Mechanically enhanced dynamically cross-linked polyurethane material and method for its production

Abstract

The application discloses a kind of mechanics enhanced dynamic crosslinking polyurethane material and preparation method thereof, by polyether / polyester dihydric alcohol, block type macromolecular chain extender containing boron-nitrogen internal coordination structure, isocyanate, catalyst and crosslinking agent are made by in-situ polymerization reaction.This application will be synthesized block type macromolecular chain extender by nucleophilic addition reaction of dihydric alcohol compound containing boron-nitrogen internal coordination with isocyanate, then with polyether / polyester dihydric alcohol, isocyanate, catalyst and crosslinking agent are prepared polyurethane covalent adaptive network by prepolymerization-chain extension-crosslinking reaction, borate dynamic covalent bond in the network is enveloped protection by hard field phase.Compared with conventional polyurethane dynamic adaptive network, the phase lock dynamic bond regulation strategy based on block type macromolecular chain extender containing boron-nitrogen internal coordination structure in the application increases the thermodynamic incompatibility between soft segment and hard segment, strengthens microphase separation, improves the strength and toughness and other mechanical properties of material.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a mechanically reinforced dynamically crosslinked polyurethane material and its preparation method. Background Technology

[0002] Thermosetting polymer materials are widely used in various fields of production and daily life due to their excellent mechanical properties and relatively low production costs. However, once these materials are cured, they form an irreversible covalent cross-linked network, making them difficult to reprocess or recycle using conventional methods after disposal. Their insoluble and infusible properties put serious pressure on the environment and also cause resource waste. How to maintain the high performance of thermosetting materials while endowing them with recyclability has become a core issue of long-term concern in the field of polymer materials.

[0003] In recent years, scientists have developed Dynamic Covalent Adaptive Networks (CANs) by introducing dynamic covalent bonds into polymer networks. These networks enable topological rearrangement of materials under specific conditions, thereby granting them reprocessing, self-healing, and recyclability, providing a "second life" for thermosetting waste. However, the introduction of dynamic bonds is often accompanied by a significant decrease in the mechanical properties of the materials, a defect that severely restricts the large-scale practical application of dynamic adaptive materials.

[0004] Among numerous dynamic covalent bond systems, boronic acid ester bonds formed by the dehydration condensation of boric acid and diol have attracted much attention due to their excellent reversibility and are widely used to construct dynamic adaptive materials with self-healing and reprocessing capabilities. However, boronic acid ester bonds have low bond energy and are sensitive to moisture, making them prone to hydrolytic fracture in complex service environments. This results in poor mechanical strength and hydrolysis resistance of the materials, making it difficult to meet the long-term stability requirements of practical applications.

[0005] To improve the stability of the dynamic bonds of borate esters, Jing et al. reported a small molecule chain extender with a boron-nitrogen internal coordination structure. When introduced into the polyurethane system, the nitrogen atom's lone electron pair occupies the empty orbitals of the boron atom to form internal coordination, which improves the hydrolysis resistance of the borate ester bond to a certain extent, and the mechanical properties and weather resistance of the material are improved (J.Am. Chem. Soc., 2020, 142, 52, 21852–21860). However, these small-molecule boron-nitrogen coordination chain extenders have inherent drawbacks: First, the regulation of dynamic bond energy depends on the precise synthesis and specific chemical structure of the small-molecule monomers, and good mechanical strength and reprocessing properties can only be achieved simultaneously in a few special systems. Second, based on existing polyurethane synthesis methods, material properties can only be controlled by adjusting the ratio of soft to hard segments, and the size of the hard phase region cannot be precisely controlled. Third, small-molecule chain extenders can only optimize stability at the molecular bonding level through chemical interactions such as hydrogen bonding and coordination, and it is difficult to effectively form physical shielding and constraint on dynamic boron-oxygen bonds at the microscopic phase separation structure level. Therefore, the fundamental problem of the easy hydrolysis of dynamic bonds in borate esters has not been fundamentally solved, and the potential for improving the overall performance of the material is significantly limited.

[0006] Currently, while borate-based polyurethane dynamic covalent adaptive networks possess advantages such as reprocessability and self-healing, the low activation energy of the boron-oxygen dynamic bonds in the borate structure makes them susceptible to moisture corrosion, leading to bond breakage during long-term service and resulting in overall material performance degradation. This has become a core bottleneck restricting the transition of such materials from the laboratory to practical applications. To address these shortcomings of existing technologies, a new technical approach is urgently needed to simultaneously improve the material's mechanical properties, hydrolysis resistance, and reprocessing performance by synergistically regulating molecular and microphase structures while preserving the reversibility of dynamic covalent bonds. Summary of the Invention

[0007] The purpose of this invention is to overcome the defects of the prior art and provide a mechanically reinforced dynamic crosslinked polyurethane material.

[0008] Another object of the present invention is to provide a method for preparing the above-mentioned mechanically reinforced dynamic crosslinked polyurethane material.

[0009] The technical solution of the present invention is as follows:

[0010] A mechanically reinforced dynamically crosslinked polyurethane material is prepared by in-situ polymerization of polyether / polyester diol, a block macromolecular chain extender with boron-nitrogen internal coordination structure, isocyanate, catalyst, and crosslinking agent.

[0011] The structural formula of this boron-nitrogen internal coordination block macromolecular chain extender is:

[0012] ,

[0013] Wherein, R1 is selected from and R2 is selected from aliphatic or aromatic isocyanate moieties.

[0014] In a preferred embodiment of the present invention, the polyether / polyester diol is selected from polytetrahydrofuran ether elastomer diol, polyethylene glycol, and polycaprolactone.

[0015] In a preferred embodiment of the present invention, the isocyanate is selected from isophorone diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, dicyclohexylmethane diisocyanate, isophenyl dimethyl isocyanate, toluene diisocyanate, diphenylmethane diisocyanate and 1,5-naphthalene diisocyanate.

[0016] In a preferred embodiment of the present invention, the preparation method of the block-type macromolecular chain extender with boron-nitrogen internal coordination structure includes the following steps:

[0017] a. Nucleophilic substitution reaction, the reaction route is as follows:

[0018] ;

[0019] b. Dehydration condensation reaction, the reaction route is as follows: ;

[0020] R3 is selected from , and ;

[0021] c. Nucleophilic addition reaction, the reaction route is as follows:

[0022] .

[0023] In a preferred embodiment of the present invention, the crosslinking agent is tetramethylphosphoric acid and the catalyst is dibutyltin dilaurate.

[0024] In a preferred embodiment of the present invention, the molar ratio of the isocyanate, polyether / polyester diol, boron-nitrogen internally coordinated block macromolecular chain extender and crosslinking agent is 0.5-1.5: 0.2-0.8: 0.05-0.8: 0.05-0.3.

[0025] The preparation method of the above-mentioned mechanically reinforced dynamic crosslinked polyurethane material includes the following steps:

[0026] (1) Under the action of the catalyst, the polyether / polyester diol and the isocyanate are reacted in an organic solvent to generate a prepolymer;

[0027] (2) The prepolymer obtained in step (1) is subjected to a chain extension reaction with the block macromolecular chain extender containing boron and nitrogen internal coordination structure;

[0028] (3) Add the crosslinking agent to the material obtained in step (2) to carry out an in-situ crosslinking and curing reaction;

[0029] (4) Dry the material obtained in step (3) to obtain the final product.

[0030] In a preferred embodiment of the present invention, the reaction temperature of step (1) is 40–90 °C and the time is 1–3 h.

[0031] In a preferred embodiment of the present invention, the chain extension reaction in step (2) is carried out at a temperature of 25–80 °C for a time of 0.5–6 h.

[0032] In a preferred embodiment of the present invention, the temperature of the in-situ crosslinking curing reaction in step (3) is 50–100 °C and the time is 2–12 h.

[0033] The beneficial effects of this invention are:

[0034] 1. This invention prepares a novel dynamically crosslinked polyurethane material with phase region size control capability through a prepolymerization-chain extension-crosslinking reaction involving polyether / polyester diol, a boron-nitrogen internally coordinated block macromolecular chain extender, isocyanate, catalyst, and crosslinking agent. By simply controlling the molar ratio of the boron-nitrogen internally coordinated diol compound to isocyanate, the molecular weight of the block macromolecular chain extender and the number of urethane linking units can be precisely controlled. Compared to traditional polymerization processes where each small molecule chain extender can only form two urethane bonds with isocyanate, the block macromolecular chain extender in this invention forms multiple and clearly defined urethane bonds during chain extension, while π-π interactions also exist between benzene rings. These structural features significantly increase the thermodynamic incompatibility between soft and hard segments in the polymer network, effectively increasing the size of the hard domain phase region, resulting in more complete hard segment aggregation and a more complete hydrogen bond network, thereby significantly improving the mechanical properties of the material.

