Thermosetting recoverable method based on multifunctional photoinitiator

Abstract

The invention discloses a multifunctional photoinitiator, which is synthesized by grafting diacylphosphine oxide onto hydroxyapatite, and the multifunctional photoinitiator can be degraded under an acidic condition. The photoinitiator can effectively polymerize a plurality of monofunctional acrylic esters to generate a cured material which can be degraded by acid. After degradation, the resulting linear polymer can be easily dissolved in a corresponding monomer for re-curing. Compared with the original polymer, the recuring material has more excellent mechanical properties due to physical crosslinking points formed by the linear polymer in a curing network. According to the invention, the diacylphosphine oxide is grafted to the hydroxyapatite, so that the photoinitiator has the functions of crosslinking, blue light initiation and degradability. Therefore, the universality of the material is enhanced, and multifunctional integration of the material is realized. And compared with a photoinitiator which needs to be initiated under a relatively short radiation wavelength, environmental pollution can be greatly reduced, and the problem of high energy consumption is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of material chemistry and relates to a method for recycling thermosetting plastics containing a multifunctional photoinitiator. Background Art

[0002] 3D printing is one of the key development areas. 3D printing materials are a key foundation for the advancement of the 3D printing industry and a core element of its technological innovation. Thermosetting photosensitive resins, due to their excellent mechanical properties, thermal stability, chemical resistance, and excellent compatibility with 3D printing systems, account for nearly half of the 3D printing material market. However, after curing, these materials often form permanent covalent bonds with a high cross-link density, making the recycling and reuse of printed structures a significant challenge, and ultimately, they are destined for incineration or landfill. The explosive growth in global 3D printing material consumption is expected to lead to massive resource waste and serious environmental impacts.

[0003] Faced with this challenge, domestic and foreign scholars have adopted some alternative materials in the printing process: 1) Thermoplastic polymers. Reference 1 achieved digital light processing (DLP) 3D printing of 4-acryloylmorpholine thermoplastic polymer by controlling the kinetic process of competition between polymerization and polymer dissolution during the printing process, and further constructed functional 3D devices by printing water-soluble sacrificial molds. In order to achieve rapid solid-liquid separation, thermoplastic polymers need to have both a fast polymerization rate and a high glass transition temperature, which results in fewer monomer selectivities; and because the cross-linking density is zero, polymer dissolution cannot be completely suppressed during printing, and the printing accuracy is lower than that of thermosetting polymers (Deng S, Wu J, Dickey MD, et al. Rapid open-air digital light 3D printing of thermoplastic polymer [J]. Advanced Materials, 2019, 31 (39): 1903970.). 2) Glass-like polymers (Vitrimers). Reference 2 uses Vitrimers, which have both the high cross-linking density of thermosetting polymers and the reprocessability of thermoplastic polymers, to print high-precision complex three-dimensional structures. The ester exchange reaction promoted by high temperature gives the material the ability to repair, reshape and reprocess. However, because the cross-linking density of Vitrimers is too high and constant, it often requires high-temperature treatment before it can be recycled and reused, making this type of material unsuitable for use in certain scenarios that are not resistant to high temperatures (Zhang B, Kowsari K, Serjouei A, et al. Reprocessable thermosets for sustainable three-dimensional printing [J]. Nature Communications, 2018, 9 (1): 1831.). 3) Cleavable cross-linker. Reference 3 adds a hydrolyzable cross-linker to 4-acryloylmorpholine monomer, improves the printing resolution, and produces a high-performance 3D sensor using a sacrificial mold. The dissociation of the small molecule cleavable cross-linker effectively reduces the cross-linking density of the resin material, thereby achieving the decomposition of the resin material.However, due to the disordered distribution of cross-linking points in the system, the molecular weight distribution of the polymer chains between the cross-linking points is relatively wide, which affects the performance of the decomposition products and needs further optimization (Peng S, Wang Z, Lin J, et al. Tailored and highly stretchable sensor prepared by crosslinking an enhanced 3D printed uv-curable sacrificial mold[J]. Advanced Functional Materials, 2021, 31(10): 2008729.).

[0004] It is not difficult to find that current research focuses on monomers / cross-linkers with specific structures. There is no universal strategy to achieve the recycling and reuse of photosensitive resins after curing, and it is difficult to simultaneously meet the specific requirements of printing accuracy, mechanical strength, material safety, etc. in practical applications. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention introduces cleavable groups on the surface of nanoparticles grafted with bisacylphosphine oxide to prepare a multifunctional photoinitiator capable of initiation, crosslinking, and cleavage. The crosslinking density of the curing material is regulated by adjusting the grafting rate on the surface of the nanoparticles and the amount used in the resin. The influence of the crosslinking density on the photocuring process, the properties of the curing material, and the decomposition efficiency is systematically studied, and the regulatory mechanism between the composition structure of the multifunctional photoinitiator (HAP-BAPO) and its initiation, crosslinking, and cleavage properties is established.

[0006] Selecting high-performance photosensitive resins enables high-precision 3D printing. The printed structures are then decomposed under mild conditions. The resulting linear polymers are dissolved in corresponding monomers to produce recycled resins for re-use in 3D printing, thus enabling the recycling and reuse of cured photosensitive resin materials. This provides a new, universal strategy for the development of recyclable photosensitive resin materials for 3D printing. This is expected to significantly increase material selection and allow for the addition of more functionalities to printed structures, thereby expanding the application of 3D printing. Furthermore, material recycling and reuse can effectively reduce resource consumption, minimize environmental impact, and promote the development of a sustainable circular economy.

