A recyclable and hydrolytically degradable polyurethane vitreous body, its preparation method and application

Abstract

This invention belongs to the field of biodegradable materials and discloses a recyclable and hydrolytically degradable polyurethane-like glass, its preparation method, and its applications. The preparation method includes: dispersing a macromolecular diol, a B-N internally coordinated cyclic boron ester diol, a small molecule polyol, and a diisocyanate in a polar solvent; mixing and adding a catalyst to carry out a polymerization reaction; followed by a curing reaction and solvent removal to obtain the recyclable and hydrolytically degradable polyurethane-like glass. The polyurethane-like glass prepared by this invention contains stable boron ester dynamic covalent bonds. Under certain stimulating conditions, the material can be reshaped, degraded, and recycled through the breaking and recombination of boron esters. Therefore, it can not only achieve the reshaping of thermosetting polyurethane under mild conditions but also achieve hydrolytic recycling under relatively mild conditions without a catalyst, thus having high value for the complete recycling of resin-based composite materials.

Description

Technical Field

[0001] This invention relates to the field of biodegradable materials technology, and in particular to a recyclable and hydrolytically degradable polyurethane-based glass body, its preparation method, and its application. Background Technology

[0002] Polyurethane is one of the most widely commercialized polymer materials (ranking sixth among all polymers) and is widely used in many fields due to its excellent properties. Thermosetting polyurethane materials, in particular, possess superior dimensional stability, mechanical properties, creep resistance, and chemical resistance due to their irreversible covalent cross-linked network, making them widely used in a variety of demanding applications. However, the cross-linked structure restricts the flowability of the polymer chains. Therefore, once fully cured, the highly cross-linked chemical structure makes thermosetting polyurethane materials insoluble and inmeltable, unable to be reprocessed and reused. Consequently, the inability to reprocess and reuse them after disposal results in serious resource waste and environmental pollution.

[0003] Dynamic covalent bonds can be "broken" and "reconstructed" under external stimuli (heat, light, force, pH), thereby enabling the recycling of polymer materials through changes in molecular-scale topology. Therefore, introducing dynamic covalent bonds, which combine the dynamic reversibility of non-covalent bonds with the stability of covalent bonds, into thermosetting polymers allows them to possess the excellent mechanical properties, chemical and dimensional stability of traditional thermosetting materials, while also enabling self-healing, reprocessing, and recycling of cross-linked polymers under certain external stimuli. In particular, during the exchange reaction of dynamic covalent bonds in the covalent adaptive network, the breaking of original covalent bonds and the formation of new covalent bonds occur simultaneously. Throughout the process, the thermosetting polymer system based on dynamic covalent bonds maintains a stable cross-linking density and an intact network structure. In 2011, the Leibler team first proposed the concept of "vitrimer," which exhibits glass-like rheological behavior at high temperatures, hence the term "glass-like polymer."

[0004] Currently, the main types of dynamic covalent bonds include transesterification, urethane exchange, imine exchange, disulfide exchange, and borate ester exchange. Transesterification and urethane exchange typically require additional catalysts or high temperatures, which can easily lead to catalyst leakage and deactivation, material aging, and side reactions. Disulfide exchange is a complex process, potentially involving the oxidation of thiol groups, quenching of free radicals, and the need for high temperatures or light exposure. Imine exchange usually requires acidic conditions. Borate ester bonds have high bond energies, allowing for repeated extrusion or injection molding of glass-like materials at high temperatures without catalysts through metathesis reactions. However, borate ester structures are highly susceptible to hydrolysis. To address this issue, Professor Jing Xinli's research group proposed a strategy to improve the stability of borate ester groups using boron-nitrogen internal coordination. By introducing the highly stable dynamic covalent bond structure of boron-nitrogen internally coordinated cyclic borate diesters (NCB) into a polymer crosslinking network, they synthesized NCB-based glass-like materials with higher water and thermal stability. However, due to its high crosslinking density, its hot-pressing recovery requires very high temperatures. Furthermore, its liquid-phase recovery process is also quite complex. Therefore, although this boron ester structure exhibits excellent hydrothermal stability, its cumbersome recovery process and demanding remolding conditions limit its application in the field of functional materials.

