Photosensitive hydrophilic-hydrophobic conversion gel and preparation method thereof
By blending PNIPAM with cellulose acetate, electrospinning into a film, and growing polypyrroles in situ, a photosensitive hydrophilic conversion gel was prepared, which solved the problem of lack of mature preparation methods in the prior art, and achieved the characteristics of efficient water absorption and rapid water release, which were suitable for applications such as air water collection.
Patent Information
- Application Number
- CN202510277689.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-10
- Publication Date
- 2025-05-16
AI Technical Summary
The prior art lacks a mature preparation method for photosensitive hydrophilic conversion gels, which cannot efficiently adsorb moisture in the air under low temperature conditions without light, and quickly release liquid water after the light is warmed up.
By blending PNIPAM with cellulose acetate, electrospinning into a film, and then growing polypyrroles in situ, a photosensitive hydrophilic conversion gel is prepared to achieve low temperature absorption in the absence of light and high temperature dehydration in the presence of light.
It realizes the dual response characteristics of the gel, has excellent intelligent response capabilities, shows high water collection capacity and low energy consumption drive, and is suitable for applications such as air water collection.
Abstract
Description
Technical Field
[0001] The invention belongs to the field of functional polymer materials, and in particular relates to a photosensitive hydrophilic-hydrophobic conversion gel and a preparation method thereof. Background Art
[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.
[0003] The regulation of the surface hydrophilicity and hydrophobicity of materials is an important research direction in materials science. Traditional hydrophilicity and hydrophobicity conversion materials mostly rely on temperature, pH or chemical stimulation to achieve property changes. Light-controlled materials have become a research hotspot in recent years due to their advantages such as non-invasiveness and easy triggering. Among them, photosensitive hydrophilicity and hydrophobicity conversion gel materials show broad prospects in the field of smart materials. For example, in air water collection applications, they can achieve efficient adsorption of moisture in the air under low-temperature conditions without light, and quickly release liquid water after light and temperature rise, thereby realizing the collection of water resources in arid areas. However, there is currently no fully mature method for preparing photosensitive hydrophilicity and hydrophobicity conversion gels.
[0004] Patent CN 114854046 A discloses a triple stimulus responsive double-layer hydrogel actuator, wherein the second layer of hydrogel is composed of poly (N-isopropylacrylamide) and carboxymethyl cellulose, and the polymerization is initiated by light. However, the above hydrogel does not have the ability of photosensitive hydrophilic-hydrophobic conversion. Summary of the invention
[0005] In order to solve the above problems, the present invention provides a photosensitive hydrophilic-hydrophobic conversion gel and a preparation method thereof. The present invention prepares a photosensitive hydrophilic-hydrophobic conversion gel by blending PNIPAM and cellulose acetate and then electrospinning the mixture into a film, and then growing polypyrrole in situ, so as to achieve the characteristics of low-temperature water absorption in the absence of light and heating and dehydration in the presence of light.
[0006] In order to achieve the above object, the present invention adopts the following technical solution:
[0007] The first aspect of the present invention provides a method for preparing a photosensitive hydrophilic-hydrophobic switching gel, comprising:
[0008] dissolving cellulose acetate and PNIPAM in an organic solvent to obtain a spinning solution;
[0009] The spinning solution is subjected to electrostatic spinning, and after the spinning is completed, the residual solvent is removed to obtain a CA-PNIPAM fiber membrane;
[0010] The CA-PNIPAM fiber membrane is immersed in a pyrrole monomer aqueous solution, allowed to stand and cooled, and then an oxidant is added to carry out an in-situ polymerization reaction of pyrrole. After the reaction is completed, purification is performed to obtain a photosensitive hydrophilic-hydrophobic conversion gel.
[0011] The present invention is based on the thermosensitive material poly (N-isopropylacrylamide) (PNIPAM), uses cellulose acetate (CA) to give it high mechanical strength, and uses polypyrrole (PPy) to give it the function of converting from thermosensitivity to photosensitivity, so as to realize the preparation of photosensitive hydrophilic-hydrophobic conversion gel. PNIPAM has a suitable critical phase transition temperature (LCST≈32°C), but its mechanical strength is relatively low, which can easily lead to the collapse of the gel structure after multiple cycles. Cellulose acetate, as a common cellulose derivative in life, has excellent mechanical strength, biocompatibility and film-forming properties, but it lacks intelligent responsiveness. Polypyrrole has a high absorbance of more than 95% in the entire solar spectrum, which can achieve efficient photothermal conversion.
