High-toughness dynamic waterborne polyurethane as well as preparation method and application thereof

Abstract

The invention discloses high-performance dynamic crosslinking waterborne polyurethane based on an orthogonal photochemical system and a preparation method of the high-performance dynamic crosslinking waterborne polyurethane. A visible light mediated in-situ metal coordination strategy is adopted, space-time coordination of metal ion release and free radical polymerization is achieved through an ethylenediamine tetraacetic acid salt photosensitive system, and a uniform metal coordination network is constructed. The technology breaks through the limitation of traditional step-by-step synthesis, and coordinate bond construction and polymer network curing are synchronously completed within 5 seconds (gelation time lt; the obtained material has ultrahigh mechanical properties (tensile strain of 1050%, stress of 8.4 MPa and toughness of 70 MJ / m < 3 >) and dynamic characteristics (shape memory rate gt; the self-repairing efficiency is 80.2%, and the reconfigurability is excellent). Meanwhile, the efficient preparation strategy greatly shortens the gelation time of the polyurethane, improves the printability of the polyurethane, facilitates flexible structural design, and is applied to customized manufacturing of intelligent devices such as flexible actuators and self-adaptive sealing elements. The preparation system provides a new normal form for performance breakthrough and engineering application of dynamic high polymer materials.

Description

Technical Field

[0001] The present invention belongs to the cross - field of intelligent dynamic polymer material design and flexible device manufacturing. Background Art

[0002] Polyurethanes have been widely studied worldwide due to their adjustable mechanical properties, excellent chemical stability, good weather resistance, versatility, etc. Waterborne polyurethanes (WPUs), as an important branch of polyurethane materials, have the advantages of being non - toxic and free of organic solvents. In addition, they have good compatibility with a variety of functional components and provide considerable flexibility in molecular structure design. By changing the types and compositions of reactive monomers, waterborne polyurethanes can be designed to have various characteristics and functions. In recent years, so - called dynamic cross - linked waterborne polyurethanes (DCWPUs) have received much attention. The involved dynamic cross - linked network can effectively dissipate energy under external forces, endowing DCWPUs with high toughness, improved stretchability, and increased tensile strength. At the same time, these dynamic networks can disassociate, exchange, or transform in response to external stimuli such as heat, light, pH changes, and solvents [1-4] . Therefore, DCWPUs also exhibit some advanced properties such as self - healing, shape - memory, shape - reconfigurability, or recyclability. In addition, combining their preparation with emerging additive manufacturing technologies such as 3D printing enables flexible customized design of DCWPU structures, greatly expanding the advanced applications of DCWPUs in the fields of flexible sensors, soft robots, and bioelectronics. Based on these advantages and environmental - friendly characteristics, developing strong, tough, multifunctional, and printable DCWPUs is a key and interesting research area in these fields.

[0003] The synthesis of DCWPUs is usually achieved by introducing reversible bonds into the polyurethane framework, such as host - guest interactions, metal - ligand coordination, ionic interactions, and hydrogen bonds [5-10]。It is worth noting that, compared with other ligands, metal ligands provide a wide range of bond strengths from strong covalent to weak non-covalent interactions. This synergy also allows for tunable metal ion exchange, enabling other functions such as aggregation-induced emission, photothermal conversion, and fluorescence. Therefore, DCWPU incorporating metal ligand coordination not only retains the inherent advantages of dynamic crosslinking but also acquires highly tunable mechanical properties and better environmental adaptability. However, the typical method of introducing metal ligands is to soak WPU in metal salt solutions. The diffusion of metal ions and their subsequent coordination with the polymer backbone are difficult to control. The resulting non-uniform network structure significantly reduces the mechanical properties of DCWPU. Direct blending of WPU with metal salts can form a relatively uniform network structure. Unexpected metal ligand coordination occurring during the mixing stage may induce unexpected gelation and affect the reaction efficiency of other functional groups. This makes the manufacturing process difficult to control and hinders the production of high-performance DCWPU with multiple reactions. In-situ polymerization is a very effective method for achieving precise control of metal-ligand coordination. However, the associated thermal-initiated polymerization, multi-step, and long manufacturing times limit their further combination with advanced additive manufacturing technologies to achieve customizable designs of DCWPU structures.

