A degradable self-polishing resin containing hydrolytically activated zwitterionic dendritic units and a method of making the same

Abstract

This invention discloses a biodegradable self-polishing resin containing hydrolyzed zwitterionic dendritic units and its preparation method. The resin consists of a biodegradable polymer backbone and dendritic polymer side chains. The backbone is composed of hydrolyzable ester bonds, and the side chains have a multi-level branched structure and are distributed with zwitterionic precursor groups containing hydrolyzable ester bonds. Before hydrolysis, the zwitterionic structure is shielded, and after hydrolysis, the zwitterionic structure is exposed. The resin is prepared by using a compound containing diazid groups as the core, and progressively amplifying it through a thiol-ene click reaction and esterification reaction to obtain a dendritic polymer intermediate, which is then reacted with a biodegradable polymer containing alkyne groups in an azido-alkyne click reaction. This invention combines a biodegradable polymer backbone, dendritic functional side groups, and a hydrolyzable zwitterionic precursor, giving the resin both biodegradability, continuous surface renewal capability, and hydrolyzed antifouling function, making it suitable for use in marine antifouling coatings.

Description

Technical Field

[0001] This application relates to the field of polymer technology, specifically to a biodegradable self-polishing resin containing hydrolysis-activated zwitterionic dendritic units and its preparation method. Background Technology

[0002] Marine biofouling refers to the attachment, growth, and reproduction of marine organisms such as bacteria, algae, and barnacles on the surfaces of ships and marine equipment. It increases ship drag and energy consumption, and accelerates the corrosion of marine equipment. Currently, applying marine antifouling coatings remains the primary means of controlling biofouling.

[0003] Self-polishing antifouling systems utilize polymers capable of hydrolysis in seawater as film-forming resins. Continuous renewal is achieved through resin surface dissolution and shedding, while controlling the release of antifouling agents such as cuprous oxide. For example, CN118496727A uses metal acrylate salts and silane acrylates to construct a self-polishing resin, compounded with antifouling agents such as cuprous oxide to achieve antifouling. With increasing environmental requirements, marine antifouling technology is gradually shifting towards reducing the release of toxic antifouling agents and developing non-biogenic antifouling materials. Among these, zwitterionic materials, which can form a stable hydrated layer on the coating surface through strong hydration, reducing the non-specific adhesion of fouling substances such as proteins and microorganisms, have become an important research direction for environmentally friendly marine antifouling materials. At the same time, microplastic pollution caused by polymer particles generated during the service of the antifouling coating itself is also receiving increasing attention.

[0004] Against this backdrop, utilizing the interfacial properties of materials to achieve non-biological antifouling has attracted attention. Zwitterionic groups can form a stable hydration layer at the seawater interface, inhibiting the initial adhesion of proteins and fouling organisms, providing a technical pathway to reduce the use of traditional antifouling agents such as cuprous oxide.

[0005] While existing marine antifouling resins and coatings can reduce the adhesion of marine fouling organisms through various means such as self-polishing, low surface energy, hydrophilic antifouling, and biodegradability, different technical routes still have certain limitations.

[0006] Zwitterionic materials can form a hydration layer on the material surface through strong interaction with water molecules, thereby reducing the adhesion of proteins, bacteria, and other fouling organisms. This has made them one of the more important non-toxic antifouling technologies in recent years. However, existing zwitterionic antifouling materials usually introduce hydrophilic groups directly through copolymerization, grafting, or surface modification. Their hydrophilic structure is exposed during material preparation and early service life, such as in hydrogel systems. This can easily affect the resin's solubility, compatibility, water absorption, and film-forming properties, making it difficult to balance antifouling performance with coating processing, mechanical properties, and long-term service performance.

[0007] Existing self-polishing antifouling resins primarily control the dissolution and renewal of the resin surface through hydrolyzable or ion-exchangeable groups, and further regulate the release of antifouling agents. While this type of system is technologically mature, the antifouling effect of some products still heavily relies on the continuous release of copper-based or other active antifouling agents. Furthermore, polymer debris formed by traditional film-forming resins during service, corrosion, and surface renewal is often difficult to further degrade, indicating room for improvement in reducing the use of toxic antifouling agents and minimizing polymer residues from coating sources.

[0008] Dendritic or hyperbranched polymers are characterized by high branching degree and abundant terminal functional groups, making them suitable for constructing multifunctional antifouling materials. However, their compact molecular structure and relatively weak interchain entanglement result in lower system viscosity compared to linear polymers of similar molecular weight. When used directly as the main film-forming material, their application rheology, coating integrity, and mechanical properties still require further adjustment.

[0009] In summary, while existing technologies utilize zwitterionic hydration, self-polishing, biodegradability, and multifunctional synergy to improve marine antifouling performance, these different functions are typically relatively independent, making it difficult to simultaneously achieve antifouling performance, continuous surface renewal, material biodegradability, and coating processing and application performance. Therefore, further optimization of the molecular structure and functional combination of antifouling resins remains necessary. Summary of the Invention

[0010] Purpose of the invention: The purpose of this invention is to provide a biodegradable self-polishing resin containing hydrolyzed zwitterionic dendritic units. By combining a biodegradable polymer backbone, dendritic functional side groups, and hydrolyzed zwitterionic precursors, the zwitterionic functions are gradually formed or exposed in an aqueous environment during the hydrolysis process. Combined with the gradual degradation of the polymer backbone, the material surface is continuously renewed, thus taking into account marine antifouling performance, material biodegradability, and resin processing and film-forming properties.

[0011] Technical solution: This invention provides a biodegradable self-polishing resin containing hydrolyzed zwitterionic dendritic units, the overall structure of which is as follows: Figure 1 As shown. The resin is generally composed of a biodegradable dendritic polymer and a biodegradable polymer backbone. The biodegradable dendritic polymer is composed of a hydrolyzable zwitterionic precursor and dendritic polymer side chains, while the biodegradable polymer backbone is composed of biodegradable polylactic acid units.

[0012] The structure can serve as a representative structural unit of the resin of the present invention, and multiple structural units can be connected to form a polymer resin with an adjustable degree of polymerization.

