Polyhydroxyurethane-ureas and methods for their preparation

Abstract

The application belongs to the technical field of high polymer materials, and discloses a carbon dioxide biobased polyhydroxy urethane-urea with closed-loop recycling and a preparation method thereof. The application takes renewable resources carbon dioxide and vanillin as raw materials, introduces reversible hydrogen bonds and imine bonds, and prepares a series of novel cross-linked polyhydroxy urethane-urea which is new, remodelable, self-repairable and degradable and recyclable. The prepared polyhydroxy urethane-urea exhibits excellent thermal stability and mechanical properties, and the self-repairing efficiency is more than 95%. In addition, the polyhydroxy urethane-urea can be reprocessed and recycled through physical or chemical means without changing the original chemical structure and mechanical properties. The application takes renewable vanillin and carbon dioxide as raw materials, and prepares cross-linked non-isocyanate polyurethane materials with closed-loop recycling through a simple, green and environmentally-friendly synthesis process, and exhibits the potential to replace traditional thermosetting materials.

Description

Technical Field

[0001] This invention relates to the field of polymer technology, and specifically to a method for preparing a closed-loop recyclable carbon dioxide bio-based polyhydroxycarbamate-urea. Background Technology

[0002] Polyurethane (PU) is widely used in textiles, construction, aerospace, shipbuilding, transportation, medicine, and electronics due to its excellent properties. Traditional polyurethane material preparation requires the use of binary or polyisocyanates, but the high toxicity of isocyanates and their synthetic raw material phosgene may pose health and environmental risks. With the development of green chemistry, researchers have conducted a series of studies on the preparation of polyurethane using safe, environmentally friendly, and green production processes. Among these, the preparation of polyhydroxycarbamate (PHU) via addition polymerization using di- or polyfunctional (five-membered cyclic carbonates) and di- or polyamines is considered one of the most effective strategies. Five-membered cyclic carbonates can be synthesized by reacting carbon dioxide with epoxides, and carbon dioxide is considered a major contributor to global warming and climate change. Therefore, the chemical preparation of PHU using carbon dioxide gas is of great significance for the development of sustainable chemistry and the mitigation of the environmental crisis.

[0003] Currently, most polymer materials are produced from non-renewable fossil fuels. The extensive use of fossil fuels has led to a series of environmental problems. Therefore, using renewable resources as raw materials to prepare sustainable polymer materials to replace petroleum-based materials is beneficial for reducing environmental impact and achieving sustainable development. In recent years, various renewable bio-based raw materials have been used to prepare bio-based non-isocyanate polyurethanes (NIPUs). Among them, vanillin, a lignin derivative, is currently the only industrially commercialized bio-based monomer. Therefore, using vanillin as a raw material to construct NIPUs seems to be a better choice. In the PHU crosslinking network, urethane bonds and hydroxyl groups can undergo urethane esterification under temperature stimulation, giving PHU crosslinked materials reprocessing capabilities. However, the urethane esterification process in the PHU crosslinking structure requires high temperature and long time conditions. Prolonged high temperatures lead to side reactions such as oxidation, resulting in performance degradation. Therefore, it is necessary to design the PHU network structure to achieve self-healing and reprocessing under mild conditions.

[0004] Introducing dynamic covalent bonds into polymer crosslinking networks can effectively reduce the activation energy required during remodeling, thereby achieving remodeling at lower temperatures and in shorter timeframes. Currently, various dynamic covalent bonds, such as disulfide bonds, BO bonds, imine bonds, and Diels-Alder bonds, are frequently used in the design of self-healing and recyclable polymers. To date, several self-healing and recyclable carbon dioxide-based polymeric unit (PHU) materials have been reported. In 2021, Yang [Green Chem 2021, 23, 6349-6355.] and colleagues successfully synthesized a novel, self-healing, and recyclable PHU material by introducing disulfide bonds using CO2 and epoxidized soybean oil as raw materials. However, previous studies have not achieved closed-loop recycling of the PHU. Imine bonds are a commonly used dynamic covalent bond, and due to their easy decomposition under acidic conditions and their ability to form under mild conditions, they have great potential in manufacturing bio-based PHUs with closed-loop recyclability. Zhang et al. [Adv. Mater. 2022, 35, 2208619] prepared a ring-closed recyclable thermosetting polymer based on supramolecular interactions—imine bonds. This type of polymer can be degraded and recycled at room temperature. Therefore, it is feasible to combine the degradability of imine bonds and simple synthetic processes with PHU materials. Summary of the Invention