[0004] Based on the above research background, it is not difficult to find that developing new high-performance dynamic aqueous polyurethane materials with in-situ metal coordination and simultaneously developing simple, efficient, and rapid controllable synthesis and preparation methods have important theoretical and practical significance for realizing the printability of high-performance polyurethanes and expanding their application scope. Summary of the Invention

[0005] In view of the problems existing in the preparation process of existing dynamically crosslinked polyurethanes, such as difficult process control, non-uniform network structure, and low forming efficiency, the present invention innovatively proposes an in-situ metal coordination dynamic polyurethane based on an orthogonal photoreaction and its preparation method, and integrates 3D printing technology to achieve the forming of complex structures. The method simultaneously realizes through a photocontrolled orthogonal reaction system: 1) the precise release and coordination of metal ions in ethylenediaminetetraacetate; 2) vinyl radical polymerization reaction. This synergistic mechanism can construct a dynamic polyurethane material with a uniform metal coordination network within seconds, significantly enhancing the tensile stress, elongation at break, and toughness of the material. The thermoresponsive characteristics of dynamic coordination bonds endow the material with excellent shape memory, shape reconfigurability, and self-healing properties. In particular, this method shortens the gelation time and, combined with the direct-write 3D printing process, can precisely construct different structures, breaking through the structural design limitations of traditional thermal curing processes. The present invention provides a material solution with both high performance and high forming freedom for the development of customized intelligent devices in the fields of flexible electronics, biomedicine, etc., and is particularly suitable for the rapid manufacturing of precision devices such as wearable sensors and bionic soft robots.

[0006] The present invention provides a high-strength and tough dynamic aqueous polyurethane, which is a high-strength and tough dynamic aqueous polyurethane based on visible light-mediated in-situ metal coordination and is composed of the following components by mass parts:

[0007] Macromolecular material containing vinyl and carboxyl groups: 0 - 30 parts

[0008] Crosslinking agent: The addition amount of the crosslinking agent is 0.02% - 0.15% of the total mass of the gel

[0009] Initiator: The addition amount of the initiator is 0.5% - 5% of the total mass of the gel

[0010] Ruthenium(III) chloride hexahydrate photocatalyst: The addition amount of the ruthenium(III) chloride hexahydrate photoinitiator is 0.01% - 0.1% of the total mass of the gel

[0011] Solvent: 60 - 95 parts.

[0012] Furthermore, the polyurethane containing vinyl and carboxyl groups can be a single component or a mixture of multiple components with different functional groups;

[0013] Furthermore, the crosslinking agent is a disodium salt of ethylenediaminetetraacetic acid metal salt, including zinc disodium ethylenediaminetetraacetate or disodium salts of ethylenediaminetetraacetic acid containing other metals;

[0014] Furthermore, the initiator can be a water-soluble initiator or an oil-soluble initiator;

[0015] Furthermore, the solvent can be water or a mixture of water and other solvents.

[0016] The present invention provides a preparation method of a high-strength and tough dynamic aqueous polyurethane:

[0017] (1) Add 1 - 30 parts of the macromolecular material containing vinyl and carboxyl groups to 60 - 95 parts of the solvent, continuously stir, and after the solution is completely dissolved, add the crosslinking agent with an addition amount of 0.02% - 0.15% of the total mass of the gel, and stir evenly until completely dissolved;

[0018] (2) Add the catalyst with an addition amount of 0.5% - 5% of the total mass of the gel and the initiator with an addition amount of 0.02% - 0.15% of the total mass of the gel, and stir evenly until completely dissolved to obtain a reaction solution;

[0019] (3) After removing the bubbles in the reaction solution, a high-strength and tough dynamic aqueous polyurethane reaction solution based on visible light-mediated in-situ metal coordination can be obtained;

[0020] (4) Pour the high-strength and tough dynamic aqueous polyurethane reaction solution into a mold, place it under blue light irradiation for a certain period of time, and wait for the reaction to be complete to obtain a high-performance polyurethane;

[0021] (5) The obtained product from step (4) is dried to obtain a high-strength and tough dynamic aqueous polyurethane.