[0013] The biodegradable polymer backbone consists of multiple hydrolyzable ester bonds, which gradually hydrolyze and break down in an aqueous environment, causing the backbone to degrade into shorter segments. The degree of polymerization of the backbone can be controlled by monomer ratio, reaction conditions, and reaction time.

[0014] The dendritic functional side groups are grafted onto the main chain through connecting units, and have a multi-level branched structure and multiple functional sites. The branching level, the number of branches and the number of terminal groups can be adjusted through the dendritic intermediate structure, thereby regulating the content and spatial distribution of functional groups.

[0015] The dendritic functional side groups are distributed with multiple hydrolyzable zwitterionic precursor groups, which contain hydrolyzable ester bonds. In the unhydrolyzed state, the zwitterionic structure is shielded. When the ester bonds are hydrolyzed in an aqueous environment, zwitterionic structures with positive and negative charges are generated or exposed, so that the material surface gradually exhibits hydrophilicity and anti-bioadhesion properties.

[0016] This invention also provides a method for preparing a biodegradable self-polishing resin containing hydrolysis-activated zwitterionic dendritic units, comprising the following steps:

[0017] Step 1, Preparation of dendritic polymer intermediates containing diazid groups: Using compounds containing diazid groups as the core, dendritic polymer intermediates with terminal diazid groups are prepared by successive generation amplification through thiol olefin click reaction and esterification reaction.

[0018] Step 2: The dendritic polymer intermediate obtained in Step 1 is subjected to an azide-yne ​​click reaction with an alkyne-containing biodegradable polymer derivative to obtain the biodegradable self-polishing resin.

[0019] Specifically, the generational amplification described in step 1 includes: G1 preparation, preparation of dendritic polymer resin containing multiple hydroxyl groups; G1.5 preparation, preparation of dendritic polymer resin containing carboxylic acid groups; G2 preparation, preparation of dendritic polymer resin containing multiple hydroxyl groups; and amplification of dendritic polymer resin to G4.5 through repeated reactions.

[0020] Furthermore, the compound containing the diazid group mentioned in step 1 is an intermediate containing the diazid group prepared by esterification reaction of triallyl cyanurate and azidocarboxylic acid.

[0021] Further, the generational amplification described in step 1 includes: esterifying the peripheral hydroxyl groups of the dendritic polymer with N-methyliminodiacetic acid to introduce a branched structure containing tertiary amine and carboxyl groups; then esterifying the resulting carboxyl-containing intermediate with glycerol to convert the peripheral carboxyl groups into a glycerol ester structure containing multiple terminal hydroxyl groups; and growing the dendritic structure step by step through the above-mentioned "carboxyl functionalization-multi-hydroxyl expansion" cyclic reaction.

[0022] Furthermore, step 1 also includes: esterifying the free carboxyl groups on the periphery of the obtained dendritic polymer intermediate with methanol to cap the terminal groups.

[0023] Furthermore, the alkyne-containing biodegradable polymer-derived polymer mentioned in step 2 is an alkyne-containing polylactic acid-derived polymer.

[0024] Furthermore, the azide-yne ​​click reaction described in step 2 is carried out in the presence of a copper catalyst and ascorbic acid.

[0025] More specifically, the synthetic route of the present invention is as follows:

[0026] .

[0027] Detailed explanation is as follows:

[0028] Synthesis of bisazide-containing intermediates: The bisazide-containing intermediates of this invention have the following properties: Figure 2 The chemical structure shown in a contains two azide groups (N3) that can participate in subsequent click reactions, which are used to react with polylactic acid-derived polymers containing alkynyl groups to construct the biodegradable main chain structure of the biodegradable hyperbranched self-polishing resin described in this invention.

[0029] The intermediate containing two azido groups can be prepared by the following method: A triallyl cyanurate substrate derivative is added to a reaction vessel and dissolved by stirring in dichloromethane as a solvent. Then, dicyclohexylcarbodiimide (DCC), 4-dimethylaminopyridine (DMAP) are added as catalysts, along with an azide carboxylic acid derivative, wherein the molar ratio of the triallyl cyanurate derivative, the azide carboxylic acid derivative, and DCC / DMAP is 1:2.2:2.2:0.2. The reaction system is controlled at approximately 25°C and stirred for 24 hours to allow the carboxyl group to undergo esterification with the carboxylic acid, yielding an intermediate containing two azido groups. After the reaction is complete, the system is allowed to stand to separate the white DCU precipitate. Anhydrous sodium sulfate is added for dehydration, and the precipitate is separated using a funnel. The obtained product is washed sequentially with saturated sodium bicarbonate and brine three times to remove unreacted raw materials, byproducts, and residual DCU. Subsequently, purification is performed by column chromatography, and dichloromethane is removed under vacuum to obtain the intermediate containing two azido groups. The obtained bis-azide intermediate was characterized by NMR, and the characteristic signal of 3.2 ppm indicated the successful introduction of the azide group. The intermediate was subsequently used in a click reaction with an organo-alkyne polylactic acid derivative polymer to form an interlocking structure within the resin.

[0030] ¹H NMR (300 MHz, DMSO-d6) δ 6.30 (t, J = 7.0 Hz, 1H), 6.07 (ddd, J =16.8, 10.0, 6.2 Hz, 2H), 5.43 (dd, J = 16.8, 2.1 Hz, 2H), 5.31 (dd, J = 10.0,2.1 Hz, 2H), 4.82–4.57 (m, 2H), 4.68 (d, J = 6.2 Hz, 4H), 4.31 (t, J = 7.1Hz, 2H), 2.86 (t, J = 7.1 Hz, 2H), 2.30 (t, J = 7.1 Hz, 4H), 1.90 (t, J = 7.1Hz, 4H).

[0031] Synthesis of first-generation dendritic polymers: The polyhydroxy dendritic intermediate G1 described in this invention has the following properties... Figure 2 The structure shown in b uses the intermediate containing a diazid group from the previous step as its core, and gradually constructs a branched structure through a thiol olefin click reaction, forming multiple hydroxyl functional groups on the molecular periphery. The multi-hydroxyl dendritic intermediate is used for subsequent reactions with the precursor monomer to further construct the biodegradable dendritic polymer described in this invention.

