Polylactic acid-based material and preparation method thereof

Abstract

The invention discloses a polylactic acid-based material and a preparation method thereof, and belongs to the technical field of controllable degradable bio-based materials. The polylactic acid-based material comprises a polylactic acid polymer, polypeptide and polyethylene glycol ketal, polypeptide is embedded into a main chain of a polylactic acid polymer, and polyethylene glycol ketal and a molecular chain of the polylactic acid polymer form crosslinking and end capping through hydrogen-bond interaction. The polylactic acid-based material is applied to the aspects of short-term, medium-term and long-term use products such as food packaging, 3D printing and electronic appliances, the problem that an existing polyester material cannot keep stable and controllably degraded in the use period at the same time is solved, the polylactic acid-based material can keep stable in the use period, and degradation can be selectively accelerated or slowed down in different environments after the polylactic acid-based material is abandoned.

Description

Technical Field

[0001] This invention belongs to the field of controlled-degradable bio-based materials technology, and particularly relates to a polylactic acid-based material and its preparation method. Background Technology

[0002] The non-degradability of traditional petroleum-based plastics has led to increasingly serious environmental pollution problems. Polyester materials (such as PLA and PBAT) have become a research hotspot due to their biodegradability potential, but they still have significant drawbacks in practical applications: 1) Degradation conditions are singular, relying solely on high-temperature composting or the action of specific microorganisms, making it difficult to achieve controllable degradation in various scenarios such as seawater, soil, and freshwater; 2) The contradiction between stability and degradability is prominent, and premature degradation is easily triggered by changes in temperature and humidity during use, affecting functional lifespan and making it difficult to achieve long-term stability of more than 5 years; 3) Existing modification methods (such as blending and end-capping) often sacrifice performance (such as mechanical properties and appearance) to increase or slow down the degradation rate, resulting in unclear degradation patterns and a lack of external environmental response mechanisms.

[0003] Furthermore, existing technologies primarily focus on mechanical and heat resistance properties as the main research objectives for materials, while lacking understanding of performance changes during use. There is insufficient systematic research (proactive) on controllable degradation, and a lack of design for synergistic controllable degradation across multiple environments, making it difficult to meet the requirements for long-term (>5 years) stable use. Therefore, there is an urgent need to develop a PLA-based material that combines stability in use with controllable degradation capabilities in multiple environments, achieving designable performance, controllable degradation, and an adjustable service life (degradation cycle) of 1-10 years. This material should be mass-produced using efficient preparation methods to fill the technological gap in the field of controllable degradable environmentally friendly polymer materials.

[0004] Chinese patent CN115677993A discloses a polyester polymer that degrades entirely in its natural domain. This patented solution uses PBS as a matrix and incorporates lactic acid monomers to achieve rapid degradation in terrestrial and marine environments, but it does not consider the controllability of the degradation rate. Chinese patent CN115746521A discloses a high-temperature resistant, low-migration, and slow-degrading polylactic acid straw. By adding the anti-hydrolysis agent polycarbodimethylamine, the degradation rate is slowed down, extending the shelf life of the straw to some extent, but it does not truly achieve controllable degradation. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the technical problem to be solved by the present invention is to overcome the problem that existing polyester materials cannot simultaneously maintain stability and controllable degradation during use. The present invention proposes a polylactic acid-based material that can remain stable during use and selectively accelerate or slow down degradation under different environments after disposal, as well as its preparation method.

[0006] To solve the aforementioned technical problem, the technical solution adopted by the present invention is as follows:

[0007] The present invention provides a polylactic acid-based material, comprising a polylactic acid polymer, a polypeptide, and a polyethylene glycol ketal; the polypeptide is embedded in the main chain of the polylactic acid polymer, and the polyethylene glycol ketal is cross-linked and capped with the molecular chain of the polylactic acid polymer through hydrogen bonding;

[0008] The structural formula of polylactic acid-based materials is as follows:

[0009]

[0010] The polylactic acid (PLA)-based material of this invention utilizes PLA as a matrix to achieve a multi-mechanism degradation mechanism involving enzymatic degradation and pH hydrolysis through block and non-covalent interactions, thereby enabling adjustable degradation rates. Starting from the molecular structure, multiple tunable degradation sites, including those for enzymatic degradation and pH hydrolysis, are designed to achieve organic regulation of degradation rates under multiple environmental factors. The PLA-based material with adjustable degradation rates provided by this invention has a degradation rate adjustable from 1 to 10 years and can be used in short-, medium-, and long-term products such as food packaging, 3D printing, and electronic appliances.

[0011] Under normal use conditions, the stable structure of the polylactic acid-based material gives it excellent mechanical properties; however, when exposed to specific environments, the corresponding sites of the structure will degrade selectively and irreversibly, thus possessing a controllable degradation rate and excellent mechanical properties.

