to 110-3: 0.15-0.3 by mass ratio, stirring at a constant speed, reacting for 20-30h, distilling the solution under reduced pressure to remove the solvent, washing and drying by using distilled water and diethyl ether, and preparing a solid product into a standard sample strip by using a double-screw extruder and an injection molding machine to obtain the functionalized graphene grafted modified polylactic acid material.

Example 1

(1) Adding a dichloromethane solvent, polyethylene glycol with the molecular weight of 800 and an accelerator triethylamine into a reaction bottle, uniformly stirring, adding p-toluenesulfonyl chloride, reacting with uniform stirring at the mass ratio of 100:5:2.5, and separating and purifying by column chromatography to obtain the single-ended p-toluenesulfonyl polyethylene glycol.

(2) Adding an acetonitrile solvent, single-ended p-toluenesulfonyl polyethylene glycol and sodium azide with the mass ratio of 100:2 into a reaction bottle, placing the reaction bottle in a constant temperature reactor, wherein the constant temperature reactor comprises a magnetic stirring heater, a screw rod is fixedly connected above the magnetic stirring heater, a rotating gear is movably connected above the screw rod, the rotating gear is movably connected with an oil bath heat preservation pot, a reaction bottle is arranged inside the oil bath heat preservation pot, heating the reaction bottle to 80 ℃, stirring at a constant speed for reaction for 24 hours, adding distilled water and dichloromethane for extraction, removing an organic phase, carrying out reduced pressure distillation, recrystallization and purification, and preparing the single-ended azido polyethylene glycol.

(3) Adding a tetrahydrofuran solvent, single-ended azido polyethylene glycol with the mass ratio of 100:12 and a catalyst triphenylphosphine into a reaction bottle, uniformly stirring and reacting for 36 hours at room temperature, distilling under reduced pressure to remove the solvent, adding dilute hydrochloric acid, uniformly stirring until a large amount of precipitate is separated out, filtering the solvent, washing with diethyl ether and treating with a dilute sodium hydroxide solution to prepare the single-ended amino polyethylene glycol.

(4) Adding a distilled water solvent and carboxylated graphene into a reaction bottle in a nitrogen atmosphere, adding single-terminal amino polyethylene glycol, a condensing agent 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride and an accelerator N-hydroxysuccinimide in a mass ratio of 100:75:20:20 after uniformly ultrasonic dispersing, heating to 50 ℃, uniformly stirring for reaction for 20 hours, filtering to remove the solvent, washing with distilled water and ethanol, and drying to prepare the polyethylene glycol covalent modified graphene.

(5) Adding an anhydrous toluene solvent, D, L-lactide and polyethylene glycol to covalently modify graphene into a reaction bottle, uniformly stirring, adding a catalyst stannous octoate, heating to 110 ℃, uniformly stirring for reaction for 20 hours, distilling the solution under reduced pressure to remove the solvent, washing and drying by using distilled water and diethyl ether, and preparing a solid product into a standard sample strip by using a double-screw extruder and an injection molding machine to obtain the functionalized graphene grafted modified polylactic acid material 1.

Example 2

(1) Adding a dichloromethane solvent, polyethylene glycol with the molecular weight of 1000 and an accelerator triethylamine into a reaction bottle, uniformly stirring, adding p-toluenesulfonyl chloride, reacting by uniformly stirring at the mass ratio of 100:8:4, and separating and purifying through column chromatography to obtain the single-end p-toluenesulfonyl polyethylene glycol.

(2) Adding an acetonitrile solvent, single-ended p-toluenesulfonyl polyethylene glycol and sodium azide in a mass ratio of 100:3 into a reaction bottle, placing the reaction bottle in a constant temperature reactor, wherein the constant temperature reactor comprises a magnetic stirring heater, a screw rod is fixedly connected above the magnetic stirring heater, a rotating gear is movably connected above the screw rod, the rotating gear is movably connected with an oil bath heat preservation pot, a reaction bottle is arranged in the oil bath heat preservation pot, heating the reaction bottle to 100 ℃, stirring at a constant speed for reaction for 36 hours, adding distilled water and dichloromethane for extraction, removing an organic phase, carrying out reduced pressure distillation, recrystallization and purification, and preparing the single-ended azido polyethylene glycol.

(3) Adding a tetrahydrofuran solvent, single-ended azido polyethylene glycol and triphenylphosphine serving as a catalyst in a mass ratio of 100:18 into a reaction bottle, uniformly stirring at room temperature for 72 hours, distilling under reduced pressure to remove the solvent, adding dilute hydrochloric acid, uniformly stirring until a large amount of precipitate is separated out, filtering the solvent, washing with diethyl ether and treating with a dilute sodium hydroxide solution to prepare the single-ended amino polyethylene glycol.