[0032] The polyhydroxy dendritic intermediate can be prepared by the following method: An intermediate containing a diazid group and 1-thioglycerol are added to a reaction vessel, methanol is added as a solvent, and the mixture is stirred until fully dissolved. Then, benzoin dimethyl ether (DMPA) photoinitiator is added, wherein the molar ratio of the diazid group intermediate, 1-thioglycerol, and benzoin dimethyl ether is 1:2.2:0.05. The reaction system is controlled at room temperature, and a click reaction is initiated by irradiation under a UV lamp for 2 hours, causing the thiol group to undergo a thiol-ene click reaction with the double bond, yielding a first-generation intermediate. After the reaction is complete, methanol is removed under vacuum, and byproducts and unreacted substrates are removed by washing and extraction with diethyl ether. The product obtained from higher-generation intermediates (generations >2 require column chromatography purification) is dried under vacuum to obtain the polyhydroxy dendritic intermediate. Further, the branching generation of the polyhydroxy dendritic intermediate is first generation, with a theoretical number of 4 hydroxyl groups on the molecular periphery; its number-average molecular weight is 711.78 g / mol. The obtained polyhydroxy dendritic intermediates can be structurally characterized by ¹H NMR.

[0033] ¹H NMR (300 MHz, DMSO-d6)δ 6.30 (t, J = 7.0 Hz, 1H), 5.37 (br s, 2H,OH), 4.94 (br s, 2H, OH), 4.82–4.57 (m, 2H), 4.31–4.30 (t, J = 7.1 Hz, 6H), 3.87 (m, 2H), 3.59–3.53 (m, 4H), 2.86 (t, J = 7.1 Hz, 6H), 2.69–2.45 (m, 4H), 2.30 (t, J = 7.1 Hz, 4H), 1.90 (t, J = 7.1 Hz, 4H).

[0034] Synthesis of 1.5th generation dendritic polymers: The carboxyl-containing dendritic intermediates of this invention have the following properties... Figure 2 The structure shown in c is prepared by esterification of the aforementioned polyhydroxy dendritic intermediate with N-methyliminodiacetic acid. During this reaction, the hydroxyl groups surrounding the polyhydroxy dendritic intermediate react with the carboxyl groups in the N-methyliminodiacetic acid, thereby introducing functional side chains containing tertiary amine groups and free carboxyl groups onto the periphery of the dendritic structure.

[0035] Specifically, the aforementioned polyhydroxy dendritic intermediate was dissolved in tetrahydrofuran and stirred under nitrogen protection until a homogeneous solution was formed. N-methyliminodiacetic acid was added to the solution, along with the condensing agent DCC and the catalyst DMAP. The molar ratio of hydroxyl groups, N-methyliminodiacetic acid, condensing agent, and catalyst in the polyhydroxy dendritic intermediate was 1:8:8:0.5. The reaction system was stirred at room temperature for 12 hours to allow the hydroxyl groups on the periphery of the polyhydroxy dendritic intermediate to undergo esterification with some of the carboxyl groups in N-methyliminodiacetic acid, forming multiple branched structures containing tertiary amines and carboxyl groups on the periphery of the dendritic molecule. After the reaction was complete, the precipitate and / or byproducts generated during the reaction were removed by filtration, followed by vacuum concentration. The crude product was purified by washing with sodium bicarbonate and brine and column chromatography to remove unreacted N-methyliminodiacetic acid, condensing agent, byproducts, and other small molecule impurities. The purified product was dried under vacuum to obtain a carboxyl-containing dendritic intermediate, which is a 1.5 generation dendritic polymer. The resulting first-generation dendritic polymers can be structurally characterized by methods such as ¹H NMR or MALDI-TOF.

[0036] ¹H NMR (300 MHz, DMSO-d6)δ 13.03 (br s, 4H, COOH), 6.30 (t, J = 7.0Hz, 1H), 5.53 (t, J = 7.0 Hz, 2H), 4.82–4.57 (m, 2H), 4.42–4.18 (m, 4H), 4.31–4.30 (t, J = 7.1 Hz, 6H), 3.32 (s, 8H), 3.30 (s, 8H), 2.86 (t, J = 7.1Hz, 6H), 2.79–2.54 (m, 4H), 2.30 (t, J = 7.1 Hz, 4H), 2.26 (s, 12H), 1.90 (t,J = 7.1 Hz, 4H).

[0037] Synthesis of second-generation dendritic polymers: The multi-hydroxyl functionalized dendritic intermediates of this invention have the following properties: Figure 2 The structure shown in d is prepared by esterification of the aforementioned carboxyl-containing dendritic intermediate with glycerol. During the reaction, the free carboxyl groups on the periphery of the carboxyl-containing dendritic intermediate undergo esterification with the hydroxyl groups in glycerol, introducing glycerol ester side chains containing multiple free hydroxyl groups onto the periphery of the dendritic structure while retaining the tertiary amine and azide groups.

[0038] Specifically, the aforementioned carboxyl-containing dendritic intermediate was added to a reaction vessel and stirred under nitrogen in a 1:1 mixture of tetrahydrofuran and water until fully dissolved. Glycerol was then added, along with EDC as a condensing agent and DMAP as a catalyst. The molar ratio of carboxyl groups to glycerol in the carboxyl-containing dendritic intermediate was 1:2, the molar ratio of the condensing agent to carboxyl groups was 1:1.2, and the amount of catalyst added was 0.5 mol% of the glycerol. The reaction system was controlled at room temperature and stirred for 12 hours to allow the carboxyl groups on the periphery of the carboxyl-containing dendritic intermediate to esterify with one hydroxyl group in glycerol, forming a glycerol monoester structure while retaining the remaining hydroxyl groups in the glycerol molecule, thus obtaining a dendritic intermediate with multiple hydroxyl groups on the periphery. After the reaction was completed, reaction byproducts and unreacted substances were removed using a funnel, and the mixture was concentrated under vacuum. The crude product was purified by adding dichloromethane and washing with sodium bicarbonate and brine, followed by column chromatography, dialysis with 1 wt% brine, precipitation, or a combination thereof to remove unreacted glycerol, condensing agent, catalyst, and other small molecule impurities. The purified product was dried under vacuum to obtain the polyhydroxy functionalized dendritic intermediate. The obtained polyhydroxy functionalized dendritic intermediate can be structurally characterized by ¹H NMR or MALDI-TOF.

