CN113512180A - Preparation method of ultra-high molecular weight L-polylactic acid - Google Patents
Preparation method of ultra-high molecular weight L-polylactic acid Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
- C08G63/06—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from hydroxycarboxylic acids
- C08G63/08—Lactones or lactides
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/78—Preparation processes
- C08G63/82—Preparation processes characterised by the catalyst used
- C08G63/85—Germanium, tin, lead, arsenic, antimony, bismuth, titanium, zirconium, hafnium, vanadium, niobium, tantalum, or compounds thereof
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/54—Improvements relating to the production of bulk chemicals using solvents, e.g. supercritical solvents or ionic liquids
Abstract
The invention discloses a preparation method of ultra-high molecular weight L-polylactic acid, which adopts a microwave ultrasonic method to carry out ring-opening polymerization of L-lactide to prepare L-polylactic acid and carries out supercritical treatment on the L-polylactic acid, thereby realizing high energy yield and high molecular weight centralized control of the L-polylactic acid. The beneficial effects of improving production benefits, reducing cost and protecting environment are achieved.
Description
Technical Field
The invention belongs to the field of biological materials, and particularly relates to a preparation method of ultra-high molecular weight L-polylactic acid.
Background
Polylactic acid (PLA) is a novel green material, and has good biocompatibility and biodegradability. PLA is a high molecular material polymerized from micromolecular lactic acid obtained by fermenting biomass raw materials (starch), is not only natural and harmless on the raw materials, but also can be decomposed into CO by enzymolysis in organisms2And H2O participates in the metabolism of the human body. Therefore, PCL has a wide prospect in the biomedical field, such as tissue repair engineering, drug controlled release, medical suture and the like. The synthesis and preparation of the current ultra-high molecular weight polylactic acid are also a great research hotspot, and the excellent heat of the current ultra-high molecular weight polylactic acidThe mechanical property can replace metal materials to be used as biodegradable orthopedic implant materials, such as degradable bone nails, and the requirement value of molecular weight can reach more than million.
The preparation method of PLA includes a direct polymerization method and an indirect polymerization method (lactide ring-opening polymerization method). The direct polymerization method refers to a method for continuously removing water molecules from lactic acid molecules and polymerizing the lactic acid molecules into PLA under certain conditions, and generally does not need to use a catalyst. The direct method has the advantages of simple process flow and low treatment cost, but has the defects of low relative molecular mass, low strength and easy decomposition of the synthesized PLA. The lactide ring-opening polymerization method is a common method for synthesizing high molecular weight PLA at home and abroad, and is prepared by adding an initiator and a tin catalyst and controlling the conditions of high vacuum degree, high temperature gasification and the like. The current lactide ring-opening polymerization method also has the problems of limitation of ultrahigh molecular weight, long preparation time, high catalyst consumption and non-centralized molecular weight distribution, and extensive researchers are required to continuously develop innovations to improve the molecular weight distribution.
At present, lactide ring-opening polymerization is commonly adopted to prepare polylactic acid with the molecular weight of hundreds of thousands to millions. For example, CN 108285528A discloses a method for preparing medical polylactic acid with ultrahigh molecular weight, which comprises reacting dodecanol as an initiator with stannous octoate as a catalyst at 100-180 deg.C under a vacuum degree of 1-1000Pa for 6-120h to obtain polylactic acid with a weight-average molecular weight of 210-2160 KDa. CN 111499844A discloses a medical polylactic acid and a preparation method thereof, which adopts an alcohol initiator and a tin catalyst to react for 12-72h under the conditions of temperature of 130-150 ℃ and vacuum degree of 1-20pa to prepare the polylactic acid with high molecular weight. CN 111690124A discloses a molecular weight controllable medical polylactic acid and a preparation method thereof, which adopts 0.005-10 parts of lactic acid, 0.1-1 part of catalyst and 150 parts of lactide to react for 5-24h under the conditions of 120-180 ℃ and vacuum degree not lower than-0.07 MPa to prepare a polylactic acid product with the weight-average molecular weight of 5-500 KDa. The invention adopts lactide ring-opening polymerization method to prepare high molecular weight levorotatory polylactic acid product, but has the disadvantages of long preparation time, high initiator and catalyst dosage, poor controllability of molecular weight distribution and the like.
