Environmental response type degradable bionic composite membrane and preparation method thereof

Abstract

The invention discloses an environmental response type degradable bionic composite membrane and a preparation method thereof, the composite membrane is formed by alternately stacking hydrophobic layers and hydrophilic layers, the hydrophobic layers are PHA / PBS (3: 1-5: 1) blends and added with 2-8 wt% of oleic acid grafted nano-hydroxyapatite, and the hydrophilic layers are modified starch / PVA composite materials with the crosslinking degree of 15-35% and contain 0.5-3 wt% of thermo-sensitive PNIPAM-b-PAA. Mechanical interlocking is realized between layers through a lotus leaf-like micro-nano mastoid structure (the height is 1-5 microns, and the density is 106-107 / cm < 2 >) treated by plasma; micro gravure coating, electrostatic spraying and blade coating processes are adopted for preparation, and the controllable degradation period of 30-180 days can be achieved by regulating and controlling the layer thickness ratio (1: 2-3: 1); the degradation rate of the material in the pH range of 5.5-8.5 is positively correlated with the pH value (R2 is greater than 0.95), the degradation rate is increased by 8-12% when the temperature is increased by 1 DEG C, the degradation rate is greater than 90% in 20-50 days under the composting condition, the degradation product is ecologically safe (LC50 is greater than 1000mg / kg), and the material is suitable for intelligent agricultural mulching films and environment-friendly packaging.

Description

Technical Field

[0001] The present invention relates to the technical field of composite membrane preparation, and in particular to an environmentally responsive degradable biomimetic composite membrane and a preparation method thereof. Background Art

[0002] As the global plastic pollution problem becomes increasingly serious, the long-term residues of traditional petroleum-based plastics, especially disposable plastic products such as agricultural mulch films, in the natural environment have caused serious damage to soil ecology, crop growth and the microbial environment. The development of degradable and environmentally friendly alternative materials has become an important research direction for sustainable development. However, existing degradable materials still face many technical challenges: Uncontrollable degradation behavior: The degradation rate of currently widely used biodegradable materials (such as polylactic acid PLA, polybutylene adipate / terephthalate PBAT, etc.) is greatly affected by environmental factors, making it difficult to accurately match the growth cycle requirements of different crops. For example, some crops require mulch films to remain stable during the growing season and degrade rapidly after harvest, but the degradation process of existing materials is often highly random and cannot be intelligently controlled. Insufficient mechanical properties and weather resistance: Many degradable materials are prone to early degradation or loss of mechanical properties in high temperature and high humidity environments, resulting in an inability to meet the strength requirements of agricultural mulch films in actual applications. In addition, traditional single material systems are difficult to achieve flexibility, tear resistance and water resistance, which affects their actual service life. Weak interlayer bonding: Existing multilayer composite films are mostly prepared by physical lamination or co-extrusion processes, but the interfacial compatibility between the hydrophobic layer and the hydrophilic layer is poor, and delamination and peeling are prone to occur, affecting the overall performance of the material. Although some studies have improved interfacial bonding through plasma treatment or chemical modification, it is still difficult to achieve a coordinated response of each layer during the degradation process. Single environmental responsiveness: Current environmentally responsive materials mostly rely on a single stimulus (such as pH, temperature or enzymatic hydrolysis), but in the actual natural environment, the degradation process is often affected by multiple factors (humidity, microorganisms, temperature fluctuations, etc.). For example, materials that rely solely on pH response may fail when the temperature changes, and purely thermosensitive materials cannot adapt to different soil microbial environments, resulting in unpredictable degradation behavior. Additive contamination risk: Some degradable materials accelerate degradation by adding photosensitizers, oxidants or metal catalysts, but these additives may remain in the soil, causing secondary pollution to the ecological environment. In addition, simple blending of natural polymers (such as starch, cellulose) and synthetic polyesters (such as PBS, PHA) can easily lead to phase separation, affecting the uniformity and functional stability of the material.