[0005] Addressing the challenges of recycling and environmental friendliness of existing petroleum-based thermosetting materials, this invention utilizes renewable resources such as carbon dioxide and vanillin as raw materials. By introducing reversible hydrogen bonds and imine bonds, a series of novel cross-linked polyhydroxycarbamate-urea materials are prepared, exhibiting remodelability, self-healing properties, and biodegradability. By altering the ratio of urea-containing diamine to triamine, the internal chemical bonds and chain structure of the polyhydroxycarbamate-urea are adjusted, ultimately achieving performance regulation. The prepared polyhydroxycarbamate-urea exhibits excellent thermal stability and mechanical properties. Due to the high reversibility of imine and hydrogen bonds, the prepared polyhydroxycarbamate-urea can achieve self-healing at 60°C with a self-healing efficiency exceeding 95%. Furthermore, polyhydroxycarbamate-urea can be reprocessed and recycled through physical or chemical means without altering its original chemical structure and mechanical properties. This invention, using renewable vanillin and carbon dioxide as raw materials, employs a simple and environmentally friendly synthesis process to prepare cross-linked non-isocyanate polyurethane materials with closed-loop recyclability, demonstrating the potential to replace traditional thermosetting materials.

[0006] To achieve the above objectives, the present invention adopts the following technical solution.

[0007] In a first aspect, this application provides a polyhydroxycarbamate-urea having a structure as shown in general formula I:

[0008]

[0009] In a second aspect, this application provides a method for preparing a closed-loop recyclable carbon dioxide bio-based polyhydroxycarbamate-urea, comprising the following steps:

[0010] (1) Vanillin compounds were placed in a three-necked flask, epichlorohydrin was added, the reaction temperature was 70-90℃, the reaction was carried out for 2-5 hours, and then sodium hydroxide solution was added dropwise. Vanillin-based epoxy compounds were prepared by extraction, crystallization and drying.

[0011] (2) The vanillin-based epoxy compound obtained in (1) is put into a closed reaction vessel, a catalyst is added, the reaction temperature is 120-170℃, the carbon dioxide pressure in the reaction vessel is 2-5MPa, and the reaction is carried out for 6-12h to prepare a vanillin-based five-membered cyclic carbonate compound.

[0012] (3) Add diamine compounds into a closed reaction vessel, react at a temperature of 180-200℃, with a carbon dioxide pressure of 2-5MPa inside the reaction vessel, and react for 6-12 hours to prepare amino-terminated polyurea oligomers.

[0013] (4) The vanillin-based five-membered cyclic carbonate compound prepared in step (2), the amino-terminated polyurea oligomer prepared in step (3) and the crosslinking agent polyamine are put into a reaction flask, an appropriate amount of solvent is added, nitrogen gas is introduced as a protective gas, the reaction temperature is 80-150℃, and the reaction time is 10-14h to prepare carbon dioxide bio-based polyhydroxycarbamate-urea.

[0014] Preferably, in step (1), the vanillin compound is at least one of m-hydroxybenzaldehyde, o-hydroxybenzaldehyde, p-hydroxybenzaldehyde, vanillin, o-vanillin and ethylvanillin.

[0015] Preferably, in step (1), the catalyst is one of tetrabutylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium hydrogen sulfate, trioctylmethylammonium chloride, dodecyltrimethylammonium chloride and tetradecyltrimethylammonium chloride.

[0016] Preferably, in step (1), the reaction temperature is 70-90°C.

[0017] Preferably, in step (2), the carbon dioxide pressure is 2-5 MPa.

[0018] Preferably, in step (2), the reaction time is 6-12 hours.

[0019] Preferably, in step (3), the diamine compound is at least one of hexamethylenediamine, polyetheramine D-230, 1,8-diamino-3,6-dioxaoctane, 1,11-diamino-3,6,9-trioxaundecanane, and 4,7,10-trioxa-1,13-tridecanediamine.