[0039] ¹H NMR (300 MHz, DMSO-d6)δ 6.77 (m, 4H), 6.30 (t, J = 7.0 Hz, 1H), 5.53 (t, J = 7.0 Hz, 2H), 5.22 (br s, 4H, OH), 4.94 (br s, 4H, OH), 4.82–4.57(m, 2H), 4.42–4.18 (m, 4H), 4.31–4.30 (t, J = 7.1 Hz, 6H), 4.08–3.84 (m, 8H), 3.32 (s, 16H), 2.86 (t, J = 7.1 Hz, 6H), 2.79–2.54 (m, 4H), 2.30 (t, J*= 7.1Hz, 4H), 2.26 (s, 12H), 1.90 (t, J = 7.1 Hz, 4H).

[0040] Dendritic polymers were extended to the 4.5th generation and then capped with methyl esterification: Based on the second-generation dendritic polymers described above, a repeated generation-by-generation branching reaction was carried out according to the methods described in 5.5 and 5.6. First, the peripheral hydroxyl groups of the dendritic polymer were esterified with N-methyliminodiacetic acid, reintroducing a branched structure containing tertiary amine and carboxyl groups onto the molecular periphery; subsequently, the resulting carboxyl-containing intermediate was esterified with glycerol, converting the peripheral carboxyl groups into a glycerol ester structure containing multiple terminal hydroxyl groups. Through the above-mentioned cyclic reaction of "carboxyl functionalization - multi-hydroxyl extension", the dendritic structure was grown stepwise to obtain the 4.5th generation dendritic polymer, as shown below. Figure 2 As shown in e.

[0041] The reaction principles, reactant types, and post-processing methods for each generation of dendritic polymers are basically the same as those described above. The reactant ratios, reaction times, and purification conditions can be adjusted according to the increase in the generation of the dendritic polymer and the change in the number of peripheral functional groups. After completing the construction of the 4.5 generation dendritic structure, the obtained 4.5 generation carboxyl-containing dendritic polymer is subjected to an esterification reaction with methanol, converting some or all of its peripheral free carboxyl groups into methyl carboxylate, thereby achieving end-group capping. Specifically, the 4.5 generation carboxyl-containing dendritic polymer is dissolved in methanol and reacted at 30°C for 12 hours under DCC / DMAP catalysis. After the reaction is complete, it is purified under vacuum and dried to obtain the 4.5 generation dendritic polymer. The obtained 4.5 generation dendritic polymer retains two azide groups in the molecule and can be further reacted with polylactic acid-derived polymers containing alkyne groups via a click reaction to construct the biodegradable dendritic polymer self-polishing resin described in this invention.

[0042] ¹H NMR (300 MHz, DMSO-d6) δ (ppm): 8.43 (d, J = 7.0 Hz, 28H), 6.30 (d, J = 7.0 Hz, 1H), 5.53 (t, J = 7.0 Hz, 2H), 5.09 (s, 6H), 4.82–4.57 (m,2H), 4.60 (d, J = 7.0 Hz, 56H), 4.42–4.18 (m, 4H), 3.66 (s, 96H), 3.32 (s,240H), 2.79–2.54 (m, 4H), 2.30 (t, J = 7.1 Hz, 4H), 2.26 (s, 180H), 1.90 (t,J = 7.1 Hz, 4H).

[0043] 4th and 5th generation dendritic polymers polymerized with alkynyl lactic acid: The biodegradable dendritic polymer self-polishing resin of this invention has the following properties: Figure 2 The structure shown in f is obtained by polymerizing the aforementioned 4.5 generation dendritic polymer with an alkyne-containing polylactic acid derivative polymer via an azide-ytylene click reaction (CuAAC). Under copper catalysis, the azide group and the alkyne group undergo a cycloaddition reaction to form a stable 1,2,3-triazole linkage structure, thereby sequentially linking the 4.5 generation dendritic polymer with polylactic acid segments to construct a polymer resin with biodegradable polylactic acid segments and high-density dendritic functional units.

[0044] This embodiment uses commercially available alkynyl-containing polylactic acid derivative polymers as raw materials. The polymer backbone consists of polylactic acid segments, and the molecular chain ends contain alkynyl functional groups that can participate in the azide-alkynyl click reaction. The number-average molecular weight (Mn) of the alkynyl-containing polylactic acid derivative polymer is approximately 1000 g / mol.

[0045] Specifically, the aforementioned 4.5 generation dendritic polymer and alkynyl-containing polylactic acid derivative polymer were added to a reaction vessel, using a tetrahydrofuran-water mixed solvent as the reaction environment, and stirred until fully dissolved or uniformly dispersed. Subsequently, copper sulfate (CuSO4) and ascorbic acid were added, wherein the molar ratio of the azide groups in the 4.5 generation dendritic polymer to the alkynyl groups in the alkynyl-containing polylactic acid derivative polymer was 1:1, the amount of copper sulfate added was 0.5 wt%, and the amount of ascorbic acid added was 5 wt%. Under nitrogen protection, the reaction was stirred at 40 degrees Celsius for 48 hours to allow the azide groups and alkynyl groups to fully undergo the CuAAC click reaction. After the reaction was completed, the reaction product was purified by precipitation, dialysis, and column chromatography to remove unreacted small molecules, copper catalyst, ascorbic acid, and other residual impurities. Subsequently, the product was precipitated with chloroform, dialyzed, filtered, or vacuum concentrated, and then vacuum dried to obtain the biodegradable dendritic polymer self-polishing resin described in this invention. The obtained resin can be characterized in terms of structure and molecular weight using ¹H NMR, FTIR, GPC, MALDI-TOF, or other polymer characterization methods.