[0012] In some embodiments, the polypeptide is a weakly polar short-chain polypeptide.

[0013] In some embodiments, the polyethylene glycol ketal is polyethylene glycol containing a ketal group. The polyethylene glycol ketal bond (-OC) 32 -O-) hydrolyzes into ketones and diols under acidic (pH<5) or alkaline (pH>9) conditions, triggering the depolymerization of the main chain PLA, thereby achieving the pH degradation response of the material.

[0014] In some embodiments, the molecular weight of polyethylene glycol is 1000-2000.

[0015] Another aspect of the present invention provides a method for preparing polylactic acid-based materials according to any of the above-mentioned technical solutions, comprising:

[0016] The ring-opening polymerization of lactide generates oligomers of polylactic acid polymers. Peptides are added to prepare PLAAm-GAG-PLAn block copolymers. Polyethylene glycol ketal is added to prepare PLA-GAG-PLA@PEGO block polymer materials, i.e., polylactic acid-based materials.

[0017] In the preparation of the aforementioned polylactic acid (PLA)-based material, a polymer copolymer is formed through block copolymerization and non-covalent bonding using lactide, polyethylene glycol ketal, and peptide chains as raw materials. Short peptide chains are embedded in the PLA polymer backbone, and the PLA molecular chains are cross-linked and end-capped through hydrogen bonding. This PLA-based material maintains mechanical properties comparable to PLA polymers to meet practical applications, with a designed lifespan of 1-10 years. It remains stable during use, but when exposed to specific environments (pH, enzymes, moisture), corresponding sites in the structure undergo selective and irreversible degradation, thus exhibiting a controllable degradation rate and excellent mechanical properties.

[0018] In some embodiments, the molar ratio of lactide, peptide, and polyethylene glycol ketal is 100:10:1 to 100:1:10. By adjusting the molar ratio of lactide, peptide, and polyethylene glycol ketal, the peptide block density and PEGO grafting rate (10-30%) in the polylactic acid-based material can be adjusted, thereby controlling the intrachain enzymatic degradation sites and the ketal bond density, and achieving adjustable degradation time from 30 days (high grafting rate) to 180 days (low grafting rate).

[0019] In some embodiments, lactide is L-type.

[0020] In some embodiments, the ring-opening polymerization of lactide to generate oligomers of polylactic acid polymers includes: reacting lactide under vacuum conditions with an initiator and a catalyst at a reaction temperature of 155-165°C to prepare oligomers of polylactic acid polymers.

[0021] In some embodiments, the preparation of PLAm-GAG-PLAn block copolymer by adding a polypeptide includes: mixing oligomers of polylactic acid polymers with polypeptides in DMF, reacting at room temperature under the action of a catalyst, and separating and purifying to obtain PLAm-GAG-PLAn block copolymer.

[0022] In some embodiments, the addition of polyethylene glycol ketal to prepare PLA-GAG-PLA@PEGO block polymer material includes: mixing PLAm-GAG-PLAn block copolymer with polyethylene glycol ketal in a mixer at 160-180°C and 40-60 rpm, and grafting polyethylene glycol ketal to the side chains and terminal hydroxyl sites of polylactic acid polymer through in-situ reaction to form PLA-GAG-PLA@PEGO block polymer material with an interpenetrating network structure. Attached Figure Description

[0023] Figure 1 This is a schematic diagram illustrating the controllable degradation mechanism of polylactic acid-based materials provided in the embodiments of the present invention;

[0024] Figure 2The infrared difference spectrum is for pure PLA.

[0025] Figure 3 The infrared differential spectrum of the polylactic acid-based material provided in Example 1 of this invention;

[0026] Figure 4 This is a graph showing the trend of infrared spectral intensity of the ester peak (C=O) of the polylactic acid-based material provided in Example 1 of the present invention as a function of temperature.

[0027] Figure 5 This is a schematic diagram of the polarizing microscope detection results of the polylactic acid-based material provided in Embodiment 1 of the present invention;

[0028] Figure 6 The images show a comparison of the morphology of the polylactic acid-based material provided in Example 1 of this invention before and after degradation in a simulated natural soil environment (25°C, 85% humidity) for observation using scanning electron microscopy.

[0029] Figure 7 The images show a comparison of the morphology of the polylactic acid-based material provided in Example 2 of this invention before and after degradation in a simulated natural soil environment (25°C, 85% humidity) using scanning electron microscopy.

[0030] Figure 8 The images show a comparison of the morphology of the polylactic acid-based material provided in Example 3 of this invention before and after degradation in a simulated natural soil environment (25°C, 85% humidity) for observation using scanning electron microscopy.

[0031] Figure 9 The images show a comparison of the morphology of the polylactic acid-based material provided in Example 4 of this invention before and after degradation in a simulated natural soil environment (25°C, 85% humidity) using scanning electron microscopy.

