A new method for surface and interface functional modification of electro-fogging in-situ radical polymerization

Abstract

The present application relates to a kind of electric atomization in-situ radical polymerization surface interface function modification new method, the method utilizes the hydroxyl radical (·OH) induced by high-voltage electric atomization, initiates the in-situ radical polymerization of polymer precursor on material surface interface, realizes the functional modification of one-step method in the condition of no crosslinking agent, no additional initiator.The method includes: polymer monomer or functional material is dissolved to form electric atomization precursor liquid, stable electric atomization is carried out by setting voltage, liquid flow rate, electrode spacing and other parameters, active mist drop is deposited on the surface of material and triggers polymerization, forms dense stable function modification layer.The method has the advantages of green environmental protection, simple operation, modification layer strong adhesion, performance lasting etc., is suitable for the antibacterial, antiviral, mildewproof, hydrophilic, anti-ultraviolet, anti-fouling, flame-retardant, antioxidant, electrically conductive etc. functional treatment of textile, membrane material, plastic, composite material, glass, metal, ceramic, biomaterial and other fields.

Description

Technical Field

[0001] This invention belongs to the field of material surface and interface modification technology, and relates to a novel one-step method for functional modification of material surface and interface. Background Technology

[0002] The surface chemical composition and topology of polymers are crucial factors determining their surface properties. Reassembling or modifying polymer surfaces through effective methods to create new compositions or topologies is key to achieving transformative advancements in material surface properties.

[0003] Surface-initiated polymerization, as a novel polymerization reaction, is widely used in the surface modification and alteration of materials. This method first forms a self-assembled monolayer of initiator on the substrate surface. Under the action of a catalyst, the monomer polymerizes only on the substrate surface, yielding polymer chains with a certain grafting density and brush-like structure. Common methods include: surface-initiated atom transfer radical polymerization, surface-initiated reversible addition-fragmentation chain transfer polymerization, surface-initiated nitrile radical-controlled polymerization, and surface-initiated photopolymerization. Before the surface-initiated polymerization reaction, the initiator needs to be anchored to the substrate surface. There are two main methods for initiator anchoring: 1) directly anchoring the initiator to the substrate surface; 2) first anchoring the active groups to the substrate, and then using a chemical reaction to modify the initiator onto the surface.

[0004] However, this method of polymerization by generating free radicals through anchoring initiators on the material surface is limited in the following aspects during actual preparation:

[0005] (1) Traditional surface-initiated polymerization methods often require a complex multi-step wet chemical synthesis process for the initiator layer, which is cumbersome and time-consuming.

[0006] (2) The mechanical wear resistance of the initiator layer and its chemical stability in a humid environment have long been neglected. The prepared functional layer will be peeled off under a certain shear force. Once it is contaminated or otherwise mechanically damaged, the initiator must be re-anchored to the material surface for assembly and modification before re-initiation grafting can be carried out.

[0007] (3) These initiators are usually expensive and most are not environmentally friendly, making them difficult to transport and store;

[0008] (4) The initiator remaining on the substrate surface may also affect the mechanical properties of the material itself.

[0009] To address these issues, scholars both domestically and internationally have developed a series of novel technologies in recent years to replace the use of traditional chemical initiators.

[0010] Irradiation-induced grafting is widely used to induce free radical formation due to its advantages such as rapid processing, homogeneous reaction systems, and direct initiation without additives. For example, Asadollahi et al. used ultraviolet irradiation to graft hydrophilic and antifouling polymers onto the surface of polyamide materials; Elsawy et al. grafted chitosan nanoparticles onto the surface of polylactic acid materials using gamma rays. However, the free radical sites instantly generated on the polymer backbone by high-energy radiation processing polymerization can lead to chain crosslinking and bond breakage, affecting the appearance and mechanical properties of the material. In addition, radiation sources such as gamma rays have the potential hazards of radioactive decay, which can affect human health and the environment.