Disclosure of Invention
Aiming at the problems of long preparation time, high initiator and catalyst consumption and uncontrollable molecular weight concentration in the preparation of polylactic acid, the invention provides a microwave ultrasonic method for carrying out the ring-opening polymerization reaction of lactide, and the lactide can be fully melted and uniformly mixed with a catalyst by utilizing microwave heating and ultrasonic modes, so that the ring-opening polymerization reaction of the lactide is accelerated and promoted, the time cost and the catalyst consumption cost are greatly saved, meanwhile, the process material is simpler and more environment-friendly, and finally, the high-molecular polylactic acid with the concentratedly distributed and controllable molecular weight is prepared.
A preparation method of ultra-high molecular weight L-polylactic acid mainly comprises the following steps:
(1) putting a reactant L-lactide into a glass reaction kettle which is pretreated in advance, then putting the reaction kettle into a microwave ultrasonic reactor, heating the reaction kettle to 90-120 ℃ until a monomer is molten, adding an initiator, and then adding a certain amount of catalyst; vacuumizing the reactor to below 100Pa, breaking the vacuum with argon, replacing residual air in the system, repeating the operation for 2-3 times, and finally vacuumizing to below 100Pa and sealing;
(2) setting microwave radiation power (50-150W) and ultrasonic frequency (10-30KHz), so that the L-lactide monomer can be fully and uniformly mixed with the catalyst, and finally carrying out polymerization reaction;
(3) after the polymerization reaction is finished, obtaining a blocky levorotatory polylactic acid material, slicing the product, freezing the product by liquid nitrogen, and putting the product into a crusher to obtain granular levorotatory polylactic acid;
(4) and (3) removing impurities from the granular L-polylactic acid, collecting, dissolving the L-polylactic acid by using dichloromethane, adding an ethanol solvent to precipitate the polylactic acid, and finally performing vacuum drying on the polylactic acid to obtain the high-molecular L-polylactic acid.
Preferably, the initiator is n-octanol, and the catalyst is stannous octoate.
The preferable scheme is that the molar ratio of the L-lactide to the initiator is 10000:1-4000:1, and the molar ratio of the L-lactide to the catalyst is 800000:1-8000: 1.
Preferably, the polymerization conditions in step (2) are as follows: the polymerization reaction is carried out for 4 to 240 hours at the temperature of between 40 and 160 ℃.
Preferably, the weight average molecular weight of the obtained high molecular levorotatory polylactic acid ranges from 30000-3000000g/mol (preferably from 50000-1200000 g/mol).
Compared with the prior art, the invention has the characteristics and beneficial effects that:
1. the production benefit is improved: the microwave ultrasonic heating mode is adopted, the limitation of the traditional heating and stirring mode is overcome, the process is simple, and the process time is shortened;
2. the cost is reduced, and the environment is protected and beneficial: the initiator and the catalyst can fully contact with the reactant lactide by means of microwave heating and ultrasonic dispersion to promote the reaction to be accelerated, so that the consumption is greatly reduced compared with that of the traditional mode, the cost is reduced, and the method is more environment-friendly;
3. optimizing the molecular weight and the distribution of the polylactic acid product: the microwave and ultrasonic combined mode enables a reaction system to be heated uniformly, and is beneficial to promoting the continuous progress of the lactide ring-opening reaction, thereby further improving the molecular weight of the product and optimizing the concentration ratio of the molecular weight compared with the traditional mode.
Detailed Description
The present invention will be further described with reference to the following embodiments. The following description is given for the purpose of explanation and not limitation. Unless otherwise specified, the contents of the respective components used below are weight percent contents.
The experimental materials and equipment sources used in the examples are shown in tables 1 and 2
TABLE 1 Main test materials and specifications
Table 2 main experimental equipment and specifications:
example 1 weighing 3kg of L-lactide into a pre-treated glass reactor (5L), placing into a microwave ultrasonic reactor and heating to 110 ℃ until the monomer melts, adding 0.2713g of n-octanol, controlling the molar ratio of L-lactide to initiator to 10000:1, and then adding 0.0105g of stannous octoate to make the molar ratio of L-lactide to catalyst 800000: 1. Vacuumizing the reactor to be below 100Pa, breaking the vacuum by using argon, replacing residual air in the system, repeating the operation for 3 times, and finally vacuumizing to be below 100Pa and sealing; setting the microwave radiation power at 90W and the ultrasonic frequency at 25KHz, fully and uniformly mixing the L-lactide monomer and the catalyst, and finally carrying out polymerization reaction for 8 hours at 65 ℃; after the reaction is finished, slicing the blocky L-polylactic acid material, freezing the blocky L-polylactic acid material by liquid nitrogen, and putting the blocky L-polylactic acid material into a crusher to obtain granular L-polylactic acid; and (3) removing impurities from the granular L-polylactic acid, collecting, dissolving the L-polylactic acid by using dichloromethane, adding an ethanol solvent to precipitate the polylactic acid, and finally performing vacuum drying on the polylactic acid for 12 hours to obtain the high-molecular L-polylactic acid.