[0005] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of this invention is to provide a remodelable and hydrolytically degradable recyclable polyurethane glass-like body, its preparation method and application, aiming to solve the problem that the existing borosilicate glass-like bodies are restricted from the application in the field of functional materials due to the cumbersome recycling process and the harsh remodeling conditions.

[0007] The technical solution of the present invention is as follows:

[0008] A first aspect of the present invention provides a method for preparing a recyclable and hydrolytically degradable polyurethane-based glass, comprising the steps of:

[0009] Macromolecular diols, BN-coordinated cyclic boron ester diols, small molecule polyols, and diisocyanates were dispersed in polar solvents to obtain solutions A, B, C, and D, respectively.

[0010] Solution A is mixed with solution D, a catalyst is added, and the mixture is reacted at 60–80°C for 1–3 hours to obtain solution E;

[0011] Solution B is added to solution E and reacted at 60–80°C for 0.5–2 hours to obtain solution F;

[0012] Solution C is added to solution F, and the reaction is carried out at 60-80°C for 0.5-2 hours. Then, the mixture is transferred to a mold and cured at 60-90°C for 6-24 hours. After removing the solvent, the remodelable and hydrolyzable recyclable polyurethane glass is obtained.

[0013] Optionally, the macromolecular diol includes one or more of polyethylene glycol, polyester polyol, polypropylene glycol, polytetrahydrofuran polyol, polycarbonate polyol, polycaprolactone polyol, and hydroxyl-terminated polydimethylsiloxane.

[0014] Optionally, the borate ester diol has the chemical structural formulas shown in formulas (I) to (VII):

[0015]

[0016] Optionally, the small molecule polyol includes one or more of glycerol, trimethylolpropane, hexanetriol, and pentaerythritol.

[0017] Optionally, the diisocyanate includes one or more of isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, phenylmethylene diisocyanate, hydrogenated phenylmethylene diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, lysine diisocyanate, and naphthalene diisocyanate.

[0018] Optionally, the catalyst is one or more of the following: dimethylaminoethyl ether, pentamethyldiethylenetriamine, dimethylcyclohexylamine, dibutyltin dilaurate, organobismuth, triazine trimer catalyst, stannous octoate, and dibutyltin maleate.

[0019] Optionally, the ratio between the total molar amount of alcohol hydroxyl groups contained in the macromolecular diol, the BN-coordinated cyclic boron ester diol and the small molecule polyol and the molar amount of isocyanate groups contained in the diisocyanate is 1:(0.8~1.4).

[0020] Optionally, the mass of the catalyst accounts for 0.05% to 5% of the theoretical mass of the polyurethane glass, wherein the theoretical mass of the polyurethane glass is the sum of the masses of the macromolecular diol, the cyclic boron ester diol coordinated within BN, the small molecule polyol, and the diisocyanate.

[0021] Optionally, the polar solvent is one or more of acetone, tetrahydrofuran, ethyl acetate, N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), benzene, toluene, butyl acetate, xylene and cyclohexanone, dichloromethane and chloroform.

[0022] Optionally, the solvent removal step includes: removing the solvent under vacuum at 75–130°C for 6–48 hours.

[0023] In a second aspect, the present invention provides a recyclable and hydrolytically degradable polyurethane-based glass body, which is prepared by the method for preparing the polyurethane-based glass body.

[0024] A third aspect of the present invention provides the application of a remodelable and hydrolytically degradable polyurethane glass body in coatings, adhesives, and flexible sensors.