[0020] Preferably, in step (4), the polyamine crosslinking agent used is at least one of tris(2-aminoethyl)amine, trimethylolpropane tripropylene glycol ether (amino-terminated), and 3,3',4,4'-biphenyltetramine.

[0021] Preferably, in step (4), the ratio of the amount of amino-terminated polyurea oligomer to the amount of crosslinking agent polyamine used is (0.5-2.5):1.

[0022] Preferably, in step (4), the solvent is at least one of N,N-dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone.

[0023] Preferably, in step (4), the amount of solvent added is 100-200% of the total mass of vanillin-based pentaneous cyclic carbonate compound, amino-terminated polyurea oligomer, and crosslinking agent.

[0024] Preferably, in step (4), the reaction temperature is 80-150℃ and the reaction time is 10-14h.

[0025] Compared with the prior art, the present invention has the following obvious and prominent substantive features and significant advantages:

[0026] 1. This invention uses renewable vanillin and carbon dioxide as raw materials to prepare polyhydroxycarbamate-urea materials, which can effectively alleviate the current tight supply of petroleum resources and contribute to the carbon peaking and carbon neutrality strategy;

[0027] 2. The polyhydroxycarbamate-urea material prepared by this invention has similar reprocessability, self-healing and closed-loop recyclability to thermoplastic materials, providing a new approach to solving the environmental pollution and resource waste caused by traditional petroleum-based thermosetting polymer materials;

[0028] 3. This invention can adjust the degree of crosslinking of polyhydroxycarbamate-urea by controlling the ratio of amino-terminated polyurea oligomer and crosslinking agent triamine, thereby ultimately achieving the adjustment of its thermal and mechanical properties;

[0029] 4. The synthesis process described in this invention has the advantages of mild reaction conditions, simple process, and green environmental protection. Attached Figure Description

[0030] Figure 1The infrared spectrum of VL-TTD*s.

[0031] Figure 2 The graph shows the gel content of VL-TTD*s.

[0032] Figure 3 The mechanical property curves of VL-TTD*s are shown.

[0033] Figure 4 The curve is the VL-TTD*s DSC curve.

[0034] Figure 5 Infrared spectra of VL-TTD*-50 before and after hot-pressing recovery.

[0035] Figure 6 The mechanical property curves of VL-TTD*-50 before and after hot-pressing recovery are shown.

[0036] Figure 7 The mechanical property recovery curve of VL-TTD*-50 during self-healing process.

[0037] Figure 8 Infrared spectra of samples before and after VL-TTD*-50 closed-loop recovery.

[0038] Figure 9 The mechanical property curves of the VL-TTD*-50 samples before and after closed-loop recovery are shown.

[0039] Figure 10 Show the synthesis route diagram of VL-TTD*s. Detailed Implementation

[0040] Unless otherwise stated, implied from the context, or as is customary in the art, all parts and percentages in this application are based on weight, and all testing and characterization methods used are concurrent with the filing date of this application. Where applicable, any patent, patent application, or disclosure relating to this application is incorporated herein by reference in its entirety, and its equivalent patent families are also incorporated herein by reference, particularly the definitions disclosed in these documents concerning synthetic techniques, product and processing design, polymers, comonomers, initiators, or catalysts in the art. If any definition of a specific term disclosed in the prior art is inconsistent with any definition provided in this application, the definition provided in this application shall prevail.

[0041] The numerical ranges in this application are approximate values ​​and therefore may include values ​​outside the range unless otherwise stated. A numerical range includes all values ​​from the lower limit to the upper limit, increasing by one unit, provided there is an interval of at least two units between any lower and any higher value. For example, if a component, physical, or other property (such as molecular weight, melt index, etc.) is described as 100 to 1000, this means that all individual values, such as 100, 101, 102, etc., are explicitly listed, as well as all subranges, such as 100 to 166, 155 to 170, 198 to 200, etc. For ranges containing values ​​less than 1 or fractions greater than 1 (e.g., 1.1, 1.5, etc.), one unit is appropriately considered as 0.0001, 0.001, 0.01, or 0.1. For ranges containing single digits less than 10 (e.g., 1 to 5), one unit is generally considered as 0.1. These are merely specific examples of what is intended to be expressed, and all possible combinations of values ​​between the listed minimum and maximum values ​​are considered to be clearly stated in this application. It should also be noted that the terms "first," "second," etc., used herein are not intended to specify a particular order, but are merely used to distinguish substances with different structures.

