Light / humidity dual-response liquid crystal polymer as well as preparation method and application thereof

Abstract

The invention relates to a liquid crystal polymer, in particular to a light / humidity double-response liquid crystal polymer as well as a preparation method and application thereof, the chemical formula of the liquid crystal polymer is PABnNHm, and the structural formula of the liquid crystal polymer is as shown in formula (I): # imgabs0 #. Compared with the prior art, introduction of a non-traditional humidity-sensitive group is realized; the liquid crystal polymer has excellent light / humidity dual-response deformation performance and a rapid pH response color changing function.

Description

Technical Field

[0001] The invention relates to a liquid crystal polymer, in particular to a light / humidity dual-responsive liquid crystal polymer and a preparation method and application thereof. Background Art

[0002] In the new era of smart materials, multi-stimulus responsive liquid crystal polymers have attracted extensive attention due to their ability to exhibit rich deformation, color change and multiple functions in complex environments. However, due to the limitations of functional group tolerance in direct polymerization methods, many stimuli-responsive functional groups cannot be introduced into liquid crystal polymers by direct polymerization.

[0003] Post-polymerization modification (PPM) provides an efficient and universal strategy to solve this problem. Its main principle is to first synthesize a reactive polymer precursor, and then introduce the functional group into the polymer precursor by chemical modification, thereby breaking the limitation of direct polymerization. Although methods for preparing liquid crystal polymers using PPM have been reported, they are limited by the applicable scope of each reaction type and chemical monomer, and relevant reports are rare. In addition, the preparation method is relatively complicated and the obtained products still have many performance limitations.

[0004] In order to further expand the application scope of PPM, especially its universality in the field of multi-responsive functional liquid crystal polymers, and to fully tap its application potential, it is necessary to further explore the synergistic preparation effect of PPM combined with other methods, and propose a more comprehensive and reliable multi-stimulus responsive liquid crystal polymer. Researchers have previously prepared a light / humidity dual-responsive linear liquid crystal polymer containing carboxyl groups by combining ring-opening metathesis polymerization (ROMP) with PPM. This study uses the traditional hydrophilic group - carboxyl to form a carboxylic acid dimer due to hydrogen bonding in the system, and the dimer is treated with alkali to form a hygroscopic carboxylate ion, thereby showing humidity sensitivity. However, the humidity response deformation of this type of material still takes a long time (about 1 minute).

[0005] Therefore, it is still necessary to further explore and obtain light / humidity dual-responsive liquid crystal polymers with high practical application value. Summary of the invention

[0006] The purpose of the present invention is to provide a light / humidity dual-responsive liquid crystal polymer and its preparation method and application in order to solve at least one of the above problems, so as to solve the defect of long response time of light / humidity dual-responsive materials in the prior art, realize the introduction of non-traditional humidity-sensitive groups, and make the liquid crystal polymer have excellent light / humidity dual-responsive deformation performance and rapid pH response color change function. The humidity-sensitive group dimethylamino in the polymer can be easily quaternized by acidic solution treatment to produce a cationic polymer. After one side of the liquid crystal polymer film is contacted with an acidic solution (activated), through this "activation" process, the -N(CH3)2 group can be converted into -NH with a stronger electron-withdrawing effect. + (CH3)2 group means that the protonation of dimethylamino group is completed. The increase in hydrophilicity of the acid-treated side of the liquid crystal polymer surface after activation makes the polymer asymmetric sensitive to moisture, that is, the activated surface side expands when the relative humidity of the environment increases, while the inactivated side surface remains hydrophobic and does not expand. Therefore, when the polymer film is immersed in water or exposed to moisture, it will bend toward the inactivated surface due to the stress gradient generated by the film thickness, showing a rapid humidity response behavior.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] The first aspect of the present invention discloses a light / humidity dual-responsive liquid crystal polymer, wherein the chemical formula of the liquid crystal polymer is PAB n NH m , the structural formula is shown in formula (I):

[0009]

[0010] Preferably, the liquid crystal polymer is PAB n NH m , m and n are positive integers not exceeding 5 respectively, that is, m:n=1:5-5:1.

