A porous polymer holder for surface functionalization mediated by polydopamine and a preparation method thereof

Abstract

This invention discloses a polydopamine-mediated surface-functionalized porous polymer cage and its preparation method. The porous polymer cage comprises three functionally synergistic parts: a porous polymer substrate as the main structural component, a multifunctional interface layer chemically grafted onto the substrate surface through molecular design, and a functional lubricant stabilized by the interface layer. This invention constructs a universal adhesion platform on the pore wall surface of the porous polymer substrate. Through alternating or sequential reactions between bifunctional monomers, a chemically anchored, three-dimensionally cross-linked flexible polymer network interface is constructed in situ. This interface not only achieves strong adhesion, efficient oil storage, and long-lasting lubrication, but also, due to the responsiveness of its flexible molecular chain segments to external frictional heat, stress, and other stimuli, actively adjusts the release of lubricant and the interface friction characteristics, thereby endowing the cage with adaptive operating conditions and realizing intelligent lubrication.

Description

Technical Field

[0001] This invention belongs to the field of intelligent lubrication materials technology. More specifically, this invention relates to a polydopamine-mediated surface-functionalized porous polymer cage with adaptive lubrication capability and its preparation method. Background Technology

[0002] Space bearings are core transmission components of space inertial attitude control systems such as flywheels and gyroscopes, and their performance and reliability directly determine the lifespan and accuracy of spacecraft. These bearings operate for extended periods in harsh environments characterized by high vacuum, extreme temperature fluctuations, strong radiation, and microgravity, and cannot be replenished with lubrication in orbit. Therefore, porous material cages with self-lubricating capabilities have become a key technological solution. Porous materials utilize their interconnected pores to store lubricating oil. Under the influence of frictional heat or centrifugal force, the lubricating oil is released to the friction interface to form a lubricating film; after operation ceases, it is drawn back into the pores through capillary action, achieving lubricant recycling.

[0003] Porous polyimide materials are considered ideal for manufacturing space bearing cages due to their excellent high-temperature resistance, extremely low vacuum outgassing rate, and good stability in the space environment. Their abundant internal pores can act as a storage reservoir for lubricating oil, enabling the supply and recovery of lubricating oil through capillary action, forming a self-lubricating system. This is crucial for space bearings that cannot be lubricated in orbit and operate in high vacuum, extreme temperatures, and strong radiation environments.

[0004] However, this oil storage-supply model based on physical pores has inherent drawbacks. Under the centrifugal force generated by high-speed rotation and the continuous shear stress between friction pairs, lubricating oil stored in the pores solely through physical adsorption is easily ejected or rapidly dissipated, leading to premature lubrication failure. Simultaneously, the polyimide matrix itself has poor thermal conductivity, and frictional heat accumulation accelerates the aging of both the material and the lubricating oil, further shortening component lifespan. To improve performance, existing research often focuses on improving the material bulk, such as blending solid lubricants or thermally conductive fillers. However, this often comes at the cost of sacrificing porosity and oil storage capacity, and fails to strengthen the weak interfacial bond between the lubricating oil and the pore walls. Another approach is surface chemical modification, such as grafting substances like amino silicone oil onto polyimide chains to improve wettability and oil retention. However, these methods typically face core challenges such as uneven penetration and reaction of the modifier within the complex three-dimensional porous network, weak bonding of the formed modified layer (mostly physical adsorption or single-point chemical bonding grafting), and easy peeling under dynamic loads. More importantly, most of these improvements are single-function or only focus on "oil retention" or only attempt to introduce low-friction substances.

[0005] Many existing surface modification techniques (such as traditional impregnation and partial chemical grafting) struggle to ensure the uniform penetration and distribution of reactants or precursors within the complex three-dimensional network of porous materials, resulting in uneven and discontinuous modified layers. Furthermore, the bonding between the modified layer and the polyimide matrix is ​​often based on physical adsorption or weak chemical interaction, leading to weak adhesion and easy delamination failure under dynamic shear stresses such as centrifugation and friction. Existing technologies often focus on improving single properties, such as enhancing matrix strength, optimizing lubricant properties, or simply introducing friction-reducing substances. These "divide and conquer" strategies fail to construct a synergistic system at the material-lubricant interface that integrates strong anchoring, efficient oil locking, and long-lasting lubrication, limiting the overall improvement of the material's tribological properties. Some precision surface technologies (such as atom transfer radical polymerization) are extremely sensitive to reaction conditions, involve complex processes, and are severely limited by mass transfer within porous materials, making them difficult to implement and precisely control. This prevents the reliable and predictable acquisition of interface layers with specific structures and properties through adjusting key process parameters, hindering the directional design and performance optimization of materials. Furthermore, even if the above basic functions can be achieved, it is difficult to meet the more advanced adaptive lubrication requirements—that is, the interface can intelligently adjust lubrication behavior according to changes in operating conditions.