[0042] When referring to chemical compounds, unless explicitly stated otherwise, the singular includes all isomers and vice versa (e.g., "hexane" includes all isomers of hexane, individually or collectively). Additionally, unless explicitly stated otherwise, nouns described with "an," "a," or "the" also include their plural forms.

[0043] The terms “comprising,” “including,” “having,” and their derivatives do not exclude the presence of any other components, steps, or processes, regardless of whether such other components, steps, or processes are disclosed in this application. To eliminate any doubt, unless expressly stated otherwise, all compositions using the terms “comprising,” “including,” or “having” in this application may contain any additional additives, excipients, or compounds. Conversely, except for those necessary for operational performance, the term “substantially constitutes…” excludes any other components, steps, or processes described below with respect to that term. The term “consisting of…” does not include any components, steps, or processes not specifically described or listed. Unless expressly stated otherwise, the term “or” refers to the individual members listed or any combination thereof.

[0044] like Figure 10 As shown, this invention provides a method for preparing a closed-loop recyclable carbon dioxide bio-based polyhydroxycarbamate-urea, comprising the following steps:

[0045] (1) Vanillin compounds were put into a three-necked flask, epichlorohydrin was added, the reaction temperature was 70-90℃, the reaction was carried out for 2-5 hours, sodium hydroxide solution was added dropwise, and then the vanillin-based epoxy compounds were prepared by extraction, crystallization and drying.

[0046] (2) The vanillin-based epoxy compound obtained in (1) is put into a closed reaction vessel, a catalyst is added, the reaction temperature is 120-170℃, the carbon dioxide pressure in the reaction vessel is 2-5MPa, and the reaction is carried out for 6-12h to prepare a vanillin-based five-membered cyclic carbonate compound.

[0047] (3) Add diamine compounds into a closed reaction vessel, react at a temperature of 180-200℃, with a carbon dioxide pressure of 2-5MPa inside the reaction vessel, and react for 6-12 hours to prepare amino-terminated polyurea oligomers.

[0048] (4) The vanillin-based five-membered cyclic carbonate compound prepared in step (2), the amino-terminated polyurea oligomer prepared in step (3) and the crosslinking agent polyamine are put into a reaction flask, an appropriate amount of solvent is added, nitrogen gas is introduced as a protective gas, and the reaction is carried out to prepare carbon dioxide bio-based polyhydroxycarbamate-urea (VL-TTD*s).

[0049] In step (1), the vanillin compound is at least one of m-hydroxybenzaldehyde, o-hydroxybenzaldehyde, p-hydroxybenzaldehyde, vanillin, o-vanillin and ethylvanillin, and vanillin is selected in the specific embodiment.

[0050] In step (1), the catalyst is one of tetrabutylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium hydrogen sulfate, trioctylmethylammonium chloride, dodecyltrimethylammonium chloride and tetradecyltrimethylammonium chloride. In a specific embodiment, tetrabutylammonium bromide is selected.

[0051] In step (1), the reaction temperature is 70-90℃, and in a specific embodiment, the reaction temperature is 80℃.

[0052] In step (2), the carbon dioxide pressure is 2-5 MPa, and in a specific embodiment, the carbon dioxide pressure is 3.0 MPa.

[0053] In step (2), the reaction time is 6-12 hours, and in a specific embodiment, the reaction time is 10 hours.

[0054] In step (3), the diamine compound is at least one of hexamethylenediamine, polyetheramine D-230, 1,8-diamino-3,6-dioxaoctane, 1,11-diamino-3,6,9-trioxaundecanane, and 4,7,10-trioxa-1,13-tridecanediamine. In a specific embodiment, 4,7,10-trioxa-1,13-tridecanediamine is selected.

[0055] In step (4), the polyamine crosslinking agent used is at least one of tri(2-aminoethyl)amine, trimethylolpropane tripropylene glycol ether (amino-terminated) and 3,3',4,4'-biphenyltetramine. In a specific embodiment, tri(2-aminoethyl)amine is selected.