[0011] More preferably, m:n=1:1 or 1:2 or 2:1.

[0012] The second aspect of the present invention discloses a method for preparing the light / humidity dual-responsive liquid crystal polymer as described above, comprising the following steps:

[0013] S1: Reactive liquid crystal polymer precursor PAB is prepared by ring-opening metathesis polymerization of a liquid crystal monomer CAB containing an azobenzene group and a monomer containing a reactive pentafluorophenyl ester group PFP n PFP m ;

[0014] S2: Using the humidity-responsive primary amine small molecule 2-dimethylaminoethylamine and the reactive liquid crystal polymer precursor PAB obtained in step S1 n PFP m Performing a post-polymerization modification reaction to prepare the liquid crystal polymer PAB n NH m .

[0015] Preferably, the azobenzene-containing liquid crystal monomer CAB is prepared by the following method:

[0016] In an anhydrous dichloromethane environment, in the presence of a catalyst and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC), 4'-(11-hydroxyundecanyloxy)-4-n-hexyloxyazobenzene reacts with 5-succinate-1-cyclooctene, and a crude product is obtained by vacuum distillation. After column chromatography and recrystallization, a CAB monomer is obtained.

[0017] Preferably, the catalyst is 4-dimethylaminopyridine (DMAP);

[0018] The molar ratio of 4'-(11-hydroxyundecyloxy)-4-n-hexyloxyazobenzene to 5-succinate-1-cyclooctene is 1:1.2-1:8, and the reaction is carried out at room temperature overnight;

[0019] The recrystallization uses methanol as solvent.

[0020] Generally, in order to ensure that azobenzene is fully reacted, cyclooctene is slightly excessive, and the ratio can be between 1:1.2 and 1:8, preferably 1:1.5.

[0021] The equation for preparing CAB monomer is as follows:

[0022]

[0023] Preferably, the monomer containing the reactive pentafluorophenyl ester group PFP is prepared by the following method:

[0024] In an anhydrous dichloromethane environment, 5-succinate-1-cyclooctene reacts with thionyl chloride to obtain a crude product, which is then distilled under reduced pressure to obtain an intermediate;

[0025] In an anhydrous dichloromethane environment and in the presence of triethylamine, pentafluorophenol reacts with the intermediate, and a crude product is obtained after column chromatography and reduced pressure rotary evaporation, and a PFP monomer is obtained by vacuum drying and crystallization.

[0026] Preferably, 5-succinate-1-cyclooctene is reacted with excess thionyl chloride, thionyl chloride is added dropwise to 5-succinate-1-cyclooctene in an ice-water bath, and the reaction is carried out at 50° C. overnight under the protection of a reflux device;

[0027] The mass ratio of pentafluorophenol to the intermediate is 2:2.6;

[0028] Triethylamine was added dropwise to the mixture of pentafluorophenol and the intermediate, and the mixture was stirred for 3 h in an ice-water bath and then reacted at room temperature for 12 h.

[0029] The vacuum drying temperature was 40°C and the crystallization temperature was -20°C.

[0030] The equation for preparing PFP monomer is as follows:

[0031]

[0032] Preferably, the ring-opening metathesis polymerization reaction is carried out in an inert gas atmosphere using a Grubbs second generation catalyst at 45° C. for 3-4 hours; vinyl ethyl ether is used to terminate the reaction, and after the reaction, methanol is used for washing and vacuum drying is performed at 40° C.

[0033] Preparation of PAB n PFP m The equation is as follows:

[0034]

[0035] Preferably, the post-polymerization modification reaction is carried out in the presence of tetrahydrofuran at 50° C. for 3-5 hours; after the reaction, the product is washed with methanol and vacuum dried at 40° C. overnight.