[0035] 2. The block-type macromolecular chain extender with boron-nitrogen internal coordination structure in this invention constructs boron-nitrogen internal coordination within the molecule, allowing the lone pair of electrons from the nitrogen atom to occupy the empty orbitals of the boron atom, thus stabilizing the dynamic bond of the boron ester. Furthermore, a rigid benzene ring group is introduced next to the boron ester bond, which aggregates through intermolecular π-π interactions, "locking" the dynamic bond at the molecular level. This reduces the hydrogen bond distance within the hard-domain phase region, resulting in a more compact hard-segment stacking and constructing a more effective physical barrier for the internal boron-oxygen bond, effectively preventing the intrusion of water vapor or external small molecules. In addition, the dynamic covalent bonds are mainly contained within the hard phase and protected by an envelope, restricting the molecular motion of the boron-oxygen bond and increasing the dynamic activation energy barrier. This block-hard-domain phase-locking dynamic bond regulation strategy effectively suppresses bond dissociation and hydrolysis, further enhancing the thermomechanical stability and solvent resistance of the material under service conditions.

[0036] 3. The boron-nitrogen-containing internally coordinated block macromolecular chain extender in this invention contains dynamic borate ester covalent bonds, which can undergo reversible dissociation and association under temperature or humidity induction, endowing the network topology with rearrangement capabilities. Therefore, the prepared dynamically crosslinked polyurethane material supports reversible reprocessing methods such as hot pressing or solvent-assisted processing, enabling multiple recycling without significant loss of mechanical properties. This not only solves the waste problem of traditional thermosetting polyurethanes but also promotes the upgrading, recycling, and green sustainable development of materials, making it suitable for large-scale industrial production and possessing significant environmental and economic value. Attached Figure Description

[0037] Figure 1 The boron-nitrogen-internally coordinated diol compound 2 in Example 1 of this invention 1 H NMR spectrum.

[0038] Figure 2 The boron-nitrogen-internally coordinated diol compound 2 in Example 1 of this invention 13 C10 NMR spectrum.

[0039] Figure 3 The boron-nitrogen-internally coordinated diol compound 6 in Example 3 of this invention 1 H NMR spectrum.

[0040] Figure 4 The boron-nitrogen-internally coordinated diol compound 6 in Example 3 of this invention 13 C10 NMR spectrum.

[0041] Figure 5 The infrared spectra of samples PU-1 and PU-3 in Examples 1 and 3 of this invention are shown.

[0042] Figure 6 The stress-strain curves are shown for PU-1 in Embodiment 1 and PU-1C in Comparative Example 1 of the present invention.

[0043] Figure 7 These are the small-angle X-ray scattering spectra of PU-2 in Example 2 and PU-2C in Comparative Example 2 of the present invention.

[0044] Figure 8 The stress relaxation curves of PU-1 in Example 1 and PU-1C in Comparative Example 1 at 40 °C are shown.

[0045] Figure 9 The stress relaxation curves of PU-3 in Example 3 and PU-3C in Comparative Example 3 at 40 °C are shown.

[0046] Figure 10 This shows the stress-strain curves of PU-3 immersed in deionized water for different times in Example 3 of the present invention.

[0047] Figure 11 This diagram shows the stress-strain curves of PU-3C immersed in deionized water for different times in Comparative Example 3 of the present invention. Detailed Implementation

[0048] The technical solution of the present invention will be further explained and described below with reference to specific embodiments and accompanying drawings.

[0049] Example 1

[0050] a. Nucleophilic substitution reaction:

[0051] The reaction route is as follows: 11-bromo-1-undecanol (5 g, 19.9 mmol) and diethanolamine (2 g, 19.0 mmol) were dissolved in 50 mL of DMF, transferred to a three-necked flask, and potassium iodide (0.33 g, 2 mmol) and potassium carbonate (2.62 g, 19.0 mmol) were added. The mixture was stirred at 80 °C for 20 h under a nitrogen atmosphere. After the reaction was completed, DMF was removed by rotary evaporation, and a suitable amount of saturated NaCl brine and DCM were added to extract the product. The organic phase was retained, and after removing the solvent, compound 1 was obtained.

[0052]

[0053] b. Dehydration condensation reaction:

[0054] The reaction route is as follows: Compound 1 (0.97 g, 6.5 mmol) obtained in step a and terephthalic acid (0.50 g, 3 mmol) were dissolved in an appropriate amount of anhydrous THF and stirred at 40 °C for 1 h. After filtration, the solid was retained and washed with anhydrous THF 2–3 times. After drying, boron-nitrogen internally coordinated diol compound 2 was obtained.

[0055]

[0056] Its characterization data are as follows: 1 H NMR (500 MHz, DMSO-d6): δ = 7.33 (s, 3H), 4.30 (t, J =4.1 Hz, 3H), 3.97–3.84 (m, 9H), 3.16–3.06 (m, 4H), 2.99–2.88 (m, 4H), 2.12–2.05 (m, 3H), 1.50–1.34 (m, 11H), 1.30–1.07 (m, 38H), 0.97–0.88 (m, 4H). 13 CNMR (126 MHz, DMSO-d6): δ = 133.10, 132.74, 132.27, 127.12, 62.99, 61.18, 59.93, 57.24, 57.08, 33.01, 29.57, 29.55, 29.47, 29.43, 29.41, 29.38, 29.30, 29.26, 29.21, 26.97, 25.98, 24.55. This indicates that the product is a boron-nitrogen-internal coordinated diol compound 2. 1 H and 13 The C NMR spectrum is as follows Figure 1 and Figure 2 As shown.

[0057] c. Nucleophilic addition reaction:

[0058] The boron-nitrogen-containing internally coordinated diol compound 2 (2.0 g, 3.1 mmol) obtained in step b was dissolved in an appropriate amount of anhydrous tetrahydrofuran, and one drop of the catalyst dibutyltin dilaurate (DBTDL) was added. After stirring at 80 °C for 6 h under a nitrogen atmosphere, the reaction solvent was removed by rotary evaporation to obtain the boron-nitrogen-containing internally coordinated block-type macromolecular chain extender compound 3. Its number-average molecular weight was 4331 g / mol and its polydispersity index was 1.03, characterized by gel permeation chromatography (GPC). Its structural formula is as follows:

[0059]

[0060] Polytetrahydrofuran PTMEG (M) was subjected to nitrogen atmosphere. n = 2000 g mol -12.00 g (1 mmol), diphenylmethane diisocyanate MDI (0.38 g, 1.52 mmol), 2 mL of ultra-dry DMF, and 4 μL (0.2 wt% of PTMEG) of dibutyltin dilaurate (DBTDL) catalyst were mixed and stirred at 80 °C for 2 h to obtain a prepolymer. After cooling to 60 °C, a block-type macromolecular chain extender compound 3 (0.50 g, 0.12 mmol) with a boron-nitrogen internal coordination structure was added to the prepolymer solution for a chain extension reaction for 2 h. Then, a crosslinking agent tetrahydroxymethylphosphoric acid (0.04 g, 0.2 mmol) was added, and the reaction was stirred for 1 h. The final viscous solution was transferred to a mold, cured at 60 °C for 12 h, and then vacuum dried for 24 h to obtain a dynamically crosslinked polyurethane PU-1 based on a block hard-domain phase-locked dynamic bond regulation strategy. Its infrared spectrum is as follows: Figure 5 As shown.

[0061] Example 2

[0062] a. Dehydration condensation reaction:

[0063] The reaction route is as follows: triethanolamine (1.57 g, 10.5 mmol) and p-hydroxymethylphenylboronic acid (1.52 g, 10.0 mmol) were dissolved in an appropriate amount of anhydrous DMF and stirred at 40 °C for 3 h. After filtration, the solid was retained and washed 2–3 times with anhydrous THF. After drying, boron-nitrogen internally coordinated diol compound 4 was obtained.

