Process for the photocatalytic preparation of sulfur-containing acetal / ketals degradable compounds

Abstract

The present application belongs to the technical field of high polymer materials, and particularly relates to a method for photocatalytic preparation of sulfur-containing acetal / ketone degradable compounds. The present application mixes one or more aldehyde / ketone compounds with one or more mercapto compounds, and performs a reaction under light conditions to obtain sulfur-containing acetal / ketone degradable compounds. The present application provides a novel preparation method for directly using light to prepare sulfur acetal / ketone groups without the action of a photoinitiator. The novel preparation method can not only efficiently and environmentally prepare small-molecule compounds containing sulfur acetal / ketone groups, but also can prepare main-chain sulfur acetal / ketone degradable high polymer materials. Moreover, the method provided by the present application is suitable for various aldehyde / ketone compounds and mercapto compounds.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically a method for photocatalytic preparation of degradable compounds containing thioacetals / thioketals. Background Technology

[0002] Currently, developing recyclable and biodegradable polymer materials is of great significance for solving the environmental and resource waste problems caused by traditional linear and thermosetting polymer materials. Since the concept of "vitrile polymers" was proposed in 2011, various chemical groups, such as thioether bonds, disulfide bonds, ester bonds, hydrazide bonds, polyurethanes, hindered urea, acid anhydrides, triazolinones, imines, siloxanes, borate esters, hemithioacetals, thioacetals, acetals, and trithiocarbonates, have been cleverly designed and introduced into the cross-linked network structure of polymers. This allows the special chemical groups in the cross-linked network to undergo dynamic exchange processes, thereby promoting the reconstruction of the cross-linked network structure morphology and enabling multiple recycling. Furthermore, compared to the strong carbon-carbon bonds in traditional polymers, most of these dynamic chemical bonds contain heteroatoms, which not only endow the cross-linked polymer network structure with recyclable properties but also improve the material's degradation performance. Therefore, developing new dynamic chemical groups containing heteroatoms and their preparation methods has important practical application significance for sustainable development.

[0003] However, in traditional chemistry, the reaction of thiol groups with aldehyde or carbonyl groups is catalyzed by Lewis acids or heated to form thioacetals / thioketals. The purpose of these acids is to protect the aldehyde or carbonyl groups from destruction, and deprotection occurs under certain conditions after the reaction. However, for Lewis acid-catalyzed thioacetal / thioketal formation, the catalyst is difficult to recover and reuse, increasing production costs. Heating to form thioacetals / thioketals results in slow reaction rates and low conversion rates. Summary of the Invention

[0004] To address the shortcomings of the existing technologies, the present invention aims to provide a method for photocatalytic preparation of biodegradable compounds containing thioacetals / thioketals. This invention provides a novel preparation method that directly utilizes light to form thioacetal / thioketal groups under photoinitiator-free conditions. This method not only enables the efficient and environmentally friendly preparation of small molecule compounds containing thioacetal / thioketal groups, but also allows the preparation of biodegradable polymers with thioacetal / thioketal groups in their main chain. Furthermore, the method provided by this invention is applicable to a variety of aldehyde and ketone compounds.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A method for photocatalytic preparation of degradable compounds containing thioacetals / thioketals includes the following steps: mixing one or more aldehyde / ketone compounds with one or more thiol compounds and reacting them under light conditions to obtain degradable compounds containing thioacetals / thioketals.

[0007] Aldehyde / ketone compounds are compounds containing at least one aldehyde group or carbonyl group;

[0008] A thiol compound is a compound containing at least one thiol group.

[0009] Preferably, the thiol compound is selected from:

[0010] .

[0011] Preferably, the aldehyde / ketone compound is selected from:

[0012] .

[0013] Preferably, when the aldehyde / ketone compound contains an aldehyde group or a carbonyl group, and the thiol compound is a dithiol compound containing only one thiol group or a main carbon chain ≤ 3, a small molecule monomer containing a thioacetal bond is obtained.

[0014] Preferably, when the aldehyde / ketone compound contains an aldehyde group or a carbonyl group, and the thiol compound is a dithiol compound with a main carbon chain of ≥4, a long-chain polymer material is obtained.

[0015] Preferably, when the aldehyde / ketone compound contains one aldehyde group or carbonyl group, and the thiol compound is a polythiol compound containing ≥3 thiol groups, a polymer material with a cross-linked network structure is obtained;

[0016] When the aldehyde / ketone compound contains ≥2 aldehyde groups or carbonyl groups, and the thiol compound is a polythiol compound containing ≥2 thiol groups, a polymer material with a cross-linked network structure is obtained.