[0006] In recent years, the concept of adaptive lubrication materials has received widespread attention. Its core idea is to enable the lubrication interface to intelligently adjust the lubricant release rate, surface friction characteristics, or interface molecular conformation according to changes in operating conditions (such as temperature, load, shear rate, or frictional heat accumulation), thereby maintaining a stable low-friction state under varying operating conditions. However, existing adaptive lubrication strategies are mostly concentrated on coatings or integral composite materials. Achieving adaptive functionality within the complex three-dimensional channels of porous polymer cages still faces significant challenges: on the one hand, conventional adaptive response components are difficult to uniformly introduce into the tortuous pore network; on the other hand, there is a lack of a stable interface structure capable of simultaneously carrying lubricating oil and responding to external stimuli. Therefore, current technologies in the application of porous polyimide cages still face a common unresolved problem: how to construct a uniform, stable, and adaptively lubricating intelligent chemical interface on its complex and tortuous inner surface while maintaining the advantages of the material's porous structure—one that can both lock in oil for a long time and actively regulate friction behavior, and intelligently respond to changes in operating conditions, thereby achieving truly intelligent lubrication management. Summary of the Invention

[0007] One object of the present invention is to at least solve the above-mentioned problems or defects and to provide a technical solution whose advantages will be described later.

[0008] To achieve these and other advantages of the present invention, a polydopamine-mediated surface-functionalized porous polymer retainer is provided, comprising a porous polymer substrate as the structural body, a multifunctional interface layer grafted onto the surface of the porous polymer substrate, and a functional lubricant stabilized by the multifunctional interface layer.

[0009] Preferably, the multifunctional interface layer is: an adhesion platform constructed on the surface of a porous polymer substrate and a chemically anchored oleophilic polymer network constructed on the surface of the adhesion platform through alternating or sequential reactions between bifunctional monomers.

[0010] A method for preparing a polydopamine-mediated surface-functionalized porous polymer cage includes the following steps: Step 1: Immerse the porous polymer substrate in the polydopamine biomimetic layer buffer solution to form a polydopamine biomimetic layer adhesion platform on the surface of the porous polymer substrate. Step 2: Immerse the product obtained in Step 1 in a solution of bifunctional monomer A, wash after reaction, then immerse it in a solution of bifunctional monomer B, wash after reaction, and complete one round of grafting. Then repeat the operation to complete two rounds of grafting, forming a multifunctional interface layer on the surface of the porous polymer substrate. Step 3: Immerse the grafted porous polymer substrate in functional lubricating oil, and remove it after completion to obtain a polydopamine-mediated surface-functionalized porous polymer cage.

[0011] Preferably, in step one, the porous polymer substrate is one of porous polyimide, polyetheretherketone, or polyphenylene sulfide.

[0012] Preferably, in step one, the polydopamine biomimetic layer buffer solution is a dopamine hydrochloride buffer solution, wherein the concentration of dopamine hydrochloride in the dopamine hydrochloride buffer solution is 3 mg / mL, the pH value of the solution is 8.0~10.0, the buffer solution is 6-18 mM Tris-HCl buffer solution, and the immersion time is 6~72h.

[0013] Preferably, in step two, the bifunctional monomer A is one of diisocyanate, diepoxy compound, or dicarboxyl chloride, and the bifunctional monomer B is one of diamine compound, dithiol compound, or compound containing an alkene bond.

[0014] Preferably, in step two, the diisocyanate is hexamethylene diisocyanate and the diamine compound is 1,3-propanediamine.

[0015] Preferably, in step two, the solvent for the difunctional monomer A solution is anhydrous toluene, the ratio of difunctional monomer A to anhydrous toluene is 3~10mL:25mL, and the reaction temperature is 50~120℃ for 1~6h when grafting difunctional monomer A.