[0032] Figure 10 The images show a comparison of the morphology of the polylactic acid-based material provided in Example 5 of this invention before and after degradation in a simulated natural soil environment (25°C, 85% humidity) for observation using scanning electron microscopy.

[0033] Figure 11 The images show a comparison of the morphology of the polylactic acid-based material provided in Example 6 of this invention before and after degradation in a simulated natural soil environment (25°C, 85% humidity) under scanning electron microscopy.

[0034] Figure 12 The images show a comparison of the morphology of the polylactic acid-based material provided in Example 7 of this invention before and after degradation in a simulated natural soil environment (25°C, 85% humidity) for observation using scanning electron microscopy.

[0035] Figure 13The images show a comparison of the morphology of the polylactic acid-based material provided in Comparative Example 1 of this invention before and after degradation in a simulated natural soil environment (25°C, 85% humidity) using scanning electron microscopy.

[0036] Figure 14 The images show a comparison of the morphology of the polylactic acid-based material provided in Comparative Example 2 of this invention before and after degradation in a simulated natural soil environment (25°C, 85% humidity) using scanning electron microscopy. Detailed Implementation

[0037] The technical solutions in specific embodiments of the present invention will be described in detail and completely below. Obviously, the described embodiments are only some specific implementations of the overall technical solution of the present invention, and not all implementations. Based on the overall concept of the present invention, all other embodiments obtained by those skilled in the art fall within the protection scope of the present invention.

[0038] A polylactic acid-based material comprising a polylactic acid polymer.

[0039] Polylactic acid polymers possess biodegradability potential, but their practical applications still suffer from the following drawbacks: 1) Degradation conditions are limited, relying solely on high-temperature composting or the action of specific microorganisms, making it difficult to achieve controllable degradation in various scenarios such as seawater, soil, and freshwater; 2) The contradiction between stability and degradability is prominent, with premature degradation easily triggered by changes in temperature and humidity during use, affecting functional lifespan and making it difficult to achieve long-term stability of more than 5 years; 3) Existing modification methods (such as blending and end-capping) often sacrifice performance (such as mechanical properties and appearance) to increase or slow down the degradation rate, resulting in unclear degradation patterns and a lack of external environmental response mechanisms.

[0040] A polylactic acid-based material comprising a polypeptide embedded in the backbone of a polylactic acid polymer.

[0041] The peptide chain of a polypeptide (GAG) exposed on the surface of a polylactic acid-based material provides enzymatic degradation sites. These sites can be recognized and cleaved by proteases in the environment (such as trypsin), disrupting the cross-linked network. Therefore, the intrachain enzymatic degradation sites can be controlled by adjusting the density of peptide block, thereby enabling control of the degradation rate.

[0042] A polylactic acid-based material, comprising polyethylene glycol ketal, wherein the polyethylene glycol ketal and the molecular chains of the polylactic acid polymer are cross-linked and capped through hydrogen bonding.

[0043] In the aforementioned polylactic acid-based material, the polyethylene glycol ketal and the polylactic acid polymer molecular chains crosslink and end-cap through hydrogen bonding, thereby achieving the pH degradation response of the polylactic acid-based material. The polyethylene glycol ketal bond (-OC) 32-O-) hydrolyzes into ketones and diols under acidic (pH<5) or alkaline (pH>9) conditions, triggering the depolymerization of the main chain PLA. By adjusting the PEGO grafting rate (10%-30%), the ketal bond density can be controlled, achieving an adjustable degradation time range from 30 days (high grafting rate) to 180 days (low grafting rate).

[0044] The structural formula of polylactic acid-based materials is as follows:

[0045]

[0046] The aforementioned polylactic acid (PLA)-based material covalently connects PLA segments, forming an alternating structure of "hard segments (PLA) - soft segments (flexible segments)". The flexible segments lower the glass transition temperature of the PLA segments, enhancing their mobility. Simultaneously, microphase separation occurs between the PLA chain ends and the PEGO (polyethylene glycol ketal) chain ends, optimizing the crystal morphology. Infrared differential spectroscopy reflects increased ester bond strength in the crystalline region and decreased ester bond strength in the amorphous region, further demonstrating improved crystallinity of PLA-GAG-PLA@PEGO. Furthermore, polarized light microscopy revealed a reduction in spherulite size from 80-100 μm to 20 μm, confirming the optimized crystal morphology of the PLA-GAG-PLA@PEGO material. In summary, increased crystallinity improves tensile strength, while smaller crystal size and fewer defects further enhance the material's toughness.