[0017] Preferably, the lighting conditions use a single light source with a wavelength of 254nm-460nm, a composite light source of multiple light sources, natural light, or enhanced natural light.

[0018] Preferably, an ultraviolet photoinitiator or a visible photoinitiator or a mixture of the two is used as a catalyst, and the ultraviolet photoinitiator, visible photoinitiator or a combination of ultraviolet photoinitiator and visible photoinitiator is selected according to the wavelength of light.

[0019] Preferably, the reaction conditions are: light irradiation reaction at room temperature for 1-24 hours.

[0020] Preferably, when both the aldehyde / ketone compound and the thiol compound are liquids, no solvent is required; when the aldehyde / ketone compound or the thiol compound is a solid or a high-viscosity liquid, a good solvent is used to dissolve it before the reaction.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] 1. This invention develops a novel method and polymerization system for preparing thioacetal / thioketal groups through light irradiation. It efficiently and environmentally prepares thioacetal / thioketal compounds and biodegradable linear, branched, and cross-linked polymeric materials containing thioacetal / thioketal groups, as well as "glassy polymeric" materials that can be recycled. By changing the chain length of the thiol compound (main carbon chain ≥ 4), the possibility of thiol and carbonyl groups forming cyclic structures during nucleophilic reactions is effectively avoided. This is because when the main carbon chain is ≥ 4, the resulting seven-membered or multi-membered rings are unstable structures, thus forming a stable linear polymeric structure.

[0023] 2. The present invention aims to prepare small-molecule thioacetals by using monothiol compounds and dithiol compounds with a main carbon chain ≤3, such as propanethiol, butanethiol, mercaptoethanol, mercaptopropionic acid, methyl mercaptopropionate, 3-mercapto-1,2-propanediol, ethylenedithiol, and 1,3-propanedithiol, with aldehyde and ketone compounds under light irradiation.

[0024] This invention aims to utilize dithiol and polythiol compounds with a main carbon chain ≥4, such as 1,4-butanedithiol, 1,6-hexanedithiol, 2,6-dioxa-1,8-octanedithiol, 1,9-nonanedithiol, 4,4'-dithiol diphenyl ether, 4,4'-dithiol diphenyl sulfide, 1,4-benzenedithiol, 1,4-benzenedimethylthiol, ethylene glycol dithiocarbamate, bis(3-mercaptopropionic acid)ethylene glycol, 2,7-naphthyldithiol, 1,5-dithiolnaphthalene; such as trimethylolpropane tris(3-mercaptopropionate), trimethylolpropane tris(2-ylacetate), tetramercaptobenzene, pentaerythritol tetramercaptoacetate; to prepare polymeric materials with linear, branched, or cross-linked structures with aldehydes and ketones under light irradiation, effectively avoiding the formation of small molecule thioacetal monomers by thiol groups and aldehydes and ketones.

[0025] 3. The thioacetal / thioketal biodegradable compounds provided by this invention can be widely obtained from renewable biomass raw materials and traditional chemical industries, or through simple chemical modification and conversion processes, to obtain compounds with different structures containing one or more aldehyde or carbonyl groups. By controlling the functional groups of the thiol compounds and aldehyde / ketone compounds used, not only can small molecule thioacetal / thioketal compounds be formed, but the polymer structure (linear, branched, or cross-linked), functional groups, cross-linking density, and mechanical properties can also be efficiently controlled. Furthermore, monomers containing carbonyl groups and thiol groups can be copolymerized to achieve further fine control of the material structure. This invention pioneers a simple, green, economical, and practical method for synthesizing biodegradable polymers, filling the previous gap in the lack of methods for synthesizing such thioacetal polymer materials.

[0026] 4. This invention successfully introduces thioacetal / thioketal groups into small molecule compounds and polymers containing thioacetal / thioketal groups under light irradiation. Under certain conditions (e.g., with the addition of degradation products, heating, or at a specific pH level), these groups can break down, thereby initiating the breakage of linear polymers and the degradation of cross-linked materials. Simultaneously, the cross-linked network structure containing thioacetals can undergo dynamic exchange under heating conditions, allowing the cross-linked network structure to be reshaped.