[0003] Therefore, in response to the above problems, the present invention provides an environmentally responsive degradable bionic composite membrane and a preparation method thereof, and develops a new type of bionic multilayer composite membrane. By optimizing the material composition, interface structure and preparation process, it achieves precise regulation of degradation behavior, providing innovative solutions for sustainable materials in agriculture, packaging and other fields. Summary of the Invention

[0004] The purpose of the present invention is to provide an environmentally responsive degradable biomimetic composite membrane and a preparation method thereof, so as to achieve precise regulation of degradation behavior and provide innovative solutions for sustainable materials in the fields of agriculture, packaging and so on.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] An environmentally responsive biodegradable composite membrane comprises alternately stacked hydrophobic layers and hydrophilic layers, wherein:

[0007] The hydrophobic layer comprises a blend of polyhydroxyalkanoate (PHA) and polybutylene succinate (PBS), wherein the mass ratio of the polyhydroxyalkanoate (PHA) to the polybutylene succinate (PBS) is 3 to 5:1;

[0008] The hydrophilic layer is formed by cross-linking modified starch and polyvinyl alcohol (PVA) through aldehyde-hydroxyl groups, with a cross-linking degree of 15% to 35%;

[0009] Mechanical interlocking is achieved between layers through plasma-treated micro-nano concave-convex structures.

[0010] Preferably, the hydrophobic layer contains 2-8 wt% of nano-hydroxyapatite, the surface of which is grafted with oleic acid molecules at a grafting rate of 1.2-2.5 molecules / nm. 2 .

[0011] Preferably, the hydrophilic layer contains 0.5-3 wt% of a temperature-sensitive switch molecule, and the temperature-sensitive switch molecule is poly(N-isopropylacrylamide)-b-polyacrylic acid block copolymer (PNIPAM-b-PAA) with a lower critical solution temperature (LCST) of 32-35°C.

[0012] Preferably, the micro-nano concave-convex structure is a papillary array imitating the surface of a lotus leaf, with a single papillary height of 1 to 5 μm, a diameter of 0.8 to 3 μm, and a density of 10 6 ~10 7 pieces / cm 2 .

[0013] Preferably, the degradation rate of the environmentally responsive biomimetic composite membrane is positively correlated with the pH value within the pH range of 5.5 to 8.5, and the correlation coefficient R 2 >0.95; in the range of 25-45℃, the degradation rate increases by 8%-12% with every 1℃ increase in temperature.

[0014] Preferably, the environmentally responsive degradable biomimetic composite membrane can achieve a biodegradation rate of more than 90% within 20 to 50 days under standard composting conditions after being discarded, and the acute toxicity LC50 of the degradation product to earthworms is greater than 1000 mg / kg; the standard composting conditions are 56 to 60°C and 60% humidity.

[0015] This application also claims a method for preparing the above-mentioned environmentally responsive degradable biomimetic composite membrane, comprising the following steps:

[0016] (1) The hydrophobic layer was prepared by micro-gravure coating method at a coating temperature of 85-95°C and a line speed of 2-5 m / min;

[0017] (2) electrostatically spraying the treatment liquid to construct a micro-nano concave-convex structure on the surface of the hydrophobic layer at a voltage of 8 to 12 kV and a solution flow rate of 0.5 to 1.2 mL / h;

[0018] (3) a hydrophilic layer was prepared on the modified surface by a doctor blade coating method with a wet film thickness of 200–500 μm;

[0019] (4) Gradient drying was performed at a relative humidity of 60% to 80%, first at 25°C for 2 hours and then at 45°C for 4 hours.

[0020] Preferably, it is characterized in that, in step (2), the treatment liquid is a PBS solution containing 0.1-0.5M citric acid, the plasma treatment power is 50-100W, and the treatment time is 30-90s.

[0021] The present application also claims protection for an application of the above-mentioned environmentally responsive degradable biomimetic composite membrane, which, when used as an agricultural mulch film, can achieve a controllable degradation period of 30 to 180 days by adjusting the hydrophobic layer / hydrophilic layer thickness ratio to 1 to 3:1 to 2.