[0046] Through the above structural design, hydrolyzable polylactic acid (PLA) segments and a highly branched 4.5-generation dendritic polymer structure are simultaneously introduced into the resin. The 4.5-generation dendritic polymer is constructed hierarchically from multi-level branching units, with hydrolyzable connecting structures between different levels, and multiple zwitterionic precursor functional groups distributed within the dendritic structure. In a seawater environment, the PLA segments and the hydrolyzable structures in the dendritic polymer can gradually undergo hydrolysis and degradation, causing the resin molecular structure to gradually dissociate and achieve continuous surface renewal. Simultaneously, with the gradual hydrolysis of different levels of the dendritic structure, functional groups originally located inside the dendritic structure or shielded by the outer structure are gradually exposed, forming or exposing zwitterionic structures under hydrolysis, thereby continuously regulating the hydrophilicity and anti-bioadhesion properties of the resin surface. Therefore, this invention, through the synergistic effect of degradable polymer segments and multi-level dendritic functional structures, enables the resulting resin to possess degradability, continuous surface renewal capability, and functionalized interface characteristics that are continuously formed during the hydrolysis process.

[0047] The key technical point of this invention is:

[0048] 1. A tree-like functional structure with hierarchical hydrolysis activation characteristics.

[0049] This invention introduces highly branched dendritic polymer functional units into a resin. The dendritic polymer has a multi-level branched structure and contains multiple hydrolyzable structures and zwitterionic precursor functional groups. As the dendritic structure gradually hydrolyzes in seawater, the functional sites originally located within the dendritic structure are further exposed, along with the zwitterionic structures, thereby continuously forming new functionalized interfaces during the hydrolysis process. The highly branched structure of the dendritic polymer simultaneously provides multiple functional sites, enabling a high-density distribution of zwitterionic functions within a limited molecular space.

[0050] 2. Topological division of labor between biodegradable polymer backbone and dendritic functional units.

[0051] This invention combines hydrolyzable polylactic acid (PLA) segments with highly branched dendritic polymers to construct a polymer resin. The hydrolyzable PLA segments are mainly used to form a polymer skeleton with film-forming ability, and the resin's solubility, viscosity, film-forming properties, and other physicochemical properties can be adjusted by adjusting the segment length, molecular weight, composition, and degree of polymerization. The dendritic polymers serve as high-density functional units, introducing multiple hydrolyzable and interfacial functional sites, thereby dividing the main physicochemical properties adjustment and interfacial functionalization of the resin at the molecular structure level.

[0052] 3. A two-level degradation and functional renewal mechanism combining polymer skeleton degradation and dendritic functional unit hydrolysis.

[0053] The biodegradable polylactic acid (PLA) segments and dendritic polymers of this invention both contain hydrolyzable structures. In a seawater environment, the gradual hydrolysis and breakage of the PLA segments reduces the overall molecular weight of the resin and promotes continuous surface renewal, while also reducing the risk of long-term residues of recalcitrant polymers. The gradual hydrolysis of the hydrolyzable structures within the dendritic polymers promotes the gradual dissociation and degradation of the dendritic functional units themselves, while simultaneously forming or exposing new zwitterionic functional sites. Therefore, the overall degradation of the resin, surface renewal, and continuous formation of interfacial functions are achieved jointly by different structural levels.

[0054] 4. Modular synthetic design based on multiple selective reactions to construct the above topology.

[0055] Based on the molecular topology of the target resin and the reaction characteristics of different functional groups, this invention employs a thiol-ene click reaction to construct an initial branched structure, which is then extended multiple times through esterification reactions, allowing the dendritic polymer to expand to higher generations. Finally, through an azido-acetylene click reaction between the azide group and the acetylene-containing polylactic acid derivative polymer, degradable polylactic acid segments are linked with highly branched dendritic functional units to form the target polymer resin. This modular reaction route achieves the integration of a degradable polymer structure, a highly branched dendritic structure, and hydrolysis-activating function within the same resin molecule.

[0056] The present invention also provides the application of the biodegradable self-polishing resin containing hydrolysis-activated zwitterionic dendritic units, which can be used in marine antifouling coatings.

[0057] The beneficial effects of this invention are as follows:

[0058] This invention involves the stepwise construction of dendritic polymers, followed by click polymerization of 4.5-generation dendritic polymers containing azide groups with polylactic acid (PLA)-derived polymers containing alkyne groups to prepare a biodegradable self-polishing resin containing dendritic polymer functional units and PLA segments. Compared to polymers using only linear polymers or single-functional structures, the resin of this invention simultaneously introduces highly branched dendritic units and biodegradable PLA segments into its molecular structure. Furthermore, the composition, molecular weight, and rheological properties of the resulting copolymer can be adjusted by regulating the feed ratio of dendritic polymers to PLA-derived polymers.

[0059] The structures of the intermediates and dendritic polymers at each stage of this invention were characterized by ¹H NMR. The changes in characteristic peaks and peak areas obtained were consistent with the expected structures at each stage, indicating that the functional group transformations and the step-by-step construction of the dendritic structure could proceed smoothly. The relevant ¹H NMR spectra and characteristic peak data can be found in the corresponding synthesis steps in Part 5 of this disclosure, and will not be repeated here.

[0060] For the key 4.5 generation dendritic polymer and the two lactic acid dendritic polymer copolymers, molecular weight characterization was further performed using MALDI-TOF mass spectrometry. The molecular weight of the 4.5 generation dendritic polymer was measured to be 10140.98 Da, and the molecular weights of the two lactic acid dendritic polymers were 23102.23 Da and 51070.12 Da, respectively, which are consistent with their expected molecular structures, further proving that the 4.5 generation dendritic polymer can be prepared according to the designed route.

[0061] GPC curve as shown Figure 3 As shown in the figure, the green curve represents lactic acid polymer monomers, the orange line represents dendritic polymer monomers, and the blue line represents the polymerized mixture. Figure 3 It can be seen that the 4.5 generation dendritic polymer and the polylactic acid-derived polymer each exhibit their own characteristic elution peaks, while the GPC curves of the resulting products show significant changes. The blue curve shows a new low-elution-volume component at approximately 18.7 mL of elution volume. This peak shifts towards a lower elution volume compared to the main elution peaks of the 4.5 generation dendritic polymer and the polylactic acid-derived polymer. Since a lower elution volume typically corresponds to a larger hydrodynamic volume under the same GPC testing conditions, this result indicates that a polymer with a larger molecular size was formed in the reaction system, supporting the polymerization of the 4.5 generation dendritic polymer with the polylactic acid-derived polymer to form a polylactic acid dendritic polymer copolymer.