[0016] Preferably, in step two, the solvent for the difunctional monomer B solution is anhydrous toluene, the ratio of difunctional monomer B to anhydrous toluene is 1~6mL:25mL, and the reaction temperature is room temperature for 1~6h when grafting difunctional monomer B.

[0017] Preferably, in step three, the functional lubricating oil is one or more of synthetic hydrocarbon oils, ester oils, and silicone oils, and is impregnated at 60~150℃ under vacuum conditions for 6~72 hours.

[0018] The present invention has the following beneficial effects: 1. Stronger interfacial bonding and significantly improved dynamic durability: This invention first forms a tough biomimetic adhesion layer on the substrate surface using polydopamine (PDA). This layer uniformly and continuously covers the substrate surface and achieves a strong initial bond through various interaction forces. Subsequent alternating graft polymerization constructs a three-dimensional cross-linked polymer network on the PDA layer. This "face-to-volume" interfacial structure can efficiently disperse external stresses (such as centrifugal force and shear force) into a large number of chemical bonds, thereby fundamentally overcoming the weakness of single-point connections and qualitatively improving the peel resistance and long-term stability of the modified layer under harsh working conditions.

[0019] 2. Achieved uniform and deep modification of substrate surfaces (especially the inner surfaces of complex three-dimensional pores): This invention employs a step-by-step strategy: First, a low-viscosity dopamine aqueous solution is used, whose excellent wettability ensures uniform deposition of the PDA layer throughout the entire pore inner wall. Subsequently, alternating grafting steps use small-molecule diisocyanates and diamines, which have strong diffusion capabilities in organic solvents and can penetrate deep into the pores to fully react with the PDA active sites. This strategy of "low-viscosity precursor + small-molecule stepwise growth" ensures the uniformity and integrity of the functional interface layer in three-dimensional space modification, laying the foundation for consistent product performance.

[0020] 3. A multifunctional integrated lubrication interface is constructed, resulting in outstanding comprehensive benefits: The cross-linked polymer network constructed in this invention has a dual function: On the one hand, its molecular structure can achieve molecular-level "oil locking" and controlled release through swelling and adsorption of lubricating oil, significantly improving oil retention efficiency; on the other hand, this flexible network can directly serve as a low-shear-strength lubricating layer during friction, effectively reducing the coefficient of friction (experiments show that it can reduce it by about 38% under optimal conditions). In other words, this invention solves the three major problems of "strong adhesion," "high oil retention," and "superior lubrication" simultaneously and synergistically through a single interface structure.

[0021] 4. Compared with traditional single or single-type grafting, the present invention has significant progress, and can construct a chemically anchored, three-dimensionally cross-linked flexible polymer network interface in situ. This network is the structural basis for achieving strong adhesion, oil storage and lubrication integration.

[0022] 5. This invention provides an integrated "platform-growth-loading" technical solution, which is a complete and sequential technical solution system from PDA biomimetic platform deposition to alternating graft growth of functional networks, and then to lubricant impregnation loading. This system is a systematic method to achieve deep, uniform, and functional surface modification of porous polymers.

[0023] 6. This invention uses a controllable process and a specific chemical pathway to actively construct an interface layer with a specific structure and function at the surface of porous materials. Compared with surface coating or physical filling, the product of this invention has better performance and significant improvements in performance and stability. Attached Figure Description

[0025] Figure 1 The contact angle test diagrams of the materials prepared in Examples 1 and 2 with PAO10 lubricating oil are shown. Figure 2 The contact angle test diagrams of the materials prepared in Examples 3-5 with PAO10 lubricating oil are shown. Figure 3 Contact angle test diagrams of the materials prepared in Comparative Examples 1-6 with PAO10 lubricating oil; Figure 4 This is a comparison chart of the friction coefficient curves of Example 1, Comparative Example 1, and Comparative Example 6 under corresponding process conditions; Figure 5 This is a comparison chart of the friction coefficient curves of Example 2, Comparative Example 2, and Comparative Example 6 under corresponding process conditions; Figure 6 This is a comparison chart of the friction coefficient curves of Example 3, Comparative Example 3, and Comparative Example 6 under corresponding process conditions; Figure 7 This is a comparison chart of the friction coefficient curves of Example 4, Comparative Example 4, and Comparative Example 6 under corresponding process conditions; Figure 8 This is a comparison chart of the friction coefficient curves of Example 5, Comparative Example 5, and Comparative Example 6 under the corresponding process conditions. Detailed Implementation

[0027] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments, so that those skilled in the art can implement it based on the description.

