Near-infrared light response liquid crystal elastomer crosslinked by double dynamic bonds and preparation method of near-infrared light response liquid crystal elastomer

Abstract

The invention relates to a double dynamic bond cross-linked near-infrared light response liquid crystal elastomer and a preparation method thereof, and belongs to the technical field of liquid crystal elastomers. The liquid crystal elastomer is a main chain type liquid crystal polymer containing catechol and thiolactone side groups, which is obtained by polymerizing a liquid crystal monomer, a dopamine hydrochloride monomer, a chain extender and a cross-linking agent under the action of triethylamine through a Michael addition reaction, a liquid crystal polymer forms a liquid crystal elastomer of a dynamic cross-linked network through coordination interaction of Fe < 3 + >-catechol. The photothermal effect is introduced while pre-crosslinking of the liquid crystal elastomer is achieved through coordination interaction of Fe < 3 + >-catechol, the photothermal effect is excellent, and the mechanical performance of the liquid crystal elastomer can be enhanced; the thiolactone side group and the bifunctional primary amine are subjected to ring-opening cross-linking reaction to fix the single domain state structure of the liquid crystal elastomer, and the programming preparation method is simple and efficient.

Description

Technical Field

[0001] The invention belongs to the technical field of liquid crystal elastomers, and in particular relates to a near-infrared light-responsive liquid crystal elastomer with double dynamic bond cross-linking and a preparation method thereof. Background Art

[0002] Liquid crystal elastomers have attracted more and more attention in the development and application of smart materials due to their flexible programming and large reversible deformation. Among them, photoresponsive liquid crystal elastomers have the advantages of remote control, precise operation and clean stimulation source, and are ideal materials for preparing intelligent bionic soft machines. At present, most photoresponsive liquid crystal elastomers are ultraviolet light responsive. These materials mainly achieve reversible deformation through photoisomerization of azobenzene. However, ultraviolet light is harmful to human tissue and difficult to penetrate azobenzene materials, so the application of such materials is greatly limited. Since near-infrared light has good biocompatibility, low damage and high tissue penetration, near-infrared light responsive liquid crystal elastomers have become the focus and hotspot of liquid crystal elastomer material research. In addition, with the improvement of people's awareness of energy conservation and emission reduction, the development of liquid crystal elastomers with reprocessable and recyclable properties is more in line with the concept of sustainable development.

[0003] The traditional method of preparing near-infrared light-responsive liquid crystal elastomers is mainly through physical doping, generally by doping inorganic / organic upconversion materials into ultraviolet light-responsive liquid crystal elastomer materials, converting near-infrared light into ultraviolet light through the upconversion materials to achieve near-infrared light response of the liquid crystal elastomer materials, or by adding photothermal conversion agents such as carbon nanotubes, gold nanoparticles, and graphene to liquid crystal elastomers, using the photothermal effect to convert light energy into thermal energy to achieve near-infrared light response. However, doped or added photothermal agents have problems such as aggregation and migration, which in turn affect the performance of liquid crystal elastomer materials. Introducing groups with photothermal conversion effects as crosslinking points into liquid crystal elastomers in a covalently bonded manner can effectively maintain the stability of material properties, but the introduction of non-dynamic covalent bonds makes it impossible to repeatedly process and use the material.

[0004] Therefore, there is an urgent need for a near-infrared light-responsive liquid crystal elastomer with high photothermal conversion efficiency, dynamic exchange, and no need for physical addition. Summary of the invention

[0005] In order to solve the deficiencies in the prior art, the present invention provides a near-infrared light-responsive liquid crystal elastomer with double dynamic bond crosslinking and a preparation method thereof. 3+ -The catechol coordination interaction realizes the pre-crosslinking of the liquid crystal elastomer and introduces the photothermal effect. The photothermal effect is excellent and can enhance the mechanical properties of the liquid crystal elastomer. The thiolactone side group fixes the single domain structure of the liquid crystal elastomer through a ring-opening crosslinking reaction with a bifunctional primary amine. The programming preparation method is simple and efficient.

[0006] The first object of the present invention is to provide a near-infrared light-responsive liquid crystal elastomer with double dynamic bond crosslinking, wherein the liquid crystal elastomer is polymerized by a liquid crystal monomer, a dopamine hydrochloride monomer, a chain extender and a crosslinking agent under the action of triethylamine through a Michael addition reaction to obtain a main chain liquid crystal polymer containing catechol and thiolactone side groups, and the liquid crystal polymer is crosslinked by Fe 3+ - Liquid crystal elastomers that form dynamic cross-linked networks through catechol coordination interactions;

[0007] The liquid crystal monomer is 2-methyl-1,4-phenylene bis-(4-((6-(acryloyloxy)hexyl)oxy)benzoate and / or 2-methyl-1,4-phenylene bis-(4-((3-(acryloyloxy)propyl)oxy)benzoate.