[0007] The technical solutions of the present invention are as follows:

[0008] The present invention provides a multifunctional photoinitiator with the following structural formula:

[0009]

[0010] Another aspect of the present invention provides a preparation method based on a multifunctional photoinitiator, which specifically comprises the following steps:

[0011] (1) Vacuum drying and activation of hydroxyapatite: hydroxyapatite is placed in a round-bottom flask and connected to a Schlenk system to dry the hydroxyapatite under vacuum and heating conditions to remove surface moisture and thus increase its activity;

[0012] (2) Condensation reaction of hydroxyapatite and silane coupling agent: Hydroxyapatite is dispersed in solvent 1, followed by adding a silane coupling agent, followed by dropping an organic base 1. Under an inert gas atmosphere, the reaction is heated by a step-by-step heating method. Subsequently, the solvent is removed, and a bisacylphosphine oxide precursor and solvent 2 are added thereto. Then, organic base 2 is added dropwise as an acid-binding agent, and the reaction is carried out under heating conditions. Subsequently, solvent 3 is added under low temperature conditions, and the reaction is carried out under certain conditions. Finally, the solvent is removed, purified, and dried to obtain a pure multifunctional photoinitiator.

[0013] The present invention provides a multifunctional photoinitiator, which is a functional photoinitiator obtained by the method.

[0014] Another aspect of the present invention provides a method for recycling thermosetting plastics containing a multifunctional photoinitiator, the method comprising the following specific steps:

[0015] Preparation of photosensitive resin: 0.02 wt% multifunctional photoinitiator, 0.01 wt% Sudan I and monofunctional acrylate are uniformly mixed to form a photosensitive resin;

[0016] First 3D printing: according to the preset structural model parameters, the photosensitive resin is placed in the 3D printer for 3D printing to obtain a 3D printed structure;

[0017] Degradation of 3D printed structures: The 3D printed structures were immersed in an acidic solution. After the structure was completely degraded, the solution was concentrated and purified with methanol to obtain a linear polymer.

[0018] The recyclable photosensitive resin is prepared by uniformly mixing 0.02 wt% of a multifunctional photoinitiator, 0.01 wt% of Sudan I, 5 wt% of a linear polymer, and a monofunctional acrylate to form a recyclable photosensitive resin.

[0019] Second 3D printing: According to the preset structural model parameters, the photosensitive resin is placed in the 3D printer for 3D printing to obtain a 3D printed structure.

[0020] The structural formula of the multifunctional photoinitiator is as follows:

[0021]

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The present invention synthesizes a multifunctional photoinitiator (HAP-BAPO) that is initiatable, crosslinkable, and degradable by grafting bisacylphosphine oxide onto hydroxyapatite. This photoinitiator can effectively polymerize various monofunctional acrylate monomers. The structures printed using a blue light DLP 3D printer can be degraded under acidic conditions. After degradation, the resulting linear polymer can be easily dissolved in the corresponding monomer to prepare a new photosensitive resin to reprint a new structure, realizing recyclable 3D printing of materials;

[0024] (2) The multifunctional photoinitiator of the present invention has high initiation efficiency under visible light (450nm blue light). Compared with traditional ultraviolet light, it is safer, has a greater curing depth, and is less harmful to the human body. It has significant advantages in the field of dental materials that come into contact with the human body.

[0025] (3) The degradation of the present invention breaks down at the crosslinking points, and the linear polymer obtained by degradation has a narrow molecular weight distribution. Because the linear polymer forms physical crosslinking points within the cured network, the newly cured material exhibits superior mechanical properties;

[0026] (4) The printed structure can be completely degraded in slightly acidic soil (pH 6) within approximately 75 days. The environmental safety of the material was demonstrated through plant, extracellular, and intracellular experiments. These advances can enhance the versatility of the material, enable multifunctional integration in printed structures, and expand the scope of 3D printing applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the solid-state H-NMR spectrum of the multifunctional photoinitiator of the present invention.

[0028] Figure 2 This is the solid-state nuclear magnetic carbon spectrum of the multifunctional photoinitiator of the present invention.

[0029] Figure 3 This is the solid-state NMR silicon spectrum of the multifunctional photoinitiator of the present invention.

[0030] Figure 4 This is the solid nuclear magnetic phosphorus spectrum of the multifunctional photoinitiator of the present invention.

[0031] Figure 5 This is the solid infrared spectrum of the multifunctional photoinitiator of the present invention.

[0032] Figure 6 This is the solid ultraviolet spectrum of the multifunctional photoinitiator of the present invention.

[0033] Figure 7 is the double bond conversion rate of the multifunctional photoinitiator of the present invention.

[0034] Figure 8 This is the H NMR spectrum of polyethyl acrylate.

[0035] Figure 9 This is the H NMR spectrum of polyethylene glycol monomethyl ether acrylate.

[0036] Figure 10 This is the H NMR spectrum of polylauryl acrylate.

[0037] Figure 11 Polyethylene glycol monomethyl ether acrylate (M n =480) H NMR spectrum.

[0038] Figure 12 This is the H NMR spectrum of polyisobutyl acrylate.

[0039] Figure 13 This is the H NMR spectrum of polybornyl acrylate.

[0040] Figure 14 These are stress-strain curves of a photosensitive resin and a photosensitive resin containing 5 wt% polyethyl acrylate linear polymer.

[0041] Figure 15 These are stress-strain curves of a photosensitive resin and a photosensitive resin containing 5 wt% of a linear polymer of polyethylene glycol monomethyl ether acrylate.

[0042] Figure 16 These are stress-strain curves of a photosensitive resin and a photosensitive resin containing 5 wt% polylauryl acrylate linear polymer.

[0043] Figure 17 It is a photosensitive resin and contains 5wt% polyethylene glycol monomethyl ether acrylate (M n =480) linear polymer photosensitive resin stress-strain curve.

[0044] Figure 18 These are stress-strain curves of a photosensitive resin and a photosensitive resin containing 5 wt% polyisobutyl acrylate linear polymer.

[0045] Figure 19 These are stress-strain curves of a photosensitive resin and a photosensitive resin containing 5 wt% polybornyl acrylate linear polymer.

[0046] Figure 20 Recyclable 3D printing with photosensitive resin. a) 3D printing schematic. b) Kelvin unit cell structure. c) Surface vertex center of mass structure. d) Pentagonal icosahedron structure. e) Recyclable 3D printing schematic. f) Supercube structure. g) Fischer-Koch S structure. h) Underlying supercube structure.