[0056] In step (4), the ratio of the amount of amino-terminated polyurea oligomer to the amount of crosslinking agent polyamine used is (0.5-2.5):1, and in specific embodiments it is 7:3, 6:4, 5:5 and 4:6.

[0057] In step (4), the solvent is at least one of N,N-dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone, with dimethyl sulfoxide selected in a specific embodiment.

[0058] In step (4), the amount of solvent added is 100-200% of the total mass of vanillin-based five-membered cyclic carbonate compound, amino-terminated polyurea oligomer and crosslinking agent, and is 150% in a specific embodiment.

[0059] In step (4), the reaction temperature is 80-150℃ and the reaction time is 10-14h. In a specific embodiment, the reaction temperature is 120℃ and the reaction time is 12h.

[0060] The above solution will be further described below with reference to specific embodiments. The preferred embodiments of the present invention are described in detail below:

[0061] Example 1

[0062] In this embodiment, a method for preparing a carbon dioxide-based polyhydroxycarbamate-urea includes the following steps:

[0063] Step 1: Add 20.0 g vanillin, 80.0 g epichlorohydrin, and 1.0 g tetrabutylammonium bromide to a three-necked round-bottom flask. Heat the mixture to 80 °C for 3 hours, then cool to 16 °C. Slowly add 50 wt% sodium hydroxide dropwise to the reaction solution while stirring vigorously for 3 hours. Then add a certain amount of dichloromethane and deionized water, and stir for 1 hour. Pour the mixed solution into a separating funnel to separate the organic layer, and wash three times with deionized water. Slowly pour the organic layer into a certain amount of petroleum ether, stir vigorously for 5 hours, filter the precipitate, and wash three times with ethanol. Dry in an oven at 60 °C for 12 hours to obtain the vanillin-based epoxy compound (VL-H).

[0064] Step 2: Add 20g of vanillin-based epoxy compound and 0.1g of tetrabutylammonium bromide to a stainless steel reactor. After sealing, rinse the reactor three times with carbon dioxide gas to remove air. Heat to 150℃ and keep warm for 25 minutes. Then, introduce carbon dioxide gas into the reactor to 3MPa, turn on the magnetic stirrer, and react for 12 hours to obtain vanillin-based five-membered cyclic carbonate compound (VL-C).

[0065] Step 3: Add 10g of 4,7,10-trioxo-1,13-tetanediamine to a stainless steel high-pressure reactor, seal it, and flush the system three times with carbon dioxide gas to remove air from the reactor. Then, introduce carbon dioxide gas to 3MPa, raise the temperature to 180℃, turn on magnetic stirring, and react for 10h to obtain amino-terminated polyurea oligomer (TTD*).

[0066] Step 4: Add 2.0g vanillin-based cyclic carbonate, 3.2g TTD*, 0.33g tris(2-aminoethyl)amine and 8mL dimethyl sulfoxide to a three-necked flask. Under nitrogen protection, heat to 120℃ and react for 12h. Pour into a silicone rubber mold, then place in an oven and dry at 60℃ for 48h. After drying, place in a vacuum oven and cure at 100℃ for 24h to obtain polyhydroxycarbamate-urea (VL-TTD*-30).

[0067] Example 2

[0068] This embodiment is basically the same as that in Embodiment 1, except that:

[0069] In this embodiment, a method for preparing a carbon dioxide-based polyhydroxycarbamate-urea includes the following steps:

[0070] Step 1: Add 20.0 g vanillin, 80.0 g epichlorohydrin, and 1.0 g tetrabutylammonium bromide to a three-necked round-bottom flask. Heat the mixture to 80 °C for 3 hours, then cool to 16 °C. Slowly add 50 wt% sodium hydroxide dropwise to the reaction solution while stirring vigorously for 3 hours. Then add a certain amount of dichloromethane and deionized water, and stir for 1 hour. Pour the mixed solution into a separating funnel to separate the organic layer, and wash three times with deionized water. Slowly pour the organic layer into a certain amount of petroleum ether, stir vigorously for 5 hours, filter the precipitate, and wash three times with ethanol. Dry in an oven at 60 °C for 12 hours to obtain vanillin-based epoxy compounds.