[0036] Preparation of PAB n NH m The equation is as follows:

[0037]

[0038] The third aspect of the present invention discloses an application of the light / humidity dual-responsive liquid crystal polymer as described above in a multi-stimulus responsive film.

[0039] The working principle of the present invention is:

[0040] Firstly, a linear liquid crystal polymer precursor with high molecular weight and high reactivity was synthesized by ring-opening metathesis polymerization (ROMP). Then, a linear liquid crystal polymer material with excellent light / humidity dual-responsive deformation properties was prepared by post-modification method using 2-dimethylaminoethylamine as the humidity-responsive group.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] The polymer synthesis steps proposed by the present invention are simple, and the linear structure without chemical crosslinking enables it to be processed by melting and solution methods, and the molding size and shape are unlimited. The polymer after processing and molding will change its shape under the conditions of specific wavelength light and certain humidity, and can be restored by changing the conditions, so that it can be repeatedly recycled. In addition, the light and humidity response deformation ability of this polymer can be greatly regulated by regulating the spacers on both sides of the azobenzene element and the alkyl chain primary amine small molecules containing different humidity response groups.

[0043] The present invention proves that non-traditional moisture-sensitive groups are also compatible with post-polymerization modification methods, further demonstrating its universality. In the prior art, there is a traditional carboxyl group as a hydrophilic group, which forms a carboxylic acid dimer based on hydrogen bonding in the system, and the dimer is treated with alkali to form a hygroscopic carboxylate ion, thereby showing moisture sensitivity; while the dimethylamino group used in the present invention is protonated by acid treatment to form a quaternary ammonium cation to achieve moisture sensitivity. Although both are humidity responsive, the presence of carboxylic acid dimers tends to make such polymers brittle. For the first time, the present invention introduces non-traditional moisture-sensitive groups into a linear liquid crystal polymer system through the PPM method. The dimethylamino group in the polymer can be easily quaternized by acidic solution treatment. This type of quaternary ammonium cation can quickly turn the yellow polymer into red and give the material more functionality, which further expands the universality of preparing multi-stimulus responsive liquid crystal polymers by combining ROMP and PPM.

[0044] Since the linear structure of liquid crystal polymer has good processability, the liquid crystal material can be compounded with the commercial PP membrane by solution spraying, and bionic flowers, lifting micro-robots, and bionic gripper actuators can be constructed. Under the combined action of light / humidity, they can not only simulate the opening and closing and withering of flowers in nature, but also grasp, carry and release objects, and can lift objects that are more than 20 times their own mass.

[0045] (1) The synthesis steps of the present invention are simple, and the synthesis of the polymer can be completed in two steps (ROMP+PPM), which greatly simplifies the complex reaction steps of existing liquid crystal polymers. In addition, the reaction temperature required by the present invention is lower than 100°C, no deoxygenation is required, and the requirements for the reaction environment and equipment are low, which is suitable for large-scale production.

[0046] (2) The obtained material has a linear structure and has better processing performance than traditional cross-linked liquid crystal polymers. It is fusible and soluble and can be processed into a variety of complex structures to meet the needs of practical applications.

[0047] (3) Different types of humidity-responsive groups can be replaced by simply adjusting the structure of the alkyl chain primary amine compound modified by polymerization with the PFP group, thus not being limited to traditional carboxyl groups, etc., and thus the mechanical strength, thermodynamic properties, and dual-responsive deformation properties of the material can be effectively adjusted to adapt to different application scenarios.

[0048] (4) The processed thin films or other materials with two-dimensional / three-dimensional structures can undergo one or more deformations under the stimulation of light and humidity, giving full play to the control advantages of light as a stimulus source, which is remote, precise, fixed-point, and has good wavelength selectivity.