[0064]

[0065] b. Nucleophilic addition reaction:

[0066] The boron-nitrogen internally coordinated diol compound 4 (0.82 g, 3.1 mmol) obtained in step a was dissolved in an appropriate amount of anhydrous tetrahydrofuran (THF) with diphenylmethane diisocyanate (0.62 g, 2.5 mmol). One drop of the catalyst dibutyltin dilaurate (DBTDL) was added, and the mixture was stirred at 80 °C for 6 h under a nitrogen atmosphere. The reaction solvent was then removed by rotary evaporation to obtain the boron-nitrogen internally coordinated block-type macromolecular chain extender compound 5. Its number-average molecular weight was 2350 g / mol and its polydispersity index was 1.04, characterized by gel permeation chromatography (GPC). Its structural formula is as follows:

[0067]

[0068] Polytetrahydrofuran PTMEG (M) was subjected to nitrogen atmosphere. n = 2000 g mol -12.00 g (1 mmol), diphenylmethane diisocyanate (MDI) (0.38 g, 1.52 mmol), 2 mL of ultra-dry DMF, and 4 μL (0.2 wt% of PTMEG) of dibutyltin dilaurate (DBTDL) catalyst were mixed and stirred at 80 °C for 2 h to obtain a prepolymer. After cooling to 60 °C, a block-type macromolecular chain extender compound 5 (0.28 g, 0.12 mmol) with a boron-nitrogen internal coordination structure was added to the prepolymer solution for a chain extension reaction for 2 h. Then, a crosslinking agent, tetramethylphosphoric acid chloride (0.04 g, 0.2 mmol), was added, and the reaction was stirred for 1 h. The final viscous solution was transferred to a mold, cured at 60 °C for 12 h, and then vacuum dried for 24 h to obtain dynamically crosslinked polyurethane PU-2 based on a block hard-domain phase-locked dynamic bond regulation strategy.

[0069] Example 3

[0070] Step a is the same as in Example 1.

[0071] b. Dehydration condensation reaction:

[0072] The reaction route is as follows: Compound 1 (0.97 g, 6.5 mmol) obtained in step a and 4,4′-biphenyl diboronic acid (0.73 g, 3.0 mmol) were dissolved in an appropriate amount of anhydrous THF and stirred at 40 °C for 1 h. After removing the solvent by rotary evaporation, an appropriate amount of anhydrous DCM was added and stirred at room temperature for 1 h. The solvent was removed by filtration and the solid product was retained. The product was then ultrasonically washed with anhydrous diethyl ether 3–5 times and freeze-dried to obtain boron-nitrogen internally coordinated diol compound 6.

[0073]

[0074] Its characterization data are as follows: 1 H NMR (500 MHz, DMSO-d6): δ = 7.55 (d, J = 7.9 Hz, 4H), 7.50 (d, J = 8.0 Hz, 4H), 4.31 (q, J = 5.7, 5.1 Hz, 2H), 3.93 (ddt, J = 16.3,9.5, 5.4 Hz, 8H), 3.18–3.11 (m, 4H), 3.05–2.95 (m, 4H), 2.27–2.19 (m, 4H), 1.51–1.43 (m, 4H), 1.37 (p, J = 6.7 Hz, 5H), 1.29–1.06 (m, 31H), 1.00–0.92(m, 4H). 13C NMR (126 MHz, DMSO-d6): δ = 139.52, 135.17, 134.23, 125.79, 125.21, 63.02, 61.19, 59.94, 33.01, 29.58, 29.46, 29.39, 29.29, 29.22, 29.13, 26.91, 25.95, 24.64. This indicates that the product is a boron-nitrogen-internal coordinated diol compound 6. 1 H and 13 The C NMR spectrum is as follows Figure 3 and Figure 4 As shown.

[0075] c. Nucleophilic addition reaction:

[0076] The boron-nitrogen-intermediate diol compound 6 (1.45 g, 3.1 mmol) obtained in step b was dissolved in an appropriate amount of anhydrous tetrahydrofuran (THF) along with diphenylmethane diisocyanate (0.62 g, 2.5 mmol). One drop of the catalyst dibutyltin dilaurate (DBTDL) was added, and the mixture was stirred at 80 °C for 6 h under a nitrogen atmosphere. The reaction solvent was then removed by rotary evaporation to obtain a block-type macromolecular chain extender compound 7 with a boron-nitrogen-intermediate structure. Gel permeation chromatography (GPC) characterized its number-average molecular weight as 4701 g / mol and its polydispersity index as 1.03. Its structural formula is as follows:

[0077]

[0078] Polytetrahydrofuran PTMEG (M) was subjected to nitrogen atmosphere. n = 2000 g mol -1 2.00 g (1 mmol), diphenylmethane diisocyanate MDI (0.38 g, 1.52 mmol), 2 mL of ultra-dry DMF, and 4 μL (0.2 wt% of PTMEG) of dibutyltin dilaurate (DBTDL) catalyst were mixed and stirred at 80 °C for 2 h to obtain a prepolymer. After cooling to 60 °C, a block-type macromolecular chain extender compound 7 (0.67 g, 0.12 mmol) with a boron-nitrogen internal coordination structure was added to the prepolymer solution for a chain extension reaction for 2 h. Then, a crosslinking agent tetramethylphosphoric chloride (0.04 g, 0.2 mmol) was added, and the reaction was stirred for 1 h. The final viscous solution was transferred to a mold, cured at 60 °C for 12 h, and then vacuum dried for 24 h to obtain dynamically crosslinked polyurethane PU-3 based on a block hard-domain phase-locked dynamic bond regulation strategy. Its infrared spectrum is as follows: Figure 5 As shown.

[0079] Example 4

[0080] Steps a and b are the same as in Example 1.

[0081] c. Nucleophilic addition reaction:

[0082] The boron-nitrogen-intermediate diol compound 2 (2.0 g, 3.1 mmol) obtained in step b was dissolved in an appropriate amount of anhydrous tetrahydrofuran (THF) along with pentamethylene diisocyanate (0.38 g, 2.5 mmol). One drop of the catalyst dibutyltin dilaurate (DBTDL) was added, and the mixture was stirred at 80 °C for 6 h under a nitrogen atmosphere. The reaction solvent was then removed by rotary evaporation to obtain a block-type macromolecular chain extender compound 8 with a boron-nitrogen-intermediate structure. Gel permeation chromatography (GPC) characterized its number-average molecular weight as 3925 g / mol and its polydispersity index as 1.07. Its structural formula is as follows:

[0083]

[0084] Polytetrahydrofuran PTMEG (M) was subjected to nitrogen atmosphere. n = 2000 g mol -1 2.00 g (1 mmol) of pentamethylene diisocyanate (PDI), 0.38 g (1.52 mmol) of pentamethylene diisocyanate (DMF), 2 mL of ultra-dry DMF, and 4 μL (0.2 wt% of PTMEG) of dibutyltin dilaurate (DBTDL) catalyst were mixed and stirred at 80 °C for 2 h to obtain a prepolymer. After cooling to 60 °C, a block-type macromolecular chain extender compound 8 (0.77 g (0.12 mmol) with a boron-nitrogen internal coordination structure was added to the prepolymer solution for a chain extension reaction for 2 h. Then, a crosslinking agent, tetramethylphosphoric acid chloride (0.04 g (0.2 mmol)), was added, and the reaction was stirred for 1 h. The final viscous solution was transferred to a mold, cured at 60 °C for 12 h, and then vacuum dried for 24 h to obtain dynamically crosslinked polyurethane PU-4 based on a block hard-domain phase-locked dynamic bond regulation strategy.

[0085] Example 5

[0086] Steps a and b are the same as in Example 1.

[0087] c. Nucleophilic addition reaction:

[0088] The boron-nitrogen internally coordinated diol compound 2 (2.0 g, 3.1 mmol) obtained in step b was dissolved in an appropriate amount of anhydrous tetrahydrofuran (THF) along with hexamethylene diisocyanate (0.42 g, 2.5 mmol). One drop of the catalyst dibutyltin dilaurate (DBTDL) was added, and the mixture was stirred at 80 °C for 6 h under a nitrogen atmosphere. The reaction solvent was then removed by rotary evaporation to obtain the boron-nitrogen internally coordinated block-type macromolecular chain extender compound 9. Its number-average molecular weight was 3933 g / mol and its polydispersity index was 1.06, characterized by gel permeation chromatography (GPC). Its structural formula is as follows:

[0089]

[0090] Polytetrahydrofuran PTMEG (M) was subjected to nitrogen atmosphere. n = 2000 g mol -1 2.00 g (1 mmol) of hexamethylene diisocyanate (HDI), 0.38 g (1.52 mmol) of hexamethylene diisocyanate (DMF), 2 mL of ultra-dry DMF, and 4 μL (0.2 wt% of PTMEG) of dibutyltin dilaurate (DBTDL) catalyst were mixed and stirred at 80 °C for 2 h to obtain a prepolymer. After cooling to 60 °C, a block-type macromolecular chain extender compound 9 (0.78 g, 0.12 mmol) with a boron-nitrogen internal coordination structure was added to the prepolymer solution for a chain extension reaction for 2 h. Then, a crosslinking agent, tetramethylphosphoric acid chloride (0.04 g, 0.2 mmol), was added, and the reaction was stirred for 1 h. The final viscous solution was transferred to a mold, cured at 60 °C for 12 h, and then vacuum dried for 24 h to obtain dynamically crosslinked polyurethane PU-5 based on a block hard-domain phase-locked dynamic bond regulation strategy.