[0071] Step 2: Add 20g of vanillin-based epoxy compound and 0.1g of tetrabutylammonium bromide to a stainless steel reactor. After sealing, rinse the reactor three times with carbon dioxide gas to remove air. Heat to 150℃ and keep warm for 25 minutes. Then introduce carbon dioxide gas into the reactor to 3MPa, turn on the magnetic stirrer, and react for 12 hours to obtain vanillin-based five-membered cyclic carbonate compound.

[0072] Step 3: Add 10g of 4,7,10-trioxo-1,13-tetanediamine to a stainless steel high-pressure reactor, seal it, and flush the system three times with carbon dioxide gas to remove air from the reactor. Then, introduce carbon dioxide gas to 3MPa, raise the temperature to 180℃, turn on magnetic stirring, and react for 10h to obtain amino-terminated polyurea oligomers.

[0073] Step 4: Add 2.0g vanillin-based cyclic carbonate, 2.63g TTD*, 0.43g tris(2-aminoethyl)amine and 8mL dimethyl sulfoxide to a three-necked flask. Under nitrogen protection, heat to 120℃ and react for 12h. Pour the mixture into a silicone rubber mold, then place it in an oven and dry at 60℃ for 48h. After drying, place it in a vacuum oven and cure at 100℃ for 24h to obtain polyhydroxycarbamate-urea (VL-TTD*-40).

[0074] Example 3

[0075] This embodiment is basically the same as the previous embodiments, except that:

[0076] In this embodiment, a method for preparing a carbon dioxide-based polyhydroxycarbamate-urea includes the following steps:

[0077] Step 1: Add 20.0 g vanillin, 80.0 g epichlorohydrin, and 1.0 g tetrabutylammonium bromide to a three-necked round-bottom flask. Heat the mixture to 80 °C for 3 hours, then cool to 16 °C. Slowly add 50 wt% sodium hydroxide dropwise to the reaction solution while stirring vigorously for 3 hours. Then add a certain amount of dichloromethane and deionized water, and stir for 1 hour. Pour the mixed solution into a separating funnel to separate the organic layer, and wash three times with deionized water. Slowly pour the organic layer into a certain amount of petroleum ether, stir vigorously for 5 hours, filter the precipitate, and wash three times with ethanol. Dry in an oven at 60 °C for 12 hours to obtain vanillin-based epoxy compounds.

[0078] Step 2: Add 20g of vanillin-based epoxy compound and 0.1g of tetrabutylammonium bromide to a stainless steel reactor. After sealing, rinse the reactor three times with carbon dioxide gas to remove air. Heat to 150℃ and keep warm for 25 minutes. Then introduce carbon dioxide gas into the reactor to 3MPa, turn on the magnetic stirrer, and react for 12 hours to obtain vanillin-based five-membered cyclic carbonate compound.

[0079] Step 3: Add 10g of 4,7,10-trioxo-1,13-tetanediamine to a stainless steel high-pressure reactor, seal it, and flush the system three times with carbon dioxide gas to remove air from the reactor. Then, introduce carbon dioxide gas to 3MPa, raise the temperature to 180℃, turn on magnetic stirring, and react for 10h to obtain amino-terminated polyurea oligomers.

[0080] Step 4: Add 2.0g vanillin-based cyclic carbonate, 2.1g TTD*, 0.51g tris(2-aminoethyl)amine and 8mL dimethyl sulfoxide to a three-necked flask. Under nitrogen protection, heat to 120℃ and react for 12h. Pour into a silicone rubber mold, then place in an oven and dry at 60℃ for 48h. After drying, place in a vacuum oven and cure at 100℃ for 24h to obtain polyhydroxycarbamate-urea (VL-TTD*-50).

[0081] Example 4

[0082] This embodiment is basically the same as the previous embodiments, except that:

[0083] In this embodiment, a method for preparing a carbon dioxide-based polyhydroxycarbamate-urea includes the following steps:

[0084] Step 1: Add 20.0 g vanillin, 80.0 g epichlorohydrin, and 1.0 g tetrabutylammonium bromide to a three-necked round-bottom flask. Heat the mixture to 80 °C for 3 hours, then cool to 16 °C. Slowly add 50 wt% sodium hydroxide dropwise to the reaction solution while stirring vigorously for 3 hours. Then add a certain amount of dichloromethane and deionized water, and stir for 1 hour. Pour the mixed solution into a separating funnel to separate the organic layer, and wash three times with deionized water. Slowly pour the organic layer into a certain amount of petroleum ether, stir vigorously for 5 hours, filter the precipitate, and wash three times with ethanol. Dry in an oven at 60 °C for 12 hours to obtain vanillin-based epoxy compounds.