(4) Adding a distilled water solvent and carboxylated graphene into a reaction bottle in a nitrogen atmosphere, adding single-terminal amino polyethylene glycol, a condensing agent 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride and an accelerator N-hydroxysuccinimide in a mass ratio of 100:100:24:24 after uniformly ultrasonic dispersing, heating to 60 ℃, uniformly stirring for reaction for 30 hours, filtering to remove the solvent, washing with distilled water and ethanol, and drying to prepare the polyethylene glycol covalent modified graphene.

(5) Adding an anhydrous toluene solvent, D, L-lactide and polyethylene glycol to covalently modify graphene into a reaction bottle, uniformly stirring, adding a catalyst stannous octoate, heating to 130 ℃, uniformly stirring, reacting for 20 hours, carrying out reduced pressure distillation on the solution to remove the solvent, washing and drying by using distilled water and diethyl ether, and preparing a solid product into a standard sample strip by using a double-screw extruder and an injection molding machine to obtain the functionalized graphene grafted modified polylactic acid material 2.

Example 3

(1) Adding a dichloromethane solvent, polyethylene glycol with the molecular weight of 1000 and an accelerator triethylamine into a reaction bottle, uniformly stirring, adding p-toluenesulfonyl chloride, reacting by uniformly stirring at the mass ratio of 100:8:4, and separating and purifying through column chromatography to obtain the single-end p-toluenesulfonyl polyethylene glycol.

(2) Adding an acetonitrile solvent, single-ended p-toluenesulfonyl polyethylene glycol and sodium azide in a mass ratio of 100:3 into a reaction bottle, placing the reaction bottle into a constant temperature reactor, wherein the constant temperature reactor comprises a magnetic stirring heater, a screw rod is fixedly connected above the magnetic stirring heater, a rotating gear is movably connected above the screw rod, the rotating gear is movably connected with an oil bath heat preservation pot, a reaction bottle is arranged inside the oil bath heat preservation pot, heating the reaction bottle to 80 ℃, stirring at a constant speed for reaction for 8 hours, adding distilled water and dichloromethane for extraction, removing an organic phase, carrying out reduced pressure distillation, recrystallization and purification, and preparing the single-ended azido polyethylene glycol.

(3) Adding a tetrahydrofuran solvent, single-ended azido polyethylene glycol and triphenylphosphine serving as a catalyst in a mass ratio of 100:18 into a reaction bottle, uniformly stirring at room temperature for 48 hours, distilling under reduced pressure to remove the solvent, adding dilute hydrochloric acid, uniformly stirring until a large amount of precipitate is separated out, filtering the solvent, washing with diethyl ether and treating with a dilute sodium hydroxide solution to prepare the single-ended amino polyethylene glycol.

(4) Adding a distilled water solvent and carboxylated graphene into a reaction bottle in a nitrogen atmosphere, adding single-terminal amino polyethylene glycol, a condensing agent 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride and an accelerator N-hydroxysuccinimide in a mass ratio of 100:125:27:27 after uniformly ultrasonic dispersing, heating to 55 ℃, uniformly stirring for reaction for 24 hours, filtering to remove the solvent, washing with distilled water and ethanol, and drying to prepare the polyethylene glycol covalent modified graphene.

(5) Adding an anhydrous toluene solvent, D, L-lactide and polyethylene glycol to covalently modify graphene into a reaction bottle, uniformly stirring, adding a catalyst stannous octoate, heating to 120 ℃, uniformly stirring and reacting for 24 hours, carrying out reduced pressure distillation on the solution to remove the solvent, washing and drying by using distilled water and diethyl ether, and preparing a solid product into a standard sample strip by using a double-screw extruder and an injection molding machine to obtain the functionalized graphene grafted modified polylactic acid material 3.

Example 4

(1) Adding a dichloromethane solvent, polyethylene glycol with the molecular weight of 1500 and an accelerator triethylamine into a reaction bottle, uniformly stirring, adding p-toluenesulfonyl chloride, reacting by uniformly stirring at the mass ratio of 100:12:6, and separating and purifying by column chromatography to obtain the single-end p-toluenesulfonyl polyethylene glycol.

(2) Adding an acetonitrile solvent, single-ended p-toluenesulfonyl polyethylene glycol and sodium azide with the mass ratio of 100:4 into a reaction bottle, placing the reaction bottle into a constant temperature reactor, wherein the constant temperature reactor comprises a magnetic stirring heater, a screw rod is fixedly connected above the magnetic stirring heater, a rotating gear is movably connected above the screw rod, the rotating gear is movably connected with an oil bath heat preservation pot, a reaction bottle is arranged inside the oil bath heat preservation pot, heating the reaction bottle to 100 ℃, stirring at a constant speed for reaction for 48 hours, adding distilled water and dichloromethane for extraction, removing an organic phase, carrying out reduced pressure distillation, recrystallization and purification, and preparing the single-ended azido polyethylene glycol.