[0011] Plasma graft polymerization is considered an environmentally friendly method due to its elimination of wet treatment processes and the use of chemical initiators, and it has become one of the most commonly used methods for graft polymerization on material surfaces in recent years. Kliewer et al. activated polyethylene using atmospheric pressure air plasma activation, followed by polymerization of ethylene benzyltrimethylammonium chloride monomer on its surface, obtaining a uniform polymer layer with a thickness of 300 nm. Liu et al. treated materials using different forms of atmospheric pressure plasma, such as bare electrodes and cross-field dielectric barrier discharge, and found that plasma treatment can increase the oxygen-containing active functional groups on the material surface, which is beneficial for subsequent grafting of different polymers and the formation of a dense coating. However, this method also has some drawbacks. For example, if the plasma treatment is not sufficient, the grafting process may be reversed; also, the substrate material over-exposed to plasma may be damaged.

[0012] More importantly, during radical polymerization, when the growing radical is terminated, the degenerative chain transfer process does not generate new radicals. In this case, a constant external radical source is usually required to initiate the polymerization reaction to ensure a sufficient supply of radicals for high conversion and polymerization rates. However, the methods described above are limited to the pretreatment stage of material-initiated polymerization and cannot provide a continuous and stable radical source during the polymerization process, thus leading to few or inefficient formation of active sites.

[0013] Therefore, it is necessary to further develop new methods for surface grafting polymerization of materials to perform functional modification. Summary of the Invention

[0014] The purpose of this invention is to address the problems of existing material surface modification technologies, such as cumbersome and time-consuming operation processes, high initiator costs, environmental unfriendliness, and the impact of residues on the substrate surface on the mechanical properties of the material. Furthermore, the free radical source is unstable during polymerization, resulting in few or inefficient formation of reactive sites, which does not conform to the sustainable development advocated by today's society. This invention provides a new method for material surface and interface modification that is not limited by the use of initiators, can provide a stable free radical source, and is simple and efficient, thereby at least partially solving the above-mentioned problems.

[0015] To achieve the above objectives, the present invention adopts the following solution:

[0016] A method for surface and interface functional modification via in-situ free radical polymerization using electro-atomization involves dissolving polymer monomers, natural polymers, or functional precursors to form an atomizing precursor liquid; using an electro-atomization device, under set voltage, liquid supply flow rate, and nozzle-electrode spacing conditions, the precursor liquid is subjected to high-voltage electro-atomization to form micro / nano droplets; during droplet flight, hydroxyl radicals are induced to be generated by electric field discharge; after the droplets are deposited on the surface of a substrate material, the hydroxyl radicals initiate an in-situ free radical polymerization reaction to form a functional modified layer;

[0017] The modification is completed in one step, without the introduction of any external crosslinking agents or chemical initiators throughout the process.

[0018] Based on the above technical solutions, the present invention may also employ the following further technical solutions, or combine these further technologies or solutions:

[0019] The electro-atomizing device includes a high-voltage power supply, a metal nozzle, a receiving electrode plate, and a liquid supply system.

[0020] The hydroxyl radicals are generated by the dissociation of water molecules induced by high-voltage gas-liquid interface discharge.

[0021] The polymer monomer is an organic or inorganic monomer or polymer precursor capable of participating in free radical polymerization, preferably containing at least one functional group selected from hydroxyl, carboxyl, amide, vinyl, acrylate, silyl, silyl ether, and amino groups.

[0022] The range of substrates to be selected includes textiles, film materials, plastic sheets, composite materials, paper-based materials, glass, metals, ceramics, and biomaterials.

[0023] The polymerization reaction can be carried out at room temperature, under elevated temperature or lower temperature, and the specific temperature can be adjusted according to the characteristics of the selected monomer or substrate, without the need for an external chemical initiator.

[0024] The electro-atomization voltage is 3–10 kV, the liquid flow rate is 0.1–10 μL / min, and the distance between the nozzle and the receiving electrode plate is 5–20 mm.