[0091] Example 6

[0092] Steps a and b are the same as in Example 1.

[0093] c. Nucleophilic addition reaction:

[0094] The boron-nitrogen internally coordinated diol compound 2 (2.0 g, 3.1 mmol) obtained in step b was dissolved in an appropriate amount of anhydrous tetrahydrofuran (THF) along with isophorone diisocyanate (0.56 g, 2.5 mmol). One drop of the catalyst dibutyltin dilaurate (DBTDL) was added, and the mixture was stirred at 80 °C for 6 h under a nitrogen atmosphere. The reaction solvent was then removed by rotary evaporation to obtain a block-type macromolecular chain extender compound 10 with a boron-nitrogen internally coordinated structure. Gel permeation chromatography (GPC) characterized its number-average molecular weight as 4198 g / mol and its polydispersity index as 1.05. Its structural formula is as follows:

[0095]

[0096] Polytetrahydrofuran PTMEG (M) was subjected to nitrogen atmosphere. n = 2000 g mol -1 2.00 g (1 mmol), isophorone diisocyanate IPDI (0.34 g, 1.52 mmol), 2 mL of ultra-dry DMF, and 4 μL (0.2 wt% of PTMEG) of dibutyltin dilaurate (DBTDL) catalyst were mixed and stirred at 80 °C for 2 h to obtain a prepolymer. After cooling to 60 °C, a block-type macromolecular chain extender compound 10 (0.82 g, 0.12 mmol) with a boron-nitrogen internal coordination structure was added to the prepolymer solution for a chain extension reaction for 2 h. Then, a crosslinking agent tetramethylphosphoric acid (0.04 g, 0.2 mmol) was added, and the reaction was stirred for 1 h. The final viscous solution was transferred to a mold, cured at 60 °C for 12 h, and then vacuum dried for 24 h to obtain dynamically crosslinked polyurethane PU-6 based on a block hard-domain phase-locked dynamic bond regulation strategy.

[0097] Example 7

[0098] Steps a and b are the same as in Example 1.

[0099] c. Nucleophilic addition reaction:

[0100] The boron-nitrogen-containing internally coordinated diol compound 2 (2.0 g, 3.1 mmol) obtained in step b was dissolved in an appropriate amount of anhydrous tetrahydrofuran (THF) with dicyclohexylmethane diisocyanate (0.66 g, 2.5 mmol). One drop of the catalyst dibutyltin dilaurate (DBTDL) was added, and the reaction was carried out at 80 °C for 6 h under a nitrogen atmosphere. The reaction solvent was removed by rotary evaporation to obtain a block-type macromolecular chain extender compound 11 with a boron-nitrogen internally coordinated structure. Its number-average molecular weight was 4337 g / mol and the polydispersity index was 1.04, characterized by gel permeation chromatography (GPC). Its structural formula is as follows:

[0101]

[0102] Polytetrahydrofuran PTMEG (M) was subjected to nitrogen atmosphere. n = 2000 g mol -12.00 g (1 mmol), dicyclohexylmethane diisocyanate HMDI (0.34 g, 1.52 mmol), 2 mL of ultra-dry DMF, and 4 μL (0.2 wt% of PTMEG) of dibutyltin dilaurate (DBTDL) catalyst were mixed and stirred at 80 °C for 2 h to obtain a prepolymer. After cooling to 60 °C, a block-type macromolecular chain extender compound 11 (0.85 g, 0.12 mmol) with a boron-nitrogen internal coordination structure was added to the prepolymer solution for a chain extension reaction for 2 h. Then, a crosslinking agent tetrahydroxymethylphosphoric acid (0.04 g, 0.2 mmol) was added, and the reaction was stirred for 1 h. The final viscous solution was transferred to a mold, cured at 60 °C for 12 h, and then vacuum dried for 24 h to obtain dynamically crosslinked polyurethane PU-7 based on a block hard-domain phase-locked dynamic bond regulation strategy.

[0103] Example 8

[0104] Steps a and b are the same as in Example 1.

[0105] c. Nucleophilic addition reaction:

[0106] The boron-nitrogen internally coordinated diol compound 2 (2.0 g, 3.1 mmol) obtained in step b was dissolved in an appropriate amount of anhydrous tetrahydrofuran (THF) along with isophthalic dimethyl isocyanate (0.47 g, 2.5 mmol). One drop of the catalyst dibutyltin dilaurate (DBTDL) was added, and the mixture was stirred at 80 °C for 6 h under a nitrogen atmosphere. The reaction solvent was then removed by rotary evaporation to obtain a block-type macromolecular chain extender compound 12 with a boron-nitrogen internally coordinated structure. Gel permeation chromatography (GPC) characterized its number-average molecular weight as 4028 g / mol and its polydispersity index as 1.06. Its structural formula is as follows:

[0107]

[0108] Polytetrahydrofuran PTMEG (M) was subjected to nitrogen atmosphere. n = 2000 g mol -12.00 g (1 mmol), 0.29 g (1.52 mmol) of isocyanate XDI, 2 mL of ultra-dry DMF, and 4 μL (0.2 wt% of PTMEG) of dibutyltin dilaurate (DBTDL) catalyst were mixed and stirred at 80 °C for 2 h to obtain a prepolymer. After cooling to 60 °C, a block-type macromolecular chain extender compound 12 (0.80 g (0.12 mmol) with a boron-nitrogen internal coordination structure was added to the prepolymer solution for a chain extension reaction for 2 h. Then, a crosslinking agent tetramethylphosphoric acid chloride (0.04 g (0.2 mmol)) was added, and the reaction was stirred for 1 h. The final viscous solution was transferred to a mold, cured at 60 °C for 12 h, and then vacuum dried for 24 h to obtain dynamically crosslinked polyurethane PU-8 based on a block hard-domain phase-locked dynamic bond regulation strategy.

[0109] Example 9

[0110] Steps a and b are the same as in Example 1.

[0111] c. Nucleophilic addition reaction:

[0112] The boron-nitrogen internally coordinated diol compound 2 (2.0 g, 3.1 mmol) obtained in step b was dissolved in an appropriate amount of anhydrous tetrahydrofuran (THF) with toluene-2,4-diisocyanate (0.44 g, 2.5 mmol). One drop of the catalyst dibutyltin dilaurate (DBTDL) was added, and the reaction was carried out at 80 °C for 6 h under a nitrogen atmosphere. The reaction solvent was removed by rotary evaporation to obtain a block-type macromolecular chain extender compound 13 with a boron-nitrogen internally coordinated structure. Its number-average molecular weight was 3901 g / mol and the polydispersity index was 1.07, characterized by gel permeation chromatography (GPC). Its structural formula is as follows:

[0113]

[0114] Polytetrahydrofuran PTMEG (M) was subjected to nitrogen atmosphere. n = 2000 g mol -12.00 g (1 mmol) of toluene-2,4-diisocyanate 2,4-TDI (0.26 g, 1.52 mmol), 2 mL of ultra-dry DMF, and 4 μL (0.2 wt% of PTMEG) of dibutyltin dilaurate (DBTDL) catalyst were mixed and stirred at 80 °C for 2 h to obtain a prepolymer. After cooling to 60 °C, a block-type macromolecular chain extender compound 13 (0.78 g, 0.12 mmol) with a boron-nitrogen internal coordination structure was added to the prepolymer solution for a chain extension reaction for 2 h. Then, a crosslinking agent tetramethylphosphoric acid (0.04 g, 0.2 mmol) was added, and the reaction was stirred for 1 h. The final viscous solution was transferred to a mold, cured at 60 °C for 12 h, and then vacuum dried for 24 h to obtain dynamically crosslinked polyurethane PU-9 based on a block hard-domain phase-locked dynamic bond regulation strategy.