[0025] Beneficial Effects: This invention provides a method for preparing polyurethane-like glass based on the dynamic covalent bonds of boron esters. The macromolecular diol used has a flexible molecular structure and more easily movable molecular chains, thus facilitating remodeling and degradation. When the temperature is raised to a certain level, the boron ester begins an exchange reaction, at which point the system viscosity decreases, allowing the material to be hot-pressed. The BN-coordinated cyclic boron ester diol enhances the water stability of the boron ester; however, at high temperatures, the BN coordination is unstable and may even be disrupted, leading to easy hydrolysis of the boron ester bonds. Especially with the synergistic effect of the good solvent of polyurethane, water molecules more easily contact the boron ester structure in the material, further accelerating the hydrolysis of the boron ester, destroying the cross-linked network, and thus achieving material degradation. Therefore, the polyurethane-like glass prepared by this invention not only enables the remodeling of thermosetting polyurethane under mild conditions but also allows for water degradation and recycling under relatively mild conditions without the need for catalysts, which is of great value for the complete recycling of resin-based composite materials. Attached Figure Description

[0026] Figure 1 This is a macroscopic photograph of the polyurethane-like glass sample prepared in Example 1.

[0027] Figure 2 The image shows the Fourier transform infrared (FT-IR) spectrum of the polyurethane glass obtained in Example 1.

[0028] Figure 3 The stress-strain curves are shown for the original sample of the polyurethane glass prepared in Example 1 and the recovered sample after hot pressing.

[0029] Figure 4 The results are the dynamic light scattering (DLS) test results of the polyurethane-like glass obtained in Example 1 after degradation.

[0030] Figure 5 The stress-strain curves are shown for the original sample and the recovered sample after hydrolysis and recovery of the polyurethane glass prepared in Example 1. Detailed Implementation

[0031] This invention provides a recyclable and hydrolytically degradable polyurethane-based vitreous body, its preparation method, and its applications. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0032] Unless otherwise defined, 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. The terminology used herein in the description of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0033] This invention provides a method for preparing a recyclable and hydrolytically degradable polyurethane-based glass, comprising the following steps:

[0034] Macromolecular diols, BN-coordinated cyclic boron ester diols, small molecule polyols, and diisocyanates were dispersed in polar solvents to obtain solutions A, B, C, and D, respectively.

[0035] Solution A is mixed with solution D, a catalyst is added, and the mixture is reacted at 60–80°C for 1–3 hours to obtain solution E;

[0036] Solution B is added to solution E and reacted at 60–80°C for 0.5–2 hours to obtain solution F;

[0037] Solution C is added to solution F, and the reaction is carried out at 60-80°C for 0.5-2 hours. Then, the mixture is transferred to a mold and cured at 60-90°C for 6-24 hours. After removing the solvent, the remodelable and hydrolyzable recyclable polyurethane glass is obtained.

[0038] In some embodiments, the macromolecular diol includes one or more of polyethylene glycol, polyester polyol, polypropylene glycol, polytetrahydrofuran polyol, polycarbonate polyol, polycaprolactone polyol, and hydroxyl-terminated polydimethylsiloxane.

[0039] In the preparation of polyurethane-based glass bodies, the macromolecular diols used in the embodiments of this invention have a flexible molecular structure and their molecular chains are more easily movable, thus facilitating reshaping and degradation. When the temperature is raised to a certain level, the borate ester begins to undergo an exchange reaction. At this point, the viscosity of the system decreases, allowing the polyurethane-based glass body material to be hot-pressed.

[0040] In some embodiments, the borate ester diol has the chemical structural formulas shown in formulas (I) to (VII):

[0041]

[0042] In the preparation of polyurethane-like glass, the boron-nitrogen internal coordination and bicyclic structure of the aforementioned boron ester diol employed in this invention improve the hydrothermal stability of the boron ester structure, avoiding the problem of excessive sensitivity of the boron ester group to water or heat. This allows it to exhibit the excellent stability and mechanical properties of traditional thermosetting polymer materials during use. Although the BN internal coordination structure can improve the water stability of boron esters, at high temperatures, the BN internal coordination is unstable and may even be destroyed, leading to easy hydrolysis of the boron ester bonds. Especially under the synergistic effect of the good solvent of polyurethane, water molecules can more easily contact the boron ester structure in the material, further accelerating the hydrolysis of the boron ester, destroying the cross-linked network, and thus achieving the degradation of the material. After the water is removed, the material can be returned to the original sample through an esterification reaction, ultimately achieving simple and complete recovery of polyurethane-like glass under mild conditions without a catalyst.