[0047] Furthermore, the morphology of the PLA-GAG-PLA@PEGO copolymer before and after degradation in a simulated natural soil environment (25℃, 85% humidity) was observed using a scanning electron microscope (VEGA 3Tescan). Different degrees of pores and cracks were found inside the PLA-GAG-PLA@PEGO copolymer, indicating that the product underwent degradation at varying rates. In contrast, only a few cracks appeared on the surface of pure PLA, suggesting that the natural degradation rate of PLA is very slow. This further demonstrates that the PLA-GAG-PLA@PEGO copolymer of this invention achieves a controllable degradation mechanism, exhibits stable performance during use, and can be controlled to degrade under certain conditions after disposal.

[0048] The controlled degradation mechanism of the PLA-GAG-PLA@PEGO copolymer material of this invention is as follows: Figure 1 As shown:

[0049] (1) Enzymatic degradation sites: GAG peptide chains exposed on the material surface can be recognized and cleaved by proteases in the environment (such as trypsin), destroying the cross-linked network;

[0050] (2) pH degradation response: polyethylene glycol ketal bond (-OC 32 -O-) hydrolyzes into ketones and diols under acidic (pH<5) or alkaline (pH>9) conditions, triggering the depolymerization of the main chain PLA.

[0051] By adjusting the density of peptide block to control the intrachain enzymatic degradation sites and the PEGO grafting rate (10%-30%) to control the ketal bond density, an adjustable degradation time range from 30 days (high grafting rate) to 180 days (low grafting rate) can be achieved.

[0052] In summary, the PLA-GAG-PLA@PEGO copolymer provided by this invention overcomes the bottleneck of PLA crystallization performance through multiple mechanisms, including enhanced chain segment movement, heterogeneous nucleation, microphase separation, and interface stabilization. This structural design improves the material's mechanical strength, thermal stability, and processing performance while also possessing controllable degradation characteristics, perfectly meeting the dual requirements of "high performance" and "degradability" for environmentally friendly materials. Specifically, it has the following characteristics:

[0053] Controllable degradation: Precise structural design through a two-step method of "block copolymerization + non-covalent bonding" achieves spatial separation of enzyme / pH dual-response sites, avoids degradation signal interference, and the degradation cycle is adjustable from 6 months to 10 years;

[0054] Enhancement and toughening: Under this material structure, the crystallinity is greatly improved, and the crystallinity is increased by 3 times, achieving simultaneous enhancement and toughening;

[0055] Low carbon and environmentally friendly: This copolymer material retains the biocompatibility of PLA and has a carbon footprint that is 1.5 times lower than that of traditional plastics.

[0056] This invention utilizes PLA as a matrix to achieve a multi-stage degradation mechanism involving enzymatic degradation and pH hydrolysis through block and non-covalent interactions, thereby enabling adjustable degradation rates. Starting from the molecular structure, multiple tunable degradation sites, including those for enzymatic degradation and pH hydrolysis, are designed to achieve organic regulation of degradation rates under multiple environmental factors. The polylactic acid-based material with adjustable degradation rates provided by this invention exhibits a degradation rate adjustable from 1 to 10 years and can be used in short-, medium-, and long-term products such as food packaging, 3D printing, and electronic appliances.

[0057] In some embodiments, the polypeptide is a weakly polar short-chain polypeptide. Using a weakly polar short-chain polypeptide as one of the raw materials for the polylactic acid-based material of the present invention has two advantages: firstly, its polarity is similar to that of polylactic acid, which is beneficial for block copolymerization; secondly, the weakly polar material is conducive to microbial adhesion, which can achieve regulation of the degradation rate.

[0058] In some embodiments, the polyethylene glycol ketal is polyethylene glycol containing a ketal group. The polyethylene glycol ketal bond (-OC) 32 -O-) hydrolyzes into ketones and diols under acidic (pH<5) or alkaline (pH>9) conditions, triggering the depolymerization of the main chain PLA, thereby achieving the pH degradation response of the material.

[0059] In some embodiments, the molecular weight of polyethylene glycol is 1000-2000. Polyethylene glycol with a molecular weight of 1000-2000 can be uniformly dispersed in polylactic acid resin. With a molecular weight below 1000, polyethylene glycol is mostly in a liquid state and easily decomposes at high temperatures; with a molecular weight above 2000, the polyethylene glycol molecular chains in polylactic acid are too long, resulting in greater steric hindrance and hindering dispersion. It is understood that the molecular weight of polyethylene glycol can also be any value within the range of 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, and above.

[0060] Another aspect of the present invention provides a method for preparing polylactic acid-based materials according to any of the above technical solutions, comprising: ring-opening polymerization of lactide to generate oligomers of polylactic acid polymer, adding polypeptides to prepare PLA-GAG-PLAn block copolymers, adding polyethylene glycol ketal to prepare PLA-GAG-PLA@PEGO block polymer materials, i.e., polylactic acid-based materials.

