A method for preparing a poly-n-isopropylacrylamide / polyvinylidene fluoride switchable wetting behavior film based on electrospinning
By blending poly(N-isopropylacrylamide) with polyvinylidene fluoride using electrospinning technology, a switchable wettability film with temperature-sensitive properties and good mechanical properties was prepared. This solved the shortcomings of existing films in terms of hydrophilicity, adhesion and tribological properties, and achieved the preparation of a film with high toughness and high wear resistance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JIANGSU UNIV
- Filing Date
- 2023-07-06
- Publication Date
- 2026-07-10
AI Technical Summary
Existing poly(N-isopropylacrylamide) films have shortcomings in terms of hydrophilicity, adhesion and tribological properties, and the timeliness of relevant reports is poor, making it difficult to prepare switchable wettability films with high toughness and high wear resistance.
Poly(N-isopropylacrylamide) and polyvinylidene fluoride were blended using electrospinning technology, and the two polymer fibers were fused through the electrospinning process to prepare a film with switchable wetting behavior that has temperature-sensitive properties and good mechanical properties.
The mechanical properties of poly(N-isopropylacrylamide) films were improved, the switching between hydrophilicity and hydrophobicity was enhanced, a new approach to droplet transport was provided, and the film-substrate bonding was strengthened.
Smart Images
Figure CN116791278B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the technical field of smart surfaces and relates to a method for preparing a poly(N-isopropylacrylamide) / polyvinylidene fluoride film with switchable wetting behavior based on electrospinning. Background Technology
[0002] "Survival of the fittest" is the law of nature. Over millions of years, organisms have evolved unique lifestyles and survival strategies to cope with the ever-changing environment, including unique wettability and photosensitivity. In recent years, materials with special wettability have gradually become a research hotspot and have driven the development of this field. Among them, intelligent biomimetic surfaces that can change their surface wettability in response to external stimuli have attracted increasing attention due to their unique properties. Poly(N-isopropylacrylamide) (PNIPAM) is a typical temperature-responsive polymer. This substance generally has both hydrophilic and hydrophobic groups. When its temperature is below the lower critical solution temperature (LCST), the amide groups form hydrogen bonds with water molecules, and the macromolecular chains unfold, exhibiting hydrophilicity. When the temperature is above the LCST, the hydrogen bonds break, releasing water molecules, and with the effect of the hydrophobic groups, the macromolecules rapidly curl up, exhibiting hydrophobicity. Researchers have conducted a series of studies based on its unique temperature sensitivity, among which PNIPAM hydrogels have been studied most extensively. They have shown advantages such as excellent permeability, good biocompatibility and tissue-like properties. However, research on using PNIPAM as a surface material to modify surfaces is very limited. Moreover, the corresponding reports show that PNIPAM films have many drawbacks, such as poor aging performance, poor adhesion and poor friction performance. Therefore, it is urgent to prepare switchable wettable films with high toughness, high wear resistance and excellent film-substrate bonding.
[0003] Polyvinylidene fluoride (PVDF) possesses excellent properties such as chemical resistance, high temperature resistance, high mechanical strength, good electrical insulation, strong radiation resistance, and good biocompatibility. PVDF also exhibits good hydrophobicity. Due to the high fluorine content in its chemical structure, PVDF possesses unique surface properties. Its surface energy is low, and the water contact angle is generally above 100°, sometimes even exceeding 150°. The hydrophobicity of PVDF effectively resists liquid adhesion, preventing water, oil, and stains from adhering to its surface, thus maintaining its cleanliness and smoothness. Furthermore, the hydrophobicity of PVDF prevents the growth of biological substances and bacteria on its surface, leading to its widespread application in medical and food processing fields. Utilizing this hydrophobic property can improve upon the shortcomings of PNIPAM, and this improvement will prevent PNIPAM fibers from dissolving in water, potentially enabling functions such as droplet manipulation on the PNIPAM film surface. Summary of the Invention
[0004] In view of the above problems, the present invention aims to achieve switchable wetting behavior of thin films by means of a thin film preparation method with good dissolution resistance and mechanical properties, thereby improving the mechanical properties and film-substrate adhesion, so as to make it have good functionality and practicality.