[0047] Figure 21Degradation of Kelvin units. a) Photograph of a Kelvin unit structure without linear polymers (i); plastic after burial in slightly acidic soil for 15 (ii), 45 (iii), and 60 (iv) days. b) Photograph of a Kelvin unit structure with 5% linear polymers (i); plastic after burial in slightly acidic soil for 15 (ii), 45 (iii), and 60 (iv) days.

[0048] Figure 22 The figures show the situation of wheat and mung bean seedlings after 15 days of growth in the presence of degradation products.

[0049] Figure 23 is the germination rate of wheat and mung bean after exposure to degradation products.

[0050] Figure 24 Root length and seedling length of wheat after 15 days of growth in the presence of degradation products.

[0051] Figure 25 Root length and seedling length of mung bean after 15 days of growth in the presence of degradation products.

[0052] Figure 26 The survival rates of mouse L929 fibroblasts and human LO2 cells at different concentration gradients after co-culture with degradation products for 48 hours.

[0053] Figure 27 Serum alanine aminotransferase (ALT) levels in mice treated with the control group and degradation products for 7 days.

[0054] Figure 28 Blood urea nitrogen (BUN) levels in mice treated with the control group or degradation products for 7 days.

[0055] Figure 29 Representative images of live / dead assay (Calcein-AM / PI staining) of L929 fibroblasts and LO cells at different concentration gradients after co-culture with degradation products for 48 h.

[0056] Figure 30 These are light microscopic photographs of hematoxylin-eosin (H&E)-stained heart, liver, spleen, lung, and kidney tissue sections of mice in the control group and the degradation product-treated group after 7 days of treatment with degradation products.

[0057] Figure 31 This is an explanatory diagram of the structural formula of the multifunctional photoinitiator of the present invention.

[0058] Table 1 shows the molecular weights of the measured monomers and their degraded linear polymers DETAILED DESCRIPTION

[0059] The present invention will be further described below with reference to the accompanying drawings

[0060] The present invention provides a multifunctional photoinitiator with the following structural formula:

[0061]

[0062] Another aspect of the present invention provides a preparation method based on a multifunctional photoinitiator, which specifically comprises the following steps:

[0063] (1) Vacuum drying and activation of hydroxyapatite: hydroxyapatite is placed in a round-bottom flask and connected to a Schlenk system to dry the hydroxyapatite under vacuum and heating conditions to remove surface moisture and thus increase its activity;

[0064] (2) Condensation reaction of hydroxyapatite and silane coupling agent: Hydroxyapatite is dispersed in solvent 1, followed by adding a silane coupling agent, followed by dropping an organic base 1. Under an inert gas atmosphere, the reaction is heated by a step-by-step heating method. Subsequently, the solvent is removed, and a bisacylphosphine oxide precursor and solvent 2 are added thereto. Then, organic base 2 is added dropwise as an acid-binding agent, and the reaction is carried out under heating conditions. Subsequently, solvent 3 is added under low temperature conditions, and the reaction is carried out under certain conditions. Finally, the solvent is removed, purified, and dried to obtain a pure multifunctional photoinitiator.

[0065] The present invention provides a specific embodiment, in step (1), the reaction temperature is 80-90°C;

[0066] The present invention provides a specific embodiment, in step (1), the reaction time is 24 hours.

[0067] The present invention provides a specific embodiment, in step (2), solvent 1 is one or both of cyclohexane and cyclopentane;

[0068] The present invention provides a specific embodiment, in step (2), the silane coupling agent is hex-5-en-1-yltrimethoxysilane;

[0069] The present invention provides a specific embodiment, in step (2), the ratio of hydroxyapatite to silane coupling agent is 1:2;

[0070] The present invention provides a specific embodiment, in step (2), the organic base 1 is n-propylamine;

[0071] The present invention provides a specific embodiment, in step (2), the inert gas is argon or nitrogen;

[0072] The present invention provides a specific embodiment, in step (2), the step-by-step heating method is to heat at room temperature and stir for 2 hours, then heat to 60°C and continue stirring for 2 hours;

[0073] The present invention provides a specific embodiment, in step (2), the method for removing the solvent is to first raise the temperature to 60°C under vacuum, maintain it for 2 hours, and then raise the temperature to 90°C and maintain it for 2 hours;

[0074] The present invention provides a specific embodiment, in step (2), the bisacylphosphine oxide precursor 1 is 1,1′-phosphite bis[1-(2,4,6-trimethylphenyl)methanone;

[0075] The present invention provides a specific embodiment, in step (2), solvent 2 is one or both of toluene and tetrahydrofuran;

[0076] The present invention provides a specific embodiment, in step (2), the organic base 2 is one or both of 1,1,3,3-tetramethylguanidine or triethylamine;

[0077] The present invention provides a specific embodiment, in step (2), the temperature of the heating condition reaction is 60°C;

[0078] The present invention provides a specific embodiment, in step (2), the heating condition reaction time is 24 hours;

[0079] The present invention provides a specific embodiment, in step (2), the temperature of the low temperature reaction is an ice bath at 0°C;

[0080] The present invention provides a specific embodiment, in step (2), the reaction time under low temperature conditions is 6 hours;

[0081] The present invention provides a specific embodiment, in step (2), the solvent 3 is a 30% by mass hydrogen peroxide solution;

[0082] The present invention provides a specific embodiment, in step (2), the purification method is washing with ethanol 3-5 times and removing the solvent under reduced pressure;

[0083] The present invention provides a specific embodiment, in step (2), the drying method is drying at 60° C. in a high vacuum for 1 day.