[0022] Furthermore, in method (1), the stirring temperature is between 20°C and 50°C.

[0023] Furthermore, in method (3), to remove the bubbles in the reaction solution, it can be left to disappear on its own, or the disappearance can be accelerated by external force, not limited to centrifugation, ultrasound, or shaking.

[0024] Furthermore, in method (4), the irradiation time under blue light is between 1 s and 1 h, and the blue light wavelength is between 400 nm and 500 nm.

[0025] Furthermore, in method (5), the drying temperature is higher than 20°C and lower than 60°C, and the drying time is not less than 6 hours.

[0026] The present invention provides a 3D printing application method for a high-strength and tough dynamic aqueous polyurethane, including single-needle printing: filling the reaction solution obtained from method (3) into the syringe of a direct-writing 3D printer, placing it on the three-dimensional movable platform of the printer, using drawing software such as SolidWorks to draw the required fine patterns and complex structure models, converting them into a mode recognizable by the 3D printer software and then importing them into the software, controlling the movement direction and movement speed of the 3D printer through the software, and applying pressure to the syringe through an air pump to control the extrusion amount of the solution. During the whole process, the extruded solution is irradiated with blue light to initiate an orthogonal chemical reaction inside the solution, and finally, a high-strength and tough dynamic aqueous polyurethane with fine patterns and complex structures can be obtained according to the preset.

[0027] The present invention innovatively develops an in-situ metal coordination type high-strength and tough dynamic aqueous polyurethane and its preparation method based on an orthogonal photochemical system. As Figures 1-5 shown, this method realizes the rapid curing and forming of the material within a second-level time window by synchronously triggering metal ion coordination and free radical polymerization reactions through light. The obtained material has both excellent mechanical properties and multiple intelligent response characteristics, and its performance advantages are mainly reflected in the following three aspects:

[0028] (1) The present invention uses blue light to trigger an orthogonal reaction system, enabling the formation of metal coordination bonds (sodium zinc ethylenediaminetetraacetate dynamic network) and the crosslinking of the polyurethane main chain (acrylate free radical polymerization) to proceed independently in the spatial and temporal dimensions. As Figure 1 shown, this strategy realizes the one-step construction of an interpenetrating network structure, with improved efficiency compared to the traditional step-by-step synthesis method. The whole reaction process is completed at room temperature and under solvent-free conditions, and the reaction conditions are mild, significantly superior to the thermal initiation system.

[0029] (2) The polyurethane system of the present invention achieves a double breakthrough in material properties through a photocontrolled orthogonal reaction: on the one hand, the mechanical properties are significantly improved. Under blue light triggering, the system simultaneously completes the free radical polymerization of acrylate and the construction of a dynamic coordination network of zinc ethylenediaminetetraacetate (EDTA-Zn 2+ ), obtaining a strong and tough material. On the other hand, the intelligent response is precisely regulated. The dynamic metal coordination bonds (dissociation temperature 60 - 80 °C) and hydrogen bond network endow the polyurethane material with excellent shape memory (>95%), shape reconfigurability (>95%) and self-healing properties (80.2%) under thermal stimulation.

