Templated curing agent for constructing surface energy gradient, preparation method of templated curing agent, super-hydrophobic coating and preparation method of super-hydrophobic coating

Abstract

The invention discloses a template curing agent for constructing a surface energy gradient, a preparation method of the template curing agent, a super-hydrophobic coating and a preparation method of the super-hydrophobic coating. According to the template curing agent, a cross-linking function and an interface guiding function are decoupled and coordinated through an elaborate molecular structure design, so that the maximization of the super-hydrophobic performance of the surface of a coating is realized with the minimum using amount of low-surface-energy substances. The template curing agent also has a specific topological structure and a chain segment, and can guide low-surface-energy substances to be directionally enriched to the surface in the coating curing process, so that the super-hydrophobic coating is efficiently constructed. The super-hydrophobic coating body network for constructing the surface energy gradient prepared by the invention is pure and compact, and the mechanical strength and adhesive force are obviously superior to those of a traditional blending system; and the gradient functional layer formed on the surface is uniform and stable and has excellent comprehensive performance.

Description

Technical Field

[0001] This invention belongs to the field of polymer chemistry and functional coating materials technology, specifically involving... A templated curing agent for constructing surface energy gradients and its preparation method, and a superhydrophobic coating and its preparation method. Background Technology

[0002] The construction of superhydrophobic surfaces typically relies on the combination of micro / nano rough structures and low surface energy materials. However, in existing technologies, low surface energy materials (such as expensive fluorinated / silicon compounds) are usually introduced into the coating through blending or copolymerization, resulting in their extensive distribution throughout the entire coating bulk, with only a very small portion on the surface being effective, leading to extremely low material utilization. Furthermore, the uniformly distributed hydrophobic components may degrade the overall mechanical properties and adhesion of the coating.

[0003] While current research attempts to prepare multifunctional curing agents that combine reactivity and hydrophobicity, their molecular designs often prioritize functional integration, leading to complex synthesis and mutual constraints among the various functions, making it difficult to maximize and directionally enrich the hydrophobic components at the interface. Therefore, a novel molecular design strategy is urgently needed to address the challenge of distributing and utilizing low surface energy materials in coatings. Summary of the Invention

[0004] To overcome the shortcomings and drawbacks of existing technologies, the primary objective of this invention is to provide a templated curing agent for constructing surface energy gradients. This templated curing agent, through careful molecular structure design, decouples and synergizes crosslinking and interface guiding functions, thereby maximizing the superhydrophobic properties of the coating surface with minimal amounts of low surface energy materials. Furthermore, this templated curing agent possesses a specific topology and chain segments, enabling it to guide the directional enrichment of low surface energy materials to the surface during coating curing, thus efficiently constructing superhydrophobic coatings.

[0005] A second objective of this invention is to provide a method for preparing a templated curing agent for constructing a surface energy gradient.

[0006] A third objective of this invention is to provide a method for preparing a superhydrophobic coating for constructing a surface energy gradient.

[0007] A fourth objective of this invention is to provide a superhydrophobic coating for constructing a surface energy gradient.

[0008] The primary objective of this invention can be achieved through the following technical solution: A templated curing agent for constructing surface energy gradients, comprising a star-shaped or hyperbranched amphiphilic polymer, and including: A multifunctional reactive core containing at least three first functional groups selected from epoxy, isocyanate, silanol, or alkoxysilane groups; Multiple arm units extending from the core, each arm unit having a template unit connected to its end via a dynamic connection key; The arm unit comprises polyethylene oxide segments, polypropylene oxide segments, or polyester segments; The template unit contains a binding site capable of engaging in specific intermolecular interactions with fluorine- and / or silicon-containing compounds.

[0009] Preferably, the dynamic linking bond is a borate ester bond, an imine bond, or a disulfide bond.