[0027] 5. The small molecule formation and polymerization process of this invention uses light with a wavelength of 254nm-460nm. 254nm (mercury lamp), 302nm (mercury lamp), 365nm (mercury lamp), and 450-460nm (LED lamp) are selected to participate in the reaction. An ultraviolet photoinitiator (absorbing ultraviolet light in the 250-420nm region) or a visible light initiator (absorbing visible light in the 400-700nm region) may also be added. Furthermore, the light source can be natural light or other types of composite light sources, or a single-wavelength light source, or a composite light source of more than one wavelength.

[0028] 6. This invention directly reacts aldehyde / ketone compounds with thiol compounds at room temperature, and the target product is obtained after dehydration and drying. The reaction can be carried out with or without solvent, depending on whether the chemical reagents contain solids or high-viscosity liquids. Solvent is added to ensure uniform mixing. The reaction process has a high yield, and the generated byproduct is unique and pollution-free; the byproduct is water, demonstrating good practical application prospects. Furthermore, in the preparation of linear or cross-linked polymers, reinforcing materials such as carbon nanotubes, carbon fibers, cellulose nanocrystals, silver nanoparticles, iron oxide nanoparticles, and zinc oxide nanoparticles can be introduced to obtain recyclable composite materials. Attached Figure Description

[0029] Figure 1 In the above, [1] is the reaction equation for the formation of small molecule thioacetal / thioketal compounds from aldehyde / ketone compounds and monothiol compounds; [2] is the reaction equation for the formation of small molecule thioacetal / thioketal compounds from aldehyde / ketone compounds and dithiol compounds with a main carbon chain ≤3; [3] is the reaction equation for the formation of linear thioacetal / thioketal polymers from aldehyde / ketone compounds and dithiol compounds with a main chain carbon ≥4; [4] is the reaction equation for the formation of crosslinked thioacetal / thioketal polymers from aldehyde / ketone compounds and dithiol or polythiol compounds.

[0030] Figure 2 The small molecule thioacetal prepared in Example 1 of this invention 1 H NMR MRI;

[0031] Figure 3The linearly degradable polymer material containing thioacetal in the main chain prepared in Example 2 of this invention 1 H NMR spectrum;

[0032] Figure 4 The mechanical tensile properties of the cross-linked biodegradable polymer material containing thioacetal in the main chain prepared in Example 3 of this invention are shown in the diagram.

[0033] Figure 5 Differential scanning calorimetry (DSC) image of the cross-linked biodegradable polymer material containing thioacetal in the main chain prepared in Example 3 of this invention;

[0034] Figure 6 This is a diagram showing the mechanical tensile properties of the cross-linked biodegradable polymer material containing thioacetal in the main chain prepared in Example 4 of this invention.

[0035] Figure 7 Differential scanning calorimetry (DSC) image of the cross-linked biodegradable polymer material containing thioacetal in the main chain prepared in Example 4 of this invention;

[0036] Figure 8 The mechanical tensile diagram is shown after the main chain thioacetal-containing crosslinked biodegradable polymer material prepared by Example 3 of the present invention has undergone cyclic processing.

[0037] Figure 9 To test the degradation of the cross-linked degradable polymer material containing thioacetal in the main chain prepared in Example 2 of this invention. 1 H NMR MRI;

[0038] Figure 10 This diagram illustrates the photocatalytic reaction mechanism of thioacetals / thioketals in this application, in contrast to the acid-catalyzed reaction mechanism of thioacetals / thioketals in the background technology. Detailed Implementation

[0039] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods.

[0040] Unless otherwise specified, all experimental materials and reagents used in this invention are commercially available; unless specific techniques or conditions are specified in the examples, experiments can be conducted in accordance with the techniques described in the literature in this field or the conditions in the product instructions.

[0041] This invention provides a novel preparation principle and method for thioacetal / thioketal groups, solving the technical defects of Lewis acid-catalyzed thioacetal / thioketal formation, which involves the difficulty in recovering and reusing catalysts, thus increasing production costs. It also addresses the problems of slow reaction rates and low conversion rates in the heating process for forming thioacetal / thioketal groups. The technical solution of this application is further explained below:

[0042] In the following embodiments, the linear and branched thioacetal / thioketal polymers are long-chain polymers; the cross-linked thioacetal polymers are cross-linked network polymers.

[0043] In this invention, the molecular weight of the polymer material is 300-30000; the molecular weight of the small molecule monomer is less than 3000.