Example 2 weighing 3kg of L-lactide into a pre-treated glass reactor (5L), placing into a microwave ultrasonic reactor and heating to 110 ℃ until the monomer melts, adding 0.2713g of n-octanol, controlling the molar ratio of L-lactide to initiator to 10000:1, and then adding 1.0549g of stannous octoate to make the molar ratio of L-lactide to catalyst 8000: 1. Vacuumizing the reactor to be below 100Pa, breaking the vacuum by using argon, replacing residual air in the system, repeating the operation for 3 times, and finally vacuumizing to be below 100Pa and sealing; setting the microwave radiation power at 90W and the ultrasonic frequency at 25KHz, fully and uniformly mixing the L-lactide monomer and the catalyst, and finally carrying out polymerization reaction for 8 hours at 65 ℃; after the reaction is finished, slicing the blocky L-polylactic acid material, freezing the blocky L-polylactic acid material by liquid nitrogen, and putting the blocky L-polylactic acid material into a crusher to obtain granular L-polylactic acid; and (3) removing impurities from the granular L-polylactic acid, collecting, dissolving the L-polylactic acid by using dichloromethane, adding an ethanol solvent to precipitate the polylactic acid, and finally performing vacuum drying on the polylactic acid for 12 hours to obtain the high-molecular L-polylactic acid.
Example 3kg of L-lactide was weighed into a pre-pretreated glass reactor (5L), then placed into a microwave ultrasonic reactor and heated to 110 ℃ until the monomers melted, 0.6783g of n-octanol was added, the molar ratio of L-lactide to initiator was controlled to 4000:1, then 1.0549g of stannous octoate were added, so that the molar ratio of L-lactide to catalyst was 8000: 1. vacuumizing the reactor to be below 100Pa, breaking the vacuum by using argon, replacing residual air in the system, repeating the operation for 3 times, and finally vacuumizing to be below 100Pa and sealing; setting the microwave radiation power at 90W and the ultrasonic frequency at 25KHz, fully and uniformly mixing the L-lactide monomer and the catalyst, and finally carrying out polymerization reaction for 8 hours at 65 ℃; after the reaction is finished, slicing the blocky L-polylactic acid material, freezing the blocky L-polylactic acid material by liquid nitrogen, and putting the blocky L-polylactic acid material into a crusher to obtain granular L-polylactic acid; and (3) removing impurities from the granular L-polylactic acid, collecting, dissolving the L-polylactic acid by using dichloromethane, adding an ethanol solvent to precipitate the polylactic acid, and finally performing vacuum drying on the polylactic acid for 12 hours to obtain the high-molecular L-polylactic acid.
Example 4 weighing 3kg of L-lactide into a pre-treated glass reactor (5L), placing into a microwave ultrasonic reactor and heating to 110 ℃ until the monomers melt, adding 0.6783g of n-octanol, controlling the molar ratio of L-lactide to initiator to 4000:1, and then adding 0.0105g of stannous octoate to make the molar ratio of L-lactide to catalyst 800000: 1. Vacuumizing the reactor to be below 100Pa, breaking the vacuum by using argon, replacing residual air in the system, repeating the operation for 3 times, and finally vacuumizing to be below 100Pa and sealing; setting the microwave radiation power at 90W and the ultrasonic frequency at 25KHz, fully and uniformly mixing the L-lactide monomer and the catalyst, and finally carrying out polymerization reaction for 8 hours at 65 ℃; after the reaction is finished, slicing the blocky L-polylactic acid material, freezing the blocky L-polylactic acid material by liquid nitrogen, and putting the blocky L-polylactic acid material into a crusher to obtain granular L-polylactic acid; and (3) removing impurities from the granular L-polylactic acid, collecting, dissolving the L-polylactic acid by using dichloromethane, adding an ethanol solvent to precipitate the polylactic acid, and finally performing vacuum drying on the polylactic acid for 12 hours to obtain the high-molecular L-polylactic acid.