[0010] Preferably, the binding site is selected from the macrocyclic main molecule structure, the urea / thiourea group modified by the long-chain alkyl (C8-C22) group, or the perfluoro aromatic group; the macrocyclic main molecule structure is a β-cyclodextrin derivative or a calix[4] aromatic derivative modified by monosubstitution.

[0011] The second objective of this invention can be achieved through the following technical solution: A method for preparing a templated curing agent for constructing a surface energy gradient includes the following steps: (1) Using pentaerythritol as an initiator, under the action of catalyst I, it is polymerized with an epoxy compound or a lactone compound to synthesize a hydroxyl-terminated hyperbranched polyether; the mass ratio of pentaerythritol, catalyst I and epoxy compound or lactone compound is 5:0.1-1:80-100. (2) The hydroxyl-terminated hyperbranched polyether prepared in step (1) is reacted with 2-bromoisobutyryl bromide, and then nucleophilically substituted with sodium azide to obtain a hyperbranched core with azido groups; the mass-volume ratio of the hydroxyl-terminated hyperbranched polyether, 2-bromoisobutyryl bromide and sodium azide is 5-50g: 2-10ml: 1-5g. (3) Dissolve the hyperbranched core with terminal azido groups prepared in step (2) and mono-6-propynyl-β-cyclodextrin in an organic solvent, add catalyst II, heat and react to obtain a reaction solution; the mass-volume ratio of the hyperbranched core with terminal azido groups, mono-6-propynyl-β-cyclodextrin, organic solvent and catalyst II is 5-10g: 5-15g: 100-200ml: 0.1-1g; (4) The reaction solution in step (3) is dialyzed with deionized water and freeze-dried to prepare a template curing agent for constructing surface energy gradient.

[0012] Preferably, the catalyst I in step (1) is a bimetallic cyanide or stannous octoate; the epoxy compound refers to propylene oxide or ethylene oxide; and the lactone compound refers to ε-caprolactone.

[0013] Preferably, the catalyst II in step (3) is sodium ascorbate or a mixture of ascorbic acid and copper salt; the copper salt is at least one of copper sulfate, copper acetate, copper chloride or their crystalline hydrates; the mass ratio of sodium ascorbate or ascorbic acid to copper salt is 5-7:3-5.

[0014] Preferably, the organic solvent is at least one selected from N,N-dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone.

[0015] Preferably, the heating reaction temperature in step (3) is 25-80°C and the heating reaction time is 20-30 hours.

[0016] Preferably, the dialysis time in step (4) is 48-96 hours, and the molecular weight cutoff for dialysis is 1000.

[0017] The third objective of this invention can be achieved through the following technical solution: A method for preparing a superhydrophobic coating for constructing a surface energy gradient includes the following steps: preparing a film-forming resin, a low surface energy substance, a template curing agent for constructing a surface energy gradient, and a solvent in a mass ratio of 5-30:1:1-20:49-93, mixing them evenly, spin-coating the mixture onto a glass substrate, and curing it twice to obtain a superhydrophobic coating for constructing a surface energy gradient; wherein the film-forming resin is an epoxy resin, polyurethane resin, acrylate resin, silicone resin, or a combination thereof; the low surface energy substance is a fluorine-containing and / or silicon-containing compound containing at least one molecular weight less than 10,000; and the solvent is at least one selected from ester solvents, ketone solvents, ether ester solvents, and aromatic hydrocarbon solvents.

[0018] Preferably, the curing method includes one of thermal curing, photocuring, or moisture curing. During the curing process, based on the difference between the first and second bonding forces, the low surface energy material undergoes directional migration towards the coating-air interface and accumulates at the interface after curing, forming a low surface energy functional layer; the thickness of the low surface energy functional layer is 2 nm to 2000 nm; the directional migration and accumulation are completed autonomously without the application of an additional external physical field.