[0044] Method I: Small molecule thioacetal monomers are prepared by reacting aldehydes and ketones with monothiol compounds or dithiol compounds with a main carbon chain ≤3, as shown in the following reaction formula:

[0045]

[0046] Aldehyde and ketone compound A-Ⅰ is selected from any of the following structures;

[0047]

[0048] The monothiol compound B-I is selected from any of the following structures:

[0049]

[0050] The dithiol compound B-II with a main carbon chain ≤3 is selected from any of the following structures:

[0051]

[0052] Method II: Linear polymers are prepared by reacting aldehydes and ketones with dithiol compounds having ≥4 carbon atoms in the main chain, as shown in the following reaction formula:

[0053]

[0054] Aldehyde and ketone compound A-II is selected from any of the following structures;

[0055]

[0056] The dithiol compound B-II with a main carbon chain ≥4 is selected from any of the following structures:

[0057]

[0058] Method III, using aldehyde / ketone compound R6 and polythiol compound R7 (compound B-IV) to prepare cross-linked thioacetal polymers, wherein the polythiol compound contains ≥2 thiol groups, and the reaction formula is as follows:

[0059]

[0060] Among them, (1) when the aldehyde-ketone compound R6 (compound A-III) is selected from a monofunctional aldehyde group or a carbonyl group, the multi-thiol compound contains ≥3 thiol groups;

[0061] Aldehyde compound R6 (compound A-III) is selected from any of the following structures;

[0062]

[0063] The polythiol compound R7 (compound B-Ⅳ) is selected from any of the following structures;

[0064]

[0065] (2) When the aldehyde or ketone compound R6 (compound A-III) is selected from a difunctional or polyfunctional aldehyde group or carbonyl group, the polythiol compound contains ≥2 thiol groups;

[0066] Aldehyde compound R6 (compound A-III) is selected from any of the following structures;

[0067]

[0068] The polythiol compound R7 (compound B-Ⅳ) is selected from any of the following structures;

[0069]

[0070] For example, when a dialdehyde compound R' reacts with a dithiol compound R, the partial structural formula of the crosslinked thioacetal polymer is as follows:

[0071]

[0072] Finally, small molecule thioacetal / thioketal compounds and linear, branched, or cross-linked polymers containing thioacetal / thioketal backbones were degraded:

[0073] This degradation can be achieved through organic molecules such as dimethyl sulfoxide (DMSO) and mercaptoethanol; in addition, copper salts, zinc salts, or silver salts can also be used to degrade monomers and polymers containing thioacetals.

[0074] The copper salt is selected from one or more of copper chloride, copper bromide, copper nitrate, copper sulfate, copper acetate, and copper trifluoromethanesulfonate; the zinc salt is selected from one or more of zinc chloride, zinc bromide, zinc iodide, zinc nitrate, zinc acetate, and zinc trifluoromethanesulfonate; the silver salt is selected from one or more of silver chloride, silver bromide, silver iodide, silver nitrate, and silver trifluoromethanesulfonate; the metal salt may also be a copper salt, zinc salt, or silver salt containing other anions.

[0075] In methods I, II, and III, the main reaction involves a condensation reaction between the aldehyde or ketone group on compound A and the thiol group on compound B. During the reaction, the thiol group reacts with the carbonyl group under light irradiation to form small-molecule thioacetal / thioketal compounds and polymers with linear, branched, or cross-linked structures containing thioacetal / thioketal in the main chain.

[0076] The following examples illustrate specific synthetic methods for small molecule thioacetal / thioketal compounds and biodegradable polymers with thioacetal / thioketal backbones.

[0077] In this embodiment of the invention, no catalyst is needed in the reaction system when preparing thioacetal / thioketal compounds because light participates in the reaction. Therefore, a photoinitiator is added to the reaction system to accelerate the reaction. Different photoinitiators are selected according to the absorption wavelength range. For example, the photocatalyst for light with a wavelength of 365 nm is 1173 (2-hydroxy-2-methyl-1-phenyl-1-propanone). Alternatively, different wavelengths of light, such as 450-460 nm, 302 nm, and 254 nm, can be selected for the reaction, and corresponding photoinitiators can be chosen. In addition, the light source can be natural light or other types of composite light sources, or a single wavelength light source, or a composite light source of more than one wavelength light source.

[0078] Example 1

[0079] A method for preparing a small molecule thioacetal includes the following steps:

[0080] Small molecule thioacetal monomers were prepared using aldehydes and monothiol compounds. The reaction equation is as follows: :

[0081] Weigh out 0.5246g of benzaldehyde ( Add mercaptoethanol ( The reaction mixture was prepared by irradiating benzaldehyde and mercaptoethanol in a molar ratio of 1:2.05 at room temperature with stirring, followed by vacuum drying to remove water, yielding a small molecule thioacetal monomer.