[0028] Table 1 shows the specific process parameters for Examples 1-5 and Comparative Examples 1-6; Table 1 Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Polydopamine film immersion time (h) 6 12 18 24 72 6 12 18 24 72 0 Is it possible to alternately graft polyurea? √ √ √ √ √ coefficient of friction at steady state 0.090 0.079 0.074 0.066 0.087 0.096 0.095 0.101 0.106 0.098 0.091 Example 1: A method for preparing a polydopamine-mediated surface-functionalized porous polymer cage includes the following steps: Step 1: The cleaned porous polyimide is immersed in a solution prepared with dopamine hydrochloride and 6mM Tris-HCl buffer, wherein the concentration of dopamine hydrochloride is 3mg / mL, the pH of the solution is controlled at 8.0, and the reaction is carried out at room temperature for 6 hours to form a polydopamine (PDA) biomimetic layer adhesion platform on the surface of the porous polyimide substrate. Step 2: Dissolve 3 ml of hexamethylene diisocyanate (HDI) in 25 ml of anhydrous toluene to prepare a solution. Immerse the porous polyimide with the PDA biomimetic layer formed at the interface in the HDI solution and react at 120°C for 1 hour, then wash thoroughly. Next, dissolve 1 ml of 1,3-propanediamine in 25 ml of anhydrous toluene to prepare a solution. Immerse the HDI-grafted porous polyimide in the 1,3-propanediamine solution and react at room temperature for 6 hours, then wash thoroughly. The isocyanate and diamine react to form polyurea, completing one round of grafting. Repeat the above operation once to form a multifunctional interface layer on the surface of the porous polyimide substrate. Step 3: The grafted porous polyimide is immersed in synthetic hydrocarbon lubricating oil (PAO10) at 60°C under vacuum for 72 hours. After immersion, it is removed to obtain a polydopamine-mediated surface-functionalized porous polymer cage.

[0029] Example 2: A method for preparing a polydopamine-mediated surface-functionalized porous polymer cage includes the following steps: Step 1: The cleaned porous polyimide is immersed in a solution prepared with dopamine hydrochloride and 18mM Tris-HCl buffer, wherein the concentration of dopamine hydrochloride is 3 mg / mL, the pH of the solution is controlled at 10.0, and the reaction is carried out at room temperature for 12 hours to form a polydopamine (PDA) biomimetic layer adhesion platform on the surface of the porous polyimide substrate. Step 2: Dissolve 10 ml of hexamethylene diisocyanate (HDI) in 25 ml of anhydrous toluene to prepare a solution. Immerse the porous polyimide with the PDA biomimetic layer formed at the interface in the HDI solution and react at 50°C for 6 hours, then wash thoroughly. Next, dissolve 6 ml of 1,3-propanediamine in 25 ml of anhydrous toluene to prepare a solution. Immerse the HDI-grafted porous polyimide in the 1,3-propanediamine solution and react at room temperature for 1 hour, then wash thoroughly. The isocyanate and diamine react to form polyurea, completing one round of grafting. Repeat the above operation once to form a multifunctional interface layer on the surface of the porous polyimide substrate. Step 3: Immerse the grafted porous polyimide in synthetic hydrocarbon lubricating oil (PAO10) at 150°C under vacuum for 6 hours. After immersion, remove the material to obtain a polydopamine-mediated surface-functionalized porous polymer cage.

[0030] Example 3: A method for preparing a polydopamine-mediated surface-functionalized porous polymer cage includes the following steps: Step 1: The cleaned porous polyimide is immersed in a solution prepared with dopamine hydrochloride and 15mM Tris-HCl buffer, wherein the concentration of dopamine hydrochloride is 3 mg / mL, the pH of the solution is controlled at 9.0, and the reaction is carried out at room temperature for 18 hours to form a polydopamine (PDA) biomimetic layer adhesion platform on the surface of the porous polyimide substrate. Step 2: Dissolve 5 ml of hexamethylene diisocyanate (HDI) in 25 ml of anhydrous toluene to prepare a solution. Immerse the porous polyimide with the PDA biomimetic layer formed at the interface in the HDI solution and react at 90°C for 2 hours, then wash thoroughly. Next, dissolve 3 ml of 1,3-propanediamine in 25 ml of anhydrous toluene to prepare a solution. Immerse the HDI-grafted porous polyimide in the 1,3-propanediamine solution and react at room temperature for 3 hours, then wash thoroughly. The isocyanate and diamine react to form polyurea, completing one round of grafting. Repeat the above operation once to form a multifunctional interface layer on the surface of the porous polyimide substrate. Step 3: The grafted porous polyimide is immersed in synthetic hydrocarbon lubricating oil (PAO10) at 100°C under vacuum for 48 hours. After immersion, it is removed to obtain a polydopamine-mediated surface-functionalized porous polymer cage.