[0019] like Figure 1 This is a schematic diagram illustrating the mechanism by which the templated curing agent used to construct a surface energy gradient guides the formation of a surface energy gradient during the curing process of a superhydrophobic coating, as described in this invention. Figure 1 As can be seen, the superhydrophobic coating film formation process for constructing a surface energy gradient described in this invention includes the following three stages, starting from spin-coating each component onto a glass substrate: Initial wet film state: After coating, a wet film is formed on the surface of the substrate. The wet film is in an initial uniformly mixed state, wherein the curing agent and low surface energy substances are randomly distributed to form a uniformly mixed layer. Mid-term migration process during curing: Under curing conditions (such as heating and light), the system undergoes the following key changes, driving component redistribution; the multifunctional reactive core of the curing agent reacts chemically with the substrate and resin to form anchor points and initially construct a cross-linking network; under the action of driving forces (mainly including: (i) energy provided by heat or light curing; (ii) concentration changes and interfacial tension changes caused by solvent evaporation; (iii) the fundamental trend of minimizing the total interfacial energy of the system), the flexible arm units of the curing agent extend, and the template units at their ends capture low surface energy substances through specific intermolecular interactions and guide them to migrate spontaneously and directionally to the coating-air interface; The final cured coating structure forms a stable surface energy gradient coating, i.e., a superhydrophobic coating used to construct the surface energy gradient: The bottom layer mainly consists of a dense three-dimensional network formed by the curing agent core and resin, firmly attached to the substrate through chemical bonding, providing excellent mechanical strength, adhesion, and durability; this region has a high surface energy. The intermediate transition layer shows a continuous gradient change in the concentration of low surface energy substances from the bottom layer to the top layer. The top layer is highly enriched with low surface energy substances, forming an extremely thin (typically 5 nm to 500 nm) but dense functional layer. This coating surface has low surface energy, a water contact angle ≥150°, and a roll-off angle ≤10°.

[0020] The fourth objective of this invention can be achieved through the following technical solution: A superhydrophobic coating for constructing a surface energy gradient is prepared by the above-described preparation method.

[0021] Preferably, the superhydrophobic coating for constructing a surface energy gradient comprises: (a) Film-forming resin; (b) A low surface energy material comprising at least one fluorine- and / or silicon-containing compound with a molecular weight of less than 10,000; (c) Templated curing agents used to construct surface energy gradients; Wherein, the first bonding force between the low surface energy material and the template unit in the template curing agent is stronger than the second bonding force between the low surface energy material and the film-forming resin; Based on the total solid weight of the superhydrophobic coating used to construct the surface energy gradient, the content of the low surface energy material is 0.1%-15%, and the content of the template curing agent used to construct the surface energy gradient is 2%-40%.

[0022] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) High efficiency guidance and enrichment: The unique arm unit design (such as polyether / polyester segments) of the templated curing agent used to construct surface energy gradients in this invention provides the necessary flexibility and compatibility, enabling the template unit to move flexibly during the curing process, efficiently capture and guide low surface energy substances to migrate to the surface, and has high efficiency guidance and enrichment performance. (2) Cost reduction: The templated curing agent used to construct the surface energy gradient described in this invention can increase the utilization rate of low surface energy materials by several times through interfacial directional enrichment. Under the premise of achieving the same hydrophobic performance, its dosage can be reduced by more than 60%, effectively reducing costs. (3) Excellent overall performance: The superhydrophobic coating bulk network prepared by the present invention for constructing surface energy gradient is pure and dense, and its mechanical strength and adhesion are significantly better than those of traditional blending systems; the gradient functional layer formed on the surface is uniform and stable, and has excellent overall performance. Attached Figure Description

[0023] Figure 1 This is a schematic diagram illustrating the mechanism by which the templated curing agent used to construct the surface energy gradient guides the formation of the surface energy gradient during the curing process of preparing a superhydrophobic coating, as described in this invention. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto. All materials used in the embodiments of the present invention can be purchased commercially.