[0115] Example 10

[0116] Steps a and b are the same as in Example 1.

[0117] c. Nucleophilic addition reaction:

[0118] The boron-nitrogen internally coordinated diol compound 2 (2.0 g, 3.1 mmol) obtained in step b was dissolved in an appropriate amount of anhydrous tetrahydrofuran (THF) with 1,5-naphthalene diisocyanate (0.53 g, 2.5 mmol). One drop of the catalyst dibutyltin dilaurate (DBTDL) was added, and the reaction was carried out at 80 °C for 6 h under a nitrogen atmosphere. The reaction solvent was removed by rotary evaporation to obtain a block-type macromolecular chain extender compound 14 with a boron-nitrogen internally coordinated structure. Its number-average molecular weight was 4155 g / mol and the polydispersity index was 1.05, characterized by gel permeation chromatography (GPC). Its structural formula is as follows:

[0119]

[0120] Polytetrahydrofuran PTMEG (M) was subjected to nitrogen atmosphere. n = 2000 g mol -12.00 g (1 mmol), 1,5-naphthalene diisocyanate NDI (0.32 g, 1.52 mmol), 2 mL of ultra-dry DMF, and 4 μL (0.2 wt% of PTMEG) of dibutyltin dilaurate (DBTDL) catalyst were mixed and stirred at 80 °C for 2 h to obtain a prepolymer. After cooling to 60 °C, a block-type macromolecular chain extender compound 14 (0.81 g, 0.12 mmol) with a boron-nitrogen internal coordination structure was added to the prepolymer solution for a chain extension reaction for 2 h. Then, a crosslinking agent tetramethylphosphoric acid (0.04 g, 0.2 mmol) was added, and the reaction was stirred for 1 h. The final viscous solution was transferred to a mold, cured at 60 °C for 12 h, and then vacuum dried for 24 h to obtain dynamically crosslinked polyurethane PU-10 based on a block hard-domain phase-locked dynamic bond regulation strategy.

[0121] Example 11

[0122] The difference between this embodiment and Embodiment 1 is that polytetrahydrofuran (PTMEG) is replaced with polycaprolactone (PCL). This embodiment is specifically as follows: under a nitrogen atmosphere, polycaprolactone (PCL) (M...) n = 2000 g mol -1 2.00 g (1 mmol), diphenylmethane diisocyanate (MDI) (0.38 g, 1.52 mmol), 2 mL of ultra-dry DMF, and 4 μL (0.2 wt% of PCL) of dibutyltin dilaurate (DBTDL) catalyst were mixed and stirred at 80 °C for 2 h to obtain a prepolymer. After cooling to 60 °C, a block-type macromolecular chain extender compound 3 (0.50 g, 0.12 mmol) with a boron-nitrogen internal coordination structure was added to the prepolymer solution for a chain extension reaction for 2 h. Then, a crosslinking agent tetramethylphosphoric acid (0.04 g, 0.2 mmol) was added, and the reaction was stirred for 1 h. The final viscous solution was transferred to a mold, cured at 60 °C for 12 h, and then vacuum dried for 24 h to obtain dynamically crosslinked polyurethane PU-11 based on a block hard-domain phase-locked dynamic bond regulation strategy.

[0123] Example 12

[0124] The difference between this embodiment and Embodiment 1 is that polytetrahydrofuran (PTMEG) is replaced with polyethylene glycol (PEG). This embodiment is specifically as follows: under a nitrogen atmosphere, polyethylene glycol (PEG) (M... n = 2000 g mol -12.00 g (1 mmol), diphenylmethane diisocyanate (MDI) (0.38 g, 1.52 mmol), 2 mL of ultra-dry DMF, and 4 μL (0.2 wt% of PEG) of dibutyltin dilaurate (DBTDL) catalyst were mixed and stirred at 80 °C for 2 h to obtain a prepolymer. After cooling to 60 °C, a block-type macromolecular chain extender compound 3 (0.50 g, 0.12 mmol) with a boron-nitrogen internal coordination structure was added to the prepolymer solution for a chain extension reaction for 2 h. Then, a crosslinking agent, tetramethylphosphoric acid chloride (0.04 g, 0.2 mmol), was added, and the reaction was stirred for 1 h. The final viscous solution was transferred to a mold, cured at 60 °C for 12 h, and then vacuum dried for 24 h to obtain dynamically crosslinked polyurethane PU-12 based on a block hard-domain phase-locked dynamic bond regulation strategy.

[0125] Example 13

[0126] Steps a and b are the same as in Example 1.

[0127] c. Nucleophilic addition reaction:

[0128] A boron-nitrogen internally coordinated diol compound 2 (2.0 g, 3.1 mmol) and diphenylmethane diisocyanate (0.58 g, 2.3 mmol) were dissolved in an appropriate amount of anhydrous tetrahydrofuran. One drop of the catalyst dibutyltin dilaurate (DBTDL) was added, and the mixture was stirred at 80 °C for 6 h under a nitrogen atmosphere. The reaction solvent was then removed by rotary evaporation to obtain a boron-nitrogen internally coordinated block-type macromolecular chain extender compound 15. Gel permeation chromatography (GPC) characterized its number-average molecular weight as 3331 g / mol and its polydispersity index as 1.04. Its structural formula is as follows:

[0129]

[0130] Polytetrahydrofuran PTMEG (M) was subjected to nitrogen atmosphere. n = 2000 g mol -12.00 g (1 mmol) of diphenylmethane diisocyanate (MDI), 0.41 g (1.60 mmol) of diphenylmethane diisocyanate (DMF), 2 mL of ultra-dry DMF, and 4 μL (0.2 wt% of PTMEG) of dibutyltin dilaurate (DBTDL) catalyst were mixed and stirred at 80 °C for 2 h to obtain a prepolymer. After cooling to 60 °C, a block-type macromolecular chain extender compound 15 (0.40 g, 0.12 mmol) with a boron-nitrogen internal coordination structure was added to the prepolymer solution for a chain extension reaction for 2 h. Then, a crosslinking agent, tetramethylphosphoric acid chloride (0.04 g, 0.2 mmol), was added, and the reaction was stirred for 1 h. The final viscous solution was transferred to a mold, cured at 60 °C for 12 h, and then vacuum dried for 24 h to obtain dynamically crosslinked polyurethane PU-13 based on a block hard-domain phase-locked dynamic bond regulation strategy.

[0131] Comparative Example 1

[0132] The difference between this comparative example and Example 1 is that in the chain extension step, the block-type macromolecular chain extender compound 3 with boron-nitrogen internal coordination structure is replaced with boron-nitrogen internal coordination diol compound 2.

[0133] The specific comparison is as follows:

[0134] Polytetrahydrofuran ether PTMEG (M) was applied under a nitrogen atmosphere. n = 2000 g mol -1 A mixture of diphenylmethane diisocyanate (MDI) (0.50 g, 2 mmol), 2 mL of ultra-dry DMF, and 4 μL (0.2 wt% of PTMEG) of dibutyltin dilaurate (DBTDL) catalyst was stirred at 80 °C for 2 h to obtain a prepolymer. After cooling to 60 °C, a boron-nitrogen internally coordinated diol compound 2 (0.39 g, 0.6 mmol) was added to the prepolymer solution for chain extension for 2 h, followed by the addition of a crosslinking agent, tetramethylphosphoric acid chloride (0.04 g, 0.2 mmol), and the reaction was stirred for 1 h. The final viscous solution was transferred to a mold, cured at 60 °C for 12 h, and then vacuum dried for 24 h to obtain dynamically crosslinked polyurethane PU-1C based on a block hard-domain phase-locked dynamic bond regulation strategy.

[0135] Comparative Example 2

[0136] The difference between this comparative example and Example 2 is that in the chain extension step, the block-type macromolecular chain extender compound 5 with boron-nitrogen internal coordination structure is replaced with boron-nitrogen internal coordination diol compound 4.

[0137] The specific comparison is as follows:

[0138] Polytetrahydrofuran ether PTMEG (M) was applied under a nitrogen atmosphere. n = 2000 g mol -1 A mixture of diphenylmethane diisocyanate (MDI) (0.50 g, 2 mmol), 2 mL of ultra-dry DMF, and 4 μL (0.2 wt% of PTMEG) of dibutyltin dilaurate (DBTDL) catalyst was stirred at 80 °C for 2 h to obtain a prepolymer. After cooling to 60 °C, a boron-nitrogen internally coordinated diol compound 4 (0.16 g, 0.6 mmol) was added to the prepolymer solution for chain extension for 2 h, followed by the addition of a crosslinking agent, tetramethylphosphoric chloride (0.04 g, 0.2 mmol), and the reaction was stirred for 1 h. The final viscous solution was transferred to a mold, cured at 60 °C for 12 h, and then vacuum dried for 24 h to obtain dynamically crosslinked polyurethane PU-2C based on a block hard-domain phase-locked dynamic bond regulation strategy.