[0030] (3) The light-triggering property (gel time < 5 s) of this system and the shear-thinning rheological behavior are perfectly adapted to the direct-write 3D printing process. As Figure 5 shown, through the regulation of printing parameters, structural design can be achieved, and bionic scaffolds, flexible grippers and smart bracelets for real-time monitoring of human movement are successfully prepared, verifying its application potential in the fields of biomedicine and flexible electronics. Description of the Drawings

[0031] Figure 1 It is a design diagram of DCWPU based on the VSMC strategy. (a) The design principle of the VSMC strategy for preparing DCWPU, explaining the orthogonal chemical reaction initiated by Ru(II) / aps, including the photodegradation of EDTA-Zn and free radical photopolymerization, making the one-step, rapid and controllable construction process of DCWPU possible; Demonstration of DCWPU performance: (b) Demonstration of the tensile performance of DCWPU; (c) Demonstration of the shape memory performance of DCWPU; (d) Demonstration of the self-healing performance of DCWPU; (e) Demonstration of the performance radar chart of DCWPU.

[0032] Figure 2 It is a diagram of the formation mechanism and mechanical properties of DCWPU. (a) Real-time rheological tests on sodium alginate precursors with and without EDTA-Zn added, indicating that EDTA-Zn can photolytically release Zn2+ and successfully coordinate with carboxyl groups; (b) Real-time viscosities of carboxyl-containing WPU, EDTA-Zn, Ru(II) and APS under blue light irradiation and non-irradiation; (c) X-ray diffraction spectra of DCWPU with different EDTA-Zn contents; (d) The toughness, stress and strain of DCWPU as a function of EDTA-Zn content; (e) Comparison of the toughness, strain and stress of DCWPU prepared by the VSMC strategy, heating at 70 °C and UV irradiation; (f) Stress of DCWPU prepared with different EDTA salts; (g) Comparison of the displacement-force curves of the puncture tests of DCWPU and WPU; (h) Stress relaxation behaviors of DCWPU and WPU; (i) Tensile performance of more than 1000 cycles, comparing DCWPU and WPU.

[0033] Figure 3Mechanism diagrams for improving mechanical properties. (a) Comparison of the mechanical properties of DCWPU prepared by soaking, mixing, and VSMC strategies; (b) Cyclic tensile properties of DCWPU prepared by soaking, mixing, and VSMC strategies at 300% strain; (c) Summary of the dissipated energy of DCWPU prepared by soaking, mixing, and VSMC strategies at 100%, 300%, and 500% strain; (d) Cyclic compression properties of DCWPU prepared by soaking, mixing, and VSMC strategies at 40% strain; (e) Summary of the hysteresis of DCWPU prepared by soaking, mixing, and VSMC strategies at 10%, 40%, and 70% strain; (f) Swelling test results of DCWPU prepared by soaking, mixing, and VSMC strategies; (g) Scanning electron microscope images and elemental maps of DCWPU prepared by soaking, mixing, and VSMC strategies; (h) Polymer network structure elucidating the potential mechanism for enhanced mechanical properties.

[0034] Figure 4 Diagrams for dynamic metal coordination networks and multifunctional properties. (a) Reversibility of the dynamic metal coordination network under thermal stimulation; (b) Summary of the self-healing efficiency at different temperatures (25 °C, 50 °C, and 75 °C) and durations (6 h, 12 h, and 24 h); (c) Stress relaxation time of DCWPU at different temperatures; (d) Variation of the solid angle (θ) of shape-reconstructed DCWPU with time; (e) Dynamic mechanical properties of DCWPU; (f) Comprehensive demonstration of the multifunctional properties of DCWPU, including shape reconstruction, shape memory, and self-healing ability.

[0035] Figure 5 Diagrams for the application of dynamic polyurethane in customizable intelligent soft devices. (a) Combining 3D-printed customizable scaffolds and fixtures; (b) Demonstrating self-wearable 3D sensors utilizing the shape reconstruction, shape memory, and conductivity of polyurethane, showing its application in real-time monitoring of limb movement. Specific implementation manners

[0036] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. However, this should not be construed as limiting the scope of the above-mentioned subject matter of the present invention to the following embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0037] Specific Example 1: A preparation method for a high-strength and tough printable dynamic aqueous polyurethane, and the specific preparation steps are as follows:

[0038] Synthesis of polyurethane containing vinyl and carboxyl groups:

[0039] Under nitrogen protection, polyethylene glycol (PEG-2000, 5.00 g) dried under vacuum at 100 °C for 5 hours, dimethylolpropionic acid (DMPA, 0.28 g) and phosphorus pentoxide were placed in a drying system and transferred to a 100 mL three-necked flask equipped with a mechanical stirrer. Isophorone diisocyanate (IPDI, 0.91 mL), catalyst dibutyltin dilaurate (DBTDL, 50 μL) and anhydrous N,N-dimethylformamide (DMF, 15 mL) were added in sequence, and the reaction was carried out at a constant temperature of 80 ± 1 °C in an oil bath for 3 hours to form a terminal isocyanate prepolymer (OCN-PEG-NCO); Subsequently, a DMF solution of DMPA (2 mL) was added dropwise to the system, and the reaction was continued at 80 °C for 3 hours until the -NCO groups were completely consumed; After the system was cooled to 30 ± 2 °C, anhydrous potassium carbonate (0.60 g) was added for a neutralization reaction for 30 minutes, and finally acryloyl chloride (1.00 mL) was slowly added dropwise under an ice bath condition of 0 - 5 °C for end-group modification, and the reaction was terminated after 10 hours of continuous reaction; The product was precipitated and purified three times with ether, and dried under vacuum for 24 hours to obtain bifunctionalized waterborne polyurethane (WPU).

[0040] Preparation of high-strength and tough dynamic waterborne polyurethane:

[0041] Disperse vinyl-carboxyl bifunctionalized polyurethane (0.37 ± 0.01 g) in 1.50 ± 0.05 mL of deionized water, and stir magnetically (600 rpm) for 2.0 ± 0.1 hours until completely dissolved. Add photoinitiator ruthenium bipyridine ([Ru(bpy)3]Cl2, final concentration 52.0 ± 0.5 μM), radical initiator ammonium persulfate (APS, 30.0 ± 0.3 mM) and zinc ion chelator sodium zinc ethylenediaminetetraacetate (Zn-EDTA, 0.080 ± 0.005 mM) in sequence, and ultrasonically disperse (40 kHz, 200 W) for 10 minutes under light-shielding conditions to form a homogeneous reaction solution; After injecting the mixture into a polytetrafluoroethylene mold, vacuum degassing treatment was carried out for 15 ± 1 minutes to remove bubbles; Subsequently, use a blue light source (λ = 450 ± 5 nm, irradiance 15.0 ± 0.2 mW / cm 2 ) Irradiate vertically for 2.0 ± 0.1 minutes to complete photo-crosslinking curing, and the obtained polyurethane sample was dried at 25 ± 1 °C for 24 hours to enhance toughness.

[0042] Demonstration of the dynamic properties of high-strength and tough dynamic waterborne polyurethane:

[0043] (a) Self-healing: Use a blade cutting device (blade thickness 0.1 mm, blade angle 30°) to perform through mechanical cutting on the polyurethane material. Align the cut sections of the two separated specimens precisely to ensure that the contact surfaces coincide, and place the formed polyurethane specimen in a laboratory environment at 70 °C for 7 h to complete self-healing.

[0044] (Figure 4 -b)

[0045] (b) Remolding: Place the rectangular specimen in a constant temperature environment of 70 ± 1 °C for heat treatment for 3 hours, then perform equiaxed plastic deformation treatment to form it into a standard U-shaped structure; after the shape is stable, cool it to the ambient temperature of 25 ± 2 °C at a controlled cooling rate of 0.5 °C / min; transfer the shaped specimen to a constant temperature and humidity chamber at 25 ± 0.5 °C and a relative humidity of 45 ± 5% for storage in the dark. Set the aging observation nodes at 0d, 15d, 30d, 45d, 60d, 75d, and 90d respectively, and use an angle measuring instrument (resolution 0.1°) to perform three-dimensional space measurement on the apex angle of the bent part of the specimen.( Figure 4 -d)