[0022] Due to the application of the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0023] 1. The present invention has precise and controllable degradation performance and pH / temperature dual-responsive degradation: the temperature-sensitive switch molecule (PNIPAM-b-PAA) in the hydrophilic layer can undergo a phase transition at a specific temperature (LCST 32-35°C), while the degradation rate of the hydrophobic layer is significantly accelerated with increasing pH (5.5-8.5), achieving environmentally adaptive degradation; the degradation cycle is adjustable (30-180 days): by adjusting the hydrophobic layer / hydrophilic layer thickness ratio (1-3:1-2), it can be flexibly matched to the needs of different crop growth cycles to avoid premature or late degradation; composting degradation is efficient and safe: under standard composting conditions (56-60°C, 60% humidity), the degradation rate is >90% within 20-50 days, and the acute toxicity LC50 of the degradation product to earthworms is >1000 mg / kg, with high ecological safety;

[0024] 2. The present invention has excellent mechanical properties and stability; bionic micro-nanostructure enhances interlayer bonding: the plasma-treated lotus leaf papilla array (height 1-5 μm, density 10 6 ~10 7 pieces / cm 2 ) to achieve mechanical interlocking, interlayer peeling strength increased by more than 40%, avoiding the use of traditional adhesives; Nano-enhanced hydrophobic layer: Nano-hydroxyapatite (2-8wt%, oleic acid grafting rate 1.2-2.5 / nm) in the hydrophobic layer 2 ) can be evenly dispersed, increasing tensile strength by 25% to 30% while maintaining flexibility; excellent weather resistance: the aldehyde-hydroxyl cross-linking network in the hydrophilic layer (cross-linking degree 15% to 35%) gives the material resistance to hydrolysis and remains stable in hot and humid environments;

[0025] 3. The present invention is environmentally friendly and sustainable. Fully bio-based / degradable components: Uses fully biodegradable materials such as PHA, PBS, modified starch, and PVA to avoid microplastic residues. No harmful additives: Degradation is regulated through molecular design (such as thermosensitive block copolymers), eliminating the need for photosensitizers or metal catalysts, reducing the risk of soil pollution. Energy-saving preparation process: Combining micro-gravure coating (85-95°C) and electrostatic spraying (8-12kV), it reduces energy consumption by more than 30% compared to traditional multi-layer co-extrusion processes.

[0026] 4. The present invention has a wide range of applications. Agricultural mulch films can have their degradation cycles customized to suit different climates and crop requirements, such as temperate regions (slow degradation) and tropical regions (fast degradation). Food packaging: The oxygen barrier properties of the hydrophilic layer and the moisture barrier properties of the hydrophobic layer can synergistically extend the shelf life of food, allowing for easy composting after disposal. Medical dressings: Their temperature-sensitive properties can be used in wound dressings, triggering drug release or accelerated degradation in response to body temperature.

[0027] 5. The present invention is feasible for industrial production and has strong process compatibility: steps such as coating and electrostatic spraying can be adapted to existing roll-to-roll production lines without the need for complex equipment modification; and cost is controllable: PHA / PBS blending (3-5:1) reduces raw material costs while ensuring performance, and modified starch replaces part of the synthetic polymer to further save costs. DETAILED DESCRIPTION

[0028] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, a specific implementation scheme is now described in detail.

[0029] The present invention is further described below with reference to the following examples, but the present invention is not limited to the following examples. The implementation conditions used in the examples can be further adjusted according to the different requirements of specific applications. The implementation conditions not specified are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention may be combined with each other as long as they do not conflict with each other.

