A fully bio-based vitrimer material based on carboxyl-modified β-cyclodextrin, its preparation method and application

Abstract

The present invention discloses a fully bio-based vitrimer material based on carboxyl-modified β-cyclodextrin, its preparation method and application, which relates to the technical field of vitrimer material preparation. The preparation method includes: mixing carboxyl-modified β-cyclodextrin, citric acid and epoxidized soybean oil with solvent 3, heating for reaction, and then hot-pressing and curing the reaction product to obtain the fully bio-based vitrimer material based on carboxyl-modified β-cyclodextrin. The present invention uses carboxyl-modified β-cyclodextrin as the core cross-linking agent, combines citric acid and epoxidized soybean oil to construct a fully bio-based Vitrimer material, and the obtained fully bio-based material has excellent mechanical properties and is easy to recycle. The fully bio-based Vitrimer material of the present invention does not need to rely on amino or mercapto curing agents during the preparation process, nor does it need to introduce metal catalysts or synthetic amine compounds, and the preparation process is simple and environmentally friendly.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of vitrimer materials, and particularly to a fully bio-based vitrimer material based on carboxyl-modified β-cyclodextrin, and a preparation method and application thereof. Background Art

[0002] The development of glass-like polymer (vitrimer) materials that combine the stability of thermosetting materials and the reprocessability of thermoplastic materials is regarded as a key direction for current degradable and recyclable bio-based polymer materials.

[0003] In recent years, the development of fully bio-based Vitrimer materials has focused on breaking through the dependence on fossil raw materials and metal catalysts of traditional dynamic covalent bonds. However, the existing systems still face two major bottlenecks: one is that the types of bio-based crosslinking agents are limited, and it is difficult to balance high strength and efficient dynamic exchange; the other is that the crosslinking networks of vegetable oil-based resins such as epoxidized soybean oil usually rely on amino or mercapto curing agents, and metal catalysts (such as zinc acetylacetonate) or synthetic amine compounds need to be introduced, resulting in complex processes and reduced environmental compatibility; for example, the system of epoxidized soybean oil and disulfide curing agent (such as APD) requires high temperature to trigger dynamic exchange, and the biomass content is less than 60%; while the imine bond system based on vanillin has achieved a fully bio-based design, but the mechanical properties and the number of recyclable times are still limited. Therefore, it is very necessary to develop a fully bio-based vitrimer material with high performance, easy recyclability and simple preparation process. Summary of the Invention

[0004] The purpose of the present invention is to provide a fully bio-based vitrimer material based on carboxyl-modified β-cyclodextrin, and a preparation method and application thereof, so as to solve the problems existing in the above-mentioned prior art.

[0005] To achieve the above purpose, the present invention provides the following solutions:

[0006] One of the technical solutions of the present invention: a fully bio-based vitrimer material based on carboxyl-modified β-cyclodextrin, the raw materials include carboxyl-modified β-cyclodextrin (CDS), citric acid (CA) and epoxidized soybean oil (ESO);

[0007] The ratio of the total molar amount of carboxyl groups contained in the raw materials (i.e., carboxyl-modified β-cyclodextrin and citric acid) to the molar amount of epoxy groups contained in the epoxidized soybean oil is 1-1.5:1;

[0008] The molar ratio of the carboxyl-modified β-cyclodextrin to the citric acid is 1:25-100.

[0009] As a natural cyclic oligosaccharide, the hydrophobic cavity of β-cyclodextrin can encapsulate the epoxy groups of ESO, enhancing the interfacial compatibility through host-guest interactions; carboxyl modification can further increase the density of reactive sites, enabling the formation of multiple dynamic ester bonds and transesterification networks with the polycarboxylic acid groups of citric acid and the epoxy groups of ESO. This design first introduces the topological structure advantages of cyclodextrin into the dynamic covalent network: its rigid cavity can inhibit the excessive flexibility of the bio-based long chain, endowing the material with high modulus and effectively improving its mechanical properties; at the same time, the α-hydroxycarboxylic acid structure in citric acid has both catalytic activity and the ability to form dynamic bonds, triggering the transesterification reaction under metal-free catalytic conditions and reducing the preparation and recycling temperature of the vitrimer material. In addition, the ternary system of ESO / CDS / citric acid achieves a 100% bio-based raw material ratio, and the biodegradability of citric acid enables the vitrimer material to degrade into monomers under mild acidic conditions, and the monomers can be used for the re-synthesis of the vitrimer material, breaking through the energy consumption limit of traditional hot pressing recycling.