[0043] In some embodiments, the small molecule polyol includes one or more of glycerol, trimethylolpropane, hexanetriol, and pentaerythritol, but is not limited thereto.

[0044] In some embodiments, the diisocyanate includes, but is not limited to, one or more of isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, phenylmethylene diisocyanate, hydrogenated phenylmethylene diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, lysine diisocyanate, and naphthalene diisocyanate.

[0045] In some embodiments, the catalyst is one or more of bis(dimethylaminoethyl) ether, pentamethyldiethylenetriamine, dimethylcyclohexylamine, dibutyltin dilaurate, organobismuth, triazine trimerizing catalyst, stannous octoate, and dibutyltin maleate, but is not limited thereto.

[0046] In some embodiments, the ratio between the total molar amount of hydroxyl groups in the macromolecular diol, the BN-coordinated cyclic boron ester diol and the small molecule polyol and the molar amount of isocyanate groups in the diisocyanate is 1:(0.8 to 1.4).

[0047] In some embodiments, the mass of the catalyst accounts for 0.05% to 5% of the theoretical mass of the polyurethane glass, wherein the theoretical mass of the polyurethane glass is the sum of the masses of the macromolecular diol, the cyclic boron ester diol coordinated within BN, the small molecule polyol, and the diisocyanate.

[0048] In some embodiments, the polar solvent is one or more of acetone, tetrahydrofuran, ethyl acetate, N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), benzene, toluene, butyl acetate, xylene and cyclohexanone, dichloromethane and chloroform, but is not limited thereto.

[0049] In some embodiments, the solvent removal step includes: removing the solvent under vacuum at 75–130°C for 6–48 hours.

[0050] This invention also provides a recyclable and hydrolytically degradable polyurethane-based glass, prepared by the method described above. Under certain stimulating conditions, the polyurethane-based glass prepared by this invention contains stable boron ester dynamic covalent bonds, which can be broken and recombined to achieve remodeling, degradation, and recycling of the material under mild conditions without a catalyst, thus facilitating the complete recycling of resin-based composite materials.

[0051] This invention also provides an application of a recyclable and hydrolytically degradable polyurethane-based glass body in coatings, adhesives, and flexible sensors.

[0052] The following detailed description uses specific examples.

[0053] Example 1

[0054] (1) Synthesis of polyurethane-based glass

[0055] 1.14g of polyethylene glycol (PEG)(M) n =600) was dissolved in 2 ml of dimethylformamide (DMF), 0.4 g of borate diol (IV) was dissolved in 2 ml of DMF, and 0.13 g of trimethylolpropane (TMP) was dissolved in 5 ml of anhydrous DMF. 1220 g of isophorone diisocyanate (IPDI) was dissolved in 10 ml of anhydrous DMF. The PEG solution, IPDI solution, and 5 mg of dibutyltin dilaurate were mixed and reacted at 60 °C for 2 h. The borate diol solution was added to the above solution, and the reaction was carried out at 60 °C for 1 h. Then, the trimethylolpropane solution was added to the above solution, and the reaction was carried out at 80 °C for 1 h. After that, the solution was transferred to a mold and reacted at 80 °C for another 8 h. Then, the solvent was removed under vacuum at 90 °C for 12 h to obtain the polyurethane glass based on the dynamic covalent bond of borate ester. Its macroscopic image is shown below. Figure 1 As shown.