[0030] Example 1

[0031] This embodiment provides an environmentally responsive biomimetic degradable composite membrane, comprising alternately stacked hydrophobic layers and hydrophilic layers, wherein:

[0032] The hydrophobic layer comprises a blend of polyhydroxyalkanoate (PHA) and polybutylene succinate (PBS), wherein the mass ratio of the polyhydroxyalkanoate (PHA) to polybutylene succinate (PBS) is 4:1; 5 wt% oleic acid grafted nano-hydroxyapatite (grafting rate 1.8 / nm) is added. 2 );

[0033] The hydrophilic layer is formed by cross-linking modified starch and polyvinyl alcohol (PVA) through aldehyde-hydroxyl groups, with a modified starch:PVA ratio of 7:3, a cross-linking degree of 25%, and containing 1.5 wt% PNIPAM-b-PAA (LCST 33°C);

[0034] The mechanical interlocking is achieved by plasma-treated micro-nano concave-convex structures between layers; citric acid (0.3 M) PBS solution is electrostatically sprayed (10 kV, 0.8 mL / h) and plasma treated (80 W, 60 s);

[0035] The method for preparing the environmentally responsive degradable biomimetic composite membrane comprises the following steps:

[0036] (1) The hydrophobic layer was prepared by micro-gravure coating method with a coating temperature of 90°C and a line speed of 3 m / min;

[0037] (2) The treatment liquid is electrostatically sprayed to construct a micro-nano concave-convex structure on the surface of the hydrophobic layer at a voltage of 10 kV and a solution flow rate of 0.8 mL / h;

[0038] (3) A hydrophilic layer was prepared on the modified surface by a doctor blade coating method with a wet film thickness of 300 μm;

[0039] (4) Gradient drying was performed at a relative humidity of 70%, first drying at 25°C for 2 h and then drying at 45°C for 4 h.

[0040] The thickness ratio of the hydrophobic layer to the hydrophilic layer in the dry film after drying was 1:1 (total thickness 100 μm).

[0041] Example 2

[0042] This embodiment provides an environmentally responsive biomimetic degradable composite membrane, comprising alternately stacked hydrophobic layers and hydrophilic layers, wherein:

[0043] The hydrophobic layer comprises a blend of polyhydroxyalkanoate (PHA) and polybutylene succinate (PBS), wherein the mass ratio of the polyhydroxyalkanoate (PHA) to polybutylene succinate (PBS) is 4:1; 5 wt% oleic acid grafted nano-hydroxyapatite (grafting rate 1.8 / nm) is added. 2 );

[0044] The hydrophilic layer is formed by cross-linking modified starch and polyvinyl alcohol (PVA) through aldehyde-hydroxyl groups, with a modified starch:PVA ratio of 7:3, a cross-linking degree of 25%, and containing 1.5 wt% PNIPAM-b-PAA (LCST 33°C);

[0045] The mechanical interlocking is achieved by plasma-treated micro-nano concave-convex structures between layers; citric acid (0.3 M) PBS solution is electrostatically sprayed (10 kV, 0.8 mL / h) and plasma treated (80 W, 60 s);

[0046] The method for preparing the environmentally responsive degradable biomimetic composite membrane comprises the following steps:

[0047] (1) The hydrophobic layer was prepared by micro-gravure coating method with a coating temperature of 90°C and a line speed of 3 m / min;

[0048] (2) The treatment liquid is electrostatically sprayed to construct a micro-nano concave-convex structure on the surface of the hydrophobic layer at a voltage of 10 kV and a solution flow rate of 0.8 mL / h;

[0049] (3) A hydrophilic layer was prepared on the modified surface by blade coating method with a wet film thickness of 360 μm;

[0050] (4) Gradient drying was performed at a relative humidity of 70%, first drying at 25°C for 2 h and then drying at 45°C for 4 h.

[0051] The thickness ratio of the hydrophobic layer to the hydrophilic layer in the dried film after drying was 1:2 (total thickness 100 μm).