[0084] The present invention provides a method for recycling thermosetting plastics containing a multifunctional photoinitiator, the method comprising the following specific steps:

[0085] Preparation of photosensitive resin: 0.02 wt% multifunctional photoinitiator, 0.01 wt% Sudan I and monofunctional acrylate are uniformly mixed to form a photosensitive resin;

[0086] First 3D printing: according to the preset structural model parameters, the photosensitive resin is placed in the 3D printer for 3D printing to obtain a 3D printed structure;

[0087] Degradation of 3D printed structures: The 3D printed structures were immersed in an acidic solution. After the structure was completely degraded, the solution was concentrated and purified with methanol to obtain a linear polymer.

[0088] The recyclable photosensitive resin is prepared by uniformly mixing 0.02 wt% of a multifunctional photoinitiator, 0.01 wt% of Sudan I, 5 wt% of a linear polymer, and a monofunctional acrylate to form a recyclable photosensitive resin.

[0089] Second 3D printing: According to the preset structural model parameters, the photosensitive resin is placed in the 3D printer for 3D printing to obtain a 3D printed structure.

[0090] The present invention provides a specific embodiment, in which during the first 3D printing, the monofunctional acrylate is ethyl acrylate, ethylene glycol monomethyl ether acrylate, lauryl acrylate, polyethylene glycol monomethyl ether acrylate (M n =480), one or more of isobutyl acrylate and isobornyl acrylate.

[0091] The present invention provides a specific embodiment, the printing parameters are as follows: printer light wavelength: 450nm; printing layer thickness: 0.05mm; substrate light intensity: 30mW / cm 2 ; Light intensity of other layers 20mW / cm 2 Base exposure time: 7s; exposure time for the remaining layers: 5s; platform separation speed: 4mm / s; waiting time after separation: 4s; post-curing time: 10min. Using these printing parameters can significantly improve the resolution of printed structures and reduce defect rates.

[0092] The present invention provides a specific implementation method, wherein the acidic solution is a hydrochloric acid solution with a pH of 5; and the degradation time is 60 hours.

[0093] The present invention provides a specific embodiment, wherein the monofunctional acrylate is ethyl acrylate, ethylene glycol monomethyl ether acrylate, lauryl acrylate, polyethylene glycol monomethyl ether acrylate (M n =480), one or more of isobutyl acrylate and isobornyl acrylate; the linear polymer polyethyl acrylate, polyethylene glycol monomethyl ether acrylate, polylauryl acrylate, poly (polyethylene glycol monomethyl ether acrylate (M n =480)), one of polyisobutyl acrylate and polyisobornyl acrylate.

[0094] The present invention provides a specific embodiment. During the second 3D printing, the printing parameters are as follows: printer light wavelength: 450nm; print layer thickness: 0.05mm; base light intensity: 30mW / cm²; remaining layer light intensity: 20mW / cm²; base exposure time: 7s; remaining layer exposure time: 5s; platform separation speed: 4mm / s; post-separation waiting time: 4s; post-curing time: 10min. Using these printing parameters can significantly improve the resolution of printed structures and reduce defect rates.

[0095] Example 1

[0096] (1) 25 g (25 mmol, 1 equivalent) of hydroxyapatite (HAP) was added to a 250 mL Schlenk flask containing 50 mL of cyclohexane. 12.36 g (50 mmol, 2 equivalents) of hex-5-en-1-yltrimethoxysilane was then added, followed by the dropwise addition of 3.00 g (50 mmol, 2 equivalents) of n-propylamine. The reaction was stirred at room temperature under an argon atmosphere for 2 hours, after which the temperature was raised to 60°C and stirring continued for 2 hours. Subsequently, the solvent was removed under vacuum, and the temperature was further raised to 90°C and maintained for 2 hours to remove unreacted hex-5-en-1-yltrimethoxysilane. 8.2 g (25 mmol) of bisacylphosphine oxide precursor 1 (BAP-H) and 500 mL of toluene were then added. 0.3 g of tetramethylguanidine (TMG, 2.5 mmol, 0.35 mL) was then added dropwise as a catalyst. The reaction was allowed to proceed at 50°C for 24 hours. Subsequently, hydrogen peroxide (H₂O₂, 0.95 g, 2.8 mL, 27.5 mmol, 30%) was added dropwise at 0°C in the dark, and the mixture was vigorously stirred at room temperature for 6 hours. The solvent was then removed under reduced pressure to obtain a crude product. After purification with ethanol, the product was dried under high vacuum for 1 day to obtain the final product, the multifunctional photoinitiator HAP-BAPO (48.05 g, 78% yield).

[0097] The solid-state NMR spectra of hydrogen, carbon, silicon and phosphorus of the multifunctional photoinitiator obtained in this example are as follows: Figure 1 、 Figure 2 、 Figure 3 and Figure 4 As shown, the infrared and ultraviolet spectra of the multifunctional photoinitiator are as follows Figure 5 He Ru Figure 6 The target product prepared by the present invention is shown in FIG.

[0098] Example 2

[0099] (1) 0.3 g of multifunctional photoinitiator HAP-BAPO and 9.7 g of ethylene glycol monomethyl ether acrylate (M n=480) was added to a 20 mL sample bottle, stirred overnight, and then ultrasonicated for 10 min to obtain a photosensitive resin. Under a nitrogen atmosphere, NETZSCHDSC 204 F1 PhotoDSC analysis was performed with a light intensity of 20 mW / cm 2 (λ max =365 nm), collecting 600 data points per minute, with the light on for 3 seconds per minute, repeated 60 times. The sample mass used for photo-DSC analysis was 1.0 mg ± 0.1 mg. The light source used for the test was an Omnicure S2000.

[0100] The double bond conversion rate of the multifunctional photoinitiator obtained in this embodiment reached 92%. Figure 7 shown.

[0101] Example 3

[0102] (1) 0.3 g of multifunctional photoinitiator HAP-BAPO and 9.7 g of ethyl acrylate were added to a 20 mL sample bottle, stirred overnight, and then ultrasonicated for 10 min to obtain a photosensitive resin. The photosensitive resin was then cured in a 1×1 cm silica gel film using a point light source. The cured material was degraded in an acidic solution at pH = 5, and the solution was concentrated and finally purified with methanol to obtain a pure linear polymer polyethyl acrylate. The obtained linear polymer was characterized by H NMR and size exclusion chromatography as shown below. Figure 8 As shown in Table 1, it indicates that the linear polymer is polyethyl acrylate.