[0061] In the preparation of the aforementioned polylactic acid (PLA)-based material, a polymer copolymer is formed through block copolymerization and non-covalent bonding using lactide, polyethylene glycol ketal, and peptide chains as raw materials. Short peptide chains are embedded in the PLA polymer backbone, and the PLA molecular chains are cross-linked and end-capped through hydrogen bonding. This PLA-based material maintains mechanical properties comparable to PLA polymers to meet practical applications, with a designed lifespan of 1-10 years. It remains stable during use, but when exposed to specific environments (pH, enzymes, moisture), corresponding sites in the structure undergo selective and irreversible degradation, thus exhibiting a controllable degradation rate and excellent mechanical properties.

[0062] In some embodiments, the molar ratio of lactide, peptide, and polyethylene glycol ketal is 100:10:1 to 100:1:10. By adjusting the molar ratio of lactide, peptide, and polyethylene glycol ketal, the peptide block density and PEGO grafting rate (10-30%) in the polylactic acid-based material can be adjusted, thereby controlling the intra-chain enzymatic degradation sites and inter-chain hydrolytic degradation sites, achieving adjustable degradation time from 30 days (high site) to 180 days (low site).

[0063] In some embodiments, lactide is L-type. L-type lactide is used for homopolymerization to obtain polylactic acid (PLA). This homopolymer is optically active, stereoregular, has a certain degree of crystallinity and melting point, good mechanical strength, good biocompatibility, and is non-toxic.

[0064] In some embodiments, the ring-opening polymerization of lactide to generate oligomers of polylactic acid polymers includes: reacting lactide under vacuum conditions with an initiator and a catalyst at a reaction temperature of 155-165°C to obtain oligomers of polylactic acid polymers. It is understood that the reaction temperature can also be any value within the range of 155°C, 160°C, 165°C, or similar temperatures.

[0065] In some embodiments, the initiator is methanol.

[0066] In some embodiments, the catalyst is stannous octoate.

[0067] In some embodiments, the preparation of PLAm-GAG-PLAn block copolymer by adding a polypeptide includes: mixing oligomers of polylactic acid polymers with polypeptides in DMF, reacting at room temperature under the action of a catalyst, and separating and purifying to obtain PLAm-GAG-PLAn block copolymer.

[0068] In some embodiments, the catalyst is stannous octoate.

[0069] In some embodiments, the addition of polyethylene glycol ketal to prepare PLA-GAG-PLA@PEGO block polymer material includes: mixing PLAm-GAG-PLAn block copolymer with polyethylene glycol ketal in a blender at 160-180°C and 40-60 rpm; and grafting polyethylene glycol ketal onto the side chains and terminal hydroxyl sites of polylactic acid polymer through an in-situ reaction to form an interpenetrating network structure PLA-GAG-PLA@PEGO block polymer material. It is understood that the reaction temperature can also be any value within the range of 165°C, 170°C, 175°C, and the rotation speed can also be any value within the range of 45 rpm, 50 rpm, 55 rpm.

[0070] To provide a clearer and more detailed description of the polylactic acid-based materials and their preparation methods provided in the embodiments of the present invention, specific embodiments will be described below.

[0071] Example 1

[0072] A controllable degradable polylactic acid-based material, wherein the molar ratio of lactide, polypeptide and PEGO in the polymer is 100:10:1.

[0073] (1) Preparation of PLA-GAG-PLA copolymer:

[0074] First, lactide was reacted with initiator (methanol) and catalyst (stannous octoate) at a reaction temperature of 160°C under vacuum for 6 hours to obtain PLA oligomers; then, PLA oligomers and GAG peptide chains were mixed in DMF and reacted at room temperature for 24 hours under the action of catalyst (stannous octoate), and the PLA-GAG-PLA block copolymer was obtained by separation and purification.

[0075] (2) Preparation of PLA-GAG-PLA@PEGO copolymer:

[0076] PLA-GAG-PLA and PEGO were mixed in a mixer at 170℃ and 50rpm for 10 minutes. PEGO was grafted onto the side chains and terminal hydroxyl sites of PLA through in-situ reaction to form an interpenetrating network structure PLA-GAG-PLA@PEGO copolymer.

[0077] Example 2

[0078] A controllable degradable block copolymer, wherein the molar ratio of lactide, polypeptide and PEGO in the polyester polymer is 100:8:1.

[0079] (1) Preparation of PLA-GAG-PLA copolymer:

[0080] First, lactide was reacted with initiator (methanol) and catalyst (stannous octoate) at a reaction temperature of 160°C under vacuum for 6 hours to obtain PLA oligomers; then, PLA oligomers and GAG peptide chains were mixed in DMF and reacted at room temperature for 24 hours under the action of catalyst (stannous octoate), and the PLA-GAG-PLA block copolymer was obtained by separation and purification.