[0052] Example 3

[0053] This embodiment provides an environmentally responsive biomimetic degradable composite membrane, comprising alternately stacked hydrophobic layers and hydrophilic layers, wherein:

[0054] The hydrophobic layer comprises a blend of polyhydroxyalkanoate (PHA) and polybutylene succinate (PBS), wherein the mass ratio of the polyhydroxyalkanoate (PHA) to polybutylene succinate (PBS) is 4:1; 5 wt% oleic acid grafted nano-hydroxyapatite (grafting rate 1.8 / nm) is added. 2);

[0055] The hydrophilic layer is formed by cross-linking modified starch and polyvinyl alcohol (PVA) through aldehyde-hydroxyl groups, with a modified starch:PVA ratio of 7:3, a cross-linking degree of 25%, and containing 1.5 wt% PNIPAM-b-PAA (LCST 33°C);

[0056] The mechanical interlocking is achieved by plasma-treated micro-nano concave-convex structures between layers; citric acid (0.3 M) PBS solution is electrostatically sprayed (10 kV, 0.8 mL / h) and plasma treated (80 W, 60 s);

[0057] The method for preparing the environmentally responsive degradable biomimetic composite membrane comprises the following steps:

[0058] (1) The hydrophobic layer was prepared by micro-gravure coating method with a coating temperature of 90°C and a line speed of 3 m / min;

[0059] (2) The treatment liquid is electrostatically sprayed to construct a micro-nano concave-convex structure on the surface of the hydrophobic layer at a voltage of 10 kV and a solution flow rate of 0.8 mL / h;

[0060] (3) A hydrophilic layer was prepared on the modified surface by a doctor blade coating method with a wet film thickness of 200 μm;

[0061] (4) Gradient drying was performed at a relative humidity of 70%, first drying at 25°C for 2 h and then drying at 45°C for 4 h.

[0062] The thickness ratio of the hydrophobic layer to the hydrophilic layer in the dry film after drying was 2:1 (total thickness 120 μm).

[0063] Example 4

[0064] This embodiment provides an environmentally responsive biomimetic degradable composite membrane, comprising alternately stacked hydrophobic layers and hydrophilic layers, wherein:

[0065] The hydrophobic layer comprises a blend of polyhydroxyalkanoate (PHA) and polybutylene succinate (PBS), wherein the mass ratio of the polyhydroxyalkanoate (PHA) to the polybutylene succinate (PBS) is 4:1; 8 wt% oleic acid grafted nano-hydroxyapatite (grafting rate 1.8 / nm) is added. 2 );

[0066] The hydrophilic layer is formed by cross-linking modified starch and polyvinyl alcohol (PVA) through aldehyde-hydroxyl groups, with a modified starch:PVA ratio of 7:3, a cross-linking degree of 25%, and containing 1.5 wt% PNIPAM-b-PAA (LCST 33°C);

[0067] The mechanical interlocking is achieved by plasma-treated micro-nano concave-convex structures between layers; citric acid (0.3 M) PBS solution is electrostatically sprayed (10 kV, 0.8 mL / h) and plasma treated (80 W, 60 s);

[0068] The method for preparing the environmentally responsive degradable biomimetic composite membrane comprises the following steps:

[0069] (1) The hydrophobic layer was prepared by micro-gravure coating method with a coating temperature of 90°C and a line speed of 3 m / min;

[0070] (2) The treatment liquid is electrostatically sprayed to construct a micro-nano concave-convex structure on the surface of the hydrophobic layer at a voltage of 10 kV and a solution flow rate of 0.8 mL / h;

[0071] (3) A hydrophilic layer was prepared on the modified surface by a doctor blade coating method with a wet film thickness of 200 μm;

[0072] (4) Gradient drying was performed at a relative humidity of 70%, first drying at 25°C for 2 h and then drying at 45°C for 4 h.

[0073] The thickness ratio of the hydrophobic layer to the hydrophilic layer in the dry film after drying was 1:1 (total thickness 100 μm).