[0056] The product was subjected to infrared spectroscopy, and the spectral results are as follows: Figure 2 As shown. From Figure 2 As can be seen, at 2270cm -1 The characteristic absorption peak of isocyanate (-NCO) at 1700 cm⁻¹ disappears, indicating that the isocyanate has been completely consumed by the reaction. Meanwhile, at 1700 cm⁻¹... -1 A strong absorption peak appeared at 1353 cm⁻¹, which is a characteristic absorption peak of the carbonyl group on the newly formed urethane bond. Furthermore, a strong absorption peak was observed at 1353 cm⁻¹. -1A new characteristic absorption peak of borosilicate appeared. Therefore, the measured infrared spectrum confirmed that the isocyanate reaction was complete, the polyurethane was formed, and the presence of borosilicate bonds in the crosslinking network. These results confirm that this embodiment successfully prepared a polyurethane-like glass containing a borosilicate structure.

[0057] (2) Recycling of polyurethane glass

[0058] First, the polyurethane glass matrix is ​​ground into powder. Then, the polyurethane glass matrix powder is spread evenly in a polytetrafluoroethylene (PTFE) mold and molded at 130℃ / 2MPa for 40 minutes to obtain a uniform recycled sample.

[0059] Tensile tests were performed on the membrane material obtained after remodeling and recycling, such as... Figure 3 As shown, the polyurethane glass matrix (recycled sample) after hot pressing cycles exhibits similar mechanical properties to the original polyurethane glass matrix (original sample), with no decrease in tensile strength, Young's modulus, or elongation at break.

[0060] (3) Hydrolytic degradation and recycling of polyurethane glass

[0061] 2g of polyurethane-based glass was completely immersed in 15ml of DMF / H2O (v / v, 1:1), and heated and stirred at 120℃ for 2h until the sample was completely dissolved. The degradation products were further characterized by DLS, and the test results are as follows: Figure 4 As shown, it was confirmed that polyurethane-based vitreous bodies can be degraded by water at 120°C. The degraded solution was then transferred to a mold and heated to 100°C in an oven. After 3 hours, the solvent was completely removed, yielding the recovered sample.

[0062] Tensile tests were performed on the membrane material obtained after hydrolysis and recycling, such as... Figure 5 As shown, the polyurethane glass recovered through water degradation (recovered sample) also exhibits mechanical properties comparable to the original polyurethane glass (original sample), with no significant decrease in tensile strength, Young's modulus, and elongation at break.

[0063] Example 2

[0064] (1) Synthesis of polyurethane-based glass

[0065] 1.9 g of PEG (Mn = 1000) was dissolved in 3 ml of DMF, 0.4 g of borate diol (IV) was dissolved in 2 ml of DMF, and 0.089 g of glycerol was dissolved in 5 ml of anhydrous DMF. 1220 g of isophorone diisocyanate (IPDI) was dissolved in 10 ml of anhydrous DMF. The PEG solution, IPDI solution, and 5 mg of dibutyltin dilaurate were mixed and reacted at 60 °C for 2 h. The borate diol solution was added to the above solution, and the reaction was carried out at 60 °C for 1 h. Then, the glycerol solution was added to the above solution, and the reaction was carried out at 80 °C for 1 h. The mixture was then transferred to a mold and reacted at 80 °C for another 8 h. Finally, the solvent was removed under vacuum at 90 °C for 12 h to obtain the polyurethane glass based on the dynamic covalent bonds of borate ester.

[0066] (2) Recycling of polyurethane glass

[0067] First, the polyurethane glass matrix was ground into powder. Then, the polyurethane glass matrix powder was spread evenly in a PTFE mold and molded at 120℃ / 3MPa for 50 minutes to obtain a uniform recycled sample. Tensile tests were performed on the recycled membrane material after remolding. It can be seen that the polyurethane glass matrix after hot pressing cycles exhibits similar mechanical properties to the original material, with no decrease in tensile strength, Young's modulus, and elongation at break.

[0068] (3) Hydrolytic degradation and recycling of polyurethane vitreous bodies:

[0069] 4g of polyurethane glass was completely immersed in 20ml of DMF / H2O (v / v, 1:1) and heated and stirred at 125℃ for 3h until the sample was completely dissolved. The degraded solution was then transferred to a mold and heated to 110℃ in an oven for 2h until the solvent was completely removed, yielding the recovered sample.