[0031] Example 4: A method for preparing a polydopamine-mediated surface-functionalized porous polymer cage includes the following steps: Step 1: The cleaned porous polyimide is immersed in a solution prepared with dopamine hydrochloride and 16mM Tris-HCl buffer, wherein the concentration of dopamine hydrochloride is 3 mg / mL, the pH of the solution is controlled at 9.5, and the reaction is carried out at room temperature for 24 hours to form a polydopamine (PDA) biomimetic layer adhesion platform on the surface of the porous polyimide substrate. Step 2: Dissolve 4 ml of hexamethylene diisocyanate (HDI) in 25 ml of anhydrous toluene to prepare a solution. Immerse the porous polyimide with the PDA biomimetic layer formed at the interface in the HDI solution and react at 60°C for 5 hours, then wash thoroughly. Next, dissolve 4 ml of 1,3-propanediamine in 25 ml of anhydrous toluene to prepare a solution. Immerse the HDI-grafted porous polyimide in the 1,3-propanediamine solution and react at room temperature for 5 hours, then wash thoroughly. The isocyanate and diamine react to form polyurea, completing one round of grafting. Then repeat the above operation for one round to form a multifunctional interface layer on the surface of the porous polyimide substrate. Step 3: The grafted porous polyimide is immersed in synthetic hydrocarbon lubricating oil (PAO10) at 80°C under vacuum for 12 hours. After immersion, it is removed to obtain a polydopamine-mediated surface-functionalized porous polymer cage.

[0032] Example 5: A method for preparing a polydopamine-mediated surface-functionalized porous polymer cage includes the following steps: Step 1: The cleaned porous polyimide is immersed in a solution prepared with dopamine hydrochloride and 12mM Tris-HCl buffer, wherein the concentration of dopamine hydrochloride is 3 mg / mL, the pH of the solution is controlled at 8.0, and the reaction is carried out at room temperature for 72 hours to form a polydopamine (PDA) biomimetic layer adhesion platform on the surface of the porous polyimide substrate. Step 2: Dissolve 5 ml of hexamethylene diisocyanate (HDI) in 25 ml of anhydrous toluene to prepare a solution. Immerse the porous polyimide with the PDA biomimetic layer formed at the interface in the HDI solution and react at 70°C for 4 hours, then wash thoroughly. Next, dissolve 5 ml of 1,3-propanediamine in 25 ml of anhydrous toluene to prepare a solution. Immerse the HDI-grafted porous polyimide in the 1,3-propanediamine solution and react at room temperature for 3 hours, then wash thoroughly. The isocyanate and diamine react to form polyurea, completing one round of grafting. Repeat the above operation once to form a multifunctional interface layer on the surface of the porous polyimide substrate. Step 3: The grafted porous polyimide is immersed in synthetic hydrocarbon lubricating oil (PAO10) at 90°C under vacuum for 36 hours. After immersion, it is removed to obtain a polydopamine-mediated surface-functionalized porous polymer cage.

[0033] Comparative Example 1: A method for preparing a porous polymer cage includes the following steps: Step 1: The cleaned porous polyimide is immersed in a solution prepared with dopamine hydrochloride and 6 mM Tris-HCl buffer, wherein the concentration of dopamine hydrochloride is 3 mg / mL, the pH of the solution is controlled at 8.0, and the reaction is carried out at room temperature for 6 hours to form a polydopamine (PDA) biomimetic layer adhesion platform on the surface of the porous polyimide substrate. Step 2: The porous polyimide with the PDA biomimetic layer formed on the surface is immersed in synthetic hydrocarbon lubricating oil (PAO10) at 60°C under vacuum for 72 hours. After immersion, it is removed to obtain a porous polymer cage.