[0025] The functional modification is one or more of the following properties: antibacterial, antiviral, antifungal, hydrophilic, hygroscopic, UV resistant, antifouling, self-cleaning, flame retardant, biocompatible, antioxidant, conductive, and antistatic.

[0026] No additional curing or heat treatment steps are required after the modified layer is formed.

[0027] The modified layer has good stability and durability, and can maintain its basic functional performance even after multiple water washes.

[0028] Furthermore, the modification method of the present invention includes the following preparation steps:

[0029] Preparing the substrate material: Pre-treat the substrate material according to the processing requirements. Prepare the pre-treated material to a suitable size and place it on a stage for electro-atomization. The purpose of the pre-treatment is to remove surface impurities and improve the bonding strength of the modified layer. Pre-treatment methods include: for example, for textile substrates, deionized water rinsing, ultrasonic cleaning, ethanol degreasing, or surfactant cleaning can be used; for non-woven materials such as plastics, metals, and glass, solvent wiping, plasma treatment, ultraviolet irradiation, or hot air drying can be used.

[0030] Furthermore, the modification process of the present invention is as follows: (1) Atomization precursor solution: Prepare an atomization precursor solution of a certain concentration, pour the solution into the syringe of the electro-atomization device, adjust the voltage and flow rate of the electro-atomization device, use a suitable discharge needle, set a suitable needle-plate spacing, and electro-atomize the atomization precursor solution. At this time, the atomized substance is a micro-nano scale water droplet encapsulating a large number of ∙OH and monomers, such as Figure 1 As shown in section I.

[0031] (2) Droplet coalescence: As the droplet concentration gradually increases, the droplets generated by electro-atomization coalesce in the air and slowly settle onto the surface of the substrate material, such as... Figure 1 As shown in Part II.

[0032] (3) Droplet deposition and spreading: Under the combined action of electric field force and gravity, droplets are deposited on the surface of the substrate material and further spread on the surface of the substrate material, so that the droplets are uniformly coated on the surface of the substrate material, such as Figure 1 As shown in Part III.

[0033] (4) ∙OH hydrogen abstraction reaction: When a droplet wets the surface of a substrate material, a water layer containing a large number of ∙OH radicals and monomers is formed on the substrate material surface. The ∙OH radicals in the water layer have a strong hydrogen abstraction ability and can quickly abstract hydrogen atoms from the surface of the substrate material, causing the formation of corresponding carbon free radicals (C∙) on the substrate material surface, thereby increasing the surface activity of the substrate material, such as... Figure 1 As shown in section IV.

[0034] (5) Surface grafting polymerization: The carbon free radicals (C∙) on the surface of the substrate material have strong chemical activity and can further react with the monomers in the droplets to undergo polymerization reactions, thereby grafting the monomers onto the surface of the substrate material, such as... Figure 1 The V part is shown.

[0035] (6) Preparation completed by water layer evaporation: Once the water layer on the material surface has evaporated, the modification of the substrate material surface can be completed, such as... Figure 1 As shown in section VI.

[0037] Electro-atomization, as an additive manufacturing technology, works by using an applied electric field to generate a large number of free charges on the liquid surface at the tip of a capillary. The accumulation of these charges on the liquid surface forms a Taylor cone. When the electric field overcomes the surface tension of the liquid, a jet is generated at the tip of the Taylor cone, and under the influence of charge repulsion, it continuously breaks down, resulting in a large number of micro / nano-scale droplets. According to the applicant's previous research, electro-atomized polymer aqueous solutions can generate abundant hydroxyl radicals (·OH), a characteristic that gives electro-atomization the potential for free radical polymerization on material surfaces.

[0038] Compared with the prior art, the beneficial effects of the present invention are:

[0039] (1) This modification method does not require the use of any additional initiators. Compared with the traditional method of modifying materials by chemical initiators, it is lower in cost and cleaner and more environmentally friendly.