[0012] Compared with carboxymethyl cellulose, cellulose acetate has a certain hydrophobicity and will not significantly reduce its strength due to water absorption. Therefore, in some embodiments, the molecular weight of the cellulose acetate is 25,000-35,000, and the acetyl content is 38-42wt%;
[0013] In order to obtain better photosensitivity hydrophilic-hydrophobic conversion ability, the present invention screened existing thermosensitive materials. Preferably, the thermosensitive material is poly (N-isopropylacrylamide) (PNIPAM), which has the following advantages: 1. The response temperature is close to the daily temperature, which can be suitable for temperature response under the temperature transition when the light is heated up and the light is not cooled. 2. The response time is short. 3. The response temperature LCST is adjustable. 4. It has good biocompatibility. 5. It can be dissolved in an acetone-ethanol mixture with cellulose acetate CA, and can smoothly realize electrospinning.
[0014] In some embodiments, the molecular weight of PNIPAM is 200,000-400,000;
[0015] In some embodiments, the mass ratio of cellulose acetate to PNIPAM is 2:1-1:2.
[0016] In some embodiments, the organic solvent is an acetone-ethanol solvent, and the ratio of acetone to ethanol is 1:0.5-0.5:1;
[0017] In some embodiments, the mass volume ratio of the total mass of the cellulose acetate and PNIPAM to the acetone ethanol solvent is 1:10-12.
[0018] In some embodiments, the dissolution temperature of the cellulose acetate and PNIPAM in the organic solvent is 20-30°C.
[0019] In some embodiments, the drying temperature when removing the residual solvent is 50-65°C.
[0020] Research has found that the use of polypyrrole (PPy) can not only give the CA-PNIPAM fiber membrane the function of converting from thermosensitivity to photosensitivity, but also form a micro-nano structure with the fiber network to increase the hydrophobic performance when heated. Therefore, preferably, the present invention grows polypyrrole in situ on the CA-PNIPAM fiber membrane. In addition, the use of polypyrrole (PPy) has the following advantages: 1. Strong absorption from visible light to near infrared. 2. Efficient light energy-heat energy conversion is achieved through the conjugated π electron structure, with high photothermal efficiency, close to gold nanoparticles. 3. Good biocompatibility. 4. The fiber surface is generated in situ and can be combined with the fiber into a micro-nano structure to enhance the hydrophobic ability and facilitate the release of water.
[0021] In some embodiments, the concentration of the pyrrole monomer aqueous solution is 0.1-0.5M;
[0022] In some embodiments, the CA-PNIPAM fiber membrane is immersed in the pyrrole monomer aqueous solution for 2-4 hours.
[0023] In some embodiments, the temperature after cooling is 0-10°C.
[0024] In some embodiments, the oxidant is ferric chloride or ammonium persulfate;
[0025] In some embodiments, the amount of the oxidant is 0.1-0.6 M, preferably, the amount of ferric chloride is 0.2-0.6 M or the amount of ammonium persulfate is 0.1-0.5 M;
[0026] In some embodiments, the pyrrole in-situ polymerization reaction time is 6-12 hours.
[0027] The second aspect of the present invention provides a photosensitive hydrophilic-hydrophobic switching gel prepared by the above method.
[0028] The third aspect of the present invention provides the use of the above-mentioned photosensitive hydrophilicity-hydrophobicity conversion gel in the preparation of a water collector.
[0029] Beneficial Effects of the Invention
[0030] (1) The gel has dual response characteristics: The introduction of PNIPAM gives the gel dual responsiveness regulation of temperature response and light response, which enables the gel to have excellent intelligent response capabilities.
[0031] (2) The gel exhibits high water collection capacity: The CA-PNIPAM fiber membrane prepared by electrospinning has a three-dimensional nanofiber network with a large specific surface area and high porosity, which can significantly increase the contact area with water vapor in the air and improve the water capture capacity.
[0032] (3) Low-energy drive: The gel has photothermal responsiveness and can achieve hydrophilic-hydrophobic conversion and water collection by only intermittent switching of natural light sources. Compared with traditional electric heating or mechanical water collection and desorption technology, energy consumption is greatly reduced.
[0033] Through the above innovative design, the present invention prepares a hydrophilic-hydrophobic conversion gel with obvious photosensitivity, which provides a solution for the realization of applications such as air water collection. DETAILED DESCRIPTION
[0034] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.
[0035] The present invention will be further described in detail below in conjunction with specific embodiments. It should be noted that the specific embodiments are intended to explain the present invention rather than to limit it.
[0036] Example 1
[0037] 1 g of cellulose acetate (CA, molecular weight 30,000, acetyl content 39.8 wt%) and 1 g of poly (N-isopropylacrylamide) (PNIPAM, molecular weight 300,000) were added to a mixture of 10 ml of acetone and 10 ml of ethanol, and stirred at room temperature until completely dissolved to obtain a spinning solution.