[0005] This invention provides a method for preparing a poly(N-isopropylacrylamide) / polyvinylidene fluoride (PVDF) film with switchable wetting behavior based on electrospinning, the specific steps of which are as follows:
[0006] (1) Mix N,N dimethylformamide with acetone to obtain a mixed solution;
[0007] (2) Dissolve poly(N-isopropylacrylamide) and polyvinylidene fluoride in the mixed solution obtained in step (1), and heat in a water bath for a certain time under stirring to obtain electrospinning solution;
[0008] (3) Inject the electrospinning solution obtained in step (2) into the syringe, add it into the electrospinning device, place the receiving screen vertically with the syringe and keep a certain distance from the syringe, and electrospin under certain environmental humidity and voltage conditions and set the corresponding propulsion speed, so that a poly(N-isopropylacrylamide) / polyvinylidene fluoride fiber membrane is obtained on the receiving screen.
[0009] (4) The fiber membrane obtained in step (3) is vacuum dried at room temperature to obtain a poly(N-isopropylacrylamide) / polyvinylidene fluoride switchable wetting behavior film.
[0010] In step (1), the volume ratio of N,N dimethylformamide to acetone is (5-8):(1-4), preferably 7:3. The stirring speed is 100-500 r / min, preferably 200 r / min; the stirring time is 1-3 h, preferably 2 h.
[0011] In step (2), the mass ratio of polyvinylidene fluoride to poly(N-isopropylacrylamide) is (2-5):(1-2), preferably (3-4):(1.5-1.8);
[0012] The mass ratio of the total mass of poly(N-isopropylacrylamide) and polyvinylidene fluoride to the mass of the mixed solution is (11-15):(50-150), preferably (12-14):(90-120);
[0013] In step (2), the water bath heating temperature is 50℃~80℃, preferably 60℃; the water bath heating time is 6~10h, preferably 8h;
[0014] In step (2), the stirring speed is 100-300 r / min; the stirring time is 6-10 h, preferably 8 h.
[0015] In step (3), the distance between the syringe and the receiving screen is 10-30cm, preferably 15cm;
[0016] In step (3), the relative humidity of the environment is 15% to 25%, preferably 20%;
[0017] In step (3), the voltage is 20-30kV, preferably 25kV;
[0018] In step (3), the propulsion speed is 0.1 to 1 ml / h, preferably 0.5 ml / h;
[0019] In step (4), the drying time is 10 to 24 hours, preferably 20 hours.
[0020] The preparation steps of poly-N-isopropylacrylamide are as follows:
[0021] S1: Add monomer N-isopropylacrylamide and crosslinking agent to deionized water, heat and stir at 60°C for the first time to fully dissolve, continuously introduce N2, add initiator, heat and stir at 60°C for the second time for 1-2 hours, continuously introduce inert gas during the process, and obtain a uniform mixed dispersion.
[0022] S2: Heat the mixed dispersion obtained in step S1 to the required polymerization temperature of 70°C and maintain it for more than 7 hours, stirring continuously during the process, to obtain a polymer solution;
[0023] S3: Centrifuge and purify the polymer solution obtained in step S2 to obtain a solid product;
[0024] S4: Place the solid product obtained in step S3 in a vacuum drying oven to dry it, and you will get poly-N-isopropylacrylamide.
[0025] The crosslinking agent is NN′methylenediacrylamide, and the initiator is azobisisobutyronitrile;
[0026] The molar ratio of N-isopropylacrylamide to NN′methylenediacrylamide is (50-100):(1-3), preferably 100:1;
[0027] The molar ratio of N-isopropylacrylamide to azobisisobutyronitrile is (80-150):(0.5-1.5), preferably 100:1;
[0028] The precipitant used in the purification is a mixed solution of toluene and n-hexane, wherein the volume ratio of toluene to n-hexane is (0.5-2):(1-3), preferably 1:4.
[0029] The process and mechanism of the method of this invention are as follows:
[0030] In the electrospinning process, the polymer in the blend solution is stretched. Polyvinylidene fluoride (PVDF) and poly(N-isopropylacrylamide) possess different properties. During the stretching and deposition process, the two polymer fibers are fused together, resulting in a final product that exhibits both temperature-sensitive properties and good mechanical properties. Because this invention requires high purity and resistance to solvents and acid / alkali corrosion, the addition of PVDF not only improves the mechanical properties of PNIPAM but also provides it with resistance to corrosion and dissolution.