[0082] Prepared small molecule thioacetal compounds 1 The H NMR spectrum is shown in [reference]. Figure 2Since benzaldehyde and mercaptoethanol are both liquids, solvents are not required; to prepare small molecule thioketal compounds, the aldehydes can be replaced with ketones.

[0083] Example 2

[0084] A method for preparing a linear biodegradable polymer material containing thioacetal in its main chain, comprising the following steps:

[0085] Linear thioacetal polymers were prepared using aldehyde compounds and dithiol compounds with a main carbon chain ≥4. The reaction equation is as follows:

[0086] ;

[0087] Weigh out 0.5537g of p-methoxybenzaldehyde ( ), add 1,6-hexanedithiol ( The reaction mixture was prepared by reacting p-methoxybenzaldehyde and 1,6-hexanedithiol in a molar ratio of 1:1.02, under stirring conditions, and irradiated with light at a wavelength of 365 nm for 65 min at room temperature. After vacuum drying to remove water, a linear biodegradable polymer material containing sulfur acetal in the main chain was obtained.

[0088] Linear biodegradable polymer materials containing thioacetals in the main chain were prepared. 1 The H NMR spectrum is shown in [reference]. Figure 3 Since both p-methoxybenzaldehyde and 1,6-hexanedithiol are liquids, no solvent is used. To prepare linear thioketals, the starting aldehyde can be replaced with a ketone.

[0089] Example 3

[0090] A method for preparing a cross-linked biodegradable polymer material with a main chain containing thioacetal includes the following steps:

[0091] Crosslinked thioacetal polymers were prepared using aldehyde compounds and polythiol compounds, wherein the polythiol compounds had ≥3 thiol groups. The reaction equation is as follows:

[0092]

[0093] Weigh out 5.3127g of benzaldehyde ( Add trimethylolpropane tris(3-mercaptopropionic acid) ester ( The molar ratio of benzaldehyde to trimethylolpropane tris(3-mercaptopropionic acid) ester was 3:2.02. Under stirring conditions, the mixture was irradiated with light at a wavelength of 365 nm at room temperature for 2 hours, and then dried under vacuum to remove water, resulting in a cross-linked biodegradable polymer material with a main chain containing sulfur acetal.

[0094] The mechanical tensile diagram of the cross-linked biodegradable polymer material containing thioacetal in the main chain prepared in this embodiment is shown below. Figure 4DSC curves are shown below. Figure 5 To prepare crosslinked thioacetal polymers, since benzaldehyde and trimethylolpropane tris(3-mercaptopropionic acid) ester are both liquids, a solvent could be omitted. However, it was found that adding a solvent resulted in better crosslinking. This is because the viscosity of trimethylolpropane tris(3-mercaptopropionic acid) ester is too high, leading to uneven mixing of benzaldehyde and trimethylolpropane tris(3-mercaptopropionic acid) ester. Therefore, adding a solvent ensures more uniform mixing of the two monomers in the system, resulting in better crosslinking. To prepare crosslinked thioketal compounds, the aldehyde raw material can be replaced with a ketone.

[0095] Example 4

[0096] A method for preparing a cross-linked biodegradable polymer material with a main chain containing thioacetal includes the following steps:

[0097] Crosslinked thioacetal polymers were prepared using bifunctional aldehyde compounds and polythiol compounds, wherein the polythiol compounds contained ≥2 thiol groups. The reaction equation is as follows:

[0098]

[0099] Weigh out 5.4231g of terephthalaldehyde ( ), add 3,6-dioxa-1,8-octanedithiol ( The reaction mixture was prepared by mixing terephthalaldehyde and 3,6-dioxa-1,8-octanedithiol in a molar ratio of 1:2.01, then adding dichloromethane, and reacting with light at a wavelength of 356 nm for 4 hours at room temperature under stirring. The mixture was then dried under vacuum to remove water, resulting in a cross-linked biodegradable polymer material with a main chain containing sulfur acetal.

[0100] The mechanical tensile diagram of the cross-linked biodegradable polymer material containing thioacetal in the main chain prepared in this embodiment is shown below. Figure 6 DSC curves are shown below. Figure 7 To prepare cross-linked thioacetal polymers, since terephthalaldehyde is a solid and 3,6-dioxa-1,8-octanedithiol is a liquid, an organic solvent needs to be added to mix the terephthalaldehyde and 3,6-dioxa-1,8-octanedithiol evenly. Any solvent that can mix them evenly can be used. To prepare cross-linked thioketal compounds, the dialdehyde raw material can be replaced with a diketone.