[0040] (2) This modification method does not involve complicated initiation steps and graft polymerization occurs simultaneously with monomer deposition, so the surface modification of the substrate material can be completed in one step.

[0041] (3) Since electro-atomization can continuously generate ·OH, this modification method can provide a stable free radical source during the grafting polymerization process on the substrate material surface, thereby achieving a higher conversion rate and polymerization rate than traditional methods.

[0042] (4) Since the droplets generated by electro-atomization are micro-nano scale, the water layer on the substrate material can also evaporate quickly after the electro-atomization process is stopped. Therefore, this modification method does not require secondary processing compared with the conventional "wet treatment" method.

[0043] (5) This modification method can graft different monomers and has high reactivity, thereby modifying the material surface to give the substrate material different functions, such as antibacterial, antiviral, anti-ultraviolet, hydrophilic, antifouling, etc., with high flexibility and greater selectivity. Attached Figure Description

[0044] Figure 1 The modification process diagram is shown to illustrate the core technical principle of this invention;

[0045] Figure 2 The characterization results of OH· under two different voltage conditions are shown.

[0046] Figure 3 The results of infrared testing of polyester fabrics before and after electro-atomization of bisphenol A solution according to the present invention;

[0047] Figure 4 The antibacterial test results of polyester fabrics before and after electro-atomization of bisphenol A solution according to the present invention are as follows: (a) Photograph of the antibacterial test drop plate of polyester fabric, (b) Antibacterial rate of polyester fabric;

[0048] Figure 5 The results of the contact angle test of polyester fabrics before and after treatment with the electro-atomized sericin solution of the present invention;

[0049] Figure 6 The infrared test results of polyester fabrics before and after electro-atomized sericin solution of the present invention are shown. Detailed Implementation

[0050] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0051] Example 1

[0052] The ·OH generated from electronebulized ultrapure water was detected. The ·OH was characterized using a FA200 electron spin resonance paramagnetic spectrometer (JEOL, Japan) under illumination assisted by a CEL-HXUV300 xenon lamp (China Education Jinyuan Technology Co., Ltd., China). The trapping agent used for characterization was 5,5-dimethyl-1-pyrroline-N-oxide (DMPO, Dojin Chemical Research Institute, Japan). Specifically, 30 μL of DMPO was dissolved in 1 mL of deionized water, shaken thoroughly, and then placed in a 5 mL centrifuge tube. The centrifuge tube was placed directly below the induction electrode plate of the electronebulizer, allowing the ·OH generated from the electronebulized ultrapure water to react fully with the DMPO aqueous solution for 20 minutes. The reacted solution was then irradiated under a xenon lamp for 5 minutes before being poured into a centrifuge tube in the ESR instrument for analysis.

[0053] The generation of ·OH was characterized under two sets of electronegation parameters: [1.2 μL / min, -5 kV, 0.5 cm] and [1.2 μL / min, -6.8 kV, 1 cm] (the first parameter is the supply flow rate, the second is the voltage, and the third is the needle-plate spacing). The results are as follows: Figure 2 As shown. The formation rate of ·OH is expressed in "spin / s". "spin" represents the signal strength of ·OH captured by the ESR, and " / s" means per second. The results show that the OH· formation rates under -5kV and -6.8kV conditions are 6.44 × 10⁻⁶. 15spin / s and 3.68×10 15 spin / s. This confirms that electro-atomized aqueous solutions can generate abundant ·OH.

[0054] Example 2

[0055] In this embodiment, an 8 wt% bisphenol A solution was used as the reaction precursor, and electro-atomization technology was employed to perform surface functionalization modification on polyester fabrics. The specific steps are as follows:

[0056] First, polyester fabric samples were cut into 2cm × 2cm sizes and pretreated to remove impurities and enhance surface activity. The pretreatment process included: ultrasonic cleaning with sodium dodecyl sulfate (SDS) solution, followed by cleaning with anhydrous ethanol, rinsing with deionized water, and finally drying at 60°C for later use.