[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0032] 1. This invention proposes a method to improve the mechanical properties of poly(N-isopropylacrylamide) fibers after spinning by using polyvinylidene fluoride.
[0033] 2. This invention improves the hydrophilicity of poly(N-isopropylacrylamide) fibers by utilizing the hydrophobic properties of polyvinylidene fluoride, allowing water droplets to remain on the surface while still exhibiting temperature sensitivity.
[0034] 3. The raw materials used in this invention are abundant, the method is simple, and it can be mass-produced. At the same time, this invention also provides a new approach to droplet transportation. Attached Figure Description
[0035] Figure 1 The image shown is a scanning electron microscope image of the thin film obtained in Example 1.
[0036] Figure 2 The image shows the contact angle of the thin film obtained in Example 1 at 25°C.
[0037] Figure 3 The image shows the contact angle of the thin film obtained in Example 1 at 40°C.
[0038] Figure 4 This is a scanning electron microscope image of the thin film obtained in Example 1 after the contact angle test.
[0039] Figure 5 The image shown is a scanning electron microscope image of the thin film obtained in Example 2.
[0040] Figure 6 The image shows the contact angle of the film obtained in Example 2 at 25°C.
[0041] Figure 7 The image shows the contact angle of the film obtained in Example 2 at 40°C.
[0042] Figure 8 This is a scanning electron microscope image of the thin film obtained in Example 2 after the contact angle test.
[0043] Figure 9The image shown is a scanning electron microscope image of the thin film obtained in Example 3.
[0044] Figure 10 The image shows the contact angle of the film obtained in Example 3 at 25°C.
[0045] Figure 11 The image shows the contact angle of the film obtained in Example 3 at 40°C.
[0046] Figure 12 This is a scanning electron microscope image of the thin film obtained in Example 3 after the contact angle test.
[0047] Figure 13 The image shown is a scanning electron microscope image of the thin film obtained in Example 4.
[0048] Figure 14 The image shows the contact angle of the film obtained in Example 4 at 25°C.
[0049] Figure 15 The image shows the contact angle of the film obtained in Example 4 at 40°C.
[0050] Figure 16 This is a scanning electron microscope image of the thin film obtained in Example 4 after the contact angle test. Detailed Implementation
[0051] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.
[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
[0053] The following examples will provide further details, but are not limited to these.
[0054] Example 1
[0055] (1) Preparation of poly-N-isopropylacrylamide:
[0056] S1: Add 2.2g of N-isopropylacrylamide and 0.089g of N-N′methylenediacrylamide to 100ml of deionized water, heat to 60℃ and stir for 2-5h to fully dissolve them, continuously bubbling N2 during the process to remove oxygen from the system; then add 0.044g of azobisisobutyronitrile, and keep at 60℃ and stir for 1-2h to obtain a mixed solution;
[0057] S2: Heat the mixed solution obtained in step S1 to 70°C and stir for 7 hours to allow it to fully polymerize, thereby obtaining a polymer solution;
[0058] S3: Place the product obtained in step S2 into a centrifuge at 10000 r / min for 30 min. After removing the sample, remove the supernatant. Dry the product under vacuum at 60℃ for 5 h. Add a large amount of acetone to dissolve it. Then add it dropwise to 100 ml of a mixed solution of toluene and n-hexane. Filter to obtain the precipitate.
[0059] S4: The precipitate obtained in step S3 was vacuum dried at room temperature for 4 hours to obtain a white powder, namely poly-N-isopropylacrylamide.
[0060] (2) Weigh 0.2g of the poly(N-isopropylacrylamide) prepared in step (1) above and mix it with 0.6g of polyvinylidene fluoride into a small glass bottle. Add 3.5ml of N,N-dimethylformamide and 1.5ml of acetone, and stir magnetically for 2 hours to fully dissolve it, which is the spinning solution.
[0061] (3) Add the spinning solution to the syringe and place it in the electrospinning equipment for electrospinning. The voltage is 25kV, the syringe advance speed is 0.5ml / h, the receiving distance is 15cm, a No. 22 needle is selected, and a copper sheet is used for receiving to obtain a 25mm×75mm mixed nanofiber membrane.
[0062] (4) The obtained nanofiber membrane was placed at room temperature and vacuum dried to remove the solvent, and finally a poly(N-isopropylacrylamide) / polyvinylidene fluoride switchable wetting behavior film was obtained.