[0038] The spinning solution was placed in the syringe of the electrospinning machine (20 mL, equipped with a 23G needle), the voltage was 15 kV, the distance from the needle to the collector was 20 cm, the solution advancement rate was 1.0 mL / h, and electrospinning was performed at room temperature to obtain a CA-PNIPAM fiber membrane. The obtained CA-PNIPAM fiber membrane was placed in a 60°C oven for heat treatment for 4 hours to completely remove the residual solvent.
[0039] The CA-PNIPAM fiber membrane was immersed in 100 ml of 0.3 M pyrrole monomer aqueous solution for 3 h, then cooled to 5 ° C, 10 ml of 4 M ferric chloride solution was slowly added, and the low temperature immersion was continued for 12 h. After the reaction was completed, the membrane was taken out and washed with deionized water for 3 times, each time for 20 minutes, to obtain a photosensitivity hydrophilic-hydrophobic conversion gel PPy-CA-PNIPAM.
[0040] The film-like photosensitive hydrophilic-hydrophobic conversion gel prepared in this embodiment has a thickness of 0.3 cm, and the water contact angle at 20°C is 0°, and the water contact angle at 40°C is 125°, showing good thermosensitive hydrophilic-hydrophobic conversion properties. The water contact angle is 0° in the absence of light irradiation, and the water contact angle is 123.6° after 10 minutes of sunlight irradiation, also showing good photosensitive hydrophilic-hydrophobic conversion properties.
[0041] Example 2
[0042] 2 g of cellulose acetate (CA, molecular weight 30,000, acetyl content 39.8 wt%) and 1 g of poly (N-isopropylacrylamide) (PNIPAM, molecular weight 300,000) were added to a mixture of 15 ml of acetone and 10 ml of ethanol, and stirred at room temperature until completely dissolved to obtain a spinning solution.
[0043] The spinning solution was placed in the syringe of the electrospinning machine (20 mL, equipped with a 23G needle), the voltage was 15 kV, the distance from the needle to the collector was 20 cm, the solution advancement rate was 1.0 mL / h, and electrospinning was performed at room temperature to obtain a CA-PNIPAM fiber membrane. The obtained CA-PNIPAM fiber membrane was placed in a 50°C oven for heat treatment for 4 hours to completely remove the residual solvent.
[0044] The CA-PNIPAM fiber membrane was immersed in 100 ml of 0.1 M pyrrole monomer aqueous solution for 4 h, then cooled to 0 ° C, 10 ml of 4 M ammonium persulfate solution was slowly added, and the low temperature immersion was continued for 12 h. After the reaction was completed, the membrane was taken out and washed with deionized water for 3 times, each time for 20 minutes, to obtain a photosensitivity hydrophilic-hydrophobic conversion gel PPy-CA-PNIPAM.
[0045] The photosensitive hydrophilic-hydrophobic conversion gel prepared in this embodiment has a water contact angle of 0° at 20°C and a water contact angle of 119° at 40°C, showing good thermosensitive hydrophilic-hydrophobic conversion properties. The water contact angle is 0° in the absence of light irradiation and is 115° after 10 minutes of sunlight irradiation, also showing good photosensitive hydrophilic-hydrophobic conversion properties.
[0046] Example 3
[0047] 1 g of cellulose acetate (CA, molecular weight 30,000, acetyl content 39.8 wt%) and 2 g of poly (N-isopropylacrylamide) (PNIPAM, molecular weight 300,000) were added to a mixture of 10 ml of acetone and 15 ml of ethanol, and stirred at room temperature until completely dissolved to obtain a spinning solution.
[0048] The spinning solution was placed in the syringe of the electrospinning machine (20 mL, equipped with a 23G needle), the voltage was 15 kV, the distance from the needle to the collector was 20 cm, the solution advancement rate was 1.0 mL / h, and electrospinning was performed at room temperature to obtain a CA-PNIPAM fiber membrane. The obtained CA-PNIPAM fiber membrane was placed in a 65°C oven for heat treatment for 4 hours to completely remove the residual solvent.
[0049] The CA-PNIPAM fiber membrane was immersed in 100 ml of 0.5 M pyrrole monomer aqueous solution for 2 h, then cooled to 10 ° C, 10 ml of 4 M ferric chloride solution was slowly added, and the low temperature immersion was continued for 12 h. After the reaction was completed, the membrane was taken out and washed with deionized water for 3 times, each time for 20 minutes, to obtain a photosensitivity hydrophilic-hydrophobic conversion gel PPy-CA-PNIPAM.
[0050] The photosensitive hydrophilic-hydrophobic conversion gel prepared in this embodiment has a water contact angle of 0° at 20°C and a water contact angle of 128° at 40°C, showing good thermosensitive hydrophilic-hydrophobic conversion properties. The water contact angle is 0° in the absence of light irradiation and is 121° after 10 minutes of sunlight irradiation, also showing good photosensitive hydrophilic-hydrophobic conversion properties.