[0010] Furthermore, the preparation steps of the carboxyl-modified β-cyclodextrin include:

[0011] Mix β-cyclodextrin (β-CD), succinic anhydride and 4-dimethylaminopyridine (DMAP) to obtain a mixture; dissolve the mixture in solvent 1 to obtain a mixed solution; dialyze the mixed solution, and mix the dialysate with solvent 2, then concentrate and dry to obtain the carboxyl-modified β-cyclodextrin.

[0012] Furthermore, the mass ratio of β-cyclodextrin, succinic anhydride and 4-dimethylaminopyridine is 1:3.7:0.03.

[0013] Further preferably, the step of mixing β-cyclodextrin, succinic anhydride and 4-dimethylaminopyridine to obtain a mixture includes: adding β-cyclodextrin into a container, vacuum drying at 120 °C for 2 - 3 h, then adding succinic anhydride and 4-dimethylaminopyridine, and heating and stirring at 140 °C for 8 - 10 h to obtain a mixture.

[0014] Furthermore, the solvent 1 includes a mixed solvent of acetone and water.

[0015] Further preferably, the volume ratio of acetone to water in the solvent 1 is 2:1.

[0016] Furthermore, the solvent 2 includes acetone.

[0017] Furthermore, the dissolution of the mixture in solvent 1 is carried out under heating conditions; the heating temperature is 40 - 60 °C.

[0018] Furthermore, the dialysis is carried out in water for 80 - 100 h.

[0019] Furthermore, the molecular weight cut-off of the dialysis bag used in the dialysis is 1000Da.

[0020] The second technical solution of the present invention: The preparation method of the above-mentioned all-biobased vitrimer material based on carboxyl-modified β-cyclodextrin comprises the following steps:

[0021] The carboxyl-modified β-cyclodextrin, citric acid and epoxidized soybean oil are mixed with solvent 3, heated for reaction, and then the reaction product is hot-pressed and cured to obtain the fully bio-based vitrimer material based on carboxyl-modified β-cyclodextrin.

[0022] Furthermore, the solvent 3 includes acetone.

[0023] Furthermore, the heating reaction includes: reflux reaction at 60° C. for 30-50 min.

[0024] More preferably, the step of vacuum drying the reaction product is further included before the hot pressing curing.

[0025] Furthermore, the parameters of the hot pressing curing include: pressure of 10 MPa, temperature of 170° C., and time of 4-5 h.

[0026] The third technical solution of the present invention: Application of the above-mentioned fully bio-based vitrimer material based on carboxyl-modified β-cyclodextrin in the preparation of medical materials or intelligent packaging materials.

[0027] In the prior art, β-cyclodextrin is mostly used to reinforce nanocomposites, and its cross-linking effect in dynamic covalent networks has not yet been explored; and citric acid as a cross-linking agent is only found in polyester Vitrimer, and its synergistic effect with epoxy resin is still blank. The present invention opens up the reaction paths of the three through molecular design, which not only solves the difficult problem of balancing the mechanical properties and recyclability of all-biobased Vitrimer materials, but also provides a structural basis for multifunctionality (such as drug sustained release and selective adsorption), and is expected to open up new application scenarios in the fields of medical materials, smart packaging, etc.

[0028] The present invention discloses the following technical effects:

[0029] The present invention uses carboxyl-modified β-cyclodextrin (β-CD) as a core cross-linking agent, combines citric acid and epoxidized soybean oil (ESO) to construct a fully bio-based Vitrimer material. The obtained fully bio-based material has excellent mechanical properties and is easy to recycle.