[0081] (2) Preparation of PLA-GAG-PLA@PEGO copolymer:

[0082] PLA-GAG-PLA and PEGO were mixed in a mixer at 170℃ and 50rpm for 10 minutes. PEGO was grafted onto the side chains and terminal hydroxyl sites of PLA through in-situ reaction to form an interpenetrating network structure PLA-GAG-PLA@PEGO copolymer.

[0083] Example 3

[0084] A controllable degradable block copolymer, wherein the molar ratio of lactide, polypeptide and PEGO in the polyester polymer is 100:6:1.

[0085] (1) Preparation of PLA-GAG-PLA copolymer:

[0086] First, lactide was reacted with initiator (methanol) and catalyst (stannous octoate) at a reaction temperature of 160°C under vacuum for 6 hours to obtain PLA oligomers; then, PLA oligomers and GAG peptide chains were mixed in DMF and reacted at room temperature for 24 hours under the action of catalyst (stannous octoate), and the PLA-GAG-PLA block copolymer was obtained by separation and purification.

[0087] (2) Preparation of PLA-GAG-PLA@PEGO copolymer:

[0088] PLA-GAG-PLA and PEGO were mixed in a mixer at 170℃ and 50rpm for 10 minutes. PEGO was grafted onto the side chains and terminal hydroxyl sites of PLA through in-situ reaction to form an interpenetrating network structure PLA-GAG-PLA@PEGO copolymer.

[0089] Example 4

[0090] A controllable degradable block copolymer, wherein the molar ratio of lactide, polypeptide and PEGO in the polyester polymer is 100:4:1.

[0091] (1) Preparation of PLA-GAG-PLA copolymer:

[0092] First, lactide was reacted with initiator (methanol) and catalyst (stannous octoate) at a reaction temperature of 160°C under vacuum for 6 hours to obtain PLA oligomers; then, PLA oligomers and GAG peptide chains were mixed in DMF and reacted at room temperature for 24 hours under the action of catalyst (stannous octoate), and the PLA-GAG-PLA block copolymer was obtained by separation and purification.

[0093] (2) Preparation of PLA-GAG-PLA@PEGO copolymer:

[0094] PLA-GAG-PLA and PEGO were mixed in a mixer at 170℃ and 50rpm for 10 minutes. PEGO was grafted onto the side chains and terminal hydroxyl sites of PLA through in-situ reaction to form an interpenetrating network structure PLA-GAG-PLA@PEGO copolymer.

[0095] Example 5

[0096] A controllable degradable block copolymer, wherein the molar ratio of lactide, polypeptide and PEGO in the polyester polymer is 100:2:1.

[0097] (1) Preparation of PLA-GAG-PLA copolymer:

[0098] First, lactide was reacted with initiator (methanol) and catalyst (stannous octoate) at a reaction temperature of 160°C under vacuum for 6 hours to obtain PLA oligomers; then, PLA oligomers and GAG peptide chains were mixed in DMF and reacted at room temperature for 24 hours under the action of catalyst (stannous octoate), and the PLA-GAG-PLA block copolymer was obtained by separation and purification.

[0099] (2) Preparation of PLA-GAG-PLA@PEGO copolymer:

[0100] PLA-GAG-PLA and PEGO were mixed in a mixer at 170℃ and 50rpm for 10 minutes. PEGO was grafted onto the side chains and terminal hydroxyl sites of PLA through in-situ reaction to form an interpenetrating network structure PLA-GAG-PLA@PEGO copolymer.

[0101] Example 6

[0102] A controllable degradable block copolymer, wherein the molar ratio of lactide, polypeptide and PEGO in the polyester polymer is 100:8:1.

[0103] (1) Preparation of PLA-GAG-PLA copolymer:

[0104] First, lactide was reacted with initiator (methanol) and catalyst (stannous octoate) at a reaction temperature of 160°C under vacuum for 6 hours to obtain PLA oligomers; then, PLA oligomers and GAG peptide chains were mixed in DMF and reacted at room temperature for 24 hours under the action of catalyst (stannous octoate), and the PLA-GAG-PLA block copolymer was obtained by separation and purification.

[0105] (2) Preparation of PLA-GAG-PLA@PEGO copolymer:

[0106] PLA-GAG-PLA and PEGO were mixed in a mixer at 170℃ and 50rpm for 10 minutes. PEGO was grafted onto the side chains and terminal hydroxyl sites of PLA through in-situ reaction to form an interpenetrating network structure PLA-GAG-PLA@PEGO copolymer.

[0107] Example 7

[0108] A controllable degradable block copolymer, wherein the molar ratio of lactide, polypeptide and PEGO in the polyester polymer is 100:8:5.