[0063] Test 1: The obtained poly(N-isopropylacrylamide) / polyvinylidene fluoride switchable wetting behavior film was placed in an environment of 25°C and its contact angle was measured using an optical contact angle meter.
[0064] Test 2: The obtained poly(N-isopropylacrylamide) / polyvinylidene fluoride switchable wetting behavior film was placed in an environment of 40°C, and its contact angle was measured using an optical contact angle meter.
[0065] Test 3: The poly(N-isopropylacrylamide) / polyvinylidene fluoride switchable wetting behavior film was placed in a vacuum drying oven at 60°C for 1 hour and then cooled to room temperature before being characterized by scanning electron microscopy.
[0066] Figure 1 The image shown is a scanning electron microscope image of the thin film obtained in this example, demonstrating that a layer of nanofibers can be spun on a copper sheet in this example.
[0067] Figure 2 The contact angle diagram of the film obtained in this example at 25°C shows that the film exhibits hydrophilic properties at 25°C.
[0068] Figure 3 The contact angle diagram of the film obtained in this example at 40°C shows that the film exhibits hydrophobic properties at 40°C.
[0069] Figure 4 The image shown is a scanning electron microscope image obtained after the thin film contact angle test in this example, indicating that the morphology of the thin film did not change before and after the test.
[0070] Example 2:
[0071] The difference between this embodiment and Embodiment 1 is that the voltage is set to 30kV during electrospinning. All other steps are the same as in Embodiment 1.
[0072] Figure 5 The image shown is a scanning electron microscope image of the thin film obtained in this example, indicating that the nanofibers generated at 30 kV in this example are finer than those in Example 1.
[0073] Figure 6 The contact angle diagram of the film obtained in this example at 25°C shows that the film exhibits hydrophilic properties at 25°C.
[0074] Figure 7 The contact angle diagram of the film obtained in this example at 40°C shows that the film exhibits hydrophobic properties at 40°C.
[0075] Figure 8 The image shown is a scanning electron microscope image of the thin film obtained in this example, indicating that the morphology of the thin film did not change before and after the test.
[0076] Example 3:
[0077] The difference between this embodiment and Embodiment 1 is that the nanofiber membrane is received by a glass slide. All other steps are the same as in Embodiment 1.
[0078] Figure 9 The image shown is a scanning electron microscope image of the thin film obtained in this example, demonstrating that fibers can also be spun on a glass slide in this case.
[0079] Figure 10 The contact angle diagram of the nanofiber film obtained in this example at 25°C shows that the film exhibits hydrophilic properties at 25°C.
[0080] Figure 11 The contact angle diagram of the nanofiber film obtained in this example at 40°C shows that the film exhibits hydrophobic properties at 40°C.
[0081] Figure 12 The image shown is a scanning electron microscope image of the nanofiber film obtained in this example after the contact angle test, indicating that the film morphology did not change before and after the test.
[0082] Example 4:
[0083] The difference between this embodiment and Embodiment 1 is that the nanofiber membrane is received by an acrylic plate. All other steps are the same as in Embodiment 1.
[0084] Figure 13 The image shown is a scanning electron microscope image of the film obtained in this example, demonstrating that fibers can be spun onto an acrylic sheet.
[0085] Figure 14 The contact angle diagram of the film obtained in this example at 25°C shows that the film exhibits hydrophilic properties at 25°C.
[0086] Figure 15 The contact angle diagram of the film obtained in this example at 40°C shows that the film exhibits hydrophobic properties at 40°C.
[0087] Figure 16 The image shown is a scanning electron microscope image obtained after the thin film contact angle test in this example, indicating that the morphology of the thin film did not change before and after the test.
[0088] The above embodiments demonstrate that films with different fiber diameters and spacing can be prepared by changing the electrospinning voltage and the receiving substrate material. The above embodiments also demonstrate that, through the blending of polyvinylidene fluoride (PVDF), poly(N-isopropylacrylamide) can be easily prepared into structurally stable and insoluble films; films can still be successfully fabricated on different substrates; the films exhibit two different properties near the LCST, and below the LCST, they are not dissolved in water.
[0089] Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the feasibility of the invention. Various changes and modifications can be made to the invention without departing from its principles, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.
