阅读说明：本技术 聚乳酸嵌段共聚物的共混物的制备方法 (Preparation method of blend of polylactic acid block copolymer ) 是由 邵俊 陈赟 王丽英 封从姝 候豪情 陈水亮 于 2020-07-07 设计创作，主要内容包括：本发明提供了聚乳酸嵌段共聚物的共混物的制备方法。以一系列聚乙二醇-聚左旋乳酸嵌段共聚物(PEG-PLLA)和聚乙二醇-聚右旋乳酸嵌段共聚物(PEG-PDLA)为原料,并采用溶液共混法制备了PEG-PLLA/PEG-PDLA共混物。该方法在溶液共混过程中优先形成含有立体复合物的结晶,其熔融温度在230℃左右。用本发明的方法制备得到的共混物的生物降解性和成型加工性优异,且制备方法简单,适于工业化生产。(The invention provides a preparation method of a blend of polylactic acid block copolymers. A series of polyethylene glycol-poly-L-lactic acid block copolymers (PEG-PLLA) and polyethylene glycol-poly-D-lactic acid block copolymers (PEG-PDLA) are used as raw materials, and a solution blending method is adopted to prepare the PEG-PLLA/PEG-PDLA blend. The method preferentially forms crystals containing the stereo complex in the solution blending process, and the melting temperature of the crystals is about 230 ℃. The blend prepared by the method has excellent biodegradability and molding processability, and the preparation method is simple and is suitable for industrial production.)

1. A method for preparing a blend of polylactic acid block copolymers, comprising the steps of:

dissolving a first polylactic acid block copolymer in a solvent to obtain a first polylactic acid block copolymer solution;

dissolving the second polylactic acid block copolymer in a solvent to obtain a second polylactic acid block copolymer solution;

mixing the first polylactic acid block copolymer solution with the second polylactic acid block copolymer solution, and volatilizing a solvent to obtain a blend of polylactic acid block copolymers;

wherein the first polylactic acid block copolymer is poly-L-lactic acid-polyethylene glycol-poly-L-lactic acid triblock copolymer (PLLA-b-PEG-b-PLLA) or methoxy polyethylene glycol-poly-L-lactic acid diblock copolymer (MPEG-b-PLLA); the second polylactic acid segmented copolymer is a poly-D-lactic acid-polyethylene glycol-poly-D-lactic acid triblock copolymer (PDLA-b-PEG-b-PDLA) or a methoxy polyethylene glycol-poly-D-lactic acid diblock copolymer (MPEG-b-PDLA).

2. The method of claim 1, wherein: the solvent is dichloromethane or trichloromethane, or a mixture of dichloromethane and trichloromethane.

3. The method according to claim 1 or 2, characterized in that: the concentration of the first polylactic acid block copolymer solution is 10mg mL^-1The concentration of the second polylactic acid block copolymer solution is 10mg mL^-1。

4. The method of claim 3, wherein: the dosage ratio of the first polylactic acid block copolymer solution to the second polylactic acid block copolymer solution is 1: 1.

5. A blend of polylactic acid block copolymers obtainable by the process according to any of claims 1 to 4.

6. Use of a blend of polylactic acid block copolymers according to claim 5, characterized in that: the blend of the polylactic acid segmented copolymer is used as a drug slow release agent or injectable hydrogel.

Technical Field

The invention belongs to the field of biodegradable high polymer materials, and particularly relates to a preparation method of a blend of polylactic acid block copolymers.

Background

In recent years, petroleum resources are increasingly in shortage, environmental pollution is increasingly serious, environmental and resource problems simultaneously restrict the sustainable development of economy, and people urgently hope that a green and environment-friendly material can replace the traditional petroleum-based high polymer material. The biodegradable material derived from renewable resources accords with the concepts of circular economy and sustainable development, and promotes governments, enterprises and scientific researchers of all countries to research, develop and widely apply the biodegradable material and invest a large amount of manpower and material resources.

Polylactic acid (PLA) is the most typical biodegradable plastic in aliphatic series, is derived from biomass raw materials such as corn, cassava and the like, and can be rapidly degraded into carbon dioxide and water under the composting condition after being used without polluting the environment. The raw materials are easy to obtain, the synthesis process is simple, and the composite material has good comprehensive performance, has wide application prospect in the fields of medicine, agriculture, packaging and the like, and is expected to replace the traditional high polymer material. However, the application of polylactic acid is limited in two aspects, one is that the polylactic acid has a slow crystallization rate and a low glass transition temperature (50-60 ℃), so that the use temperature cannot exceed the glass transition temperature (T)_g═ 60 ℃); secondly, the product has poor flexibility due to the higher rigidity of the polylactic acid molecular chain. The two main short plates greatly limit the wide application of the polylactic acid material, so in recent years, many researchers at home and abroad make much research work on the improvement of the heat resistance and brittleness of the polylactic acid material.