Example 5 3kg of L-lactide was weighed into a pre-treated glass reactor (5L) and then placed into a microwave ultrasonic reactor and heated to 110 ℃ until the monomers melted, 0.3875g of n-octanol was added, the molar ratio of L-lactide to initiator was controlled to 7000:1, and 0.0703g of stannous octoate was added so that the molar ratio of L-lactide to catalyst was 120000: 1. Vacuumizing the reactor to be below 100Pa, breaking the vacuum by using argon, replacing residual air in the system, repeating the operation for 3 times, and finally vacuumizing to be below 100Pa and sealing; setting the microwave radiation power at 50W and the ultrasonic frequency at 10KHz, fully and uniformly mixing the L-lactide monomer and the catalyst, and finally carrying out polymerization reaction for 8 hours at 65 ℃; after the reaction is finished, slicing the blocky L-polylactic acid material, freezing the blocky L-polylactic acid material by liquid nitrogen, and putting the blocky L-polylactic acid material into a crusher to obtain granular L-polylactic acid; and (3) removing impurities from the granular L-polylactic acid, collecting, dissolving the L-polylactic acid by using dichloromethane, adding an ethanol solvent to precipitate the polylactic acid, and finally performing vacuum drying on the polylactic acid for 12 hours to obtain the high-molecular L-polylactic acid.
Example 6 weighing 3kg of L-lactide into a pre-treated glass reactor (5L), placing into a microwave ultrasonic reactor and heating to 110 ℃ until the monomers melt, adding 0.3875g of n-octanol, controlling the molar ratio of L-lactide to initiator to 7000:1, and then adding 0.0703g of stannous octoate so that the molar ratio of L-lactide to catalyst is 120000: 1. Vacuumizing the reactor to be below 100Pa, breaking the vacuum by using argon, replacing residual air in the system, repeating the operation for 3 times, and finally vacuumizing to be below 100Pa and sealing; setting the microwave radiation power at 150W and the ultrasonic frequency at 30KHz, fully and uniformly mixing the L-lactide monomer and the catalyst, and finally carrying out polymerization reaction for 8 hours at 65 ℃; after the reaction is finished, slicing the blocky L-polylactic acid material, freezing the blocky L-polylactic acid material by liquid nitrogen, and putting the blocky L-polylactic acid material into a crusher to obtain granular L-polylactic acid; and (3) removing impurities from the granular L-polylactic acid, collecting, dissolving the L-polylactic acid by using dichloromethane, adding an ethanol solvent to precipitate the polylactic acid, and finally performing vacuum drying on the polylactic acid for 12 hours to obtain the high-molecular L-polylactic acid.
Example 7 weighing 3kg of L-lactide into a pre-treated glass reactor (5L), placing into a microwave ultrasonic reactor and heating to 110 ℃ until the monomers melt, adding 0.3875g of n-octanol, controlling the molar ratio of L-lactide to initiator to 7000:1, and then adding 0.0703g of stannous octoate so that the molar ratio of L-lactide to catalyst is 120000: 1. Vacuumizing the reactor to be below 100Pa, breaking the vacuum by using argon, replacing residual air in the system, repeating the operation for 3 times, and finally vacuumizing to be below 100Pa and sealing; setting the microwave radiation power at 50W and the ultrasonic frequency at 30KHz, fully and uniformly mixing the L-lactide monomer and the catalyst, and finally carrying out polymerization reaction for 8 hours at 65 ℃; and (3) removing impurities from the granular L-polylactic acid, collecting, dissolving the L-polylactic acid by using dichloromethane, adding an ethanol solvent to precipitate the polylactic acid, and finally performing vacuum drying on the polylactic acid for 12 hours to obtain the high-molecular L-polylactic acid.