[0051] Comparative Example 1
[0052] The difference from Example 1 is that carboxymethyl cellulose is used instead of cellulose acetate.
[0053] Due to the high hydrophilicity and viscosity of carboxymethyl cellulose, spinning cannot be carried out smoothly.
[0054] Comparative Example 2
[0055] The difference from Example 1 is that nano-gold is used as the light absorbing material to replace the pyrrole monomer.
[0056] The photosensitive hydrophilic-hydrophobic conversion gel was prepared, and the water contact angle at 20°C was 0°, and the water contact angle at 40°C was 124°, showing good thermosensitive hydrophilic-hydrophobic conversion properties. The water contact angle was 0° in the absence of light irradiation, and the water contact angle was 122° after 10 minutes of sunlight irradiation, also showing good photosensitive hydrophilic-hydrophobic conversion properties. However, the cost is relatively high.
[0057] Comparative Example 3
[0058] The difference from Example 1 is that no electrospinning process is used, and cellulose acetate and poly (N-isopropylacrylamide) are dissolved and then directly spread into a film.
[0059] The 0.3 cm thick film-like photosensitive hydrophilic-hydrophobic conversion gel was prepared, with a water contact angle of 0° at 20°C and 105° at 40°C, showing good thermosensitive hydrophilic-hydrophobic conversion properties. The water contact angle was 0° in the absence of light irradiation and 108° after 10 minutes of sunlight irradiation, also showing good photosensitive hydrophilic-hydrophobic conversion properties. However, the cost is relatively high.
[0060] From the comparison between Example 1 and Comparative Example 1, it can be seen that cellulose acetate has a suitable viscosity after being dissolved in the acetone-ethanol mixture, which can meet the requirements of electrospinning.
[0061] From the comparison between Example 1 and Comparative Example 3, it can be seen that, compared with the spreading film-forming method, the electrospinning method can better improve the photosensitizing hydrophilic-hydrophobic conversion ability of the gel.
[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.
Claims
1. A method for preparing a photosensitive hydrophilic-hydrophobic switching gel, characterized in that: include: dissolving cellulose acetate and PNIPAM in an organic solvent to obtain a spinning solution; The spinning solution is subjected to electrostatic spinning, and after the spinning is completed, the residual solvent is removed to obtain a CA-PNIPAM fiber membrane; The CA-PNIPAM fiber membrane is immersed in a pyrrole monomer aqueous solution, allowed to stand and cooled, and then an oxidant is added to carry out an in-situ polymerization reaction of pyrrole. After the reaction is completed, purification is performed to obtain a photosensitive hydrophilic-hydrophobic conversion gel.
2. The method for preparing the photosensitive hydrophilic-hydrophobic switching gel according to claim 1, characterized in that: The cellulose acetate has a molecular weight of 25,000-35,000 and an acetyl content of 38-42 wt %; or, the molecular weight of PNIPAM is 200,000-400,000; Or, the mass ratio of cellulose acetate to PNIPAM is 2:1-1:
2.
3. The method for preparing the photosensitive hydrophilic-hydrophobic switching gel according to claim 1, characterized in that: The organic solvent is an acetone ethanol solvent, and the ratio of acetone to ethanol is 1:0.5-0.5:1; Alternatively, the mass volume ratio of the total mass of the cellulose acetate and PNIPAM to the acetone ethanol solvent is 1:10-12.
4. The method for preparing the photosensitive hydrophilic-hydrophobic switching gel according to claim 1, characterized in that: The dissolution temperature of the cellulose acetate and PNIPAM in the organic solvent is 20-30°C.
5. The method for preparing the photosensitive hydrophilic-hydrophobic switching gel according to claim 1, characterized in that: The drying temperature when removing residual solvent is 50-65°C.
6. The method for preparing the photosensitive hydrophilic-hydrophobic switching gel according to claim 1, characterized in that: The concentration of the pyrrole monomer aqueous solution is 0.1-0.5M; Alternatively, the CA-PNIPAM fiber membrane is immersed in the pyrrole monomer aqueous solution for 2-4 hours.
7. The method for preparing the photosensitive hydrophilic-hydrophobic switching gel according to claim 1, characterized in that: The temperature after cooling is 0-10°C.
8. The method for preparing the photosensitive hydrophilic-hydrophobic switching gel according to claim 1, characterized in that: The oxidant is ferric chloride or ammonium persulfate; Wherein, the dosage of the oxidant is 0.1-0.6M, 0.2-0.6M or 0.1-0.5M; Alternatively, the pyrrole in-situ polymerization reaction time is 6-12 hours.
9. A photosensitive hydrophilic-hydrophobic switching gel prepared by the method according to any one of claims 1 to 8.
10. Use of the photosensitive hydrophilic-hydrophobic conversion gel according to claim 9 in preparing a water collector.