[0085] Step 2: Add 20g of vanillin-based epoxy compound and 0.1g of tetrabutylammonium bromide to a stainless steel reactor. After sealing, rinse the reactor three times with carbon dioxide gas to remove air. Heat to 150℃ and keep warm for 25 minutes. Then introduce carbon dioxide gas into the reactor to 3MPa, turn on the magnetic stirrer, and react for 12 hours to obtain vanillin-based five-membered cyclic carbonate compound.

[0086] Step 3: Add 10g of 4,7,10-trioxo-1,13-tetanediamine to a stainless steel high-pressure reactor, seal it, and flush the system three times with carbon dioxide gas to remove air from the reactor. Then, introduce carbon dioxide gas to 3MPa, raise the temperature to 180℃, turn on magnetic stirring, and react for 10h to obtain amino-terminated polyurea oligomers.

[0087] Step 4: Add 2.0g vanillin-based cyclic carbonate, 1.62g TTD*, 0.59g tris(2-aminoethyl)amine and 8mL dimethyl sulfoxide to a three-necked flask. Under nitrogen protection, heat to 120℃ and react for 12h. Pour the mixture into a silicone rubber mold, then place it in an oven and dry at 60℃ for 48h. After drying, place it in a vacuum oven and cure at 100℃ for 24h to obtain polyhydroxycarbamate-urea (VL-TTD*-60).

[0088] Experimental test analysis

[0089] like Figure 1 and 2 As shown in the infrared spectrum of VL-TTD*s, the range is 3000–2800 cm⁻¹. -1 The peaks are characteristic of NH and CH; compared with VL-C, the peak at 1793 cm⁻¹ is... -1 The C=O tensile vibration peaks in the cyclic carbonate structure completely disappear, and the peaks at 3340, 1641, and 1097 cm⁻¹ disappear. -1 Tensile vibration peaks belonging to -OH, C=N, and COC were observed at the specified locations. Simultaneously, gel content testing results showed that the gel content of all samples exceeded 85%. These structural findings indicate that VL-TTD*s with cross-linked structures were successfully prepared.

[0090] like Figure 3 and 4 As shown, with increasing crosslinking degree, the tensile strength of VL-TTD* increases, while the elongation at break decreases; when the TA content increases from 30% to 60%, the tensile strength of VL-TTD*s increases from 0.6 MPa to 6.4 MPa, while the elongation at break decreases from 1238.0% to 171.4%. Furthermore, the Tt of VL-TTD*s... g The value increases with increasing crosslinking density. This can all be attributed to the fact that a higher crosslinking density restricts the movement of VL-TTD*s molecular chains.

[0091] like Figure 5 and Figure 6 As shown, after multiple hot-pressing and recycling processes, the structure and mechanical properties of VL-TTD*-50 showed no significant changes, indicating that VL-TTD*s have good stability in repeated processing.

[0092] like Figure 7 As shown, with the further extension of the self-healing time, the tensile strength of the sample gradually increased, eventually reaching 2.5 MPa, and the healing rate was 95%. The results indicate that VL-TTD*s has good self-healing ability.

[0093] like Figure 8 and 9 As shown, the regenerated VL-TTD*-50 obtained through closed-loop recycling showed no significant changes in structure and mechanical properties compared to the original sample, indicating that the closed-loop recycling scheme is feasible.

[0094] In summary, in this embodiment of the invention, vanillin-based cyclic carbonates and amino-terminated polyurea oligomers were prepared using renewable resources vanillin and carbon dioxide as raw materials, respectively. These were then reacted with a triamine crosslinking agent to obtain a series of polyhydroxycarbamate-urea compounds with different degrees of crosslinking. With increasing crosslinking density, the tensile strength and thermal properties of VL-TTD*s improved. Simultaneously, VL-TTD*-50 exhibited excellent hot-pressing remolding efficiency (close to 98.0%) and tensile strength self-healing efficiency (over 95.0%). Furthermore, in a 1M HCl / THF (v:v = 2:8) mixed solution, VL-TTD*-50 can degrade at room temperature and then be regenerated without altering its original chemical structure and mechanical properties, achieving closed-loop recycling of VL-TTD*-50.