[0062] The above results demonstrate that the polymerization method employed in this invention can effectively link 4.5-generation dendritic polymers with polylactic acid (PLA) segments, and can obtain PLA-dendritic polymer copolymers with different numbers and molecular weights of dendritic polymer units by adjusting the reactant ratio. Simultaneously, the blue curve still exhibits peaks corresponding to PLA-derived polymers in the higher elution volume region, indicating that some PLA-derived polymers that did not participate in the polymerization reaction still exist in the reaction system. Combined with the aforementioned structural characterization results, such as NMR, it can be further confirmed that the polymerization method employed in this invention can achieve the linking of 4.5-generation dendritic polymers with PLA segments, thereby obtaining PLA-dendritic polymer copolymers.

[0063] The molecular structure and viscosity of the resin obtained by this invention are adjustable. Resins with different structures obtained by this invention exhibit different viscosity characteristics. Brookfield viscosity measurements were performed at 25°C and 50% solids content, and the viscosities of each sample are shown in the table below.

[0064] Sample Name molecular weight Viscosity (mPa.s) 4th and 5th generation hydrolyzable dendritic polymers 10140.98 75 Hydrolyzable polylactic acid dendritic polymer 2 23102.23 120 Hydrolyzable polylactic acid dendritic polymer 5 51070.12 570 Attached Figure Description

[0065] Figure 1 This is a schematic diagram of a representative structure of the biodegradable self-polishing resin of the present invention.

[0066] Figure 2 This is a synthesis route diagram for the biodegradable self-polishing resin of the present invention.

[0067] Figure 3 This is a GPC curve of the biodegradable self-polishing resin of the present invention.

[0068] Figure 4 Images of protein adsorption fluorescence on different sample surfaces and statistics of fluorescence intensity. Detailed Implementation

[0069] The technical solution of this application will be described in detail below through embodiments, but the scope of protection of this application is not limited to the embodiments described. The molecular weight mentioned in this invention is the number-average molecular weight.

[0070] Example 1 (Preparation of biodegradable self-polishing resin A)

[0071] (1) Preparation of intermediates containing bisazide groups

[0072] 10.00 g (30.4 mmol) of triallyl cyanurate derivative was added to a reaction vessel, followed by 200 mL of dichloromethane. The mixture was stirred until fully dissolved. Then, 9.57 g (66.88 mmol) of azide carboxylic acid derivative, 13.80 g (66.88 mmol) of dicyclohexylcarbodiimide (DCC), and 0.74 g (6.08 mmol) of 4-dimethylaminopyridine (DMAP) were added. The molar ratio of triallyl cyanurate derivative, azide carboxylic acid derivative, DCC, and DMAP was 1:2.2:2.2:0.2. The reaction mixture was stirred at 25 °C for 24 h. After the reaction was complete, the mixture was allowed to stand, and the resulting white precipitate was removed. The mixture was then dried with anhydrous sodium sulfate. The obtained organic phase was washed successively with saturated sodium bicarbonate aqueous solution and saturated brine, then purified by column chromatography (ethyl acetate: n-hexane = 3:7), and the solvent was removed under vacuum to obtain 13.75 g of intermediate containing diazid groups, with a yield of 78%.

[0073] The obtained product was characterized by ¹H NMR, and the results are as follows: ¹H NMR (300 MHz, DMSO-d6) δ 6.30 (t, J = 7.0 Hz, 1H), 6.07 (ddd, J = 16.8, 10.0, 6.2 Hz, 2H), 5.43 (dd, J = 16.8, 2.1 Hz, 2H), 5.31 (dd, J = 10.0, 2.1 Hz, 2H), 4.82–4.57 (m, 2H), 4.68 (d, J = 6.2 Hz, 4H), 4.31 (t, J = 7.1 Hz, 2H), 2.86 (t, J = 7.1 Hz, 2H), 2.30 (t, J = 7.1 Hz, 4H). 1.90 (t, J = 7.1 Hz, 4H).

[0074] (2) Preparation of polyhydroxy dendritic intermediates

[0075] 10.00 g (17.25 mmol) of the diazid intermediate obtained in step (1) and 4.10 g (37.95 mmol) of 1-thioglycerol were added to a reaction vessel, followed by 200 mL of methanol. The mixture was stirred until fully dissolved. 0.22 g (0.86 mmol) of benzoin dimethyl ether (DMPA) was added as a photoinitiator, with the molar ratio of the diazid intermediate, 1-thioglycerol, and DMPA being 1:2.2:0.05. The reaction system was kept at room temperature and reacted under ultraviolet light for 2 h. After the reaction was complete, methanol was removed under vacuum, and unreacted raw materials and small molecule impurities were removed by washing and extraction with diethyl ether. The mixture was then vacuum dried to obtain 11.66 g of a polyhydroxy dendritic intermediate, with a yield of 95%.

[0076] The obtained product was characterized by ¹H NMR, and the results are as follows: ¹H NMR (300 MHz, DMSO-d6) δ 6.30 (t, J = 7.0 Hz, 1H), 5.37 (br s, 2H, OH), 4.94 (br s, 2H, OH), 4.82–4.57 (m, 2H), 4.31–4.30 (t, J = 7.1 Hz, 6H), 3.87 (m, 2H), 3.59–3.53 (m, 4H), 2.86 (t, J = 7.1 Hz, 6H), 2.69–2.45 (m, 4H), 2.30 (t, J = 7.1 Hz, 4H), 1.90 (t, J = 7.1 Hz, 4H).

[0077] (3) Preparation of carboxyl-containing dendritic intermediates

[0078] 8 g (11.24 mmol) of the polyhydroxy dendritic intermediate obtained in step (2) was dissolved in 150 mL of tetrahydrofuran and stirred under nitrogen protection to form a homogeneous solution. 10.53 g (89.92 mmol) of N-methyliminodiacetic acid, 18.55 g (89.92 mmol) of DCC, and 0.69 g (5.62 mmol) of DMAP were added. The molar ratio of hydroxyl groups, N-methyliminodiacetic acid, DCC, and DMAP in the polyhydroxy dendritic intermediate was 1:8:8:0.5. The reaction system was stirred at room temperature for 12 h. After the reaction was complete, the precipitate and byproducts were removed by filtration, and the mixture was concentrated under vacuum. The crude product was washed successively with sodium bicarbonate aqueous solution and saturated brine, and further purified by column chromatography (methanol:dichloromethane = 0.35:9.65). The purified product was dried under vacuum to obtain 11.98 g of a carboxyl-containing dendritic intermediate, with a yield of 83%.