[0046] (c) Shape memory: Place the polyurethane sample in a constant temperature environment of 25.0 ± 0.5 °C, form a temporary shape through external force, then cool it to 10.0 ± 1.0 °C at a programmed rate of 2 °C / min and keep it constant for 30 minutes to complete shape freezing; after removing the external force, the material maintains the stability of the temporary shape. When the system temperature rises to 45.0 °C at a rate of 3 °C / min, the sample spontaneously returns to its initial form to verify its shape memory effect.( Figure 4 -f)

[0047] Printing performance demonstration of high-strength and tough dynamic waterborne polyurethane:

[0048] The three-dimensional printing of DCWPU is completed using a custom-designed DIW three-dimensional printer with a maximum printing size of 20 cm × 20 cm × 10 cm. Before printing, load the precursor into a 10-ml black syringe, and after centrifugal degassing at 13,000 rpm, select a nozzle with an inner diameter of 260 μm or 390 μm. Connect the syringe to a pressure supply and fix it to the robotic print head. By precisely controlling the pressure of 3 - 4 kPa, the movement speed of 15 mm / s, and visible light curing at 452 nm, the customized manufacturing of a planar scaffold of the DCWPU structure is finally achieved. The three-dimensional structure of the planar scaffold is designed and completed based on SketchUp software. Thanks to the excellent shape reconfigurability of polyurethane, the printed planar fixture can be easily remolded into a complex curved surface configuration and achieve active grasping through the shape recovery effect, demonstrating excellent shape memory performance.( Figure 5 -a)

[0049] Specific Example 2: A preparation method of high-strength, tough, and printable dynamic waterborne polyurethane, and the specific preparation steps are as follows:

[0050] Synthesis of polyurethane containing vinyl and carboxyl groups:

[0051] Under nitrogen protection, polyethylene glycol (PEG-2000, 5.00 g) dried under vacuum at 100 °C for 5 hours, dimethylolpropionic acid (DMPA, 0.28 g) and phosphorus pentoxide were placed in a drying system and transferred to a 100 mL three-necked flask equipped with a mechanical stirrer. Isophorone diisocyanate (IPDI, 0.91 mL), catalyst dibutyltin dilaurate (DBTDL, 50 μL) and anhydrous N,N-dimethylformamide (DMF, 15 mL) were added in sequence, and the reaction was carried out at a constant temperature of 80 ± 1 °C in an oil bath for 3 hours to generate an isocyanate-terminated prepolymer (OCN-PEG-NCO); Subsequently, the DMF solution (2 mL) of DMPA was added dropwise to the system, and the reaction was continued at 80 °C for 3 hours until the -NCO groups were completely consumed; The system was cooled to 30 ± 2 °C, and then anhydrous potassium carbonate (0.60 g) was added for neutralization reaction for 30 minutes. Finally, acryloyl chloride (1.00 mL) was slowly added dropwise under an ice bath condition of 0-5 °C for end-group modification, and the reaction was continued for 10 hours and then terminated; The product was precipitated and purified three times with ether, and then dried under vacuum for 24 hours to obtain bifunctionalized waterborne polyurethane (WPU).

[0052] Preparation of high-strength and tough dynamic waterborne polyurethane:

[0053] Disperse vinyl-carboxyl bifunctionalized polyurethane (0.37 ± 0.01 g) in 1.50 ± 0.05 mL of deionized water, and stir magnetically (600 rpm) for 2.0 ± 0.1 hours until completely dissolved. Add photoinitiator ruthenium bipyridine ([Ru(bpy)3]Cl2, final concentration 52.0 ± 0.5 μM), radical initiator ammonium persulfate (APS, 30.0 ± 0.3 mM) and zinc ion chelator sodium zinc ethylenediaminetetraacetate (Zn-EDTA, 0.080 ± 0.005 mM) in sequence, and ultrasonically disperse (40 kHz, 200 W) for 10 minutes under light-shielding conditions to form a homogeneous reaction solution; After injecting the mixture into a polytetrafluoroethylene mold, vacuum degassing treatment was carried out for 15 ± 1 minutes to remove bubbles; Subsequently, it was irradiated vertically with a blue light source (λ = 450 ± 5 nm, irradiance 15.0 ± 0.2 mW / cm 2 ) for 2.0 ± 0.1 minutes to complete photocrosslinking and curing, and the obtained polyurethane sample was dried at 25 ± 1 °C for 24 hours to enhance toughness.

