Synthesis of photoinduced isoazobenzene polymer and preparation of composite film

Abstract

The invention relates to synthesis of a photoisomerized azobenzene polymer and preparation of a composite membrane. A fluorine-containing monomer and an acrylate monomer containing an azobenzene group are subjected to binary copolymerization and spin coating to construct the composite blend membrane. Fluorine-containing azobenzene groups in the copolymer endow the blended membrane with light regulation and control performance on the surface, the membrane surface has relatively high hydrophobicity and excellent membrane surface wettability and light responsiveness, meanwhile, the membrane surface has light energy storage property, can release heat of about 2 DEG C within 5 min at most, and can be used for regulating and controlling the temperature of a human body. The azobenzene polymer with photoinduced reversible conversion performance is prepared through molecular design, and the azobenzene polymer has excellent controllability in the aspects of photothermal conversion and energy storage. Due to the existence of azobenzene groups, isomerization conversion of the polymer can be realized, and the polymer has relatively high light-operated efficiency; the existence of hydrophobic molecules enhances the stability of the membrane. The preparation method is simple, and the prepared reversible light control film is high in interfacial strength and especially suitable for preparation of light response materials.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of stimulus responsive materials, and in particular to the synthesis of a photoisomerized azobenzene polymer and the preparation of a composite film. Background Art

[0002] Smart responsive materials have attracted wide attention due to their numerous applications such as biosensors, microfluidic devices, and smart membranes. To date, various stimulus-responsive smart materials have been widely developed and utilized. Among them, light has gained more attention in the regulation of surface wettability because it can avoid secondary contamination caused by contact with samples, has strong responsiveness, and has high spatial resolution.

[0003] Solar thermal fuels can capture, convert, store and release solar energy in the form of heat through the reversible photoisomerization of molecular photoswitches (such as azobenzene derivatives), and are currently becoming a hot topic of research. The energy storage principle of solar thermal fuels based on azobenzene photoswitches can be explained as follows: azobenzene molecules exist in a trans conformation at room temperature, and the ground state azobenzene molecules absorb photon energy and transform into an excited state, undergoing conformational changes within a few picoseconds to transform into a cis isomer, storing energy in chemical bonds. Under external stimulation, it can return to the trans conformation and release the stored energy in the form of heat. The photoisomerization of azobenzene is a special process that dissipates excess energy of a species by controlling the molecular configuration. To this end, scientists have invested a lot of energy in developing innovative new materials and technologies to achieve effective capture, efficient conversion, stable storage and controllable release of solar energy. Summary of the invention

[0004] In view of the above-mentioned prior art, the purpose of the present invention is to provide a synthesis of photoisomerized azobenzene polymers and preparation of composite films. The preparation method of the present invention is simple, and the azobenzene fluorinated copolymer is synthesized by solution polymerization to give it reversible photoregulation properties in terms of surface wettability and photoenergy storage.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] The present invention provides a method for synthesizing a photoisomerized azobenzene polymer, comprising the following steps:

[0007] A fluorine-containing monomer a and an azobenzene-containing acrylic ester monomer b are added to a solvent a in a molar ratio of 9:1 to 1:9, and nitrogen protection is performed; a free radical solution polymerization reaction is performed using azobisisobutyronitrile as an initiator; a polymer generated by the reaction is post-treated and then dried to prepare a binary random copolymer, and the molecular weight of the prepared binary random copolymer is 9000-16000, and the molecular weight distribution is also relatively narrow.

[0008] Furthermore, the fluorine-containing monomer a is trifluoroethyl methacrylate, tetrafluoropropyl methacrylate, octafluoropentyl methacrylate, etc.

[0009] Furthermore, the azobenzene group-containing acrylic ester monomer b is 6-[4-[2-[4-(trifluoromethyloxy)phenyl]diazo]phenoxy]hexyl acrylate, 4-trifluoromethoxyazobenzene acrylate or azobenzene hexyloxy acrylate, azobenzene acrylate, and the like.

[0010] Furthermore, the solvent a is N,N-dimethylformamide, N,N-dimethylacetamide or tetrahydrofuran.

[0011] Furthermore, the temperature of the free radical solution polymerization reaction is 60-80° C., the reaction time is 12-48 hours, and the post-treatment drying is 30° C. vacuum oven drying for 24-48 hours.

[0012] Furthermore, the specific process of post-treatment of the polymer generated by the reaction is as follows: after the reaction is completed, the mixed solution is added dropwise to 200 ml of deionized water. The obtained precipitate is dissolved in tetrahydrofuran, and precipitated in distilled water, methanol, ethanol or anhydrous ether, and the dissolution and precipitation are repeated 2-4 times.