[0030] The all-biobased Vitrimer material of the present invention does not need to rely on amino or thiol curing agents during the preparation process, nor does it need to introduce metal catalysts or synthesize amine compounds. The preparation process is simple and green. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0032] Figure 1 It is an infrared comparison diagram of raw material β-cyclodextrin (β-CD) and carboxyl-modified β-cyclodextrin (CDS) prepared in step S1 of Example 1;

[0033] Figure 2 It is the nuclear magnetic resonance diagram of the carboxyl-modified β-cyclodextrin prepared in step S1 of Example 1;

[0034] Figure 3 It is an infrared comparison diagram of raw material citric acid (CA), epoxidized soybean oil (ESO) and the fully biobased vitrimer material based on carboxyl-modified β-cyclodextrin prepared in step S3 of Example 1;

[0035] Figure 4 It is a comparison diagram of stress-strain curves of the fully biobased vitrimer materials prepared in Examples 1-5 and Comparative Example 1;

[0036] Figure 5 It is a comparison diagram of stress-strain curves when the fully biobased vitrimer material prepared in Example 3 is cyclically tested three times. Detailed Embodiments

[0037] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0038] It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0039] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although this invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of this invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the said documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0040] Without departing from the scope or spirit of this invention, various improvements and changes can be made to the specific embodiments of the description of this invention, which are obvious to those skilled in the art. Other embodiments obtained from the description of this invention are obvious to those skilled in the art. The description and examples of this invention are merely exemplary.

[0041] Regarding "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0042] It should be noted that the aspects not described in detail in this invention are all conventional operation means in the art and are not the focus of this invention.

[0043] In the following examples, comparative examples and test examples of this invention, if room temperature or normal temperature is involved, it specifically refers to 20 - 30 °C.

[0044] Unless otherwise specified, all raw materials used in the following examples, comparative examples and test examples of this invention are ordinary commercially available products.

[0045] Example 1

[0046] A fully bio - based vitrimer material based on carboxyl - modified β - cyclodextrin, the preparation steps are as follows:

[0047] S1. Add β - cyclodextrin (7.41 g) into a 100 mL round - bottom flask and dry it in a vacuum drying oven at 120 °C for 2 h. Then add succinic anhydride (27.4 g) and 4 - dimethylaminopyridine (0.209 g) into the flask, and mechanically stir at 140 °C for 8 h. Dissolve the obtained mixture in a 50 mL acetone - water (volume ratio of acetone to water is 2:1) mixed solvent under heating at 50 °C, and dialyze the obtained mixed solution in ultrapure water at room temperature for 96 h (cut - off molecular weight of dialysis bag: 1000 Da). Then collect the dialysis solution and dissolve it in acetone (volume ratio of dialysis solution to acetone is 1:1), and after vacuum concentration, dry the product in a vacuum oven to remove the excess acetone to obtain carboxyl - modified β - cyclodextrin (abbreviated as CDS);

[0048] S2. Add CDS, citric acid (CA), and epoxidized soybean oil (ESO) into a 100 mL three-necked flask (wherein, the molar ratio of the total amount of carboxyl groups in CDS and CA to the molar amount of epoxy groups in ESO is 1:1 (specifically 5 mmol:5 mmol), and the molar ratio of CDS to CA is 1:100), and add 30 mL of acetone to dissolve. Then reflux and react for 30 min in an oil bath at 60 °C;

[0049] S3. Dry the reaction product in a vacuum oven for 2 h to remove acetone. Then hot-press and cure the dried product with a flat vulcanizer at a pressure of 10 MPa and 170 °C for 4 h to obtain a fully biobased vitrimer material based on carboxyl-modified β-cyclodextrin (abbreviated as (CDS1CA 100 )-ESO 5 / 5).

[0050] Example 2

[0051] The difference from Example 1 is that, when the molar ratio of the total amount of carboxyl groups in CDS and CA to the molar amount of epoxy groups in ESO is maintained at 1:1 (specifically 5 mmol:5 mmol), the molar ratio of CDS to CA is adjusted to 1:75. The finally obtained fully biobased vitrimer material based on carboxyl-modified β-cyclodextrin is abbreviated as (CDS1CA 75 )-ESO 5 / 5.

[0052] Example 3

[0053] The difference from Example 1 is that, when the molar ratio of the total amount of carboxyl groups in CDS and CA to the molar amount of epoxy groups in ESO is maintained at 1:1 (specifically 5 mmol:5 mmol), the molar ratio of CDS to CA is adjusted to 1:50. The finally obtained fully biobased vitrimer material based on carboxyl-modified β-cyclodextrin is abbreviated as (CDS1CA 50 )-ESO 5 / 5.