Claims
1. A method for preparing a poly(N-isopropylacrylamide) / polyvinylidene fluoride (PVDF) film with switchable wetting behavior based on electrospinning, characterized in that: The steps are as follows: (1) NN dimethylformamide and acetone are stirred and mixed to obtain a mixed solution; wherein, in step (1), the volume ratio of NN dimethylformamide to acetone is (5~8):(1~4); (2) Dissolve poly(N-isopropylacrylamide) and polyvinylidene fluoride in the mixed solution obtained in step (1), and heat in a water bath for a certain time under stirring to obtain electrospinning solution; The mass ratio of polyvinylidene fluoride to poly(N-isopropylacrylamide) is (2~5):(1~2). The mass ratio of the total mass of poly(N-isopropylacrylamide) and polyvinylidene fluoride to the mass ratio of the mixed solution of N-dimethylformamide and acetone is (11~15):(50~150). The poly-N-isopropylacrylamide is prepared by the following method: S1: Add monomer N-isopropylacrylamide and crosslinking agent to deionized water, heat and stir at 60°C for the first time to fully dissolve, continuously introduce N2, add initiator, heat and stir at 60°C for the second time for 1~2 hours, continuously introduce inert gas during the process, and obtain a uniform mixed dispersion. S2: Heat the mixed dispersion obtained in step S1 to the required polymerization temperature of 70°C and maintain it for more than 7 hours, stirring continuously during the process, to obtain a polymer solution; S3: Centrifuge and purify the polymer solution obtained in step S2 to obtain a solid product; S4: Place the solid product obtained in step S3 in a vacuum drying oven and dry it to obtain poly-N-isopropylacrylamide; (3) Inject the electrospinning solution obtained in step (2) into the syringe, add it into the electrospinning device, place the receiving screen vertically with the syringe and keep a certain distance from the syringe, and electrospin under certain environmental humidity and voltage conditions and set the corresponding propulsion speed, so that a poly(N-isopropylacrylamide) / polyvinylidene fluoride fiber membrane is obtained on the receiving screen. (4) The fiber membrane obtained in step (3) is vacuum dried at room temperature to obtain a poly(N-isopropylacrylamide) / polyvinylidene fluoride switchable wetting behavior film.
2. The preparation method according to claim 1, characterized in that, In step (1), the volume ratio of NN dimethylformamide to acetone is 7:3; the stirring speed is 100~500r / min; and the stirring time is 1~3h.
3. The preparation method according to claim 2, characterized in that, The stirring speed is 200 r / min; the stirring time is 2 h.
4. The preparation method according to claim 1, characterized in that, In step (2), The mass ratio of polyvinylidene fluoride to poly(N-isopropylacrylamide) is (3~4):(1.5~1.8). The mass ratio of the total mass of poly(N-isopropylacrylamide) and polyvinylidene fluoride to the mass ratio of the mixed solution of N-dimethylformamide and acetone is (12~14):(90~120). The water bath heating temperature is 50℃~80℃. The stirring speed is 100~300 r / min, and the stirring time is 6~10 h.
5. The preparation method according to claim 4, characterized in that, In step (2), the water bath heating temperature is 60°C; the stirring time is 8 hours.
6. The preparation method according to claim 1, characterized in that, In step (3), the distance between the receiving screen and the syringe is 10~30cm; the relative humidity of the environment is 15%~25%; the voltage is 20~30kV; and the propulsion speed is 0.1~1ml / h.
7. The preparation method according to claim 6, characterized in that, In step (3), the distance between the receiving screen and the syringe is 15cm; the relative humidity of the environment is 20%; the voltage is 25kV; and the propulsion speed is 0.5ml / h.
8. The preparation method according to claim 1, characterized in that, In step (4), the vacuum drying time at room temperature is 10~24h.
9. The preparation method according to claim 1, characterized in that, In the preparation of poly-N-isopropylacrylamide: The crosslinking agent is N·methylenediacrylamide, and the initiator is azobisisobutyronitrile; The molar ratio of N-isopropylacrylamide to N'-methylenediacrylamide is (50~100):(1~3); The molar ratio of N-isopropylacrylamide to azobisisobutyronitrile is (80~150):(0.5~1.5). The precipitant used in the purification is a mixed solution of toluene and n-hexane, wherein the volume ratio of toluene to n-hexane is (0.5~2):(1~3).