[0034] Comparative Example 2: A method for preparing a porous polymer cage includes the following steps: Step 1: The cleaned porous polyimide is immersed in a solution prepared with dopamine hydrochloride and 18 mM Tris-HCl buffer, wherein the concentration of dopamine hydrochloride is 3 mg / mL, the pH of the solution is controlled at 10.0, and the reaction is carried out at room temperature for 12 hours to form a polydopamine (PDA) biomimetic layer adhesion platform on the surface of the porous polyimide substrate. Step 2: The porous polyimide with a PDA biomimetic layer formed on the surface is immersed in synthetic hydrocarbon lubricating oil (PAO10) at 150°C under vacuum for 6 hours. After immersion, it is removed to obtain a porous polymer cage.

[0035] Comparative Example 3: A method for preparing a porous polymer cage includes the following steps: Step 1: The cleaned porous polyimide is immersed in a solution prepared with dopamine hydrochloride and 15 mM Tris-HCl buffer, wherein the concentration of dopamine hydrochloride is 3 mg / mL, the pH of the solution is controlled at 9.0, and the reaction is carried out at room temperature for 18 hours to form a polydopamine (PDA) biomimetic layer adhesion platform on the surface of the porous polyimide substrate. Step 2: The porous polyimide with a PDA biomimetic layer formed on the surface is immersed in synthetic hydrocarbon lubricating oil (PAO10) at 100°C under vacuum for 48 hours. After immersion, it is removed to obtain a porous polymer cage.

[0036] Comparative Example 4: A method for preparing a porous polymer cage includes the following steps: Step 1: The cleaned porous polyimide is immersed in a solution prepared with dopamine hydrochloride and 16 mM Tris-HCl buffer, wherein the concentration of dopamine hydrochloride is 3 mg / mL, the pH of the solution is controlled at 9.5, and the reaction is carried out at room temperature for 24 hours to form a polydopamine (PDA) biomimetic layer adhesion platform on the surface of the porous polyimide substrate. Step 2: The porous polyimide with a PDA biomimetic layer formed on the surface is immersed in synthetic hydrocarbon lubricating oil (PAO10) at 80°C under vacuum for 12 hours. After immersion, it is removed to obtain a porous polymer cage.

[0037] Comparative Example 5: A method for preparing a porous polymer cage includes the following steps: Step 1: The cleaned porous polyimide is immersed in a solution prepared with dopamine hydrochloride and 12mM Tris-HCl buffer, wherein the concentration of dopamine hydrochloride is 3 mg / mL, the pH of the solution is controlled at 8.0, and the reaction is carried out at room temperature for 72 hours to form a polydopamine (PDA) biomimetic layer adhesion platform on the surface of the porous polyimide substrate. Step 2: The porous polyimide with a PDA biomimetic layer formed on the surface is immersed in synthetic hydrocarbon lubricating oil (PAO10) at 90°C under vacuum for 36 hours. After immersion, it is removed to obtain a porous polymer cage.

[0038] Comparative Example 6: This comparative example uses only porous polyimide without any treatment, serving as a blank substrate reference.

[0039] Contact angle and friction properties were tested on the materials obtained in Examples 1-5 and Comparative Examples 1-6. Figures 4-8 As shown in Table 1, Examples 1-5 and Comparative Examples 1-5 form a one-to-one control relationship. Except for whether or not the alternating polyurea grafting step was performed, all other process conditions were kept consistent across groups. Test results show that, under the same PDA impregnation conditions, the friction coefficients of the examples treated with alternating polyurea grafting were significantly lower than those of the corresponding comparative examples. For example, the stable friction coefficients of Examples 1-5 were 0.090, 0.079, 0.074, 0.066, and 0.087, respectively, while those of Comparative Examples 1-5 were 0.096, 0.095, 0.101, 0.106, and 0.098, respectively. This indicates that the polyurea interface layer formed by alternating grafting can significantly reduce the material's friction coefficient and improve lubrication performance. This is because the polyurea network can form a stable, flexible cross-linked interface on the surface of the PDA biomimetic layer, which not only enhances the retention of lubricating oil on the pore wall surface but also forms a low-shear interface layer during friction, thereby effectively reducing frictional resistance.