[0070] Tensile tests were performed on the membrane materials obtained after hydrolysis and recycling. The polyurethane glass recovered through water degradation also showed mechanical properties comparable to the original polyurethane glass, with no significant decrease in tensile strength, Young's modulus, and elongation at break.

[0071] Example 3

[0072] (1) Synthesis of polyurethane-based glass

[0073] 2.66 g of polytetrahydrofuran (Mn = 1400) was dissolved in 4 ml of DMF, 0.4 g of borate diol (IV) was dissolved in 2 ml of DMF, and 0.089 g of glycerol was dissolved in 5 ml of anhydrous DMF. 1373 g of diphenylmethane diisocyanate (MDDI) was dissolved in 11 ml of anhydrous DMF. The PEG solution, MDI solution, and 2 mg of stannous octoate were mixed and reacted at 80 °C for 1.5 h. The borate diol solution was added to the above solution, and the reaction was carried out at 70 °C for 1 h. Then, the glycerol solution was added to the above solution, and the reaction was carried out at 80 °C for 1 h. The mixture was then transferred to a mold and reacted at 80 °C for another 5 h. Finally, the solvent was removed under vacuum at 90 °C for 16 h to obtain the polyurethane glass based on the dynamic covalent bonds of borate ester.

[0074] (2) Recycling of polyurethane glass

[0075] First, the polyurethane glass matrix was ground into powder. Then, the polyurethane glass matrix powder was spread evenly in a PTFE mold and molded at 110℃ / 5MPa for 40 minutes to obtain a uniform recycled sample. Tensile tests were performed on the recycled membrane material after remolding. The polyurethane glass matrix after hot pressing cycles showed similar mechanical properties to the original polyurethane glass matrix material, with no decrease in tensile strength, Young's modulus, and elongation at break.

[0076] (3) Hydrolytic degradation and recycling of polyurethane vitreous bodies:

[0077] 2g of polyurethane glass was completely immersed in 10ml of DMF / H2O (v / v, 1:1) and heated and stirred at 120℃ for 4h until the sample was completely dissolved. The degraded solution was then transferred to a mold and heated to 100℃ in an oven for 4h until the solvent was completely removed, yielding the recovered sample.

[0078] Tensile tests were performed on the membrane materials obtained after hydrolysis and recycling. The polyurethane glass recovered through water degradation also showed mechanical properties comparable to the original polyurethane glass material, with no significant decrease in tensile strength, Young's modulus, and elongation at break.

[0079] Example 4

[0080] (1) Synthesis of polyurethane-based glass

[0081] 3.8 g of hydroxyl-terminated polydimethylsiloxane (Mn = 2000) was dissolved in 6 ml of DMF, 0.4 g of boron ester diol was dissolved in 2 ml of DMF, and 0.13 g of trimethylolpropane was dissolved in 5 ml of anhydrous DMF. 923 g of hexamethylene diisocyanate was dissolved in 10 ml of anhydrous DMF. The PEG solution, hexamethylene diisocyanate solution, and 6 mg of dibutyltin dilaurate were mixed and reacted at 60 °C for 2 h. Boron ester diol solution was added to the above solution, and the reaction was carried out at 80 °C for 1 h. Glycerin solution was then added to the above solution, and the reaction was carried out at 80 °C for 1.5 h. The mixture was then transferred to a mold and reacted at 80 °C for another 6 h. Finally, the solvent was removed under vacuum at 85 °C for 12 h to obtain the polyurethane glass based on the dynamic covalent bonds of boron ester.

[0082] (2) Recycling of polyurethane glass

[0083] First, the polyurethane glass matrix was ground into powder. Then, the polyurethane glass matrix powder was spread evenly in a PTFE mold and molded at 115℃ / 6MPa for 60 minutes to obtain a uniform recycled sample. Tensile tests were performed on the recycled membrane material after remolding. The polyurethane glass matrix after hot pressing cycles showed similar mechanical properties to the original polyurethane glass matrix material, with no decrease in tensile strength, Young's modulus, and elongation at break.