[0095] The above embodiments illustrate a method for preparing carbon dioxide-based bio-based polyhydroxycarbamate-urea with closed-loop recyclability. This invention utilizes renewable carbon dioxide and vanillin to prepare a series of cross-linked polyhydroxycarbamate-ureas with reprocessability, self-healing properties, and closed-loop recyclability. The prepared polyhydroxycarbamate-ureas exhibit excellent thermal stability and solvent resistance. Furthermore, the mechanical and thermal properties of the polyhydroxycarbamate-urea can be adjusted by modifying the ratio of amino-terminated polyurea oligomers and triamines. By introducing reversible hydrogen and imine bonds into the cross-linked network, the samples exhibited significant hot-pressing remodeling efficiency (close to 98.0%) and self-healing efficiency (over 95.0%) at 60°C. Moreover, the polyhydroxycarbamate-urea can achieve closed-loop recycling under mild conditions. This work proposes a novel strategy for developing self-healing and closed-loop recyclable polyhydroxycarbamates as alternatives to traditional polyurethanes (PUs) from renewable resources.

[0096] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Various changes can be made according to the purpose of the invention. Any changes, modifications, substitutions, combinations or simplifications made based on the spirit and principle of the technical solution of the present invention shall be equivalent substitutions. As long as they meet the purpose of the invention and do not deviate from the technical principle and inventive concept of the present invention, they shall fall within the protection scope of the present invention.

Claims

1. A polyhydroxycarbamate-urea, characterized in that, It has a structure as shown in general formula I: General Formula I; Where R is or .

2. The method for preparing polyhydroxycarbamate-urea according to claim 1, characterized in that, The method includes the following steps: (1) Vanillin was put into a three-necked flask, epichlorohydrin was added, the reaction temperature was 70-90℃, the reaction was carried out for 2-5 h, sodium hydroxide solution was added dropwise, and then vanillin-based epoxy compounds were prepared by extraction, crystallization and drying. (2) The vanillin-based epoxy compound obtained in step (1) is put into a closed reaction vessel, a catalyst is added, the reaction temperature is 120-170℃, the carbon dioxide pressure in the reaction vessel is 2-5 MPa, and the reaction is carried out for 6-12 h to prepare vanillin-based five-membered cyclic carbonate compound. (3) Add diamine compounds into a closed reactor, react at 180-200℃, with carbon dioxide pressure of 2-5 MPa inside the reactor, and react for 6-12 h to prepare amino-terminated polyurea oligomers. (4) The vanillin-based five-membered cyclic carbonate compound prepared in step (2), the amino-terminated polyurea oligomer prepared in step (3) and the crosslinking agent polyamine are put into a reaction flask, an appropriate amount of solvent is added, nitrogen gas is introduced as a protective gas, the reaction temperature is 80-150℃, and the reaction time is 10-14 h to prepare carbon dioxide bio-based polyhydroxycarbamate-urea; In step (3), the diamine compound is 1,11-diamino-3,6,9-trioxaundecan or 4,7,10-trioxa-1,13-tridecanediamine; In step (4), the crosslinking agent polyamine used is tris(2-aminoethyl)amine.

3. The preparation method according to claim 2, characterized in that, In step (2), the catalyst is one of tetrabutylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium hydrogen sulfate, trioctylmethylammonium chloride, dodecyltrimethylammonium chloride and tetradecyltrimethylammonium chloride.

4. The preparation method according to claim 2, characterized in that, In step (4), the ratio of the amount of amino-terminated polyurea oligomer to the amount of crosslinking agent polyamine is (0.5-2.5):

1.

5. The preparation method according to claim 2, characterized in that, In step (4), the solvent is at least one of N,N-dimethylformamide, dimethyl sulfoxide and N-methylpyrrolidone.

6. The preparation method according to claim 2, characterized in that, In step (4), the amount of solvent added is 100-200% of the total mass of vanillin-based five-membered cyclic carbonate compound, amino-terminated polyurea oligomer and crosslinking agent polyamine.

Images