[0139] Comparative Example 3

[0140] The difference between this comparative example and Example 3 is that in the chain extension step, the block-type macromolecular chain extender compound 7 with boron-nitrogen internal coordination structure is replaced with boron-nitrogen internal coordination diol compound 6.

[0141] The specific comparison is as follows:

[0142] Polytetrahydrofuran ether PTMEG (M) was applied under a nitrogen atmosphere. n = 2000 g mol -1 A mixture of diphenylmethane diisocyanate (MDI) (0.50 g, 2 mmol), 2 mL of ultra-dry DMF, and 4 μL (0.2 wt% of PTMEG) of dibutyltin dilaurate (DBTDL) catalyst was stirred at 80 °C for 2 h to obtain a prepolymer. After cooling to 60 °C, a boron-nitrogen internally coordinated diol compound 6 (0.43 g, 0.6 mmol) was added to the prepolymer solution for chain extension for 2 h, followed by the addition of a crosslinking agent, tetramethylphosphoric acid chloride (0.04 g, 0.2 mmol), and the reaction was stirred for 1 h. The final viscous solution was transferred to a mold, cured at 60 °C for 12 h, and then vacuum dried for 24 h to obtain dynamically crosslinked polyurethane PU-3C based on a block hard-domain phase-locked dynamic bond regulation strategy.

[0143] Comparative Example 4

[0144] The difference between this comparative example and Example 4 is that in the chain extension step, the block-type macromolecular chain extender compound 8 with boron-nitrogen internal coordination structure is replaced with boron-nitrogen internal coordination diol compound 2.

[0145] The specific comparison is as follows:

[0146] Polytetrahydrofuran ether PTMEG (M) was applied under a nitrogen atmosphere. n = 2000 g mol -1 2.00 g (1 mmol) of pentamethylene diisocyanate (PDI), 0.31 g (2 mmol), 2 mL of ultra-dry DMF, and 4 μL (0.2 wt% of PTMEG) of dibutyltin dilaurate (DBTDL) catalyst were mixed and stirred at 80 °C for 2 h to obtain a prepolymer. After cooling to 60 °C, a boron-nitrogen internally coordinated diol compound 2 (0.39 g, 0.6 mmol) was added to the prepolymer solution for chain extension reaction for 2 h, followed by the addition of crosslinking agent tetramethylphosphoric chloride (0.04 g, 0.2 mmol), and the reaction was stirred for 1 h. The final viscous solution was transferred to a mold, cured at 60 °C for 12 h, and then vacuum dried for 24 h to obtain dynamically crosslinked polyurethane PU-4C based on a block hard-domain phase-locked dynamic bond regulation strategy.

[0147] Comparative Example 5

[0148] The difference between this comparative example and Example 5 is that in the chain extension step, the block-type macromolecular chain extender compound 9 with boron-nitrogen internal coordination structure is replaced with boron-nitrogen internal coordination diol compound 2.

[0149] The specific comparison is as follows:

[0150] Polytetrahydrofuran ether PTMEG (M) was applied under a nitrogen atmosphere. n = 2000 g mol -1 2.00 g (1 mmol) of hexamethylene diisocyanate (HDI), 0.34 g (2 mmol), 2 mL of ultra-dry DMF, and 4 μL (0.2 wt% of PTMEG) of dibutyltin dilaurate (DBTDL) catalyst were mixed and stirred at 80 °C for 2 h to obtain a prepolymer. After cooling to 60 °C, a boron-nitrogen internally coordinated diol compound 2 (0.39 g, 0.6 mmol) was added to the prepolymer solution for chain extension reaction for 2 h, followed by the addition of crosslinking agent tetramethylphosphoric chloride (0.04 g, 0.2 mmol), and stirring for 1 h. The final viscous solution was transferred to a mold, cured at 60 °C for 12 h, and then vacuum dried for 24 h to obtain dynamically crosslinked polyurethane PU-5C based on a block hard-domain phase-locked dynamic bond regulation strategy.

[0151] Comparative Example 6

[0152] The difference between this comparative example and Example 6 is that in the chain extension step, the block-type macromolecular chain extender compound 10 with boron-nitrogen internal coordination structure is replaced with boron-nitrogen internal coordination diol compound 2.

[0153] The specific comparison is as follows:

[0154] Polytetrahydrofuran ether PTMEG (M) was applied under a nitrogen atmosphere. n = 2000 g mol -1 2.00 g (1 mmol), isophorone diisocyanate IPDI (0.44 g, 2 mmol), 2 mL of ultra-dry DMF, and 4 μL (0.2 wt% of PTMEG) of dibutyltin dilaurate (DBTDL) catalyst were mixed and stirred at 80 °C for 2 h to obtain a prepolymer. After cooling to 60 °C, boron-nitrogen internally coordinated diol compound 2 (0.39 g, 0.6 mmol) was added to the prepolymer solution for chain extension reaction for 2 h, followed by the addition of crosslinking agent tetramethylphosphoric chloride (0.04 g, 0.2 mmol), and the reaction was stirred for 1 h. The final viscous solution was transferred to a mold, cured at 60 °C for 12 h, and then vacuum dried for 24 h to obtain dynamically crosslinked polyurethane PU-6C based on a block hard-domain phase-locked dynamic bond regulation strategy.

[0155] Comparative Example 7

[0156] The difference between this comparative example and Example 7 is that in the chain extension step, the block-type macromolecular chain extender compound 11 with boron-nitrogen internal coordination structure is replaced with boron-nitrogen internal coordination diol compound 2.

[0157] The specific comparative example is as follows: Polytetrahydrofuran ether PTMEG (M...) was introduced into the nitrogen atmosphere... n = 2000 g mol -1 2.00 g (1 mmol) of dicyclohexylmethane diisocyanate (HMDI), 0.52 g (2 mmol) of dicyclohexylmethane diisocyanate (DMF), 2 mL of ultra-dry DMF, and 4 μL (0.2 wt% of PTMEG) of dibutyltin dilaurate (DBTDL) catalyst were mixed and stirred at 80 °C for 2 h to obtain a prepolymer. After cooling to 60 °C, a boron-nitrogen internally coordinated diol compound 2 (0.39 g, 0.6 mmol) was added to the prepolymer solution for chain extension reaction for 2 h, followed by the addition of a crosslinking agent, tetrahydroxymethylphosphoric chloride (0.04 g, 0.2 mmol), and the reaction was stirred for 1 h. The final viscous solution was transferred to a mold, cured at 60 °C for 12 h, and then vacuum dried for 24 h to obtain dynamically crosslinked polyurethane PU-7C based on a block hard-domain phase-locked dynamic bond regulation strategy.

[0158] Comparative Example 8

[0159] The difference between this comparative example and Example 8 is that in the chain extension step, the block-type macromolecular chain extender compound 12 with boron-nitrogen internal coordination structure is replaced with boron-nitrogen internal coordination diol compound 2.

[0160] The specific comparison is as follows:

[0161] Polytetrahydrofuran ether PTMEG (M) was applied under a nitrogen atmosphere. n = 2000 g mol -1 2.00 g (1 mmol) of isophthalic dimethyl isocyanate XDI (0.38 g (2 mmol)), 2 mL of ultra-dry DMF, and 4 μL (0.2 wt% of PTMEG) of dibutyltin dilaurate (DBTDL) catalyst were mixed and stirred at 80 °C for 2 h to obtain a prepolymer. After cooling to 60 °C, a boron-nitrogen internally coordinated diol compound 2 (0.39 g (0.6 mmol)) was added to the prepolymer solution for chain extension reaction for 2 h, followed by the addition of crosslinking agent tetramethylphosphoric chloride (0.04 g (0.2 mmol)) and stirring for 1 h. The final viscous solution was transferred to a mold, cured at 60 °C for 12 h, and then vacuum dried for 24 h to obtain dynamically crosslinked polyurethane PU-8C based on a block hard-domain phase-locked dynamic bond regulation strategy.

[0162] Comparative Example 9

[0163] The difference between this comparative example and Example 9 is that in the chain extension step, the block-type macromolecular chain extender compound 13 with boron-nitrogen internal coordination structure is replaced with boron-nitrogen internal coordination diol compound 2.