[0103] (2) 0.3 g of multifunctional photoinitiator HAP-BAPO and 9.7 g of ethylene glycol monomethyl ether acrylate were added to a 20 mL sample bottle, stirred overnight, and then ultrasonicated for 10 min to obtain a photosensitive resin. The photosensitive resin was then cured in a 1×1 cm silica gel film using a point light source. The cured material was degraded in an acidic solution with a pH of 5, and the solution was concentrated and finally purified with methanol to obtain a pure linear polymer polyethylene glycol monomethyl ether acrylate. The obtained linear polymer was characterized by H NMR and size exclusion chromatography as shown below. Figure 9 As shown in Table 1, it indicates that the linear polymer is polyethylene glycol monomethyl ether acrylate.

[0104] (3) 0.3 g of multifunctional photoinitiator HAP-BAPO and 9.7 g of lauryl acrylate were added to a 20 mL sample bottle, stirred overnight, and then ultrasonicated for 10 min to obtain a photosensitive resin. The photosensitive resin was then cured in a 1×1 cm silica gel film using a point light source. The cured material was degraded in an acidic solution at pH = 5, and the solution was concentrated and finally purified with methanol to obtain a pure linear polymer polylauryl acrylate. The obtained linear polymer was characterized by H NMR and size exclusion chromatography as shown below. Figure 10As shown in Table 1, it indicates that the linear polymer is polylauryl acrylate.

[0105] (4) 0.3 g of multifunctional photoinitiator HAP-BAPO and 9.7 g of ethylene glycol monomethyl ether acrylate (M n =480) was added to a 20 mL sample bottle, stirred overnight, and then ultrasonicated for 10 minutes to obtain a photosensitive resin. The photosensitive resin was then cured in a 1×1 cm silica gel film using a point light source. The cured material was degraded in an acidic solution with a pH of 5, and the solution was concentrated and finally purified with methanol to obtain a pure linear polymer polyethylene glycol monomethyl ether acrylate (M n =480). The obtained linear polymer was characterized by H NMR and size exclusion chromatography. Figure 11 As shown in Table 1. It shows that the linear polymer is polyethylene glycol monomethyl ether acrylate (M n =480).

[0106] (5) 0.3 g of multifunctional photoinitiator HAP-BAPO and 9.7 g of isobutyl acrylate were added to a 20 mL sample bottle, stirred overnight, and then ultrasonicated for 10 min to obtain a photosensitive resin. The photosensitive resin was then cured in a 1×1 cm silica gel membrane using a point light source. The cured material was degraded in an acidic solution at pH = 5, and the solution was concentrated and finally purified with methanol to obtain a pure linear polymer polyisobutyl acrylate. The obtained linear polymer was characterized by H NMR and size exclusion chromatography as shown below. Figure 12 As shown in Table 1, it indicates that the linear polymer is polyisobutyl acrylate.

[0107] (6) 0.3 g of multifunctional photoinitiator HAP-BAPO and 9.7 g of isobornyl acrylate were added to a 20 mL sample bottle, stirred overnight, and then ultrasonicated for 10 min to obtain a photosensitive resin. The photosensitive resin was then cured in a 1×1 cm silica gel film using a point light source. The cured material was degraded in an acidic solution at pH = 5, and the solution was concentrated and finally purified with methanol to obtain a pure linear polymer polyisobornyl acrylate. The obtained linear polymer was characterized by H NMR and size exclusion chromatography as shown below. Figure 13 As shown in Table 1, it is shown that the linear polymer is polyisobornyl acrylate.

[0108] This example demonstrates that this photoinitiator can initiate polymerization at a wavelength of 450nm and cleave at a wavelength of 365nm, with polymerization and cleavage occurring independently and without overlap. This photoinitiator has been shown to be versatile and suitable for the polymerization of various monomers, including short-chain aliphatic acrylates, long-chain aliphatic acrylates, aromatic acrylates, and heterocyclic acrylates.

[0109] Example 4

[0110] (1) Add 0.3g of multifunctional photoinitiator HAP-BAPO and 9.7g of ethyl acrylate to a 20mL sample bottle, stir overnight, and then ultrasonicate for 10 minutes to obtain a photosensitive resin. Separately, add 0.15g of multifunctional photoinitiator HAP-BAPO, 0.5g of polyethyl acrylate, and 9.2g of ethyl acrylate to a 20mL sample bottle, stir overnight, and then ultrasonicate for 10 minutes to obtain a photosensitive resin containing 5wt% of linear polymer. The photosensitive resin and the photosensitive resin containing 5wt% of linear polymer were then cured in a dog-bone-shaped silicone mold using a point light source. The test was carried out at a strain rate of 100mm / min. Because of the physical cross-linking points formed by the linear polymer in the cured network, the newly cured material exhibited better mechanical properties. The tensile test of the photosensitive resin and the photosensitive resin containing 5wt% of linear polymer is shown in Figure 2. Figure 14 This indicates that materials containing linear polymers exhibit better mechanical properties.

[0111] (2) 0.3g of multifunctional photoinitiator HAP-BAPO and 9.7g of ethylene glycol monomethyl ether acrylate were added to a 20mL sample bottle, stirred overnight, and then ultrasonicated for 10 minutes to obtain a photosensitive resin. In addition, 0.15g of multifunctional photoinitiator HAP-BAPO, 0.5g of polyethylene glycol monomethyl ether acrylate and 9.2g of ethylene glycol monomethyl ether acrylate were added to a 20mL sample bottle, stirred overnight, and then ultrasonicated for 10 minutes to obtain a photosensitive resin containing 5wt% of linear polymer. The photosensitive resin and the photosensitive resin containing 5wt% of linear polymer were then cured in a dog-bone-shaped silicone mold using a point light source. The test was carried out at a strain rate of 100mm / min. Because of the physical cross-linking points formed by the linear polymer in the cured network, the newly cured material exhibited better mechanical properties. The tensile test of the photosensitive resin and the photosensitive resin containing 5wt% of linear polymer is as shown below. Figure 15 This indicates that materials containing linear polymers exhibit better mechanical properties.