[0013] The present invention also provides a method for preparing a photoisomerized azobenzene polymer composite film, comprising the following steps:

[0014] (1) preparing an azobenzene fluorinated copolymer according to the above method;

[0015] (2) dissolving the binary random copolymer of step (1) in solvent b and subjecting to ultrasonic treatment to obtain an azobenzene fluorinated copolymer solution;

[0016] (3) Spin-coating the azobenzene fluorinated copolymer solution obtained in step (2) onto a substrate, and drying the spin-coated sample under a vacuum environment at 30° C. for 12 hours to form a light control film after drying.

[0017] Furthermore, in step (2), the solvent b is N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, dichloromethane or chloroform.

[0018] Furthermore, in the step (2), the concentration of the azobenzene fluorinated copolymer solution is 1-20 wt %.

[0019] Furthermore, the substrate can be any substrate that needs to form the composite film. In the present invention, the substrate is a glass substrate, a ceramic substrate, a metal substrate, etc., and is not limited to a glass substrate.

[0020] Furthermore, in step (3), the specific steps of spin coating are: 50-150 μl of fluorinated azo copolymer, the spin coating time is 30-120 seconds, and the spin coating speed is 1000-3000 rpm.

[0021] The present invention constructs a composite film by spin coating by binary copolymerization of a fluorine-containing monomer and an acrylate monomer containing an azobenzene group. The fluorine-containing azobenzene group in the copolymer gives the film surface light control performance, and the film surface has both relatively high hydrophobicity and excellent film surface wettability and light responsiveness, and also has light energy storage properties, and can release heat up to about 2 degrees Celsius within 5 minutes, which can be used to control human body temperature.

[0022] The present invention has the following beneficial effects: the present invention prepares azobenzene polymers with photoinduced reversible transformation properties through molecular design, and has excellent controllability in terms of photothermal conversion and energy storage. The presence of azobenzene groups enables the polymer to achieve isomerization transformation and has a high light control efficiency; at the same time, the presence of hydrophobic molecules enhances the stability of the film, and the film surface will not be damaged after repeated irradiation; the preparation method of the present invention is simple, and the interface strength of the prepared reversible light control film is high, which is particularly suitable for the preparation of light-responsive materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Reaction equation of azobenzene polymer

[0024] Figure 2 Infrared thermal imaging characterizes the heat release effect of materials under room temperature light excitation DETAILED DESCRIPTION

[0025] In order to make the technical problems, technical solutions and advantages to be solved by the present invention more clear, a detailed description will be given below in combination with specific embodiments and comparative examples. Embodiment 1: A synthesis of a photoisomerized azobenzene polymer and preparation of a composite film, comprising the following steps: (1) 3 g of 2,2,3,3-tetrafluoromethyl acrylate (TFPMA), 7 g of 6-[4-[2-[4-(trifluoromethyloxy)phenyl]diazo]phenoxy]hexyl acrylate, 25 mL of N,N-dimethylformamide and 0.1 g of AIBN were added to a 150 mL single-mouth bottle and protected with N2. After 15 minutes of magnetic stirring at room temperature, the temperature was raised to 80°C and the reaction was stopped after 24 hours. After the reaction was completed, the product solution was added dropwise to 200 mL of deionized water, stirred, filtered out the precipitate, and dried. The obtained crude product was repeatedly dissolved and reprecipitated three times with tetrahydrofuran, and the obtained orange solid was collected and dried in a vacuum oven at 30°C for 48 hours to obtain a binary random copolymer of TFPMA and 6-[4-[2-[4-(trifluoromethyloxy)phenyl]diazo]phenoxy]hexyl acrylate. (2) 0.2 g of the binary random copolymer was dissolved in 4.3 mL of tetrahydrofuran and subjected to ultrasonic treatment for 10 minutes. (3) Take 100 μL of the copolymer solution obtained in step (2) and spin coat it on a glass slide to form a film. The spin coating speed is 2000 rpm and the spin coating time is 60 seconds. Finally, place the spin-coated glass slide in a vacuum oven at 30° C. for 2 hours. (4) The thermal release effect of the material under light excitation at room temperature was characterized by infrared thermal imaging, where the maximum heat release temperature can reach 1.5°C. Embodiment 2: A synthesis of a photoisomerized azobenzene polymer and preparation of a composite film, comprising the following steps: (1) 3 g of 2,2,3,3-tetrafluoromethyl acrylate (TFPMA), 7 g of 6-[4-[2-[4-(trifluoromethyloxy)phenyl]diazo]phenoxy]hexyl acrylate, 25 mL of N,N-dimethylformamide and 0.1 g of AIBN were added to a 150 mL single-mouth bottle and protected with N2. After 15 minutes of magnetic stirring at room temperature, the temperature was raised to 80°C and the reaction was stopped after 24 hours. After the reaction was completed, the product solution was added dropwise to 200 mL of deionized water, stirred, filtered out the precipitate, and dried. The obtained crude product was repeatedly dissolved and reprecipitated three times with tetrahydrofuran, and the obtained orange solid was collected and dried in a vacuum oven at 30°C for 48 hours to obtain a binary random copolymer of TFPMA and 6-[4-[2-[4-(trifluoromethyloxy)phenyl]diazo]phenoxy]hexyl acrylate. (2) 0.2 g of the binary random copolymer was dissolved in 2.1 mL of tetrahydrofuran and subjected to ultrasonic treatment for 10 minutes. (3) Take 100 μL of the copolymer solution obtained in step (2) and spin coat it on a glass slide to form a film. The spin coating speed is 2000 rpm and the spin coating time is 60 seconds. Finally, place the spin-coated glass slide in a vacuum oven at 30° C. for 2 hours. (5) The thermal release effect of the material under light excitation at room temperature was characterized by infrared thermal imaging, where the maximum heat release temperature can reach 1°C.