[0164] The specific comparison is as follows:

[0165] Polytetrahydrofuran ether PTMEG (M) was applied under a nitrogen atmosphere. n = 2000 g mol -12.00 g (1 mmol) of toluene-2,4-diisocyanate 2,4-TDI (0.35 g, 2 mmol), 2 mL of ultra-dry DMF, and 4 μL (0.2 wt% of PTMEG) of dibutyltin dilaurate (DBTDL) catalyst were mixed and stirred at 80 °C for 2 h to obtain a prepolymer. After cooling to 60 °C, a boron-nitrogen internally coordinated diol compound 2 (0.39 g, 0.6 mmol) was added to the prepolymer solution for chain extension for 2 h, followed by the addition of a crosslinking agent tetramethylphosphoric chloride (0.04 g, 0.2 mmol), and the reaction was stirred for 1 h. The final viscous solution was transferred to a mold, cured at 60 °C for 12 h, and then vacuum dried for 24 h to obtain dynamically crosslinked polyurethane PU-9C based on a block hard-domain phase-locked dynamic bond regulation strategy.

[0166] Comparative Example 10

[0167] The difference between this comparative example and Example 10 is that in the chain extension step, the block-type macromolecular chain extender compound 14 with boron-nitrogen internal coordination structure is replaced with boron-nitrogen internal coordination diol compound 2.

[0168] The specific comparative example is as follows: Polytetrahydrofuran ether PTMEG (M...) was introduced into the nitrogen atmosphere... n = 2000 g mol -1 2.00 g (1 mmol), 1,5-naphthalene diisocyanate NDI (0.42 g, 2 mmol), 2 mL of ultra-dry DMF, and 4 μL (0.2 wt% of PTMEG) of dibutyltin dilaurate (DBTDL) catalyst were mixed and stirred at 80 °C for 2 h to obtain a prepolymer. After cooling to 60 °C, a boron-nitrogen internally coordinated diol compound 2 (0.39 g, 0.6 mmol) was added to the prepolymer solution for chain extension for 2 h, followed by the addition of a crosslinking agent tetramethylphosphoric chloride (0.04 g, 0.2 mmol), and the reaction was stirred for 1 h. The final viscous solution was transferred to a mold, cured at 60 °C for 12 h, and then vacuum dried for 24 h to obtain dynamically crosslinked polyurethane PU-10C based on a block hard-domain phase-locked dynamic bond regulation strategy.

[0169] Comparative Example 11

[0170] The difference between this comparative example and Example 11 is that in the chain extension step, the block-type macromolecular chain extender compound 3 with boron-nitrogen internal coordination structure is replaced with boron-nitrogen internal coordination diol compound 2.

[0171] The specific comparative example is as follows: Polycaprolactone (PCL) (M) was introduced into the nitrogen atmosphere. n = 2000 g mol -12.00 g (1 mmol) of diphenylmethane diisocyanate (MDI), 0.50 g (2 mmol), 2 mL of ultra-dry DMF, and 4 μL (0.2 wt% of PCL) of dibutyltin dilaurate (DBTDL) catalyst were mixed and stirred at 80 °C for 2 h to obtain a prepolymer. After cooling to 60 °C, a boron-nitrogen internally coordinated diol compound 2 (0.39 g, 0.6 mmol) was added to the prepolymer solution for chain extension for 2 h, followed by the addition of a crosslinking agent, tetramethylphosphoric chloride (0.04 g, 0.2 mmol), and the reaction was stirred for 1 h. The final viscous solution was transferred to a mold, cured at 60 °C for 12 h, and then vacuum dried for 24 h to obtain dynamically crosslinked polyurethane PU-11C based on a block hard-domain phase-locked dynamic bond regulation strategy.

[0172] Comparative Example 12

[0173] The difference between this comparative example and Example 12 is that in the chain extension step, the block-type macromolecular chain extender compound 3 with boron-nitrogen internal coordination structure is replaced with boron-nitrogen internal coordination diol compound 2.

[0174] The specific comparative example is as follows: under a nitrogen atmosphere, polyethylene glycol (PEG) (M n = 2000 g mol -1 2.00 g (1 mmol) of diphenylmethane diisocyanate (MDI), 0.50 g (2 mmol), 2 mL of ultra-dry DMF, and 4 μL (0.2 wt% of PEG) of dibutyltin dilaurate (DBTDL) catalyst were mixed and stirred at 80 °C for 2 h to obtain a prepolymer. After cooling to 60 °C, a boron-nitrogen internally coordinated diol compound 2 (0.39 g, 0.6 mmol) was added to the prepolymer solution for chain extension for 2 h, followed by the addition of a crosslinking agent, tetramethylphosphoric chloride (0.04 g, 0.2 mmol), and the reaction was stirred for 1 h. The final viscous solution was transferred to a mold, cured at 60 °C for 12 h, and then vacuum dried for 24 h to obtain dynamically crosslinked polyurethane PU-12C based on a block hard-domain phase-locked dynamic bond regulation strategy.

[0175] Example 14

[0176] The following tests were conducted on the products obtained from the above embodiments and comparative examples. The test items and methods are as follows:

[0177] Structural characterization: The synthesized compound was characterized using an AVANCE III HD 500MHz nuclear magnetic resonance spectrometer. 1 H and 13For CNMR characterization, 5 mg of sample was dissolved in 600 μL of DMSO-d6 and then tested, with 16 scans. The chemical structure of the polyurethane elastomer was characterized using a Nicolet iS20 Fourier transform infrared spectrometer, with attenuated total reflectance (ATR) method and 32 scans.

[0178] Molecular weight determination of block-type macromolecular chain extenders: A tetrahydrofuran solution with a sample concentration of 2 mg / mL was prepared and characterized using a Waters 1515 gel permeation chromatograph.

[0179] Stress-strain performance test: The stress-strain curve of the thin film sample was tested on an MTS CMT6503 universal testing machine according to the method specified in GB / T 528-2009. The tensile rate was set to 50 mm / min and the test temperature was room temperature.

[0180] Toughness: Calculated based on the area of ​​the tensile curve and the closed curve along the X-axis in the stress-strain performance test of the sample.

[0181] Dynamic Thermomechanical Analysis (DMA) Test: Stress relaxation tests were performed on a DMA850 (TA Instruments, America). The sample was preloaded with a force of 0.01 N, and after reaching the test temperature, it was held at a constant temperature for 3 minutes to achieve thermal equilibrium. The sample was then stretched to 10% strain and kept deformed throughout the test to record the decrease in modulus during stress relaxation.

[0182] Small-angle X-ray scattering test: Characterization was performed on a Xenocs Xeuss 3.0 HR X-ray diffractometer (France). The test mode was transmission mode, the distance from the light spot to the sample was set to 500 nm, and the scanning time was set to 100 s.

[0183] The chain extenders used in the preparation of the polyurethane samples in the examples and comparative examples are shown in Table 1. The mechanical property test results of the samples in the examples and comparative examples are shown in Table 2 below.

[0184] Table 1. Comparison of chain extenders in polyurethane samples of the examples and comparative examples

[0185]

[0186] Table 2. Comparison of mechanical property characterization results of polyurethane samples from the examples and comparative examples.