Researchers have found that a completely new crystalline form can be obtained during blending of poly (l-lactic acid) (PLLA) and poly (d-lactic acid) (PDLA) (PLA stereocomplex, PLA SC). Compared with PLLA or PDLA (the melting point is about 150-180 ℃), the melting point of PLA SC can reach 230 ℃, the crystallization rate is high, and the heat resistance of the polylactic acid material can be greatly improved. In addition, the stereo complex crystal can also be used as a nucleating agent to induce the formation of the polylactic acid single crystal. As is well known, polyethylene glycol (PEG) has better molecular chain flexibility and hydrophilicity, and the physical properties of polylactic acid can be obviously improved by introducing the PEG into a PLA matrix. The block copolymer composed of PEG and PLLA has unique performance and has great application prospect in the fields of hydrogel, drug sustained release and the like.

Disclosure of Invention

The invention aims to provide a preparation method of a blend of polylactic acid block copolymers, which is to blend a polyethylene glycol-poly-L-lactic acid block copolymer and a polyethylene glycol-poly-D-lactic acid block copolymer through solution to obtain the blend.

The invention provides a preparation method of a blend of polylactic acid block copolymers, which comprises the following steps:

dissolving a first polylactic acid block copolymer in a solvent to obtain a first polylactic acid block copolymer solution;

dissolving the second polylactic acid block copolymer in a solvent to obtain a second polylactic acid block copolymer solution;

mixing the first polylactic acid block copolymer solution with the second polylactic acid block copolymer solution, and volatilizing a solvent to obtain a blend of polylactic acid block copolymers;

wherein the first polylactic acid block copolymer is poly-L-lactic acid-polyethylene glycol-poly-L-lactic acid triblock copolymer (PLLA-b-PEG-b-PLLA) or methoxy polyethylene glycol-poly-L-lactic acid diblock copolymer (MPEG-b-PLLA); the second polylactic acid segmented copolymer is a poly-D-lactic acid-polyethylene glycol-poly-D-lactic acid triblock copolymer (PDLA-b-PEG-b-PDLA) or a methoxy polyethylene glycol-poly-D-lactic acid diblock copolymer (MPEG-b-PDLA).

Further, the solvent is dichloromethane or trichloromethane, or a mixture of dichloromethane and trichloromethane.

Further, the concentration of the first polylactic acid block copolymer solution is 10mg mL^-1The second polylactic acid block copolymerThe concentration of the solution was 10mg mL^-1。

Further, the ratio of the amount of the first polylactic acid block copolymer solution to the amount of the second polylactic acid block copolymer solution is 1: 1.

The blend of polylactic acid block copolymers can be applied to the biomedical field, for example, as a drug sustained release agent or an injectable hydrogel.

The invention has the following beneficial effects: a series of unconformable polyethylene glycol-poly-L-lactic acid block copolymers and polyethylene glycol-poly-D-lactic acid block copolymers are prepared into PEG-b-PLLA/PEG-b-PDLA blends by a solution blending method. Whether in the process of solution crystallization or melt crystallization, the introduction of polyethylene glycol promotes the formation of polylactic acid stereocomplex, and as the molecular weight of PEG increases, the critical molecular weight of polylactic acid single crystal increases. The PEG molecular weight is 20kg & mol^-1In the PLLA-b-PEG-b-PLLA/PDLA-b-PEG-b-PDLA blend, when the PLA block molecular weight is increased to 10 kg-mol^-1In the case of the polylactic acid, polylactic acid alone is not crystallized in the blending system. Due to the introduction of polyethylene glycol, the movement capability of PLLA or PDLA molecular chains can be enhanced, so that the formation of polylactic acid stereo complex is promoted. Particularly, in the melt crystallization process, the critical molecular weight of the polylactic acid which is independently crystallized is greatly improved compared with the pure PLLA/PDLA blend. In addition, the blend prepared by the method of the invention has excellent biodegradability and molding processability, and the preparation method is simple and is suitable for industrial production.

Drawings

FIG. 1 is MPEG₄-b-PLLA/MPEG₄-one time temperature rise DSC profile of b-PDLA blend.