[0049] (5) On the one hand, the present invention demonstrates that the post-polymerization modification method is highly convenient and versatile in the field of preparing multi-stimulus responsive liquid crystal polymers; on the other hand, it can be regarded as an extension of the post-polymerization modification method in the field of liquid crystal polymers. At the same time, it also strongly proves that this method of combining ROMP with PPM provides an extremely convenient and promising synthetic strategy for preparing multifunctional liquid crystal polymer materials, that is, through reasonable molecular design and precise control of reaction conditions, it can theoretically be expanded to any multi-responsive liquid crystal polymers. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 Schematic diagram of the microrobot response of Application Example 1, including (a) theoretical flow chart, (b) experimental flow chart;

[0051] Figure 2 Schematic diagram of the response of the bionic flower of Application Example 2, wherein (a) is a theoretical flow chart, and (b) is an experimental flow chart;

[0052] Figure 3 Schematic diagram of the response of the bionic gripper of Application Example 3, including: (a) gripper structure diagram, (b) grasping object diagram; and (c) experimental flow chart. DETAILED DESCRIPTION

[0053] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0054] If not otherwise specified in the following description, the reagents may be commercially available products, and the methods may be those known in the art.

[0055] In the following examples, the relevant chemical reagents used to synthesize liquid crystal monomers and polymers are shown in Table 1 below.

[0056] Table 1 Reagent information

[0057]

[0058] In addition, the dichloromethane solvent used in the ring-opening metathesis polymerization process needs to be distilled and purified with calcium hydride (CaH2), and other conventional reagents and commonly used inorganic chemical reagents such as methanol, ethanol, acetone, toluene, etc. are all purchased from Sinopharm Company as analytical grade reagents.

[0059] Example 1

[0060] The polymer molecular chain is a linear structure. The photoresponsive azobenzene group and the humidity responsive group are both located in the main chain of the polymer. There is no other chemical or physical crosslinking between the molecular chains. It is first prepared by ring-opening metathesis polymerization of a liquid crystal monomer CAB containing an azobenzene group and a monomer containing a reactive pentafluorophenyl ester group PFP to obtain a reactive liquid crystal polymer precursor PAB. n PFP m In this embodiment, the m:n ratio of 2:1 is preferably used for preparation and subsequent related experiments. This is because when m:n is 2:1, there is a higher ratio of reactive pentafluorophenyl ester groups, and more functional groups can be connected through post-modification. Subsequently, the humidity-responsive primary amine small molecule 2-dimethylaminoethylamine is used to perform a polymerization post-modification reaction with the PFP therein, thereby obtaining a liquid crystal polymer material PAB1NH2 with light-humidity dual-responsive deformation properties.

[0061] The main synthetic route of the polymer is as follows:

[0062] 1) Preparation of azobenzene liquid crystal monomer CAB:

[0063] The synthetic route of monomer CAB is shown in the following equation:

[0064]

[0065] In a 250 mL eggplant-shaped bottle, add 2.3 g (5 mmol) of 4'-(11-hydroxyundecyloxy)-4-n-hexyloxyazobenzene, 1.7 g (7.5 mmol) of 5-succinate-1-cyclooctene and 0.6 g (5 mmol) of catalyst DMAP, dissolve in 100 mL of anhydrous dichloromethane, and stir thoroughly. Then, use a dropping funnel to slowly drop 20 mL of anhydrous dichloromethane solution containing 2.88 g (15 mmol) of EDC (ultrasound can be used to promote the dissolution of EDC), and react at room temperature overnight. Then, the solvent is removed by distillation under reduced pressure to obtain a crude product. And column chromatography operation is performed. Then, recrystallization is performed using methanol, and after filtering, washing and drying, a high-purity CAB monomer is obtained.