[0054] Demonstration of the dynamic properties of high-strength and tough dynamic waterborne polyurethane:

[0055] (a) Self-healing: Use a blade cutting device (blade thickness 0.1 mm, blade angle 30°) to perform through mechanical cutting on the polyurethane material. Align the cut surfaces of the two separated specimens precisely to ensure that the contact surfaces coincide, and place the formed polyurethane specimen in a laboratory environment at 25 °C for 12 h to complete self-healing.

[0056] (b) Remolding: Place the rectangular specimen in a constant temperature environment of 70 ± 1 °C for heat treatment for 3 hours, and then perform equiaxed plastic deformation treatment to form it into a standard W-shaped structure; after the shape is stable, cool it to the ambient temperature of 25 ± 2 °C at a controlled cooling rate of 0.5 °C / min; transfer the shaped specimen to a constant temperature and humidity chamber at 25 ± 0.5 °C and a relative humidity of 45 ± 5% for light-shielded storage. Set the aging observation nodes at 0d, 15d, 30d, 45d, 60d, 75d, and 90d respectively, and use an angle measuring instrument (resolution 0.1°) to perform three-dimensional space measurement on the apex angle of the bent part of the specimen.

[0057] (c) Shape memory: Place the polyurethane sample in a constant temperature environment of 25.0 ± 0.5 °C, form a temporary shape through external force, and then cool it programatically at 2 °C / min to 10.0 ± 1.0 °C and keep it constant for 30 minutes to complete shape freezing; after removing the external force, the material maintains the stability of the temporary shape. When the system temperature rises to 25.0 °C at a rate of 3 °C / min, the sample spontaneously returns to its initial form to verify its shape memory effect.

[0058] (4) Demonstration of the printing performance of high-strength and tough dynamic waterborne polyurethane:

[0059] The three-dimensional printing of DCWPU is completed by a custom-designed DIW three-dimensional printer with a maximum printing size of 20 cm × 20 cm × 10 cm. Before printing, load the precursor into a 10-ml black syringe, and select a 260-μm or 390-μm (inner diameter) nozzle after centrifugal degassing at 13,000 rpm. Connect the syringe to a pressure supply and fix it to the robotic print head. By precisely controlling a pressure of 3 - 4 kPa, a movement speed of 15 mm / s, and 452-nm visible light curing, a DCWPU wearable bracelet with a flower pattern is finally successfully customized, and its three-dimensional structure is designed by SketchUp software. Thanks to the excellent conductivity and uniform network structure of the polyurethane material, the ribbon material exhibits sensitive, stable, and uniform strain response characteristics under various tensile / compressive conditions. It is particularly worth noting that the two-dimensional printed flower ribbon can be remolded into a three-dimensional circular configuration and can be reprogrammed into a straight state through the shape memory effect. When subjected to thermal stimulation, the programmed straight flower ribbon can spontaneously recover its original three-dimensional circular structure, and this self-recovery characteristic enables it to adaptively fit different parts of the human body. Experiments have proved that the reconstructed flower ribbon can perfectly fit the wrist and knee, and its resistance signal can respond sensitively and in real time to limb movements (such as wrist bending and leg movements), and different motion states can be accurately distinguished by analyzing the amplitude change of the resistance signal.