[0054] Example 4

[0055] The difference from Example 1 is that, when the molar ratio of the total amount of carboxyl groups in CDS and CA to the molar amount of epoxy groups in ESO is maintained at 1:1 (specifically 5 mmol:5 mmol), the molar ratio of CDS to CA is adjusted to 1:25. The finally obtained fully biobased vitrimer material based on carboxyl-modified β-cyclodextrin is abbreviated as (CDS1CA 25 )-ESO 5 / 5.

[0056] Example 5

[0057] It is different from Example 1 in that the ratio of the total molar amount of carboxyl groups contained in CDS and CA to the molar amount of epoxy groups contained in ESO is adjusted to 3:2 (specifically 6 mmol:4 mmol), and the molar ratio of CDS and CA is kept at 1:100. The finally obtained carboxyl-modified β-cyclodextrin-based all-bio-based vitrimer material is abbreviated as (CDS1CA 100 )-ESO 6 / 4.

[0058] Comparative Example 1

[0059] S1. CA and ESO were added to a 100 mL three-necked flask (wherein, the molar ratio of the carboxyl groups contained in CA to the epoxy groups contained in ESO was 1:1, specifically 5 mmol:5 mmol), and 30 mL of acetone was added for dissolution. Then, the mixture was refluxed at 60 °C in an oil bath for 30 min;

[0060] S2. The reaction product was dried in a vacuum oven for 2 h to remove acetone. Then, the dried product was hot-pressed and cured at 10 MPa and 170 °C for 4 h using a flat vulcanizer to obtain an all-bio-based vitrimer material (abbreviated as CA-ESO5 / 5).

[0061] Test Example 1

[0062] Structure and Composition Characterization

[0063] Figure 1 As shown in the infrared comparison chart of the raw material β-cyclodextrin (β-CD) and the carboxyl-modified β-cyclodextrin (CDS) prepared in Step S1 of Example 1, it can be seen that the carboxyl-modified β-cyclodextrin was successfully prepared.

[0064] Figure 2 As shown in the NMR chart of the carboxyl-modified β-cyclodextrin prepared in Step S1 of Example 1, it can be seen that 17 hydroxyl groups of β-cyclodextrin were replaced by succinic anhydride.

[0065] Figure 3 As shown in the infrared comparison chart of the raw material citric acid (CA), epoxidized soybean oil (ESO) and the all-bio-based vitrimer material based on carboxyl-modified β-cyclodextrin prepared in Step S3 of Example 1, it can be seen that the epoxy groups and -COOH groups of ESO were successfully crosslinked to form a polymer.

[0066] Test Example 2

[0067] Mechanical Property Test

[0068] The stress-strain tests were carried out on the vitrimer materials prepared in each example, and the test method is as follows:

[0069] At room temperature, the hot-pressed vitrimer material was cut into dumbbell-shaped test specimens with dimensions of 2 mm × 35 mm using a manual punching machine and a cutter. Subsequently, a universal testing machine model CMT4104GD was used to measure the mechanical properties of the samples, and the tensile speed was set at 10 mm / min. Five specimens were prepared for each sample and subjected to five tensile tests repeatedly, and their average values were calculated to ensure the accuracy of the results. The tensile strength at break (σ) of the samples was calculated using the following formula:

[0070] σ = F / A (1)

[0071] where F represents the force of the sample during the tensile process, and A represents the initial cross-sectional area at the fracture of the sample.

[0072] The elongation at break (ε) of the samples was calculated using the following formula:

[0073] ε = (I - I0) / I (2)

[0074] where I represents the length of the sample at break, and I0 represents the original length of the sample.

[0075] Figure 4 For the stress (i.e., tensile strength at break)-strain (i.e., elongation at break) curve comparison diagrams of the fully bio-based vitrimer materials prepared in Examples 1-5 and Comparative Example 1, it can be seen that the fracture stress of the vitrimer material with CDS added is about twice that of CA-ESO 5 / 5 without CDS added, and the fracture stress of (CDS1CA100)-ESO 6 / 4 can reach about 1.4 MPa, and the elongation at break can reach about 105%, which is slightly higher than that of (CDS1CA100)-ESO 5 / 5. This may be because the carboxyl group is in excess, so the network is sparser. The excess CDS forms supramolecular interactions with the remaining hydroxyl and carboxyl groups of CA. At the same time, there are pendant chains in its network, thus forming internal plasticization. Therefore, the elongation at break is increased, the fracture strength becomes larger, and the toughness is improved. However, due to the sparse network and pendant chains, the Young's modulus (the slope in the figure is the Young's modulus) is lower than that of the other four vitrimer materials with CDS added.