[0066] 2) Preparation of reactive monomer PFP:

[0067] The synthetic route of monomer PFP is shown in the following equation:

[0068]

[0069] The synthetic route includes two steps. First, the reaction intermediate 1 is synthesized. The specific experiment is as follows: In a 250mL eggplant-shaped bottle, 5-succinate-1-cyclooctene (2.5g, 11mmol) is added and dissolved in 30mL of anhydrous dichloromethane. Then dichlorothionyl SOCl2 (2.6g, 22mmol) is dissolved in 20mL of anhydrous dichloromethane. Under ice-water bath conditions, dichloromethane containing SOCl2 is slowly added dropwise to the eggplant-shaped bottle, and stirred for 30min under this condition, and then reacted at 50°C overnight for 12h under the protection of a reflux device to obtain a crude product. Dichloromethane and excess SOCl2 are removed by reduced pressure distillation, and the yellow-brown solution intermediate 1 is collected.

[0070] Subsequently, pentafluorophenol (2.0 g, 11 mmol) was weighed, and 2.6 g of intermediate 1 was added to a 250 mL eggplant-shaped bottle, and then 80 mL of anhydrous CH2Cl2 was added to dissolve. Subsequently, triethylamine Et3N (1.6 mL, 12 mmol) was pre-dried with anhydrous magnesium sulfate (MgSO4), and then Et3N was slowly added dropwise to the reaction mixture and stirred for 3 h under an ice-water bath, and then the reaction was continued at room temperature for 12 hours. After the reaction was completed, silica gel powder was mixed and sampled, and the desired product was collected by column chromatography, and then the oily monomer PFP was obtained by vacuum rotary evaporation, and it was placed in a 40 ° C vacuum oven and dried overnight, and then taken out and placed in a -20 ° C refrigerator to crystallize to obtain a white solid (3.6 g, with a yield of 81.2%).

[0071] 3) Preparation of reactive liquid crystal copolymer precursor PAB1PFP2:

[0072] The synthesis steps of the liquid crystal copolymer precursor are shown in the equation:

[0073]

[0074] First, the monomers PFP and CAB were put into a 10mL reaction tube in a certain ratio (2:1), and then the vacuum-argon operation was repeated three times. A small amount of dichloromethane solution was injected into the reaction bottle with a 1mL syringe for dissolution and dilution, and then a corresponding volume of Grubbs 2nd generation catalyst (the molar ratio of catalyst to CAB monomer is about 1:1000) in dichloromethane solution was injected, and then reacted at 45°C for 3-4 hours under the protection of argon atmosphere. After the reaction, a small amount of dichloromethane solution containing vinyl ethyl ether was added to the reaction tube to terminate the polymerization reaction, and the diluted reaction solution was gradually added dropwise to methanol, and a yellow silky precipitate appeared. After suction filtration, it was washed with methanol several times and placed in a 40°C vacuum oven to fully dry to obtain a yellow polymer (PAB1PFP2 copolymer).

[0075] By controlling the molar ratio (m:n) of the two monomers, a series of PABs with different structural unit ratios can be synthesized. n PFP m Copolymers, such as PAB1PFP1, PAB2PFP1, PAB3PFP1, etc.

[0076] 4) Preparation of light / humidity dual-responsive liquid crystal copolymer PAB1NH2:

[0077] The preparation steps of the light / humidity dual-responsive liquid crystal copolymer are shown in the equation:

[0078]

[0079] First, weigh 50 mg of PAB1PFP2 sample into a 10 mL reaction tube using a balance, then add 3-5 drops of 2-dimethylaminoethylamine solution, then add 1-2 mL of tetrahydrofuran (THF) solution, and stir for 3-5 hours at 50°C. Subsequently, the product is precipitated from methanol, filtered under reduced pressure and washed several times, and then dried in a vacuum oven at 40°C overnight to obtain PAB1NH2, which is collected for later use.