[0109] (1) Preparation of PLA-GAG-PLA copolymer:

[0110] First, lactide was reacted with initiator (methanol) and catalyst (stannous octoate) at a reaction temperature of 160°C under vacuum for 6 hours to obtain PLA oligomers; then, PLA oligomers and GAG peptide chains were mixed in DMF and reacted at room temperature for 24 hours under the action of catalyst (stannous octoate), and the PLA-GAG-PLA block copolymer was obtained by separation and purification.

[0111] (2) Preparation of PLA-GAG-PLA@PEGO copolymer:

[0112] PLA-GAG-PLA and PEGO were mixed in a mixer at 170℃ and 50rpm for 10 minutes. PEGO was grafted onto the side chains and terminal hydroxyl sites of PLA through in-situ reaction to form an interpenetrating network structure PLA-GAG-PLA@PEGO copolymer.

[0113] Example 8

[0114] A controllable degradable block copolymer, wherein the molar ratio of lactide, polypeptide and PEGO in the polyester polymer is 100:8:10.

[0115] (1) Preparation of PLA-GAG-PLA copolymer:

[0116] First, lactide was reacted with initiator (methanol) and catalyst (stannous octoate) at a reaction temperature of 160°C under vacuum for 6 hours to obtain PLA oligomers; then, PLA oligomers and GAG peptide chains were mixed in DMF and reacted at room temperature for 24 hours under the action of catalyst (stannous octoate), and the PLA-GAG-PLA block copolymer was obtained by separation and purification.

[0117] (2) Preparation of PLA-GAG-PLA@PEGO copolymer:

[0118] PLA-GAG-PLA and PEGO were mixed in a mixer at 170℃ and 50rpm for 10 minutes. PEGO was grafted onto the side chains and terminal hydroxyl sites of PLA through in-situ reaction to form an interpenetrating network structure PLA-GAG-PLA@PEGO copolymer.

[0119] Comparative Example 1

[0120] A controllable degradable block copolymer, wherein the molar ratio of lactide, polypeptide and PEGO in the polyester polymer is 100:0:1.

[0121] (1) Preparation of PLA-GAG-PLA copolymer:

[0122] First, lactide was reacted with initiator (methanol) and catalyst (stannous octoate) at a reaction temperature of 160°C under vacuum for 6 hours to obtain PLA oligomers; then, PLA oligomers and GAG peptide chains were mixed in DMF and reacted at room temperature for 24 hours under the action of catalyst (stannous octoate), and the PLA-GAG-PLA block copolymer was obtained by separation and purification.

[0123] (2) Preparation of PLA-GAG-PLA@PEGO copolymer:

[0124] PLA-GAG-PLA and PEGO were mixed in a mixer at 170℃ and 50rpm for 10 minutes. PEGO was grafted onto the side chains and terminal hydroxyl sites of PLA through in-situ reaction to form an interpenetrating network structure PLA-GAG-PLA@PEGO copolymer.

[0125] Comparative Example 2

[0126] A controllable degradable block copolymer, wherein the molar ratio of lactide, polypeptide and PEGO in the polyester polymer is 100:0:0.

[0127] (1) Preparation of PLA-GAG-PLA copolymer:

[0128] First, lactide was reacted with initiator (methanol) and catalyst (stannous octoate) at a reaction temperature of 160°C under vacuum for 6 hours to obtain PLA oligomers; then, PLA oligomers and GAG peptide chains were mixed in DMF and reacted at room temperature for 24 hours under the action of catalyst (stannous octoate), and the PLA-GAG-PLA block copolymer was obtained by separation and purification.

[0129] (2) Preparation of PLA-GAG-PLA@PEGO copolymer:

[0130] PLA-GAG-PLA and PEGO were mixed in a mixer at 170℃ and 50rpm for 10 minutes. PEGO was grafted onto the side chains and terminal hydroxyl sites of PLA through in-situ reaction to form an interpenetrating network structure PLA-GAG-PLA@PEGO copolymer.

[0131] Comparative Example 3

[0132] PLA, GAG peptide chain, and PEGO were mixed at 170°C and 50 rpm for 10 minutes in a mixer with a molar ratio of PLA, GAG peptide chain, and PEGO of 100:10:1 to obtain a blended polymer (direct blending with polylactic acid will not result in copolymerization, so the obtained product is a blended polymer).

[0133] Comparative Example 4

[0134] (1) PLA and GAG peptide chains were mixed in DMF and reacted at room temperature for 24 hours under the action of catalyst (stannous octoate). The copolymer was then separated and purified.

[0135] (2) The copolymer and PEGO were mixed in a mixer at 170°C and 50 rpm for 10 minutes. The molar ratio of PLA, GAG peptide chain and PEGO was 100:10:1.

[0136] Performance testing

[0137] The raw material molar ratios and amounts used in the examples and comparative examples are shown in Table 1.