[0074] Example 5

[0075] This embodiment provides an environmentally responsive biomimetic degradable composite membrane, comprising alternately stacked hydrophobic layers and hydrophilic layers, wherein:

[0076] The hydrophobic layer comprises a blend of polyhydroxyalkanoate (PHA) and polybutylene succinate (PBS), wherein the mass ratio of the polyhydroxyalkanoate (PHA) to polybutylene succinate (PBS) is 4:1; 5 wt% oleic acid grafted nano-hydroxyapatite (grafting rate 1.8 / nm) is added. 2 );

[0077] The hydrophilic layer is formed by cross-linking modified starch and polyvinyl alcohol (PVA) through aldehyde-hydroxyl groups, with a modified starch:PVA ratio of 7:3, a cross-linking degree of 35%, and containing 1.5 wt% PNIPAM-b-PAA (LCST 33°C);

[0078] The mechanical interlocking is achieved by plasma-treated micro-nano concave-convex structures between layers; citric acid (0.3 M) PBS solution is electrostatically sprayed (10 kV, 0.8 mL / h) and plasma treated (80 W, 60 s);

[0079] The method for preparing the environmentally responsive degradable biomimetic composite membrane comprises the following steps:

[0080] (1) The hydrophobic layer was prepared by micro-gravure coating method with a coating temperature of 90°C and a line speed of 3 m / min;

[0081] (2) The treatment liquid is electrostatically sprayed to construct a micro-nano concave-convex structure on the surface of the hydrophobic layer at a voltage of 10 kV and a solution flow rate of 0.8 mL / h;

[0082] (3) A hydrophilic layer was prepared on the modified surface by a doctor blade coating method with a wet film thickness of 200 μm;

[0083] (4) Gradient drying was performed at a relative humidity of 70%, first drying at 25°C for 2 h and then drying at 45°C for 4 h.

[0084] The thickness ratio of the hydrophobic layer to the hydrophilic layer in the dry film after drying was 1:1 (total thickness 100 μm).

[0085] Comparative Example 1

[0086] This comparative example is a pure PLA single-layer film produced by extrusion casting, and the film thickness is 100 μm.

[0087] Comparative Example 2

[0088] This comparative example is a starch / PBAT (70 / 30) blend film formed by hot pressing, and the film thickness is 100 μm.

[0089] Comparative Example 3

[0090] This comparative example is a physically laminated PHA / PBS double-layer physical composite film with a thickness of 100 μm.

[0091] Comparative Example 4

[0092] This comparative example is a solution-cast PHA / PBS / starch ternary blend film with a film thickness of 100 μm.

[0093] Comparative Example 5

[0094] This comparative example is a commercially available biodegradable ground film with a film thickness of 100 μm.

[0095] The configuration of the above embodiment is listed in Table 1.

[0096] Table 1

[0097] project Hydrophobic layer thickness Hydrophilic layer thickness Thickness ratio Total thickness Design purpose Example 1 50μm 50μm 1:1 100μm Benchmark Group Example 2 40μm 80μm 1:2 120μm Hydrophilic layer dominant Example 3 80μm 40μm 2:1 120μm Hydrophobic layer dominant Example 4 50μm 50μm 1:1 100μm Enhanced Example 5 50μm 50μm 1:1 100μm High stability

[0098] The settings of the above embodiment are listed in Table 2.

[0099] Table 2

[0100] project Composition structure thickness Preparation process Purpose of comparison Comparative Example 1 Pure PLA single layer film 100μm Extrusion Casting Traditional biodegradable material benchmark Comparative Example 2 Starch / PBAT (70 / 30) blend film 100μm Hot Press Forming Non-responsive blending system Comparative Example 3 PHA / PBS double layer physical composite 100μm Physical lamination No micro-nano interlocking structure Comparative Example 4 PHA / PBS / starch ternary blend 100μm Solution casting Comparison of homogeneous systems Comparative Example 5 Commercially available biodegradable mulch 100μm - Commercial product references

[0101] The performance test results of the above embodiments are listed in Table 3.

[0102] Table 3

[0103]

[0104]

[0105] The performance test results of the above comparative examples are listed in Table 4.

[0106] Table 4

[0107]

[0108] The measured data of mastoid structural parameters of the above embodiments and comparative examples are listed in Table 5.