[0112] (3) 0.3g of multifunctional photoinitiator HAP-BAPO and 9.7g of dodecyl acrylate were added to a 20mL sample bottle, stirred overnight, and then ultrasonicated for 10 minutes to obtain a photosensitive resin. In addition, 0.15g of multifunctional photoinitiator HAP-BAPO, 0.5g of polydodecyl acrylate and 9.2g of dodecyl acrylate were added to a 20mL sample bottle, stirred overnight, and then ultrasonicated for 10 minutes to obtain a photosensitive resin containing 5wt% of linear polymer. The photosensitive resin and the photosensitive resin containing 5wt% of linear polymer were then cured in a dog-bone-shaped silicone mold using a point light source. The test was carried out at a strain rate of 100mm / min. Because of the physical cross-linking points formed by the linear polymer in the cured network, the newly cured material exhibited better mechanical properties. The tensile test of the photosensitive resin and the photosensitive resin containing 5wt% of linear polymer is shown in Figure 2. Figure 16 This indicates that materials containing linear polymers exhibit better mechanical properties.

[0113] (4) 0.3 g of multifunctional photoinitiator HAP-BAPO and 9.7 g of ethylene glycol monomethyl ether acrylate (M n =480) was added into a 20 mL sample bottle, stirred overnight, and then ultrasonicated for 10 min to obtain a photosensitive resin. In addition, 0.15 g of multifunctional photoinitiator HAP-BAPO, 0.5 g of polyethylene glycol monomethyl ether acrylate (M n =480) and 9.2g ethylene glycol monomethyl ether acrylate (M n =480) was added to a 20 mL sample bottle, stirred overnight, and then ultrasonicated for 10 minutes to obtain a photosensitive resin containing 5 wt% linear polymer. The photosensitive resin and the photosensitive resin containing 5 wt% linear polymer were then cured in a dog-bone-shaped silicone mold using a point light source. The test was carried out at a strain rate of 100 mm / min. Due to the physical cross-linking points formed by the linear polymer in the cured network, the newly cured material exhibited better mechanical properties. The tensile test of the photosensitive resin and the photosensitive resin containing 5 wt% linear polymer is shown in Figure 2. Figure 17 This indicates that materials containing linear polymers exhibit better mechanical properties.

[0114] (5) 0.3g of multifunctional photoinitiator HAP-BAPO and 9.7g of isobutyl acrylate were added to a 20mL sample bottle, stirred overnight, and then ultrasonicated for 10 minutes to obtain a photosensitive resin. In addition, 0.15g of multifunctional photoinitiator HAP-BAPO, 0.5g of polyisobutyl acrylate and 9.2g of isobutyl acrylate were added to a 20mL sample bottle, stirred overnight, and then ultrasonicated for 10 minutes to obtain a photosensitive resin containing 5wt% of linear polymer. The photosensitive resin and the photosensitive resin containing 5wt% of linear polymer were then cured in a dog-bone-shaped silicone mold using a point light source. The test was carried out at a strain rate of 100mm / min. Because of the physical cross-linking points formed by the linear polymer in the cured network, the newly cured material exhibited better mechanical properties. The tensile test of the photosensitive resin and the photosensitive resin containing 5wt% of linear polymer is shown in Figure 2. Figure 18 This indicates that materials containing linear polymers exhibit better mechanical properties.

[0115] (6) 0.3g of multifunctional photoinitiator HAP-BAPO and 9.7g of isobornyl acrylate were added to a 20mL sample bottle, stirred overnight, and then ultrasonicated for 10 minutes to obtain a photosensitive resin. In addition, 0.15g of multifunctional photoinitiator HAP-BAPO, 0.5g of polyisobornyl acrylate and 9.2g of isobornyl acrylate were added to a 20mL sample bottle, stirred overnight, and then ultrasonicated for 10 minutes to obtain a photosensitive resin containing 5wt% of linear polymer. The photosensitive resin and the photosensitive resin containing 5wt% of linear polymer were then cured in a dog-bone-shaped silicone mold using a point light source. The test was carried out at a strain rate of 100mm / min. Because of the physical cross-linking points formed by the linear polymer in the cured network, the newly cured material exhibited better mechanical properties. The tensile test of the photosensitive resin and the photosensitive resin containing 5wt% of linear polymer is shown in Figure 2. Figure 19 This indicates that materials containing linear polymers exhibit better mechanical properties.

[0116] This example shows that after degradation, the generated linear polymer can be redissolved in the corresponding monomer. After solidification, the mechanical properties of the linear polymer are better than those of the original material because the linear polymer can form physical crosslinking points in the material.

[0117] Example 5

[0118] (1) 2.4 g of multifunctional photoinitiator HAP-BAPO, 8 mg of Sudan I and 77.6 g of ethylene glycol monomethyl ether acrylate (M n =480) was added into a 100 mL sample bottle, stirred overnight, and then ultrasonicated for 10 min to obtain a photosensitive resin.

[0119] (2) Use Solidwork 3D software to create an additive 3D model, and then export the created 3D model file in STL format for subsequent layering processing and support establishment.

[0120] (3) Construct reasonable supports and slices, mainly for overhanging and thin-walled structures, to prevent deformation by adding corresponding support structures; the slice thickness is 0.01-0.05mm, and the appropriate layer thickness is selected according to the size and shape of the device. The Asiga digital light processing 3D printer supporting software composer can automatically slice the created STL file for subsequent layer-by-layer printing to build precise hydrogel structures, and the software generates slice simulation layers at each level for subsequent structural enhancement and improvement, which are transmitted wirelessly to the printer.