[0080] 5) Preparation of light / humidity dual-responsive liquid crystal copolymer composite films

[0081] The liquid crystal copolymer composite film is prepared by a solution method, and the specific steps are as follows: 40-50 mg of the copolymer PAB1NH2 is weighed and dissolved in about 1 mL of toluene in a fume hood to prepare a solution with a mass fraction of 5 wt%. The prepared solution is then loaded into a small sprayer and repeatedly sprayed on a commercial PP diaphragm with a size of 3 cm×3 cm, and then the PP diaphragm is moved horizontally into a 35°C oven. After the toluene solution is completely evaporated, a double-layer composite film with one side being yellow and the other side being off-white is obtained, which is cut to remove uneven and defective parts and stored for later use. At the same time, the liquid crystal copolymer can be dissolved again by an organic good solvent (such as toluene) or heated to a higher temperature to make it a molten state, so as to achieve material recycling.

[0082] The application method of the composite material of the linear liquid crystal polymer with dual light and humidity responses and reversible response deformation comprises the following steps:

[0083] Step 1: Prepare a polymer / PP diaphragm composite material by a solution method such as drop coating or spray coating;

[0084] Step 2: Use 1 to 50 mW / cm 2 , 365nm ultraviolet light irradiates the sample, and the illuminated position of the sample will bend away from the light source;

[0085] Step 3: Use 1-50mW / cm 2, 530nm green light is irradiated on the sample, and the bent sample will return to its initial straight state.

[0086] Step 4: Use a common small handheld humidifier to spray water mist at a certain point on the sample, and the sample will bend away from the direction of the water mist spray.

[0087] Step 5: Use power of 1-1000mW / cm 2 , an 808nm near-infrared light source is directed toward the sample, and the bent sample will return to its initial straight state.

[0088] Steps 2 to 5 can be repeated multiple times.

[0089] Example 2

[0090] In this embodiment, the ratio of m:n is 1:1 for preparation and subsequent related experiments. First, the azobenzene liquid crystal monomer CAB and the reactive monomer PFP are prepared by the method in Example 1, and then the monomers PFP and CAB are put into a 10mL reaction tube in a certain ratio (1:1), and then the vacuum-argon operation is repeated three times, and a small amount of dichloromethane solution is injected into the reaction bottle with a 1mL syringe for dissolution and dilution, and then the corresponding volume of Grubbs 2nd generation catalyst (the molar ratio of catalyst to CAB monomer is about 1:1000) is injected into the dichloromethane solution, and then reacted at 45°C for 3-4 hours under the protection of argon atmosphere. After the reaction is completed, a small amount of dichloromethane solution containing vinyl ethyl ether is added to the reaction tube to terminate the polymerization reaction, and the diluted reaction solution is gradually added dropwise to methanol, and a yellow silky precipitate appears. After suction filtration, it is washed with methanol several times, and placed in a 40°C vacuum oven to fully dry to obtain a yellow polymer (PAB1PFP1 copolymer).

[0091] Further according to step 4) in Example 1, PAB1NH1 was prepared; further according to step 5) in Example 1, a light / humidity dual-responsive liquid crystal copolymer composite film was prepared.

[0092] Example 3

[0093] In this embodiment, the ratio of m:n is 1:2 for preparation and subsequent related experiments. First, the azobenzene liquid crystal monomer CAB and the reactive monomer PFP are prepared by the method in Example 1, and then the monomers PFP and CAB are put into a 10mL reaction tube in a certain ratio (1:2), and then the vacuum-argon operation is repeated three times, and a small amount of dichloromethane solution is injected into the reaction bottle with a 1mL syringe for dissolution and dilution, and then the corresponding volume of Grubbs 2nd generation catalyst (the molar ratio of catalyst to CAB monomer is about 1:1000) is injected into the dichloromethane solution, and then reacted at 45°C for 3-4 hours under the protection of argon atmosphere. After the reaction is completed, a small amount of dichloromethane solution containing vinyl ethyl ether is added to the reaction tube to terminate the polymerization reaction, and the diluted reaction solution is gradually added dropwise to methanol, and a yellow silky precipitate appears. After suction filtration, it is washed with methanol several times, and placed in a 40°C vacuum oven to fully dry to obtain a yellow polymer (PAB2PFP1 copolymer).