[0025] Example 1 The synthesis of the templated curing agent for constructing a surface energy gradient described in this embodiment includes the following steps: Using 5g pentaerythritol as a starting agent, ring-opening polymerization was carried out with 100g propylene oxide in the presence of 0.25g bimetallic cyanide catalyst to synthesize hydroxyl-terminated hyperbranched polyether. Subsequently, the hydroxyl groups were reacted with 2.2ml of 2-bromoisobutyryl bromide, followed by nucleophilic substitution with 2.5g of sodium azide to obtain a hyperbranched core with azido groups. 8g of the hyperbranched core with azido groups and 14g of mono-6-propynyl-β-cyclodextrin were dissolved in 200ml of N,N-dimethylformamide, and 0.6g of sodium ascorbate and 0.4g of copper sulfate pentahydrate were added as catalysts. The reaction was carried out at 50°C for 24 hours. After the reaction was completed, the reaction solution was dialyzed with deionized water (molecular weight cutoff 1000) for 3 days, and then freeze-dried to obtain the target product, a templated curing agent with polypropylene oxide as the arm unit, which is the templated curing agent for constructing surface energy gradients described in this invention.

[0026] Example 2 The synthesis of the templated curing agent for constructing a surface energy gradient described in this embodiment includes the following steps: The steps are the same as in Example 1, but 76g of ethylene oxide is used instead of propylene oxide for ring-opening polymerization to synthesize hydroxyl-terminated hyperbranched polyethylene oxide. The subsequent steps are the same, and the product polyethylene oxide is used as a template curing agent for arm units, that is, the template curing agent for constructing surface energy gradients described in this invention.

[0027] Example 3 The synthesis of the templated curing agent for constructing a surface energy gradient described in this embodiment includes the following steps: The steps are the same as in Example 1, but 5g pentaerythritol is used as the starting agent and 180g ε-caprolactone is subjected to ring-opening polymerization under the catalysis of 0.38g stannous octoate to synthesize hydroxyl-terminated hyperbranched polycaprolactone. The subsequent steps are the same to obtain a template curing agent with polycaprolactone polyester as the arm unit, which is the template curing agent for constructing surface energy gradients described in this invention.

[0028] Example 4 The method for preparing a superhydrophobic coating for constructing a surface energy gradient as described in this embodiment includes the following steps: Formulation: 10g bisphenol A type epoxy resin (E44); 1g fluorinated acrylate oligomer; 21g template curing agent prepared in Example 1; 50ml solvent (butyl acetate); Process: Mix the above components evenly, spin-coat onto a glass substrate, pre-cur at 80°C for 1 hour, then cure at 150°C for 2 hours to obtain a superhydrophobic coating for constructing a surface energy gradient. Example 5 The method for preparing a superhydrophobic coating for constructing a surface energy gradient as described in this embodiment includes the following steps: Formulation: 10g of bisphenol A type epoxy resin (E44); 1g of fluorinated acrylate oligomer; 20g of template curing agent prepared in Example 2; 50ml of solvent (butyl acetate); Process: Mix the above components evenly, spin coat them onto a glass substrate, pre-cur at 80°C for 1 hour, and then cure at 150°C for 2 hours to prepare a superhydrophobic coating for constructing a surface energy gradient.

[0029] Example 6 This embodiment describes a method for preparing a superhydrophobic coating with a surface energy gradient, comprising the following steps: Formulation: 10g of bisphenol A type epoxy resin (E44); 1g of fluorinated acrylate oligomer; 20g of template curing agent prepared in Example 2; 50ml of solvent (butyl acetate); Process: Mix the above components evenly, spin coat them onto a glass substrate, pre-cur at 80°C for 1 hour, and then cure at 150°C for 2 hours to prepare a superhydrophobic coating for constructing a surface energy gradient.

[0030] Comparative Example 1: In this comparative example, an equivalent amount of ordinary polyamide curing agent was used to replace the template curing agent, and the amount of fluorinated acrylate oligomer was increased to 3g. Other steps were the same as in Example 4.