[0121] (4) According to the preset model parameters of the structure, the photosensitive resin was placed in a homemade blue light 3D printer for 3D printing to obtain the printed structure. The printing parameters were as follows: printer light wavelength: 450nm; printing layer thickness: 0.05mm; base light intensity: 30mW / cm2; remaining layer light intensity: 20mW / cm2; base exposure time: 7s; remaining layer exposure time: 5s; platform separation speed: 4mm / s; waiting time after separation: 4s; post-curing time: 10min. Using the above printing parameters, the resolution of the printed structure can be greatly improved and the defect rate can be reduced.

[0122] (5) The 3D printed structure was immersed in an acidic solution with a pH of 5. After the structure was completely degraded, the solution was concentrated and purified with methanol to obtain a linear polymer.

[0123] In this embodiment, a multifunctional photoinitiator is used in a blue light DLP 3D printer, and the printed structure can be degraded under acidic conditions. After concentration and purification, a pure linear polymer is obtained. Figure 20 shown.

[0124] Example 6

[0125] (1) 1.2g multifunctional photoinitiator HAP-BAPO, 4mg Sudan I, 4g polyethylene glycol monomethyl ether acrylate (M n =480) and 74.8g ethylene glycol monomethyl ether acrylate (M n =480) was added into a 100 mL sample bottle, stirred overnight, and then ultrasonicated for 10 min to obtain a photosensitive resin.

[0126] (2) Use Solidwork 3D software to create an additive 3D model, and then export the created 3D model file in STL format for subsequent layering processing and support establishment.

[0127] (3) Construct reasonable supports and slices, mainly for overhanging and thin-walled structures, to prevent deformation by adding corresponding support structures; the slice thickness is 0.01-0.05mm, and the appropriate layer thickness is selected according to the size and shape of the device. The Asiga digital light processing 3D printer supporting software composer can automatically slice the created STL file for subsequent layer-by-layer printing to build precise hydrogel structures, and the software generates slice simulation layers at each level for subsequent structural enhancement and improvement, which are transmitted wirelessly to the printer.

[0128] (4) According to the preset model parameters of the structure, the photosensitive resin was placed in a homemade blue light 3D printer for 3D printing to obtain the printed structure. The printing parameters were as follows: printer light wavelength: 450nm; printing layer thickness: 0.05mm; base light intensity: 30mW / cm2; remaining layer light intensity: 20mW / cm2; base exposure time: 7s; remaining layer exposure time: 5s; platform separation speed: 4mm / s; waiting time after separation: 4s; post-curing time: 10min. Using the above printing parameters, the resolution of the printed structure can be greatly improved and the defect rate can be reduced.

[0129] In this embodiment, the generated linear polymer is dissolved in the corresponding monomer to prepare a new photosensitive resin and reprint a new structure to achieve recyclable 3D printing of materials. Figure 20 shown.

[0130] test:

[0131] 3D-printed Kelvin structures (1.2 cm × 1.2 cm × 1.2 cm) containing no linear polymer and 5 wt% linear polymer were individually buried in acidic soil (pH = 5). After approximately 10 days, significant swelling and surface erosion were observed. After approximately 45 days of burial, most of the structure had degraded, leaving only small fragments. By 60 days, these remaining fragments had shrunk significantly and had almost disappeared. After approximately 75 days, the fragments had completely dissipated, ultimately degrading into carbon dioxide, water, and small amounts of calcium salts and phosphates.

[0132] In this example, structures containing no linear polymer and 5 wt% linear polymer were buried in acidic soil. After about 75 days, all structures were completely degraded, as shown in Figure 2. Figure 21 shown.

[0133] test:

[0134] (1) Plant safety test: Wheat seeds and mung bean seeds were soaked in distilled water at room temperature for 24 hours. Subsequently, the seeds were transferred to aqueous solutions of degradation products at concentrations of 0.1%, 0.3% and 1%, respectively. Each treatment group contained 15 seeds. The germination rate of each treatment was determined. After 15 days of growth, the average root length and seedling height of each group of seedlings were measured. A control group was included, which was cultured under conditions without degradation products. Figure 22 、 Figure 23 、 Figure 24 and Figure 25 shown.

[0135] (2) Extracellular experiments: Mouse L929 fibroblasts and human LO2 cells were used as model systems to evaluate cytocompatibility. These cells were co-cultured with control culture medium and culture medium containing gradient concentrations of degradation products (0, 0.1, 0.2, and 0.3 mg / mL) for 48 hours. After incubation, cell viability was determined by CCK-8 assay, and cytotoxicity was evaluated by comparative analysis. After 48 hours of co-culture, there was no statistically significant difference in the viability of cells in each group cultured with degradation products compared with the control group; the cell viability of each group exceeded 97.0%. These results indicate that the degradation products have negligible cytotoxicity in vitro. Calcein-AM and propidium iodide (PI) co-staining were further used to evaluate cell viability. Confocal microscopy showed that most cells exhibited strong green fluorescence, and only a few cells showed red fluorescence. This observation indicates that the L929 and LO2 cell lines remained highly active after 48 hours of co-culture with degradation products. In addition, no obvious changes in cell morphology were detected between cells exposed to degradation products and control cells, further confirming that the degradation products had minimal cytotoxicity. Figure 26 、 Figure 27 、 Figure 28 and Figure 29 shown.

[0136] (3) In-cell experiments: In vivo biocompatibility evaluation was performed on mice by oral administration. Mice were given 0.5 mL of degradation product solution at concentrations of 0.1, 0.2, and 0.3 mg / mL by oral gavage once a day for 7 consecutive days. At the end of this period, all animals were euthanized, and visceral organ and serum samples were collected for biochemical and histological evaluation. Analysis of serum alanine aminotransferase (ALT) and blood urea nitrogen (BUN) levels showed no significant differences between mice given degradation product solution compared with mice given deionized water. These results indicate that the liver and kidney function of mice exposed to degradation products was not impaired compared with the control group. Histopathological examination of the heart, liver, spleen, lung, and kidney of both groups was performed by hematoxylin-eosin (H&E) staining. Histological analysis did not find evidence of lipid droplet accumulation, inflammatory response, or fibrosis in any tissue section of the experimental group compared with the control tissue. These combined results collectively indicate that the degradation product is non-toxic and has good biocompatibility in vivo. Figure 30 shown.