[0094] Further according to step 4) in Example 1, PAB2NH1 was prepared; further according to step 5) in Example 1, a light / humidity dual-responsive liquid crystal copolymer composite film was prepared.

[0095] Application Example 1

[0096] Light / humidity dual-responsive lifting microrobot:

[0097] like Figure 1 As shown in (a) and 1(b), the dual-responsive liquid crystal polymer PAB1NH2 prepared by steps 1)-4) in Example 1 is compounded with an oriented polypropylene (PP) membrane by step 5) to obtain a double-layer film, and the strips formed by the double-layer film are cross-spliced ​​into a microrobot.

[0098] The microrobot with a mass of about 40 mg was able to arch upward after acid treatment and when the relative humidity increased to 80%, and lifted a glass ball (850 mg) that was about 20 times its own mass to a height of about 6 mm. -2 ) (about 10s), the lifting robot gradually became flat from the arched state, and finally became flat under the green light (530nm, 50mW·cm -2 ) and can return to its original shape under the irradiation of sunlight, which shows that it has good working ability.

[0099] Application Example 2

[0100] Light / humidity dual-responsive bionic flowers:

[0101] like Figure 2As shown in (a) and 2(b), the dual-responsive liquid crystal polymer PAB1NH2 prepared by steps 1)-4) in Example 1 is compounded with an oriented polypropylene (PP) diaphragm by step 5) to obtain a double-layer film, and the strips formed by the double-layer film are spliced ​​into bionic flowers.

[0102] When the relative humidity gradually increases from 35% to 98%, the liquid crystal layer absorbs moisture and expands due to its humidity responsiveness, and bends toward the PP film, causing the petals to change from lying flat to standing upright. When ultraviolet light (365nm, 30mW·cm -2 ) irradiates the flowers for about 10 seconds, the irradiated petals will show avoidance behavior away from ultraviolet light, thereby protecting themselves from harmful ultraviolet light. In particular, the flowers were sprayed with a diluted HCl solution (pH = 4) to simulate the scene of acid rain in nature (pH < 5.6). The results showed that after being wetted by "acid rain", the originally upright petals gradually softened and collapsed, showing a behavior similar to "withering"; at the same time, the color of the petals also quickly changed from yellow to red. When the withered flowers were subsequently sprayed with normal water mist (pH = 7), their color could be restored to their original state in a short time. The occurrence of this phenomenon is related to the molecular structure of the PAB1NH2 material. After contacting a strong acid, a conjugated paraquinone structure formed by protonation exists in the molecule, and its color change mechanism is similar to that of methyl orange.

[0103] Application Example 3

[0104] Light / humidity dual-response bionic gripper:

[0105] like Figure 3 As shown in (a), 3(b), and 3(c), the dual-responsive liquid crystal polymer PAB1NH2 prepared by steps 1)-4) in Example 1 is compounded with an oriented polypropylene (PP) membrane by step 5) to obtain a double-layer film, and the strips formed by the double-layer film are spliced ​​into a bionic gripper.

[0106] In ultraviolet light (365nm, 30mW·cm -2 ) for 10 seconds, the inner liquid crystal layer deforms with backlight, the gripper bends inward, grabs the paper ball and lifts it up; when the relative humidity gradually increases and is greater than 80%, the inner liquid crystal layer absorbs water and swells, the gripper expands outward, and releases the paper ball to fall somewhere, demonstrating the ability of the bionic actuator to grasp, move and release objects under the dual stimulation of light and humidity, and the device can also be used multiple times.

[0107] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A light / humidity dual-responsive liquid crystal polymer, characterized in that: The chemical formula of the liquid crystal polymer is PAB n NH m , the structural formula is shown in formula (I):

2. The light / humidity dual-responsive liquid crystal polymer according to claim 1, characterized in that: The liquid crystal polymer is PAB n NH m , m and n are positive integers not exceeding 5 respectively.