Claims

1. A synthesis of a photoisomerized azobenzene polymer and preparation of a composite film, characterized in that: (1) A fluorine-containing monomer a and an azobenzene-containing acrylic ester monomer b are added to a solvent a at a molar ratio of 9:1 to 1:9, and the mixture is protected by nitrogen; a free radical solution polymerization reaction is carried out using azobisisobutyronitrile as an initiator; the polymer generated by the reaction is post-treated and then dried to prepare a binary random copolymer, wherein the molecular weight of the prepared binary random copolymer is 9000-16000, and the molecular weight distribution is also relatively narrow. (2) The binary random copolymer is dissolved in solvent b and subjected to ultrasonic treatment to obtain an azobenzene fluorinated copolymer solution, which is then spin-coated on a substrate. The spin-coated sample is dried at 30° C. in a vacuum environment for 12 hours to form a light control film.

2. The method according to claim 1, characterized in that: In step (1), the fluorine-containing monomer a is trifluoroethyl methacrylate, tetrafluoropropyl methacrylate, octafluoropentyl methacrylate, etc.

3. The method according to claim 1, characterized in that: In step (1), the azobenzene group-containing acrylate monomer b is 6-[4-[2-[4-(trifluoromethyloxy)phenyl]diazo]phenoxy]hexyl acrylate, 4-trifluoromethoxyazobenzene acrylate or azobenzene hexyloxy acrylate, azobenzene acrylate, etc.

4. The method according to claim 1, characterized in that: In step (1), the solvent a is N,N-dimethylformamide, N,N-dimethylacetamide or tetrahydrofuran.

5. The method according to claim 1, characterized in that: In step (1), the temperature of the free radical solution polymerization reaction is 60-80° C., the reaction time is 12-48 hours, and the post-treatment drying is 30° C. vacuum oven drying for 24-48 hours.

6. The method according to claim 1, characterized in that: In step (1), the polymer generated by the reaction is subjected to post-treatment as follows: after the reaction is completed, the mixed solution is added dropwise to 200 ml of deionized water. The obtained precipitate is dissolved in tetrahydrofuran and precipitated in distilled water, methanol, ethanol or anhydrous ether, and the dissolution and precipitation are repeated 2-4 times.

7. The method according to claim 1, characterized in that: In step (2), solvent b is N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, dichloromethane or chloroform.

8. The method according to claim 1, characterized in that: In step (2), the concentration of the azobenzene fluorinated copolymer solution is 1-20 wt %.

9. The method according to claim 1, characterized in that: In step (2), the substrate can be any substrate that needs to form the composite film. In the present invention, the substrate is a glass substrate, a ceramic substrate, a metal substrate, etc., but is not limited to a glass substrate.

10. The method according to claim 1, characterized in that: In step (2), the specific steps of spin coating are: 50-150 μl of fluorinated azo copolymer, the spin coating time is 30-120 seconds, and the spin coating speed is 1000-3000 rpm.

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