[0109] Table 5

[0110]

[0111]

[0112] As can be seen from the above table: thickness ratio effect: 1:2 structure (Example 2) exhibits the best pH responsiveness (90% degradation rate at pH 8.5); 2:1 structure (Example 3) has the best mechanical properties (tensile strength 32.1MPa); component optimization: adding nanohydroxyapatite (Example 4) increases the tensile strength by 8%; increasing the crosslinking degree (Example 5) reduces the moisture permeability but slightly delays degradation; structural advantages: the interlayer bonding force of all examples (145-162N / m) is significantly better than that of the physical composite comparative example 3 (60N / m); the micro-nano interlocking structure reduces the moisture permeability by more than 50% compared with the blend system; environmental response specificity: the temperature / pH dual response characteristics of the example are significantly better than the single response commercial product (Comparative Example 5); Table 5 fully presents the micro-nanostructure characteristics of the present invention, confirming that the example achieves precise control of the biomimetic structure through a controllable preparation process. This experimental system, by strictly controlling the preparation parameters, confirms the comprehensive advantages of the biomimetic multilayer structure in degradation controllability, mechanical properties and environmental adaptability, providing a reliable solution for the intelligent design of degradable materials.

[0113] In summary, the present invention has precise and controllable degradation performance, pH / temperature dual-responsive degradation: the thermosensitive switch molecule (PNIPAM-b-PAA) in the hydrophilic layer can undergo phase change at a specific temperature (LCST32~35℃), while the degradation rate of the hydrophobic layer is significantly accelerated with increasing pH (5.5~8.5), realizing environmental adaptive degradation; the degradation cycle is adjustable (30~180 days): by adjusting the hydrophobic layer / hydrophilic layer thickness ratio (1~3:1~2), it can flexibly match the growth cycle requirements of different crops to avoid premature or late degradation; composting degradation is efficient and safe: under standard composting conditions (56~60℃, humidity 60%), the degradation rate is >90% within 20~50 days, and the acute toxicity LC50 of the degradation product to earthworms is >1000mg / kg, with high ecological safety; the present invention has excellent mechanical properties and stability; bionic micro-nanostructure enhances interlayer bonding: by plasma-treated imitation lotus leaf papilla array (height 1~5μm, density 10 6 ~10 7 pieces / cm 2 ) to achieve mechanical interlocking, interlayer peeling strength increased by more than 40%, avoiding the use of traditional adhesives; Nano-enhanced hydrophobic layer: Nano-hydroxyapatite (2-8wt%, oleic acid grafting rate 1.2-2.5 / nm) in the hydrophobic layer 2 ) can be evenly dispersed, which increases the tensile strength by 25% to 30% while maintaining flexibility; excellent weather resistance: the aldehyde-hydroxyl cross-linking network in the hydrophilic layer (cross-linking degree 15% to 35%) gives the material resistance to hydrolysis and can remain stable in a hot and humid environment; the present invention is environmentally friendly and sustainable; all-biobased / degradable components: PHA, PBS, modified starch, PVA and other fully biodegradable materials are used to avoid microplastic residues; no harmful additives: degradation regulation is achieved through molecular design (such as thermosensitive block copolymers), without the need to add photosensitizers or metal catalysts, reducing the risk of soil pollution; energy-saving preparation process: micro-gravure coating (85-95°C) and electrostatic spraying (8-12kV) are combined to reduce energy consumption compared to traditional multi-layer co-extrusion processes More than 30%; the present invention has a wide range of application adaptability; agricultural mulch: the degradation cycle can be customized according to different climates and crop requirements, such as temperate regions (slow degradation) and tropical regions (fast degradation); food packaging: the oxygen barrier of the hydrophilic layer and the moisture barrier of the hydrophobic layer can synergistically extend the shelf life of food, and it is easy to compost after disposal; medical dressing: the temperature-sensitive property can be used for wound dressing, releasing drugs or accelerating degradation when triggered by body temperature; the present invention has the feasibility of industrial production; strong process compatibility: coating, electrostatic spraying and other steps can be adapted to existing roll-to-roll production lines without the need for complex equipment modification; cost controllable: PHA / PBS blending (3-5:1) reduces raw material costs while ensuring performance, and modified starch replaces part of the synthetic polymer to further save costs.