[0138] Table 1. Raw material molar ratios and dosages for the examples and comparative examples.

[0139]

[0140] The examples and comparative examples were tested according to the test methods in Table 2.

[0141] Table 2 Test Methods and Standards

[0142]

[0143] The test results are shown in Table 3.

[0144] Table 3 Test Results

[0145]

[0146]

[0147] Infrared spectral analysis was performed on pure PLA and PLA-GAG-PLA@PEGO prepared in Example 1. Figure 2-4 Infrared difference spectra of pure PLA and PLA-GAG-PLA@PEGO reveal that PLA segments are covalently linked, forming an alternating structure of "hard segments (PLA) - soft segments (flexible segments)". The flexible segments lower the glass transition temperature of the PLA segments and enhance their mobility. Simultaneously, microphase separation occurs between the PLA and PEGO chain ends, optimizing the crystal morphology. The infrared difference spectra reflect increased ester bond strength in the crystalline region and decreased ester bond strength in the amorphous region, further demonstrating the improved crystallinity of PLA-GAG-PLA@PEGO.

[0148] like Figure 5 As shown, polarized light microscopy revealed that the spherulite size decreased from 80-100 μm to 20 μm, demonstrating that the crystal morphology of the PLA-GAG-PLA@PEGO material was optimized. In summary, increased crystallinity improved tensile strength, while smaller crystal size and fewer defects further improved the material's toughness.

[0149] The morphology of PLA-GAG-PLA@PEGO copolymer before and after degradation was observed using a scanning electron microscope (VEGA3Tescan) before and after the degradation in simulated natural soil environment (25℃, 85% humidity). Figures 6-14 The results show that the PLA-GAG-PLA@PEGO copolymer exhibits varying degrees of porosity and cracks, indicating degradation at different rates. In contrast, pure PLA shows only a few cracks on its surface, suggesting a very slow natural degradation rate. This further demonstrates that the PLA-GAG-PLA@PEGO copolymer of this invention achieves a controllable degradation mechanism, exhibiting stable performance during use and controllable degradation under certain conditions after disposal.

Claims

1. A polylactic acid-based material, characterized in that, The product includes polylactic acid polymer, polypeptide, and polyethylene glycol ketal; the polypeptide is embedded in the main chain of the polylactic acid polymer, and the polyethylene glycol ketal is cross-linked and capped with the molecular chain of the polylactic acid polymer through hydrogen bonding; The structural formula of the polylactic acid-based material is as follows:

2. The polylactic acid-based material according to claim 1, characterized in that, The polypeptide is a weakly polar short-chain polypeptide.

3. The polylactic acid-based material according to claim 1, characterized in that, The polyethylene glycol ketal is polyethylene glycol containing ketal groups.

4. The polylactic acid-based material according to claim 3, characterized in that, The molecular weight of the polyethylene glycol is 1000-2000.

5. The method for preparing polylactic acid-based materials according to any one of claims 1-4, characterized in that, include: The oligomer of polylactic acid polymer is generated by ring-opening polymerization of lactide, and the polypeptide is added to prepare PLA-GAG-PLAn block copolymer. The polyethylene glycol ketal is added to prepare PLA-GAG-PLA@PEGO block polymer material, i.e., the polylactic acid-based material.

6. The method for preparing polylactic acid-based materials according to claim 5, characterized in that, The molar ratio of the lactide, the polypeptide, and the polyethylene glycol ketal is 100:10:1 to 100:1:

10.

7. The method for preparing polylactic acid-based materials according to claim 5, characterized in that, The lactide is L-type.

8. The method for preparing polylactic acid-based materials according to claim 5, characterized in that, The oligomers of the polylactic acid polymer formed by the ring-opening polymerization of lactide include: The lactide was reacted with an initiator and a catalyst at a reaction temperature of 155-165°C under vacuum to prepare the oligomer of the polylactic acid polymer.

9. The method for preparing polylactic acid-based materials according to claim 5, characterized in that, The addition of the polypeptide to prepare the PLAm-GAG-PLAn block copolymer includes: The oligomer of the polylactic acid polymer was mixed with the polypeptide in DMF and reacted at room temperature under the action of a catalyst. The PLAm-GAG-PLAn block copolymer was then separated and purified.

10. The method for preparing polylactic acid-based materials according to claim 5, characterized in that, The addition of the polyethylene glycol ketal to prepare the PLA-GAG-PLA@PEGO block polymer material includes: The PLA-GAG-PLAn block copolymer and the polyethylene glycol ketal are blended in a mixer at 160-180°C and 40-60 rpm. The polyethylene glycol ketal is grafted onto the side chains and terminal hydroxyl sites of the polylactic acid polymer through an in-situ reaction to form the PLA-GAG-PLA@PEGO block polymer material with an interpenetrating network structure.

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