[0031] Comparative Example 2: This comparative example uses a similar curing agent with an arm unit derived from a dendritic polyamine core rigid alkane chain obtained by extending ethylenediamine. Other steps are the same as in Example 4.

[0032] Performance testing experiments were conducted on Examples 4 to 6 and Comparative Examples 1 to 2. The performance testing method is as follows: Surface wettability test Using a contact angle meter, under standard conditions of room temperature (23±2℃) and relative humidity (50±5)%, a 5μL droplet of ultrapure water was placed on the coating surface, and the static water contact angle and roll-off angle were measured by the pendant drop method. Each sample was measured at at least three different locations, and the average value was taken as the final result.

[0033] Characterization of low surface energy material distribution efficiency The utilization efficiency of low surface energy materials is quantitatively assessed by calculating their surface enrichment efficiency. The specific method is as follows: Surface elemental analysis: X-ray photoelectron spectroscopy (XPS) was used to perform a full-spectrum scan of the coating surface to obtain the atomic percentage of fluorine atoms (F) on the surface.

[0034] Overall elemental analysis: The cured coating is completely scraped off the substrate, and the mass percentage of fluorine in the coating is determined using an elemental analyzer and converted into an atomic percentage.

[0035] Enrichment efficiency calculation: Calculated using the following formula: Surface enrichment efficiency (%) = (Percentage of surface fluorine atoms measured by XPS) / (Percentage of total fluorine atoms measured by elemental analysis) × 100% Coating mechanical adhesion test The adhesion test was conducted using a cross-cut adhesion tester. A 6×6 grid was cut into the coating surface using a multi-blade cutter with a blade spacing of 1 mm, cutting down to the substrate. Then, 3M pressure-sensitive tape was firmly applied to the gridded areas and quickly peeled off. The adhesion grade (0-5, with grade 0 being the best) was determined based on the proportion of coating area that had peeled off.

[0036] Coating surface hardness test A pencil hardness tester was used. A set of Zhonghua brand drawing pencils, ranging in hardness from 9H to 6B, were used to scratch the coated surface at a 45° angle with a load of 750g. The hardness rating of the hardest pencil that did not cause permanent scratches on the coated surface was taken as the pencil hardness of the coating.

[0037] Table 1 is a comparison table of the performance of each sample.

[0038] Table 1

[0039] Examples 4 through 6 utilized the templated curing agents described in Examples 1 through 3 for constructing surface energy gradients. As shown in Table 1, the polyether / polyester flexible arm units (Examples 1 through 3) significantly improved the utilization rate of low surface energy materials (>75%) and achieved excellent hydrophobicity and adhesion. The rigid arm unit in Comparative Example 2 resulted in low migration efficiency and overall performance degradation. This demonstrates the significant contribution and non-obviousness of the technical feature that the arm unit contains polyethylene oxide segments, polypropylene oxide segments, or polyester segments.

[0040] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A templated curing agent for constructing surface energy gradients, characterized in that, It is an amphiphilic polymer with a star-shaped or hyperbranched structure, comprising: A multifunctional reactive core containing at least three first functional groups selected from epoxy, isocyanate, silanol, or alkoxysilane groups; Multiple arm units extending from the core, each arm unit having a template unit connected to its end via a dynamic connection key; The arm unit comprises polyethylene oxide segments, polypropylene oxide segments, or polyester segments; The template unit contains a binding site capable of engaging in specific intermolecular interactions with fluorine- and / or silicon-containing compounds.

2. The templated curing agent for constructing surface energy gradients according to claim 1, characterized in that, The dynamic linking bond is a borate ester bond, an imine bond, or a disulfide bond.

3. The templated curing agent for constructing surface energy gradients according to claim 1, characterized in that, The binding site is selected from macrocyclic main molecular structure, C8-C22 long-chain alkyl modified urea / thiourea group, or perfluorinated aromatic group; the macrocyclic main molecular structure is a monosubstituted β-cyclodextrin derivative or calix[4] aromatic derivative.