[0079] The obtained product was structurally characterized by ¹H NMR and / or MALDI-TOF, with the following results: ¹H NMR (300 MHz, DMSO-d6) δ 13.03 (br s, 4H, COOH), 6.30 (t, J = 7.0 Hz, 1H), 5.53 (t, J = 7.0 Hz, 2H), 4.82–4.57 (m, 2H), 4.42–4.18 (m, 4H), 4.31–4.30 (t, J = 7.1 Hz, 6H), 3.32 (s, 8H), 3.30 (s, 8H), 2.86 (t, J = 7.1 Hz, 6H), 2.79–2.54 (m, 4H), 2.30 (t, J = 7.1 Hz, 4H). 2.26 (s, 12H), 1.90 (t, J = 7.1 Hz, 4H).

[0080] (4) Generation-by-generation amplification of dendritic polymers

[0081] Take 10 g of the carboxyl-containing dendritic intermediate (1.5 generation) obtained in step (3) and react it alternately with glycerol / N-methyliminodiacetic acid, sequentially performing hydroxyl and carboxyl side chain introduction reactions according to the aforementioned dendritic polymer amplification method. The above reactions sequentially yield 2.0, 2.5, 3.0, 3.5, and 4.0 generation dendritic polymer intermediates.

[0082] The yields of each stage of the reaction are as follows:

[0083] Second generation intermediate: 11.28 g of product was obtained, with a yield of 95%.

[0084] 2.5th generation intermediate: 16.09 g of product was obtained, with a yield of 87%.

[0085] 3.0 generation intermediate: 19.51 g of product was obtained, with a yield of 98%.

[0086] 3.5th generation intermediate: 27.37 g of product obtained, yield 86%.

[0087] 4.0 generation intermediate: 32.02 g of product obtained, yield 98%.

[0088] 4.5th generation intermediate: 46.43 g of product obtained, yield 86%.

[0089] The products obtained at each stage were characterized by ¹H NMR, and the changes in the characteristic peaks were consistent with the stepwise construction of the corresponding dendritic structures.

[0090] (5) End capping of 4.5 generation dendritic polymers

[0091] 40 g of the 4.5 generation carboxyl-containing dendritic polymer was dissolved in 1000 mL of methanol, and 52.9 g (252.48 mmol) of DCC and 8 g of DMAP were added. The reaction was carried out at 30 °C for 12 h to esterify and cap the peripheral carboxyl groups. After the reaction was completed, the polymer was filtered, washed with diethyl ether, and dried under vacuum to obtain 41.77 g of the 4.5 generation dendritic polymer, with a yield of 99%.

[0092] The obtained 4.5 generation dendritic polymer was analyzed by MALDI-TOF, yielding a molecular weight of 10140.98 Da. Structural characterization was performed using ¹H NMR: ¹H NMR (300 MHz, DMSO-d6) δ (ppm): 8.43 (d, J = 7.0 Hz, 28H), 6.30 (d, J = 7.0 Hz, 1H), 5.53 (t, J = 7.0 Hz, 2H), 5.09 (s, 6H), 4.82–4.57 (m, 2H), 4.60 (d, J = 7.0 Hz, 56H), 4.42–4.18 (m, 4H), 3.66 (s, 96H), 3.32 (s, 240H), 2.79–2.54 (m, 4H). 2.30 (t, J = 7.1 Hz, 4H), 2.26 (s, 180H), 1.90 (t, J = 7.1 Hz, 4H).

[0093] (6) Polymerization of 4th and 5th generation dendritic polymers with alkynyl polylactic acid derivatives

[0094] Take 10 g (0.99 mmol) of the above-mentioned 4.5 generation dendritic polymer and 0.63 g (1.00 mmol) of alkyne-containing polylactic acid derivative polymer and add them to a reaction vessel. Add 10 mL of tetrahydrofuran / water mixed solvent and stir until fully dissolved or uniformly dispersed. Control the molar ratio of azide groups in the 4.5 generation dendritic polymer to alkyne groups in the alkyne-containing polylactic acid derivative polymer to be 1:1. Add 50 mg of CuSO4 and 450 mg of ascorbic acid, wherein the amount of CuSO4 added is 0.2 mmol and the amount of ascorbic acid added is 2.5 mmol.

[0095] Under nitrogen protection, the reaction was stirred at 40°C for 48 h. After the reaction was complete, purification was performed using a 10k Cutoff dialysis membrane to remove unreacted raw materials, copper catalyst, ascorbic acid, and other small molecule impurities. After purification, the product was vacuum treated to obtain 0.50 g of biodegradable self-polishing resin A1, with a yield of 98%.

[0096] The viscosity was measured at 25°C and 50% solids using a Brookfield viscometer, and was 120 mPa·s.

[0097] Anti-protein adsorption experiment

[0098] Example 2 (Preparation of biodegradable self-polishing resin B)

[0099] The preparation methods of the intermediates containing diazid groups, polyhydroxy dendritic intermediates, carboxyl-containing dendritic intermediates, and 4.5 generation dendritic polymers used in this embodiment are the same as those in Example 1.

[0100] The difference between this embodiment and Example 1 lies in the polymerization conditions of the 4.5 generation dendritic polymer and the alkynyl-containing polylactic acid derivative polymer. 10 g of the 4.5 generation dendritic polymer and 0.6 g of the alkynyl-containing polylactic acid derivative polymer were added to a reaction vessel, along with 5 mL of a tetrahydrofuran / water mixed solvent. The molar ratio of the azide groups in the 4.5 generation dendritic polymer to the alkynyl groups in the alkynyl-containing polylactic acid derivative polymer was 1:1. 25 mg of CuSO4 and 600 mg of ascorbic acid were added, and the reaction was carried out at 30°C for 72 h under nitrogen protection. After the reaction was complete, the product was purified by dialysis and dried to obtain 0.56 g of biodegradable self-polishing resin B, with a yield of 98%. The molecular weight of the obtained resin B was 51070.12; its Brookfield viscosity was 570 mPa·s at 25°C and a solid content of 50%.