[0076] The fully bio-based vitrimer material prepared in Example 3 after testing was recycled. Specifically, the specimens were cut into small pieces, then added to a mold and hot-pressed using a hot press (170 °C / 10 MPa / 4 h) to obtain the recycled fully bio-based vitrimer material, and the specimens were cut again for stress-strain testing.

[0077] Figure 5The contrast diagram of stress-strain curves when the fully bio-based vitrimer material prepared in Example 3 is recycled three times (where 1 represents after the first recycling, 2 represents after the second recycling, 3 represents after the third recycling, and 0 represents the test situation of the newly prepared fully bio-based vitrimer material, that is Figure 4 the stress-strain curve of (CDS1CA50)-ESO 5 / 5 in Figure 4 ). It can be seen that the fracture stresses after three recyclings are maintained at 142.5%, 168.1% and 123.3% of the original level (i.e., the level when the first test was carried out in Figure 4 ), and the fracture strains are maintained at 117.3%, 118.9% and 72.1% of the original level respectively.

[0078] The above-described embodiments are only descriptions of the preferred modes of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A fully bio-based vitrimer material based on carboxyl-modified β-cyclodextrin, characterized in that, The raw materials include carboxyl-modified β-cyclodextrin, citric acid and epoxidized soybean oil; The ratio of the total molar amount of carboxyl groups contained in the raw materials to the molar amount of epoxy groups contained in the epoxidized soybean oil is 1 - 1.5:1; The molar ratio of the carboxyl-modified β-cyclodextrin to the citric acid is 1:25 - 100; The preparation steps of the all-bio-based vitrimer material based on carboxyl-modified β-cyclodextrin include: Mix the carboxyl-modified β-cyclodextrin, citric acid and epoxidized soybean oil with solvent 3, heat and react, and then hot-press and cure the reaction product to obtain the all-bio-based vitrimer material based on carboxyl-modified β-cyclodextrin.

2. The all-bio-based vitrimer material based on carboxyl-modified β-cyclodextrin according to claim 1, characterized in that, The preparation steps of the carboxyl-modified β-cyclodextrin include: Mix β-cyclodextrin, succinic anhydride and 4-dimethylaminopyridine to obtain a mixture; dissolve the mixture in solvent 1 to obtain a mixed solution; dialyze the mixed solution, and mix the dialysate with solvent 2, and then concentrate and dry to obtain the carboxyl-modified β-cyclodextrin.

3. The all-bio-based vitrimer material based on carboxyl-modified β-cyclodextrin according to claim 2, characterized in that, The mass ratio of the β-cyclodextrin, succinic anhydride and 4-dimethylaminopyridine is 1:3.7:0.

03.

4. The all-bio-based vitrimer material based on carboxyl-modified β-cyclodextrin according to claim 2, characterized in that, The solvent 1 includes a mixed solvent of acetone and water; And / or, the solvent 2 includes acetone.

5. The all-bio-based vitrimer material based on carboxyl-modified β-cyclodextrin according to claim 2, characterized in that, The dialysis is carried out in water for 80 - 100 h; And / or, the cut-off molecular weight of the dialysis bag used for dialysis is 1000 Da.

6. The all-bio-based vitrimer material based on carboxyl-modified β-cyclodextrin according to claim 1, characterized in that, The solvent 3 includes acetone.

7. The all-biobased vitrimer material based on carboxyl-modified β-cyclodextrin as claimed in claim 1, wherein, The heating reaction includes: refluxing and reacting at 60 °C for 30 - 50 min.

8. The all-bio-based vitrimer material based on carboxyl-modified β-cyclodextrin according to claim 1, characterized in that, The parameters of the hot-press curing include: the pressure is 10 MPa, the temperature is 170 °C, and the time is 4 - 5 h.

9. Use of an all-bio-based vitrimer material based on carboxyl-modified β-cyclodextrin according to any one of claims 1 - 8 in the preparation of medical materials or intelligent packaging materials.

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