(3) Adding a tetrahydrofuran solvent, single-ended azido polyethylene glycol and triphenylphosphine serving as a catalyst in a mass ratio of 100:25 into a reaction bottle, uniformly stirring at room temperature for 72 hours, distilling under reduced pressure to remove the solvent, adding dilute hydrochloric acid, uniformly stirring until a large amount of precipitate is separated out, filtering the solvent, washing with diethyl ether and treating with a dilute sodium hydroxide solution to prepare the single-ended amino polyethylene glycol.

(4) Adding a distilled water solvent and carboxylated graphene into a reaction bottle in a nitrogen atmosphere, adding single-terminal amino polyethylene glycol, a condensing agent 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride and an accelerator N-hydroxysuccinimide in a mass ratio of 100:150:30:30 after ultrasonic dispersion is uniform, heating to 60 ℃, stirring at a constant speed for reaction for 30 hours, filtering to remove the solvent, washing with distilled water and ethanol, and drying to prepare the polyethylene glycol covalent modified graphene.

(5) Adding an anhydrous toluene solvent, D, L-lactide and polyethylene glycol to covalently modify graphene into a reaction bottle, uniformly stirring, adding a catalyst stannous octoate, heating to 130 ℃, uniformly stirring for reaction for 30 hours, distilling the solution under reduced pressure to remove the solvent, washing and drying by using distilled water and diethyl ether, and preparing a solid product into a standard sample strip by using a double-screw extruder and an injection molding machine to obtain the functionalized graphene grafted modified polylactic acid material 4.

Comparative example 1

(1) Adding a dichloromethane solvent, polyethylene glycol with the molecular weight of 800 and an accelerator triethylamine into a reaction bottle, uniformly stirring, adding p-toluenesulfonyl chloride, reacting by uniformly stirring at the mass ratio of 100:4:2, and separating and purifying by column chromatography to obtain the single-ended p-toluenesulfonyl polyethylene glycol.

(2) Adding an acetonitrile solvent, single-ended p-toluenesulfonyl polyethylene glycol and sodium azide with the mass ratio of 100:1.5 into a reaction bottle, placing the reaction bottle into a constant temperature reactor, wherein the constant temperature reactor comprises a magnetic stirring heater, a screw rod is fixedly connected above the magnetic stirring heater, a rotating gear is movably connected above the screw rod, the rotating gear is movably connected with an oil bath heat preservation pot, a reaction bottle is arranged inside the oil bath heat preservation pot, heating the reaction bottle to 100 ℃, stirring at a constant speed for reaction for 48 hours, adding distilled water and dichloromethane for extraction, removing an organic phase, carrying out reduced pressure distillation, recrystallizing and purifying, thus obtaining the single-ended azido polyethylene glycol.

(3) Adding a tetrahydrofuran solvent, single-ended azido polyethylene glycol and triphenylphosphine serving as a catalyst in a mass ratio of 100:10 into a reaction bottle, uniformly stirring at room temperature for 72 hours, distilling under reduced pressure to remove the solvent, adding dilute hydrochloric acid, uniformly stirring until a large amount of precipitate is separated out, filtering the solvent, washing with diethyl ether and treating with a dilute sodium hydroxide solution to prepare the single-ended amino polyethylene glycol.

(4) Adding a distilled water solvent and carboxylated graphene into a reaction bottle in a nitrogen atmosphere, adding single-terminal amino polyethylene glycol, a condensing agent 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride and an accelerator N-hydroxysuccinimide in a mass ratio of 100:60:18:18 after ultrasonic dispersion is uniform, heating to 60 ℃, stirring at a constant speed for reaction for 30 hours, filtering to remove the solvent, washing with distilled water and ethanol, and drying to prepare the polyethylene glycol covalent modified graphene.

(5) Adding an anhydrous toluene solvent, D, L-lactide and polyethylene glycol to covalently modify graphene into a reaction bottle, uniformly stirring, adding a catalyst stannous octoate, heating to 110 ℃, uniformly stirring and reacting for 30 hours, carrying out reduced pressure distillation on the solution to remove the solvent, washing and drying by using distilled water and diethyl ether, and preparing a solid product into a standard sample strip by using a double-screw extruder and an injection molding machine to obtain a functionalized graphene grafted modified polylactic acid material comparison 1.

The thermal decomposition temperature of the functionalized graphene grafted modified polylactic acid materials in the examples and the comparative examples is tested by using a TGA 8000 thermogravimetric analyzer, and the test standard is GB/T27761-2011.

And testing the tensile strength of the functionalized graphene grafted modified polylactic acid material by using a BLD-1028A plastic testing machine, wherein the test standard is GB/T1040.2-2006.