3. A method for preparing the light / humidity dual-responsive liquid crystal polymer as claimed in claim 1 or 2, characterized in that: The steps include: S1: Reactive liquid crystal polymer precursor PAB is prepared by ring-opening metathesis polymerization of liquid crystal monomers containing azobenzene groups and monomers containing reactive pentafluorophenyl ester groups n PFP m ; S2: Using the humidity-responsive primary amine small molecule 2-dimethylaminoethylamine and the reactive liquid crystal polymer precursor PAB obtained in step S1 n PFP m Performing a post-polymerization modification reaction to prepare the liquid crystal polymer PAB n NH m .

4. The method for preparing a light / humidity dual-responsive liquid crystal polymer according to claim 3, characterized in that: The liquid crystal monomer containing an azobenzene group is prepared by the following method: In the presence of a catalyst and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride in an anhydrous dichloromethane environment, 4'-(11-hydroxyundecyloxy)-4-n-hexyloxyazobenzene reacts with 5-succinate-1-cyclooctene, and a crude product is obtained by vacuum distillation. After column chromatography and recrystallization, a liquid crystal monomer containing an azobenzene group is obtained.

5. The method for preparing a light / humidity dual-responsive liquid crystal polymer according to claim 4, characterized in that: The catalyst is DMAP; The molar ratio of 4'-(11-hydroxyundecyloxy)-4-n-hexyloxyazobenzene to 5-succinate-1-cyclooctene is 1:1.2-1:8, and the reaction is carried out at room temperature overnight; The recrystallization uses methanol as solvent.

6. The method for preparing a light / humidity dual-responsive liquid crystal polymer according to claim 3, characterized in that: The monomer containing a reactive pentafluorophenyl ester group is prepared by the following method: In an anhydrous dichloromethane environment, 5-succinate-1-cyclooctene reacts with thionyl chloride to obtain a crude product, which is then distilled under reduced pressure to obtain an intermediate; In an anhydrous dichloromethane environment and in the presence of triethylamine, pentafluorophenol reacts with an intermediate, and a crude product is obtained after column chromatography and reduced pressure rotary evaporation, and a monomer containing a reactive pentafluorophenyl ester group is obtained by vacuum drying and crystallization.

7. The method for preparing a light / humidity dual-responsive liquid crystal polymer according to claim 6, characterized in that: 5-succinate-1-cyclooctene reacts with excess thionyl chloride, thionyl chloride is added dropwise to 5-succinate-1-cyclooctene in an ice-water bath, and the reaction is carried out at 50°C overnight under the protection of a reflux device; The mass ratio of pentafluorophenol to the intermediate is 2:2.6; Triethylamine was added dropwise to the mixture of pentafluorophenol and the intermediate, and the mixture was stirred for 3 h in an ice-water bath and then reacted at room temperature for 12 h. The vacuum drying temperature was 40°C and the crystallization temperature was -20°C.

8. The method for preparing a light / humidity dual-responsive liquid crystal polymer according to claim 3, characterized in that: The ring-opening metathesis polymerization reaction is carried out in an inert gas atmosphere using a Grubbs second generation catalyst at 45° C. for 3-4 hours; vinyl ethyl ether is used to terminate the reaction, and after the reaction, methanol is used for washing and vacuum drying is carried out at 40° C.

9. The method for preparing a light / humidity dual-responsive liquid crystal polymer according to claim 3, characterized in that: The post-polymerization modification reaction is carried out in the presence of tetrahydrofuran at 50° C. for 3-5 hours; after the reaction, the product is washed with methanol and vacuum dried at 40° C. overnight.

10. Use of the light / humidity dual-responsive liquid crystal polymer as claimed in claim 1 or 2 in a multi-stimulus responsive film.

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