[0187] PU-1 38.31 ± 1.86 1554 ± 69 221.08 ± 23.85 PU-1C 25.04 ± 0.85 1429 ± 38 154.93 ± 27.52 PU-2 42.82 ± 2.40 1757 ± 74 263.14 ± 30.26 PU-2C 34.13 ± 3.76 1662 ± 87 189.61 ± 7.58 PU-3 41.30 ± 1.35 1434 ± 63 207.11 ± 13.21 PU-3C 26.43 ± 1.01 1608 ± 76 178.71 ± 22.13 PU-4 38.14 ± 1.33 1634 ± 56 224.78 ± 51.26 PU-4C 22.24 ± 2.95 1721 ± 69 139.66 ± 20.41 PU-5 41.15 ± 3.12 1625 ± 32 248.65 ± 17.29 PU-5C 18.32 ± 1.71 1801 ± 106 141.21 ± 15.24 PU-6 29.48 ± 0.68 1842 ± 37 156.21 ± 2.61 PU-6C 15.14 ± 0.65 1885 ± 128 132.16 ± 34.53 PU-7 33.87 ± 3.34 1649 ± 89 197.82 ± 45.83 PU-7C 18.33 ± 2.78 1659 ± 47 138.84 ± 20.29 PU-8 35.25 ± 1.11 1381 ± 31 184.33 ± 22.21 PU-8C 18.61 ± 4.02 1507 ± 69 131.15 ± 19.63 PU-9 29.47 ± 1.03 1299 ± 44 135.22 ± 18.47 PU-9C 19.74 ± 2.30 1391 ± 79 116.54 ± 18.38 PU-10 36.22 ± 3.85 1310 ± 56 187.31 ± 18.32 PU-10C 24.53 ± 3.65 1357 ± 42 141.13 ± 36.73 PU-11 45.09 ± 1.43 1404 ± 62 223.53 ± 16.20 PU-11C 33.72 ± 5.16 1362 ± 41 163.64 ± 21.88 PU-12 34.32 ± 2.12 1628 ± 64 176.32 ± 24.83 PU-12C 17.61 ± 2.55 1676 ± 84 126.29 ± 31.37 PU-13 33.11 ± 4.90 1521 ± 39 200.76 ± 31.22

[0188] Experimental data analysis:

[0189] The chemical structure of the sample was characterized using ATR-FTIR spectroscopy. Figure 5 None of the samples were within 2270 cm. −1 The sample exhibited characteristic signal peaks at 1700 cm⁻¹, attributed to the N═C═O content in isocyanates; furthermore, the sample showed a peak at 1700 cm⁻¹. −1 and 3330 cm −1 The presence of stretching vibration signal peaks belonging to C═O and N–H respectively indicates that a complete reaction occurred between the raw materials, and the target polyurethane elastomer was successfully synthesized.

[0190] The test data for the above embodiments and comparative examples are shown in Table 2 above. The test results show that the maximum tensile strength, elongation at break, and toughness of the dynamically crosslinked polyurethane Example 1 (PU-1) prepared based on the block hard-domain phase-locked dynamic bond control strategy of this invention are 38.31 ± 1.86 MPa, 1554 ± 69%, and 221.08 ± 23.85 MJ / m, respectively. 3 The maximum tensile strength, elongation at break, and toughness of the dynamically crosslinked polyurethane Comparative Example 1 (PU-1C) prepared using the traditional non-block hard-domain phase-locked dynamic bond control strategy were 25.04 ± 0.85 MPa, 1429 ± 38%, and 154.93 ± 27.52 MJ / m, respectively. 3 ( Figure 6This demonstrates the effectiveness of the block hard-domain phase-locked dynamic bond control strategy. The mechanical properties of Examples 2 and 3 (PU-2 and PU-3), prepared by changing the chemical structure of the boron-nitrogen-internal-coordinated diol compound, a block macromolecular chain extender synthesized with a boron-nitrogen-internal-coordinated structure, are superior to those of Comparative Examples 2 and 3 (PU-2C and PU-3C). Similarly, the mechanical properties of Examples 4–10 (PU-4 to PU-10), prepared by changing the isocyanate chemical structure of the block macromolecular chain extender synthesized with a boron-nitrogen-internal-coordinated structure, are also superior to those of Comparative Examples 4–10 (PU-4C and PU-10C). Furthermore, the mechanical properties of Examples 11 and 12 (PU-11 to PU-12), prepared by changing the type of soft-segment polyether while keeping the chemical structure of the block macromolecular chain extender with a boron-nitrogen-internal-coordinated structure unchanged, are significantly improved compared to Comparative Examples 11 and 12 (PU-11C to PU-12C). The above results indicate that the polyurethane elastomer prepared by the block hard-domain phase-locked dynamic bond regulation strategy of this invention has a certain universality in improving mechanical properties compared with traditional polyurethane elastomers. Example 13 (PU-13), prepared by changing the molar ratio of the boron-nitrogen internally coordinated diol compound and isocyanate in the block macromolecular chain extender with altered boron-nitrogen internal coordination structure, exhibits slightly lower mechanical strength than Example 1 (PU-1), but a significant increase in mechanical properties compared to Comparative Example 1 (PU-1C). This indicates that controlling the molecular weight of the block chain extender can effectively regulate the mechanical properties of the material. The microstructure of the polyurethane elastomer was characterized using small-angle X-ray scattering (SAXS). Figure 7 The phase period of PU-2C (Comparative Example 2) prepared by conventional synthesis methods was 18.52 nm, while the phase period of the polyurethane elastomer in Example 2 was 20.76 nm, indicating that the size of the hard phase region can be increased through the block hard-domain phase-locked dynamic bond modulation strategy. The stress relaxation behavior of the samples was investigated using dynamic thermomechanical analysis (DMA). Figure 8 and Figure 9 The results showed that at 40 °C, the relaxation times of PU-1 (Example 1) and PU-3 (Example 3) prepared by the block hard-domain phase-locked dynamic bond control strategy were much shorter than those of Comparative Examples 1 and 3. This demonstrates that the larger hard phase size of the polyurethane samples prepared by the block hard-domain phase-locked dynamic bond control strategy leads to more dynamic covalent bonds being enveloped and shielded, thus exhibiting better stability under service conditions. Furthermore, the mechanical property degradation of Example 3 (PU-3) prepared by the block hard-domain phase-locked dynamic bond control strategy after immersion in deionized water for different times was much smaller than that of Comparative Example 3 (PU-3C). Figure 10 and 11 It exhibits better hydrolysis resistance, which highlights the effective gains of this invention over conventional polyurethane synthesis methods.

[0191] The above description is merely a preferred embodiment of the present invention, and therefore should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A mechanically reinforced dynamically crosslinked polyurethane material, characterized in that: It is prepared by in-situ polymerization of polyether / polyester diol, block macromolecular chain extender with boron-nitrogen internal coordination structure, isocyanate, catalyst and crosslinking agent. The structural formula of this boron-nitrogen internal coordination block macromolecular chain extender is: ， Wherein, R1 is selected from and R2 is selected from aliphatic or aromatic isocyanate moieties.

2. The mechanically reinforced dynamically crosslinked polyurethane material as described in claim 1, characterized in that: The polyether / polyester diol is selected from polytetrahydrofuran ether elastomer diol, polyethylene glycol, and polycaprolactone.

3. The mechanically reinforced dynamically crosslinked polyurethane material as described in claim 1, characterized in that: The isocyanate is selected from isophorone diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, dicyclohexylmethane diisocyanate, isophenyl dimethyl isocyanate, toluene diisocyanate, diphenylmethane diisocyanate, and 1,5-naphthalene diisocyanate.

4. The mechanically reinforced dynamically crosslinked polyurethane material as described in claim 1, characterized in that: The preparation method of the block-type macromolecular chain extender with boron-nitrogen internal coordination structure includes the following steps: a. Nucleophilic substitution reaction, the reaction route is as follows: ； b. Dehydration condensation reaction, the reaction route is as follows: ; R3 is selected from , and ; c. Nucleophilic addition reaction, the reaction route is as follows: 。 5. The mechanically reinforced dynamically crosslinked polyurethane material as described in claim 1, characterized in that: The crosslinking agent is tetrahydroxymethylphosphoric acid, and the catalyst is dibutyltin dilaurate.

6. A mechanically reinforced dynamically crosslinked polyurethane material as described in any one of claims 1 to 5, characterized in that: The molar ratio of the isocyanate, polyether / polyester diol, boron-nitrogen internally coordinated block macromolecular chain extender and crosslinking agent is 0.5-1.5: 0.2-0.8: 0.05-0.8: 0.05-0.

3.

7. A method for preparing a mechanically reinforced dynamically crosslinked polyurethane material according to any one of claims 1 to 6, characterized in that: Includes the following steps: (1) Under the action of the catalyst, the polyether / polyester diol and the isocyanate are reacted in an organic solvent to generate a prepolymer; (2) The prepolymer obtained in step (1) is subjected to a chain extension reaction with the block macromolecular chain extender containing boron and nitrogen internal coordination structure; (3) Add the crosslinking agent to the material obtained in step (2) to carry out an in-situ crosslinking and curing reaction; (4) Dry the material obtained in step (3) to obtain the final product.

8. The preparation method according to claim 7, characterized in that: The reaction in step (1) is carried out at a temperature of 40–90 °C for 1–3 h.

9. The preparation method according to claim 7, characterized in that: The chain extension reaction in step (2) is carried out at a temperature of 25–80 °C for a time of 0.5–6 h.

10. The preparation method according to claim 7, characterized in that: The in-situ crosslinking curing reaction in step (3) is carried out at a temperature of 50–100 °C for 2–12 h.

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