[0101] Example 3 (Anti-protein adsorption performance test)

[0102] The prepared resin was coated onto a 1 cm × 1 cm glass slide and immersed in PBS buffer (pH 7.4) for 4 h to allow the sample to reach swelling equilibrium. After removal, residual liquid was blotted off with filter paper. Uncoated and coated slides were then placed in a solution containing 5 mL of 0.2 mg / mL FITC-labeled bovine serum albumin (FITC-BSA) and incubated at 37 °C in the dark for 48 h. After incubation, the slides were washed three times with PBS buffer to remove unadsorbed or weakly adsorbed protein. The sample surface was then observed using a laser scanning confocal microscope (e.g., ...). Figure 4 As shown in the figure, a) shows strong protein fluorescence on the uncoated substrate and b) shows weak fluorescence on the coated substrate. It can be seen from the figure that the lower the average fluorescence intensity, the better the anti-protein adsorption performance of the coating.

[0103] Example 4 (Preparation of the raw material triallyl cyanurate derivative)

[0104] 22.43 g (90 mmol) of triallyl cyanurate and 0.35 g (1.38 mmol) of photoinitiator benzoin dimethyl ether were added to a reaction vessel, and 1 L of methanol was used as the solvent. The mixture was stirred until fully dissolved and then placed under UV irradiation. Separately, 3.24 g (30 mmol) of thioglycerol was dissolved in 100 mL of methanol and slowly added dropwise to the above reaction system over 60 min under continuous stirring and UV irradiation. After the addition was complete, the reaction was continued under UV irradiation for 30 min, and then the UV light source was turned off to terminate the reaction.

[0105] After the reaction was complete, methanol was removed under vacuum to obtain a viscous crude product. The crude product was washed with 100 mL of n-hexane three times to remove unreacted raw materials and other soluble impurities. After washing, the product was dried again under vacuum to obtain the target product. ¹H NMR (300 MHz, DMSO-d6) δ (ppm): 6.07 (ddt, J =16.8, 10.0, 6.2 Hz, 2H), 5.43 (dd, J = 16.8, 2.1 Hz, 2H), 5.31 (dd, J = 10.0,2.1 Hz, 2H), 5.22 (s, 1H), 4.94 (s, 1H), 4.68 (d, J = 6.2 Hz, 4H), 4.64 (t, J= 7.0 Hz, 1H), 4.31 (t, J = 7.1 Hz, 2H), 4.17–3.93 (m, 2H), 2.86 (t, J = 7.1Hz, 2H).

[0106] The above description is merely a preferred embodiment of this application and is not intended to limit this application.

Claims

1. A biodegradable self-polishing resin containing hydrolyzed zwitterionic dendritic units, characterized in that, The resin as a whole is composed of a biodegradable dendritic polymer and a biodegradable polymer backbone, wherein the biodegradable dendritic polymer is composed of a hydrolyzable zwitterionic precursor and dendritic polymer side chains. The biodegradable polymer backbone is composed of multiple hydrolyzable ester bonds, which can gradually undergo hydrolytic breakage in an aqueous environment. The dendritic polymer side chain has a multi-level branched structure, and multiple hydrolyzable zwitterionic precursor groups are distributed on the dendritic polymer side chain. The hydrolyzable zwitterionic precursor groups contain hydrolyzable ester bonds. In the unhydrolyzed state, the zwitterionic structure is shielded. When the ester bonds are hydrolyzed in an aqueous environment, a zwitterionic structure with positive and negative charges is generated or exposed.

2. The biodegradable self-polishing resin according to claim 1, characterized in that, The biodegradable polymer backbone is a biodegradable polylactic acid unit.

3. The biodegradable self-polishing resin according to claim 1, characterized in that, The dendritic polymer side chains are grafted onto the main chain via connecting units.

4. The biodegradable self-polishing resin according to claim 1, characterized in that, The branching level, number of branches, and number of terminal groups of the dendritic polymer side chains are adjusted through the dendritic intermediate structure.

5. A synthetic route for a biodegradable self-polishing resin containing hydrolyzed zwitterionic dendritic units, characterized in that... 。 6. A method for preparing a biodegradable self-polishing resin containing hydrolyzed zwitterionic dendritic units, characterized in that, Includes the following steps: Step 1, Preparation of dendritic polymer intermediates containing diazid groups: Using compounds containing diazid groups as the core, dendritic polymer intermediates with terminal diazid groups are prepared by successive generation amplification through thiol olefin click reaction and esterification reaction. Step 2: The dendritic polymer intermediate obtained in Step 1 is subjected to an azide-yne ​​click reaction with an alkyne-containing biodegradable polymer derivative to obtain the biodegradable self-polishing resin.

7. The preparation method according to claim 6, characterized in that, The generational amplification described in step 1 includes: G1 preparation, preparation of dendritic polymer resin containing multiple hydroxyl groups; G1.5 preparation, preparation of dendritic polymer resin containing carboxylic acid groups; G2 preparation, preparation of dendritic polymer resin containing multiple hydroxyl groups; and amplification of dendritic polymer resin to G4.5 through repeated reactions.

8. The preparation method according to claim 6, characterized in that, The generational amplification described in step 1 includes: esterifying the peripheral hydroxyl groups of the dendritic polymer with N-methyliminodiacetic acid to introduce a branched structure containing tertiary amine and carboxyl groups; then esterifying the resulting carboxyl-containing intermediate with glycerol to convert the peripheral carboxyl groups into a glycerol ester structure containing multiple terminal hydroxyl groups; and growing the dendritic structure step by step through the above-mentioned "carboxyl functionalization-multi-hydroxyl expansion" cyclic reaction.

9. The preparation method according to claim 6, characterized in that, The molecule containing the bisazide group intermediate contains two azide groups (N3) that can participate in subsequent click reactions.

10. The preparation method according to claim 6, characterized in that, Step 1 also includes: esterifying the free carboxyl groups on the periphery of the obtained dendritic polymer intermediate with methanol to cap the terminal groups.

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