[0057] The bisphenol acid solution was prepared by dissolving bisphenol acid in a 70:30 mixture of deionized water and ethanol. Then, the operating parameters were set in the electro-atomization device: applied voltage 5.6 kV, liquid flow rate 1.67 μL / min, and distance between the nozzle and the collecting plate 1 cm. The pretreated polyester fabric was then fixed onto the collecting plate and subjected to continuous electro-atomization treatment for 4 hours.

[0058] During this electro-atomization process, active droplets achieve in-situ deposition and grafting reactions on the fabric surface, constructing a stable functional layer. The entire modification process requires no chemical crosslinking agents or initiators, avoiding the complex multi-step reactions and damage to fabric properties in traditional modification methods, demonstrating the simplicity and efficiency of "one-step free radical grafting modification".

[0059] After undergoing 10 standard washes according to AATCC TM 61-2013e (2020) standard, the treated fabric was tested for antibacterial properties. The results showed that the unmodified polyester fabric had no inhibitory effect on bacteria, while the fabric treated with electro-atomization and then washed exhibited inhibition rates of 96.5% and 97.3% against Escherichia coli and Staphylococcus aureus, respectively, demonstrating excellent and durable antibacterial performance. Figure 3 Infrared test results of polyester fabrics before and after processing; Figure 4 Part a shows photos of antibacterial drip plates on polyester fabric before and after treatment. Figure 4 Part b shows the antibacterial rate results of polyester fabrics before and after treatment.

[0060] This embodiment verifies that the method of the present invention can achieve in-situ deposition and stable grafting of polymer functional materials on the surface of fabrics through electro-atomization without crosslinking agents, and the modified layer has excellent water washing stability and functional retention, and has broad application potential.

[0061] Example 3

[0062] This embodiment provides a method for depositing and grafting sericin onto the surface of polyester fabric using electro-atomization technology. It is one of the specific implementation methods of the present invention "A novel method for surface and interface functional modification by electro-atomization in-situ free radical polymerization". It has the advantages of being green and environmentally friendly, having a simple process, requiring no crosslinking agent, and having a significant modification effect.

[0063] The base material used is 100% polyester plain weave fabric, which is commercially available raw fabric. The warp and weft yarn linear densities are 8.3 tex and 16.7 tex, respectively, and the areal density is 132 g / m². 2 It has not undergone any dyeing or finishing treatment.

[0064] First, cut the polyester fabric to the appropriate size, wash it thoroughly with deionized water to remove impurities and oil stains from the fabric surface, and then lay it flat in a ventilated place to air dry naturally as a pretreatment step before electro-atomization treatment.

[0065] Subsequently, a low-concentration sericin solution was prepared and deposited via electro-atomization. The pretreated polyester fabric was fixed onto a metal electrode plate, positioned directly below the tip of the metal capillary needle. The operating parameters of the electro-atomization device were: applied voltage 8.05 kV, liquid flow rate 0.144 μL / min, and distance between the nozzle and the collecting plate 1 cm. The pretreated polyester fabric was then fixed onto the collecting plate.

[0066] Due to the low concentration and small droplet size of sericin, the electro-atomization treatment time was set to 5 hours to ensure uniform deposition and surface coverage. The fabric position was manually adjusted every hour to ensure even distribution of the deposition area and adequate coverage of the sericin particles on the fabric surface. After treatment, the fabric was left to stand at room temperature for 12 hours to complete the curing of the surface functional layer.

[0067] The treated fabric underwent 10 standard washes according to AATCC TM 61-2013e (2020) standard, and the relevant performance test results are as follows:

[0068] (1) Water contact angle test: The water contact angle of the original polyester fabric surface was 139.79±2.15°, and the contact angle of the modified fabric was significantly reduced to 88.48±0.94°, indicating that its surface changed from hydrophobic to hydrophilic. Figure 5 ).