4. A method for preparing a templated curing agent for constructing a surface energy gradient, characterized in that, Includes the following steps, (1) Using pentaerythritol as an initiator, under the action of catalyst I, it is polymerized with an epoxy compound or a lactone compound to synthesize a hydroxyl-terminated hyperbranched polyether; the mass ratio of pentaerythritol, catalyst I and epoxy compound or lactone compound is 5:0.1-1:80-100. (2) The hydroxyl-terminated hyperbranched polyether prepared in step (1) is reacted with 2-bromoisobutyryl bromide, and then nucleophilically substituted with sodium azide to obtain a hyperbranched core with azido groups; the mass-volume ratio of the hydroxyl-terminated hyperbranched polyether, 2-bromoisobutyryl bromide and sodium azide is 5-50g: 2-10ml: 1-5g. (3) Dissolve the hyperbranched core with terminal azido groups prepared in step (2) and mono-6-propynyl-β-cyclodextrin in an organic solvent, add catalyst II, heat and react to obtain a reaction solution; the mass-volume ratio of the hyperbranched core with terminal azido groups, mono-6-propynyl-β-cyclodextrin, organic solvent and catalyst II is 5-10g: 5-15g: 100-200ml: 0.1-1g; (4) The reaction solution in step (3) is dialyzed with deionized water and freeze-dried to prepare a template curing agent for constructing surface energy gradient.

5. The method for preparing a templated curing agent for constructing a surface energy gradient according to claim 4, characterized in that, The catalyst I mentioned in step (1) is a bimetallic cyanide or stannous octoate; the epoxy compound refers to propylene oxide or ethylene oxide; and the lactone compound refers to ε-caprolactone.

6. The method for preparing a templated curing agent for constructing a surface energy gradient according to claim 4, characterized in that, The catalyst II mentioned in step (3) is sodium ascorbate or a mixture of ascorbic acid and copper salt; the copper salt is at least one of copper sulfate, copper acetate, copper chloride or their crystalline hydrates; the mass ratio of sodium ascorbate or ascorbic acid to copper salt is 5-7:3-5.

7. A method for preparing a superhydrophobic coating for constructing a surface energy gradient, characterized in that, The method includes the following steps: preparing a film-forming resin, a low surface energy substance, a template curing agent for constructing a surface energy gradient, and a solvent in a mass ratio of 5-30:1:1-20:49-93, mixing them evenly, spin-coating the mixture onto a glass substrate, and curing it twice to obtain a superhydrophobic coating for constructing a surface energy gradient; wherein the film-forming resin is an epoxy resin, polyurethane resin, acrylate resin, silicone resin, or a combination thereof; the low surface energy substance is a fluorinated and / or silicon-containing compound containing at least one molecular weight less than 10,000; and the solvent is at least one selected from ester solvents, ketone solvents, ether ester solvents, and aromatic hydrocarbon solvents.

8. The method for preparing a superhydrophobic coating for constructing a surface energy gradient according to claim 7, characterized in that, The curing method includes one of heat curing, light curing, or moisture curing.

9. A superhydrophobic coating for constructing a surface energy gradient, characterized in that, It is prepared according to the preparation method described in claim 7 or 8.

10. The superhydrophobic coating for constructing a surface energy gradient according to claim 9, characterized in that, Include: (a) Film-forming resin; (b) A low surface energy material comprising at least one fluorine- and / or silicon-containing compound with a molecular weight of less than 10,000; (c) Templated curing agents used to construct surface energy gradients; Wherein, the first bonding force between the low surface energy material and the template unit in the template curing agent is stronger than the second bonding force between the low surface energy material and the film-forming resin; Based on the total solid weight of the superhydrophobic coating used to construct the surface energy gradient, the content of the low surface energy material is 0.1%-15%, and the content of the template curing agent used to construct the surface energy gradient is 2%-40%.

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