FIG. 2 is MPEG₄-b-PLLA/MPEG₄Secondary temperature rise DSC profile of b-PDLA blend.

FIG. 3 is MPEG₄-b-PLLA/MPEG₄-b-WAXD pattern of PDLA blends.

FIG. 4 is PLLA-b-PEG₄-b-PLLA/PDLA-b-PEG₄-one time temperature rise DSC profile of b-PDLA blend.

FIG. 5 is PLLA-b-PEG₄-b-PLLA/PDLA-b-PEG₄Secondary temperature rise DSC profile of b-PDLA blend.

FIG. 6 is PLLA-b-PEG₄-b-PLLA/PDLA-b-PEG₄-b-WAXD pattern of PDLA blends.

FIG. 7 is PLLA-b-PEG₁₀-b-PLLA/PDLA-b-PEG₁₀-one time temperature rise DSC profile of b-PDLA blend.

FIG. 8 is PLLA-b-PEG₁₀-b-PLLA/PDLA-b-PEG₁₀Secondary temperature rise DSC profile of b-PDLA blend.

FIG. 9 is PLLA-b-PEG₁₀-b-PLLA/PDLA-b-PEG₁₀-b-WAXD pattern of PDLA blends.

FIG. 10 is PLLA-b-PEG₂₀-b-PLLA/PDLA-b-PEG₂₀-one time temperature rise DSC profile of b-PDLA blend.

FIG. 11 is PLLA-b-PEG₂₀-b-PLLA/PDLA-b-PEG₂₀Secondary temperature rise DSC profile of b-PDLA blend.

FIG. 12 is PLLA-b-PEG₂₀-b-PLLA/PDLA-b-PEG₂₀-b-WAXD pattern of PDLA blends.

Detailed Description

The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

The first polylactic acid block copolymer is poly-L-lactic acid-polyethylene glycol-poly-L-lactic acid triblock copolymer (PLLA-b-PEG-b-PLLA) or methoxy polyethylene glycol-poly-L-lactic acid diblock copolymer (MPEG-b-PLLA); the second polylactic acid segmented copolymer is poly-D-lactic acid-polyethylene glycol-poly-D-lactic acid triblock copolymer (PDLA-b-PEG-b-PDLA) or methoxy polyethylene glycol-poly-D-lactic acid diblock copolymer (MPEG-b-PLLA). The first polylactic acid block copolymer is obtained by taking polyethylene glycol as a macroinitiator and performing ring-opening polymerization with levorotatory lactide under the action of a catalyst, and the second polylactic acid block copolymer is obtained by taking polyethylene glycol as a macroinitiator and performing ring-opening polymerization with dextrorotatory lactide under the action of a catalyst. For example, the synthetic route for the PLLA-b-PEG-b-PLLA triblock copolymer is:

in the following examples, the PLLA-b-PEG-b-PLLA, MPEG-b-PLLA, PDLA-b-PEG-b-PDLA or MPEG-b-PDLA used was prepared by the following steps:

(1) dissolving levorotatory lactide or dextrorotatory lactide in dried ethyl acetate respectively, and recrystallizing for three times to purify lactide. Placing methoxypolyethylene glycol (MPEG) or dihydroxypolyethylene glycol (PEG) into a 250mL flask, adding a proper amount of anhydrous toluene for azeotropic dehydration for 6 hours, then pumping out the solvent, sealing and storing.

(2) Vacuum baking and degassing a 150mL reaction bottle, repeatedly filling nitrogen for three times, and adding the dehydrated MPEG or PEG and the purified levorotatory lactide or dextrorotatory lactide with the total mass of 10 g; adding stannous octoate as a catalyst (the dosage is 0.3-0.5% of the mass of the lactide).

(3) In a sealed system, dried toluene is used as a solvent, the mixture is heated to 120 ℃, stirred and reacted for 24 hours to obtain a white crystalline polymer, chloroform is added for dissolution, excessive ether-ethanol mixed solution is used for precipitation to obtain a white solid, and the white solid is dried to constant weight by a vacuum oven at the temperature of 60 ℃ to obtain PLLA-b-PEG-b-PLLA, MPEG-b-PLLA, PDLA-b-PEG-b-PDLA or MPEG-b-PDLA.

A series of PLLA-b-PEG-b-PLLA, MPEG-b-PLLA, PDLA-b-PEG-b-PDLA or MPEG-b-PDLA with different block compositions can be obtained by changing the molecular weight and the feeding ratio of reactants, and the specific conditions are as shown in the following tables 1-4:

TABLE 1

TABLE 2

TABLE 3

TABLE 4