[0137] Table 1

[0138]

Claims

1. A multifunctional photoinitiator, characterized in that The structural formula is as follows:

2. A method for preparing a multifunctional photoinitiator, characterized in that: The following steps are involved: (1) Vacuum drying and activation of hydroxyapatite: put the hydroxyapatite into a container and dry it under vacuum and heating conditions; (2) 2-1 Condensation reaction of hydroxyapatite and silane coupling agent: hydroxyapatite is dispersed in solvent 1, followed by adding silane coupling agent, and then adding organic base 1 dropwise. Under an inert gas atmosphere, the reaction is heated by step-by-step heating; 2-2 Subsequently, the solvent is removed; a bisacylphosphine oxide precursor and solvent 2 are added thereto, followed by dropwise addition of an organic base 2 as an acid binding agent, and the reaction is carried out under heating conditions; After 2-3, solvent 3 is added under low temperature conditions and reacted under certain conditions; finally, the solvent is removed, purified, and dried to obtain a multifunctional photoinitiator.

3. The method for preparing a multifunctional photoinitiator according to claim 2, wherein: In step (1), the drying temperature is 80-90° C. and the drying time is 24 hours.

4. The method for preparing a multifunctional photoinitiator according to claim 2, wherein: In step (2), Solvent 1 is one or both of cyclohexane and cyclopentane; Solvent 2 is one or both of toluene and tetrahydrofuran; Solvent 3 is a 30% mass fraction hydrogen peroxide solution; Organic base 1 is n-propylamine; The organic base 2 is one or both of 1,1,3,3-tetramethylguanidine and triethylamine; The silane coupling agent is hex-5-en-1-yltrimethoxysilane; and the molar ratio of the hydroxyapatite to the silane coupling agent is 1:

2.

5. The method for preparing a multifunctional photoinitiator according to claim 2, wherein: In step (2) 2-1, the inert gas is argon or nitrogen; the stepwise heating method is to stir at room temperature for 2 hours, then heat to 60° C. and continue stirring for 2 hours; In 2-2, the bisacylphosphine oxide precursor is 1,1′-phosphite bis[1-(2,4,6-trimethylphenyl)methanone; The method for removing the solvent is to first raise the temperature to 60°C under vacuum, maintain it for 2 hours, and then raise the temperature to 90°C and maintain it for 2 hours; The temperature of the heating condition reaction is 60°C; the time of the heating condition reaction is 24 hours; In 2-3, the reaction temperature under low temperature conditions is an ice bath at 0°C; the reaction time under low temperature conditions is 6 hours; the purification method is washing with ethanol 3-5 times and removing the solvent under reduced pressure; the drying method is drying in a high vacuum at 60°C for 1 day.

6. A multifunctional photoinitiator, characterized in that A functional photoinitiator is obtained by the method according to any one of claims 2 to 5.

7. A thermosetting recyclable method based on a multifunctional photoinitiator, characterized in that: The method comprises the following specific steps: Preparation of photosensitive resin: 0.02 wt% multifunctional photoinitiator, 0.01 wt% Sudan I and monofunctional acrylate are uniformly mixed to form a photosensitive resin; First 3D printing: according to the preset structural model parameters, the photosensitive resin is placed in the 3D printer for 3D printing to obtain a 3D printed structure; Degradation of 3D printed structures: The 3D printed structures were immersed in an acidic solution. After the structure was completely degraded, the solution was concentrated and purified with methanol to obtain a linear polymer. The recyclable photosensitive resin is prepared by uniformly mixing 0.02 wt% of a multifunctional photoinitiator, 0.01 wt% of Sudan I, 5 wt% of a linear polymer, and a monofunctional acrylate to form a recyclable photosensitive resin. Second 3D printing: According to the preset structural model parameters, the photosensitive resin is placed in the 3D printer for 3D printing to obtain a 3D printed structure.

8. The thermosetting recyclable method based on a multifunctional photoinitiator according to claim 7, characterized in that: Monofunctional acrylates include ethyl acrylate, ethylene glycol monomethyl ether acrylate, lauryl acrylate, polyethylene glycol monomethyl ether acrylate, n =480, one or more of isobutyl acrylate and isobornyl acrylate; the linear polymer polyethyl acrylate, polyethylene glycol monomethyl ether acrylate, polylauryl acrylate, poly (polyethylene glycol monomethyl ether acrylate M n =480), one of polyisobutyl acrylate and polyisobornyl acrylate.

9. The thermosetting recycling method based on a multifunctional photoinitiator according to claim 7, characterized in that: The acidic solution used for degradation is hydrochloric acid solution with pH=5, and the degradation time is 60h.

10. The thermosetting recycling method based on a multifunctional photoinitiator according to claim 7, characterized in that: The first 3D printing parameters are as follows: Printer light wavelength: 450nm; Print layer thickness: 0.05mm; Base light intensity: 30mW / cm 2 ; The light intensity of the remaining layers is 20mW / cm 2 Exposure time for substrate: 7s; Exposure time for other layers: 5s; Platform separation speed: 4mm / s; Waiting time after separation: 4s; Post-curing time: 10min; The second 3D printing parameters were as follows: printer light wavelength: 450nm; printing layer thickness: 0.05mm; base light intensity: 30mW / cm2; light intensity for the remaining layers: 20mW / cm2; base exposure time: 7s; Exposure time of other layers: 5s; platform separation speed: 4mm / s; Waiting time after separation: 4s; post-curing time: 10min.

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