[0069] (2) Wetting time test: The water droplet immersion time of the modified fabric was 11 minutes, which was significantly shorter than the original fabric's 26 minutes, indicating that the fabric's wetting performance was significantly improved.

[0070] (3) Moisture regain test: The moisture regain of the modified fabric increased from 0.21% of the original fabric to 0.91%, an increase of about 3.3 times.

[0071] (4) FTIR spectral analysis showed that characteristic absorption peaks of sericin appeared in the modified fabric, verifying that sericin had been successfully deposited and stably attached to the surface of the polyester fabric. Figure 6 ).

[0072] In summary, the method provided in this embodiment demonstrates that the electro-atomization technology can achieve efficient and integrated grafting of natural protein materials onto the surface of fabrics. The entire process requires no cross-linking agent, and the modified polyester fabric exhibits excellent hydrophilicity and hygroscopicity, demonstrating good application stability and industrialization promotion value.

Claims

1. A method for surface and interface functional modification via electro-atomization in-situ free radical polymerization, characterized in that: Polymer monomers, natural polymers, or functional precursors are dissolved to form an atomized precursor liquid; the precursor liquid is then subjected to high-voltage electro-atomization using an electro-atomization device under set voltage, liquid supply flow rate, and nozzle-electrode spacing conditions to form micro-nano droplets. During the flight of the droplets, hydroxyl radicals are generated through electric field discharge. When the droplets are deposited on the surface of the substrate material, the hydroxyl radicals initiate free radical polymerization in situ to form a functional modified layer. The modification is completed in one step, without the introduction of any external crosslinking agents or chemical initiators throughout the process.

2. The method for surface and interface functional modification by electro-atomized in-situ free radical polymerization according to claim 1, characterized in that, The electro-atomizing device includes a high-voltage power supply, a metal nozzle, a receiving electrode plate, and a liquid supply system.

3. The method for surface and interface functional modification by electro-atomized in-situ free radical polymerization according to claim 1, characterized in that, The hydroxyl radicals are generated by the dissociation of water molecules induced by high-voltage gas-liquid interface discharge.

4. The method for surface and interface functional modification by electro-atomized in-situ free radical polymerization according to claim 1, characterized in that, The polymer monomer is an organic or inorganic monomer or polymer precursor capable of participating in free radical polymerization, preferably containing at least one functional group selected from hydroxyl, carboxyl, amide, vinyl, acrylate, silyl, silyl ether, and amino groups.

5. The method for surface and interface functional modification by electro-atomized in-situ free radical polymerization according to claim 1, characterized in that, The range of substrate materials includes textiles, film materials, plastic sheets, composite materials, paper-based materials, glass, metals, ceramics, and biomaterials.

6. The method for surface and interface functional modification by electro-atomized in-situ free radical polymerization according to claim 1, characterized in that, The polymerization reaction can be carried out at room temperature, under heating or cooling conditions.

7. The method for surface and interface functional modification by electro-atomized in-situ free radical polymerization according to claim 1, characterized in that, The electro-atomization voltage is 3–10 kV, the liquid flow rate is 0.1–10 μL / min, and the distance between the nozzle and the receiving electrode plate is 5–20 mm.

8. The method for surface and interface functional modification by electro-atomized in-situ free radical polymerization according to claim 1, characterized in that, Functional modification includes one or more of the following properties: antibacterial, antiviral, antifungal, hydrophilic, hygroscopic, UV resistant, antifouling, self-cleaning, flame retardant, biocompatible, antioxidant, conductive, and antistatic.

9. The method for surface and interface functional modification by electro-atomized in-situ free radical polymerization according to claim 1, characterized in that, No additional curing or heat treatment steps are required after the modified layer is formed.

10. The method for surface and interface functional modification by electro-atomized in-situ free radical polymerization according to claim 1, characterized in that, The modified layer has good stability and durability, and can maintain its basic functional performance even after multiple water washes.

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