[0040] Furthermore, in Examples 1-5, when the PDA immersion time was less than 24 hours, the deposited PDA layer gradually became more complete and dense as the immersion time increased, providing more active sites for subsequent polyurea grafting, thus gradually reducing the material's friction coefficient. When the immersion time reached 24 hours (Example 4), the PDA layer was the most complete and uniform, and the polyurea interface layer formed by alternating grafting had the best effect, with the material's friction coefficient dropping to the lowest level of 0.066, achieving optimal lubrication performance. When the immersion time was further extended to 72 hours, the excessive thickness of the PDA layer might affect the uniformity of the subsequent interface structure and the transport of lubricating oil, causing the friction coefficient to rise back to 0.087. Therefore, the material's lubrication performance showed a trend of first increasing and then decreasing with the increase of PDA immersion time, with 24 hours being the optimal immersion time.

[0041] In addition, from Figures 1-3 The contact angle test results also show that the material after alternating grafting of polyurea exhibits better wettability and oleophilicity to lubricating oil, further proving that the constructed polyurea functional interface layer successfully changed the surface properties of the porous polyimide substrate and is beneficial to the stable maintenance and continuous lubrication of the lubricating oil.

[0042] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A porous polymer holder for polydopamine-mediated surface functionalization, characterized in that, It includes a porous polymer substrate as the main structure, a multifunctional interface layer grafted onto the surface of the porous polymer substrate, and a functional lubricant that is stabilized by the multifunctional interface layer.

2. The porous polymeric holder of claim 1, wherein, The multifunctional interface layer consists of an adhesion platform constructed on the surface of a porous polymer substrate and a chemically anchored oleophilic polymer network constructed on the surface of the adhesion platform through alternating or sequential reactions between bifunctional monomers.

3. A method for preparing a porous polymer holder functionalized by polydopamine-mediated surface, characterized in that, Includes the following steps: Step 1: Immerse the porous polymer substrate in the polydopamine biomimetic layer buffer solution to form a polydopamine biomimetic layer adhesion platform on the surface of the porous polymer substrate. Step 2: Immerse the product obtained in Step 1 in a solution of bifunctional monomer A, wash after reaction, then immerse it in a solution of bifunctional monomer B, wash after reaction, and complete one round of grafting. Then repeat the operation to complete two rounds of grafting, forming a multifunctional interface layer on the surface of the porous polymer substrate. Step 3: Immerse the grafted porous polymer substrate in functional lubricating oil, and remove it after completion to obtain a polydopamine-mediated surface-functionalized porous polymer cage.

4. The method of claim 3, wherein the porous polymer holder is functionalized with polydopamine. In step one, the porous polymer substrate is one of porous polyimide, polyetheretherketone, or polyphenylene sulfide.

5. The method of claim 3, wherein the porous polymer holder is functionalized with polydopamine. In step one, the polydopamine biomimetic layer buffer solution is a dopamine hydrochloride buffer solution. The concentration of dopamine hydrochloride in the dopamine hydrochloride buffer solution is 3 mg / mL, the pH value of the solution is 8.0~10.0, the buffer solution is 6-18 mM Tris-HCl buffer, and the immersion time is 6~72h.

6. The method of claim 3, wherein the porous polymer holder is functionalized with polydopamine. In step two, the bifunctional monomer A is one of diisocyanate, diepoxy compound, or dicarboxyl chloride, and the bifunctional monomer B is one of diamine compound, dithiol compound, or compound containing alkene bond.

7. The method of claim 6, wherein the porous polymer holder is functionalized with polydopamine. In step two, the diisocyanate is hexamethylene diisocyanate or toluene diisocyanate, and the diamine compound is 1,3-propanediamine.

8. The method for preparing the polydopamine-mediated surface-functionalized porous polymer cage as described in claim 3, characterized in that, In step two, the solvent for the difunctional monomer A solution is anhydrous toluene, and the ratio of difunctional monomer A to anhydrous toluene is 3~10mL:25mL. When grafting difunctional monomer A, the reaction temperature is 50~120℃, and the reaction time is 1~6h.

9. The method for preparing the polydopamine-mediated surface-functionalized porous polymer cage as described in claim 3, characterized in that, In step two, the solvent for the bifunctional monomer B solution is anhydrous toluene, and the ratio of bifunctional monomer B to anhydrous toluene is 1~6mL:25mL. When grafting bifunctional monomer B, the reaction temperature is room temperature, and the reaction time is 1~6h.

10. The method for preparing the polydopamine-mediated surface-functionalized porous polymer cage as described in claim 3, characterized in that, In step three, the functional lubricating oil is one or more of synthetic hydrocarbon oils, ester oils, and silicone oils, and is impregnated at 60~150℃ under vacuum conditions for 6~72 hours.

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