Claims

1. A high-strength and tough dynamic aqueous polyurethane, characterized in that, The polyurethane is a high-toughness dynamic waterborne polyurethane based on visible light-mediated in-situ metal coordination, and is composed of the following components in parts by mass: Macromolecular materials containing vinyl and carboxyl groups: 0-30 parts Cross-linking agent: The amount of cross-linking agent added is 0.02%-0.15% of the total mass of the gel Initiator: The amount of initiator added is 0.5%-5% of the total mass of the gel Terpyridine ruthenium chloride hexahydrate photocatalyst: The amount of terpyridine ruthenium chloride hexahydrate photoinitiator added is 0.01%-0.1% of the total mass of the gel Solvent: 60-95 parts.

2. A high-toughness dynamic waterborne polyurethane as claimed in claim 1, characterized in that: The polyurethane containing vinyl and carboxyl groups may be a single component or a mixture of multiple components containing different functional groups; The cross-linking agent is a disodium metal salt of ethylenediaminetetraacetic acid, including disodium zinc salt of ethylenediaminetetraacetic acid or disodium salt of ethylenediaminetetraacetic acid containing other metals; The initiator may be a water-soluble initiator or an oil-soluble initiator; The solvent may be water or a mixture of water and other solvents.

3. A high-strength and tough dynamic aqueous polyurethane according to claim 1 or 2, characterized in that, The high-toughness dynamic waterborne polyurethane is prepared by the following preparation method: (1) adding 1-30 parts of a macromolecular material containing vinyl and carboxyl groups to 60-95 parts of a solvent, stirring continuously, and after the solution is completely dissolved, adding 0.02%-0.15% of a crosslinking agent in an amount of 0.02%-0.15% of the total mass of the gel, stirring evenly until it is completely dissolved; (2) adding 0.5% to 5% of the total mass of the gel as catalyst and 0.02% to 0.15% of the total mass of the gel as initiator, stirring evenly until completely dissolved, to prepare a reaction solution; (3) After removing the bubbles in the reaction solution, a high-strength and dynamic waterborne polyurethane reaction solution based on visible light-mediated in-situ metal coordination can be obtained; (4) pouring the high-toughness dynamic water-based polyurethane reaction solution into a mold, irradiating it under blue light for a certain period of time, and waiting for the reaction to be complete to obtain a high-strength performance polyurethane; (5) Drying the product obtained in step (4) to obtain a high-strength and high-toughness dynamic water-based polyurethane.

4. The high-strength and tough dynamic aqueous polyurethane according to claim 3, characterized in that, The stirring temperature in the method (1) is between 20°C and 50°C.

5. The high-strength and tough dynamic aqueous polyurethane according to claim 3, wherein, In the method (3), the bubbles in the reaction solution can be removed by waiting for them to disappear on their own, or by accelerating their disappearance by external force, which is not limited to centrifugation, ultrasound, and shaking.

6. The high-strength and tough dynamic aqueous polyurethane according to claim 3, wherein In the method (4), the exposure time under blue light is between 1S and 1H, and the wavelength of the blue light is between 400nm and 500nm.

7. The high-strength and tough dynamic aqueous polyurethane according to claim 3, wherein In the method (5), the drying temperature is higher than 20°C and lower than 60°C, and the drying time is not less than 6 hours.

8. The high-strength and tough dynamic aqueous polyurethane according to claim 3, characterized in that, The 3D printing application method of the high-toughness dynamic water-based polyurethane comprises the following schemes: Single-needle printing: The reaction solution obtained from method (3) is filled into the syringe of a direct-writing type 3D printer and placed on the three-dimensional movable platform of the printer. Use drawing software such as SolidWorks to draw the required fine patterns and complex structure models, convert them into a mode recognizable by the 3D printer software and then import them into the software. Control the movement direction and movement speed of the 3D printer through the software, and apply pressure to the syringe through an air pump to control the extrusion amount of the solution. During the whole process, irradiate the extruded solution with blue light to initiate the orthogonal chemical reaction inside the solution. Finally, a high-strength, tough and dynamic aqueous polyurethane with fine patterns and complex structures can be obtained according to the pre-set requirements.

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