[0084] (3) Hydrolytic degradation and recycling of polyurethane glass

[0085] 3g of polyurethane glass was completely immersed in 14ml of DMF / H2O (v / v, 1:1) and heated and stirred at 125℃ for 3h until the sample was completely dissolved. The degraded solution was then transferred to a mold and heated to 110℃ in an oven for 2h until the solvent was completely removed, yielding the recovered sample.

[0086] Tensile tests were performed on the membrane materials obtained after hydrolysis and recycling. The polyurethane glass recovered through water degradation also showed mechanical properties comparable to the original polyurethane glass material, with no significant decrease in tensile strength, Young's modulus, and elongation at break.

[0087] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing a recyclable and hydrolytically degradable polyurethane-based glass, characterized in that, Including the following steps: Macromolecular diols, BN-coordinated cyclic boron ester diols, small molecule polyols, and diisocyanates were dispersed in polar solvents to obtain solutions A, B, C, and D, respectively. Solution A is mixed with solution D, a catalyst is added, and the mixture is reacted at 60–80°C for 1–3 hours to obtain solution E; Solution B is added to solution E and reacted at 60–80°C for 0.5–2 hours to obtain solution F; Solution C is added to solution F, and the reaction is carried out at 60-80°C for 0.5-2 hours. Then, the mixture is transferred to a mold and the curing reaction is carried out at 60-90°C for 6-24 hours. After removing the solvent, the remodelable and hydrolyzable recyclable polyurethane glass body is obtained. The macromolecular diols include one or more of polyethylene glycol, polyester polyols, polypropylene glycol, polytetrahydrofuran polyols, polycarbonate polyols, polycaprolactone polyols, and hydroxyl-terminated polydimethylsiloxanes. The small molecule polyols include one or more of glycerol, trimethylolpropane, hexanetriol, and pentaerythritol.

2. The preparation method according to claim 1, characterized in that, The cyclic boron ester diol coordinated within the BN has the chemical structural formulas shown in formulas (I) to (VII):

3. The preparation method according to claim 1, characterized in that, The diisocyanate mentioned includes one or more of isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, phenyl dimethylene diisocyanate, hydrogenated phenyl dimethylene diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, lysine diisocyanate and naphthalene diisocyanate; The catalyst is one or more of the following: dimethylaminoethyl ether, pentamethyldiethylenetriamine, dimethylcyclohexylamine, dibutyltin dilaurate, organobismuth, triazine trimerizing catalyst, stannous octoate, and dibutyltin maleate.

4. The preparation method according to claim 1, characterized in that, The ratio between the total molar amount of hydroxyl groups in the macromolecular diol, the BN-coordinated cyclic boron ester diol and the small molecule polyol and the molar amount of isocyanate groups in the diisocyanate is 1:(0.8~1.4).

5. The preparation method according to claim 1, characterized in that, The mass of the catalyst accounts for 0.05% to 5% of the theoretical mass of the polyurethane glass, and the theoretical mass of the polyurethane glass is the sum of the masses of the macromolecular diol, the cyclic boron ester diol coordinated within BN, the small molecule polyol and the diisocyanate.

6. The preparation method according to claim 1, characterized in that, The polar solvent is one or more of acetone, tetrahydrofuran, ethyl acetate, dichloromethane, N-methylpyrrolidone, N,N-dimethylformamide, benzene, toluene, butyl acetate, xylene, cyclohexanone, and chloroform.

7. The preparation method according to claim 1, characterized in that, The solvent removal step includes: removing the solvent under vacuum at 75–130°C for 6–48 hours.

8. A recyclable and hydrolytically degradable polyurethane vitreous body, characterized in that, It is prepared by any one of the preparation methods described in claims 1 to 7.

9. The application of a remodelable and hydrolytically degradable polyurethane vitreous body as described in claim 8 in coatings, adhesives, and flexible sensors.

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