[0101] The cross-linked thioacetal polymer prepared in Example 3 was subjected to cyclic processing tests. The test method was as follows: the cross-linked thioacetal polymer prepared in Example 3 was pulverized and ground, and then hot-pressed at 150°C to form a film with a thickness of 0.5 mm to obtain a sample of the first-stage processed film, which was then stretched at room temperature; the hot-pressed film was pulverized and ground again, and then hot-pressed at 150°C again to obtain a sample of the first-stage cyclic processed film, which was then stretched at room temperature; the first-stage processed film was pulverized and ground again, and then hot-pressed at 150°C again to obtain a sample of the second-stage processed film, which was then stretched at room temperature; the second-stage processed film was pulverized and ground again, and then hot-pressed at 150°C again to obtain a sample of the third-stage processed film, which was then stretched at room temperature. The results are shown in […]. Figure 8 ,Depend on Figure 8 It is evident that the mechanical tensile properties were maintained even after three heat treatments.

[0102] The polymers prepared using the methods in Examples 2-4 exhibited essentially the same degradation behavior. Therefore, the following degradation experiment was conducted on the linearly degradable polymer material with a main chain containing thioacetal, obtained in Example 2, as an example:

[0103] 1g of the linearly degradable polymer material containing thioacetal in the main chain, prepared in Example 2, was placed in 5mL of saturated ZnBr2 aqueous solution and heated at 120℃ for 40min for degradation. The degradation was performed using 1H NMR spectroscopy (NMR spectroscopy). 1 (H NMR) tracking reaction, the monomer NMR results are shown in […]. Figure 9 This demonstrates that the linearly degradable polymer material containing thioacetal in the main chain prepared in Example 2 of the present invention has excellent degradation characteristics.

[0104] Figure 10 The results show that, compared with the existing acid-catalyzed reaction mechanism of thioacetals / thioketals, the present invention provides a reaction mechanism with a completely different inventive concept, under which aldehyde / ketone compounds and thiol compounds can react under light conditions.

[0105] Those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims and their equivalents, this invention is also intended to include these modifications and variations.

Claims

1. A method for photocatalytic preparation of degradable compounds containing thioacetals / thioketals, characterized in that, The process includes the following steps: mixing an aldehyde / ketone compound with a thiol compound and reacting the mixture under light to obtain a degradable compound containing a thioacetal / thioketal, wherein the thioacetal / thioketal degradable compound is a long-chain polymer or a cross-linked network polymer. The lighting conditions include a single light source with wavelengths of 254nm-460nm, a composite light source with multiple light sources, natural light, or enhanced natural light; When the degradable thioacetal / thioketal compound is a long-chain polymer, the aldehyde / ketone compound contains an aldehyde group or a carbonyl group, and the mercapto compound is a dithiol compound with a main carbon chain of ≥4. Dithiol compounds with a main carbon chain ≥ 4 are selected from any of the following structures: ； When the thioacetal / thioketal degradable compound is a polymer material with a cross-linked network structure, the aldehyde / ketone compound contains one aldehyde group or carbonyl group, and the thiol compound is a polythiol compound containing ≥3 thiol groups; Polythiol compounds containing ≥3 thiol groups are selected from any of the following structures: ； Aldehyde / ketone compounds containing an aldehyde group or a carbonyl group are selected from any of the following structures: ； When the thioacetal / thioketal degradable compound is a polymer material with a cross-linked network structure, the aldehyde / ketone compound contains ≥2 aldehyde groups or carbonyl groups, and the thiol compound is a polythiol compound containing ≥2 thiol groups. Polythiol compounds containing ≥2 thiol groups are selected from any of the following structures: Aldehyde / ketone compounds containing ≥2 aldehyde or carbonyl groups are selected from any of the following structures: 。 2. The method for photocatalytic preparation of degradable compounds containing thioacetals / thioketals according to claim 1, characterized in that, The reaction conditions are: light irradiation at room temperature for 1-24 hours.

3. The method for photocatalytic preparation of degradable compounds containing thioacetals / thioketals according to claim 1, characterized in that, Ultraviolet photoinitiators, visible photoinitiators, or a mixture of both were also used as catalysts.

4. The method for photocatalytic preparation of degradable compounds containing thioacetals / thioketals according to claim 1, characterized in that, When both the aldehyde / ketone compound and the thiol compound are liquids, no solvent is required; when the aldehyde / ketone compound or the thiol compound cannot be mixed uniformly, a solvent is used to dissolve it before the reaction.

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