Example 83 kg of L-lactide was weighed into a pre-treated glass reactor (5L) and placed in a microwave ultrasonic reactor and heated to 110 ℃ until the monomers melted, 0.3875g of n-octanol was added, the molar ratio of L-lactide to initiator was controlled to 7000:1, and 0.0703g of stannous octoate was added to make the molar ratio of L-lactide to catalyst 120000: 1. Vacuumizing the reactor to be below 100Pa, breaking the vacuum by using argon, replacing residual air in the system, repeating the operation for 3 times, and finally vacuumizing to be below 100Pa and sealing; setting the microwave radiation power at 150W and the ultrasonic frequency at 10KHz, fully and uniformly mixing the L-lactide monomer and the catalyst, and finally carrying out polymerization reaction for 8 hours at 65 ℃; after the reaction is finished, slicing the blocky L-polylactic acid material, freezing the blocky L-polylactic acid material by liquid nitrogen, and putting the blocky L-polylactic acid material into a crusher to obtain granular L-polylactic acid; and (3) removing impurities from the granular L-polylactic acid, collecting, dissolving the L-polylactic acid by using dichloromethane, adding an ethanol solvent to precipitate the polylactic acid, and finally performing vacuum drying on the polylactic acid for 12 hours to obtain the high-molecular L-polylactic acid.
Example 9 weighing 3kg of L-lactide into a pre-treated glass reactor (5L), placing into a microwave ultrasonic reactor and heating to 110 ℃ until the monomers melt, adding 0.3875g of n-octanol, controlling the molar ratio of L-lactide to initiator to 7000:1, and then adding 0.0703g of stannous octoate so that the molar ratio of L-lactide to catalyst is 120000: 1. . Vacuumizing the reactor to be below 100Pa, breaking the vacuum by using argon, replacing residual air in the system, repeating the operation for 3 times, and finally vacuumizing to be below 100Pa and sealing; setting the microwave radiation power at 90W and the ultrasonic frequency at 25KHz, fully and uniformly mixing the L-lactide monomer and the catalyst, and finally carrying out polymerization reaction for 4 hours at 40 ℃; after the reaction is finished, slicing the blocky L-polylactic acid material, freezing the blocky L-polylactic acid material by liquid nitrogen, and putting the blocky L-polylactic acid material into a crusher to obtain granular L-polylactic acid; and (3) removing impurities from the granular L-polylactic acid, collecting, dissolving the L-polylactic acid by using dichloromethane, adding an ethanol solvent to precipitate the polylactic acid, and finally performing vacuum drying on the polylactic acid for 12 hours to obtain the high-molecular L-polylactic acid.
Example 10 weighing 3kg of L-lactide into a pre-treated glass reactor (5L), placing into a microwave ultrasonic reactor and heating to 110 ℃ until the monomers melt, adding 0.3875g of n-octanol, controlling the molar ratio of L-lactide to initiator to 7000:1, and then adding 0.0703g of stannous octoate so that the molar ratio of L-lactide to catalyst is 120000: 1. Vacuumizing the reactor to be below 100Pa, breaking the vacuum by using argon, replacing residual air in the system, repeating the operation for 3 times, and finally vacuumizing to be below 100Pa and sealing; setting the microwave radiation power at 90W and the ultrasonic frequency at 25KHz, fully and uniformly mixing the L-lactide monomer and the catalyst, and finally carrying out polymerization reaction for 24 hours at 160 ℃; after the reaction is finished, slicing the blocky L-polylactic acid material, freezing the blocky L-polylactic acid material by liquid nitrogen, and putting the blocky L-polylactic acid material into a crusher to obtain granular L-polylactic acid; and (3) removing impurities from the granular L-polylactic acid, collecting, dissolving the L-polylactic acid by using dichloromethane, adding an ethanol solvent to precipitate the polylactic acid, and finally performing vacuum drying on the polylactic acid for 12 hours to obtain the high-molecular L-polylactic acid.
Example 11 weighing 3kg of L-lactide into a pre-treated glass reactor (5L), placing into a microwave ultrasonic reactor and heating to 110 ℃ until the monomers melt, adding 0.3875g of n-octanol, controlling the molar ratio of L-lactide to initiator to 7000:1, and then adding 0.0703g of stannous octoate so that the molar ratio of L-lactide to catalyst is 120000: 1. Vacuumizing the reactor to be below 100Pa, breaking the vacuum by using argon, replacing residual air in the system, repeating the operation for 3 times, and finally vacuumizing to be below 100Pa and sealing; setting the microwave radiation power at 90W and the ultrasonic frequency at 25KHz, fully and uniformly mixing the L-lactide monomer and the catalyst, and finally carrying out polymerization reaction for 24 hours at 40 ℃; after the reaction is finished, slicing the blocky L-polylactic acid material, freezing the blocky L-polylactic acid material by liquid nitrogen, and putting the blocky L-polylactic acid material into a crusher to obtain granular L-polylactic acid; and (3) removing impurities from the granular L-polylactic acid, collecting, dissolving the L-polylactic acid by using dichloromethane, adding an ethanol solvent to precipitate the polylactic acid, and finally performing vacuum drying on the polylactic acid for 12 hours to obtain the high-molecular L-polylactic acid.