[0114] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. An environmentally responsive biodegradable composite membrane, characterized in that: It comprises alternating stacks of hydrophobic and hydrophilic layers, wherein: The hydrophobic layer comprises a blend of polyhydroxyalkanoate and polybutylene succinate, wherein the mass ratio of the polyhydroxyalkanoate to the polybutylene succinate is 3 to 5:1; The hydrophilic layer is formed by cross-linking modified starch and polyvinyl alcohol through aldehyde-hydroxyl groups, with a cross-linking degree of 15% to 35%; Mechanical interlocking is achieved between layers through plasma-treated micro-nano concave-convex structures.

2. The environmentally responsive biodegradable composite membrane according to claim 1, characterized in that: The hydrophobic layer contains 2-8 wt% nano-hydroxyapatite, the surface of which is grafted with oleic acid molecules at a grafting rate of 1.2-2.5 molecules / nm. 2 .

3. The environmentally responsive biomimetic composite membrane according to claim 1, characterized in that: The hydrophilic layer contains 0.5-3 wt% of temperature-sensitive switch molecules, which are poly(N-isopropylacrylamide)-b-polyacrylic acid block copolymers with a minimum critical solution temperature of 32-35°C.

4. The environmentally responsive biodegradable composite membrane according to claim 1, characterized in that: The micro-nano concave-convex structure is a papillary array imitating the surface of a lotus leaf, with a single papillary height of 1 to 5 μm, a diameter of 0.8 to 3 μm, and a density of 10 6 ~10 7 pieces / cm 2 .

5. The environmentally responsive biodegradable composite membrane according to claim 1, characterized in that: The degradation rate of the environmentally responsive biomimetic composite membrane is positively correlated with the pH value within the pH range of 5.5 to 8.5, and the correlation coefficient R 2 >0.95; in the range of 25-45℃, the degradation rate increases by 8%-12% with every 1℃ increase in temperature.

6. The environmentally responsive biomimetic composite membrane according to claim 1, characterized in that: The environmentally responsive degradable biomimetic composite membrane can achieve a biodegradation rate of more than 90% within 20 to 50 days after being discarded under standard composting conditions, and the acute toxicity LC50 of the degradation product to earthworms is greater than 1000 mg / kg; the standard composting conditions are 56 to 60° C. and 60% humidity.

7. A method for preparing an environmentally responsive degradable biomimetic composite membrane according to any one of claims 1 to 6, characterized in that: The steps include: (1) The hydrophobic layer was prepared by micro-gravure coating method at a coating temperature of 85-95°C and a line speed of 2-5 m / min; (2) electrostatically spraying the treatment liquid to construct a micro-nano concave-convex structure on the surface of the hydrophobic layer at a voltage of 8 to 12 kV and a solution flow rate of 0.5 to 1.2 mL / h; (3) a hydrophilic layer was prepared on the modified surface by a doctor blade coating method with a wet film thickness of 200–500 μm; (4) Gradient drying was performed at a relative humidity of 60% to 80%, first at 25°C for 2 hours and then at 45°C for 4 hours.

8. The method for preparing the environmentally responsive degradable biomimetic composite membrane according to claim 7, wherein: In step (2), the treatment solution is a PBS solution containing 0.1-0.5M citric acid, the plasma treatment power is 50-100W, and the treatment time is 30-90s.

9. Use of the environmentally responsive degradable biomimetic composite membrane according to any one of claims 1 to 6 or the environmentally responsive degradable biomimetic composite membrane prepared by the method for preparing the environmentally responsive degradable biomimetic composite membrane according to any one of claims 7 to 8, characterized in that: When used as an agricultural mulch film, a controllable degradation period of 30 to 180 days can be achieved by adjusting the hydrophobic layer / hydrophilic layer thickness ratio to 1 to 3:1 to 2.

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