Example 12 weighing 3kg of L-lactide into a pre-treated glass reactor (5L), placing into a microwave ultrasonic reactor and heating to 110 ℃ until the monomers melt, adding 0.3875g of n-octanol, controlling the molar ratio of L-lactide to initiator to 7000:1, and then adding 0.0703g of stannous octoate so that the molar ratio of L-lactide to catalyst is 120000: 1. Vacuumizing the reactor to be below 100Pa, breaking the vacuum by using argon, replacing residual air in the system, repeating the operation for 3 times, and finally vacuumizing to be below 100Pa and sealing; setting the microwave radiation power at 90W and the ultrasonic frequency at 25KHz, fully and uniformly mixing the L-lactide monomer and the catalyst, and finally carrying out polymerization reaction for 4 hours at 160 ℃; after the reaction is finished, slicing the blocky L-polylactic acid material, freezing the blocky L-polylactic acid material by liquid nitrogen, and putting the blocky L-polylactic acid material into a crusher to obtain granular L-polylactic acid; and (3) removing impurities from the granular L-polylactic acid, collecting, dissolving the L-polylactic acid by using dichloromethane, adding an ethanol solvent to precipitate the polylactic acid, and finally performing vacuum drying on the polylactic acid for 12 hours to obtain the high-molecular L-polylactic acid.
Evaluation system: the molecular weight distribution of L-polylactic acid was determined by Gel Permeation Chromatography (GPC) wherein chloroform was used as a mobile phase, the amount of the sample was 100 μ M, the flow rate was 1.0mL/min, and the weight average molecular weight M was determinedWAnd the dispersibility index (PDI) are shown in Table 3.
TABLE 3 molecular weights and their distribution data for the respective examples
The weight average molecular weight of the L-polylactic acid in the examples can be up to 278X 104g/mol, high concentration of molecular weight distribution and considerable prospect in the biomedical field.
It should be understood that the above-described embodiments of the present invention are only examples for illustrating the present invention, and are not intended to limit the specific embodiments of the present invention. It will be apparent to those skilled in the art that other variations and modifications can be made on the above examples. Not all embodiments are exemplified in detail herein. All obvious changes and modifications of the present invention are within the scope of the present invention.
Claims (5)
1. A preparation method of ultra-high molecular weight L-polylactic acid is characterized by mainly comprising the following steps:
(1) putting a reactant L-lactide into a glass reaction kettle which is pretreated in advance, then putting the reaction kettle into a microwave ultrasonic reactor, heating the reaction kettle to 90-120 ℃ until a monomer is molten, adding an initiator, and then adding a certain amount of catalyst; vacuumizing the reactor to below 100Pa, breaking the vacuum with argon, replacing residual air in the system, repeating the operation for 2-3 times, and finally vacuumizing to below 100Pa and sealing;
(2) setting microwave radiation power (50-150W) and ultrasonic frequency (10-30KHz), so that the L-lactide monomer can be fully and uniformly mixed with the catalyst, and finally carrying out polymerization reaction;
(3) after the polymerization reaction is finished, the product of the levorotatory polylactic acid is purified, the obtained polymer is dissolved by adopting an organic solvent, the solvent is added to separate the levorotatory polylactic acid out, and finally the levorotatory polylactic acid is dried in vacuum to obtain the macromolecule levorotatory polylactic acid.
2. The method of claim 1, wherein the initiator is n-octanol and the catalyst is stannous octoate.
3. The method of claim 2, wherein the molar ratio of L-lactide to initiator is 10000:1 to 4000:1 and the molar ratio of L-lactide to catalyst is 800000:1 to 8000: 1.
4. The method according to claim 1, wherein the polymerization conditions in the step (2) are: the polymerization reaction is carried out for 4 to 240 hours at the temperature of between 40 and 160 ℃.
5. The method according to claim 1, wherein the weight average molecular weight of the obtained polymeric L-polylactic acid is 30000-3000000g/mol (preferably 50000-1200000 g/mol).
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