[0008] Preferably, the structural formula of the 2-methyl-1,4-phenylenebis-(4-((6-(acryloyloxy)hexyl)oxy)benzoate is as follows:

[0009]

[0010] The structural formula of the 2-methyl-1,4-phenylenebis-(4-((3-(acryloyloxy)propyl)oxy)benzoate is as follows:

[0011] Preferably, the dopamine hydrochloride monomer is 2-(3,4-dihydroxyphenyl)ethylamine hydrochloride.

[0012] Preferably, the chain extender is 2,2'-(1,2-ethylenedioxy)bisethanethiol and / or 3-mercaptopropionic acid-2-ethyl-5,11-dioxo-11-[(2-oxotetrahydrothiophen-3-yl)amino]-2-{[(3-mercaptopropionyl)oxy]methyl}-4-oxa-8-thiaundecane-1-yl ester;

[0013] The crosslinking agent is trimethylolpropane tris(3-mercaptopropionate) or pentaerythritol tetrakis(3-mercaptopropionate).

[0014] Preferably, the molar ratio of the liquid crystal monomer, dopamine hydrochloride monomer, chain extender and triethylamine is (80-130):(5-15):(95-135):(30-65).

[0015] The second object of the present invention is to provide a method for preparing a near-infrared light-responsive liquid crystal elastomer with dual dynamic bond crosslinking, comprising the following steps:

[0016] The liquid crystal monomer, dopamine hydrochloride and triethylamine are dissolved in DMF, reacted at 60-80°C in a nitrogen atmosphere for 5-12 hours, then a chain extender and triethylamine are added, reacted at 75-85°C for 24-48 hours to obtain a mixture, the mixture is poured into a mixed solution of water and methanol to precipitate, and filtered to obtain a main chain liquid crystal polymer containing catechol and thiolactone side groups;

[0017] Dissolve the liquid crystal polymer in a polar solvent and add Fe 3+ solution, and add triethylamine to adjust the pH value to 8-9, evaporate the solvent to obtain Fe 3+ -Catechol coordination interactions form a dynamic cross-linked network of liquid crystal elastomers.

[0018] Preferably, the chain extender comprises 2,2'-(1,2-ethylenedioxy)bisethanethiol and 3-mercaptopropionic acid-2-ethyl-5,11-dioxo-11-[(2-oxotetrahydrothiophen-3-yl)amino]-2-{[(3-mercaptopropionyl)oxy]methyl}-4-oxa-8-thiaundecane-1-yl ester, and the molar ratio thereof is 80-100:15-35;

[0019] The polar solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dichloromethane and acetone.

[0020] Preferably, the Fe 3+ The solution is a 1,4-dioxane solution of ferric chloride and / or a 1,4-dioxane solution of ferric nitrate.

[0021] The third object of the present invention is to provide a method for preparing an oriented liquid crystal elastomer, comprising:

[0022] The liquid crystal elastomer is placed in a polytetrafluoroethylene mold, and then transferred to a hot press for hot pressing to obtain a liquid crystal elastomer film;

[0023] The liquid crystal elastomer film is stretched 100%-400% or programmed into a desired shape, cross-linked and fixed with a cystamine solution with a molar concentration of 0.1 to 0.5 mol / L, and then placed for 0.5 to 6 hours to obtain a liquid crystal elastomer with double dynamic bond cross-linking and near-infrared light responsiveness.

[0024] The fourth object of the present invention is to provide a near-infrared light-responsive liquid crystal elastomer with double dynamic bond cross-linking for use in bionic materials.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] The present invention provides a near-infrared light-responsive liquid crystal elastomer with dual dynamic bond crosslinking, which is a main-chain liquid crystal elastomer crosslinked by dual dynamic bonds. The present invention also provides a preparation method of a near-infrared light-responsive liquid crystal elastomer with dual dynamic bond crosslinking, firstly, the amino group in dopamine is subjected to Michael addition reaction with liquid crystal monomer, then 2,2'-(1,2-ethylenedioxy)bis(ethyl mercaptan) and a dithiol chain extender containing a thiolactone group are added to extend the chain through a thiol-ene reaction, and then Fe is introduced. 3+ Between polymer chains, Fe 3+ -catechol coordination interaction to form a dynamic cross-linked network, while introducing a photothermal effect, and finally stretching and orienting the cross-linked network and using a solution of cystamine containing a disulfide bond for secondary cross-linking. The main chain liquid crystal polymer containing catechol and thiolactone side groups prepared by the method of aza Michael addition and thiol-ene click reaction is 3+ -Catechol complexation forms a dynamic cross-linked network and introduces photothermal effect. After mechanical stretching and orientation of the molecular chains, cystamine solution is used for cross-linking and fixation. Therefore, it can be driven by near-infrared light and has the characteristics of reversible deformation and reprocessability in response to near-infrared light.

[0027] The liquid crystal elastomer of the present invention is 3+ -The catechol coordination interaction realizes the pre-crosslinking of the liquid crystal elastomer and introduces the photothermal effect. The photothermal effect is excellent and can enhance the mechanical properties of the liquid crystal elastomer. The thiolactone side group fixes the single domain structure of the liquid crystal elastomer through a ring-opening crosslinking reaction with a bifunctional primary amine. The programming preparation method is simple and efficient.

[0028] The method of the present invention for synthesizing a liquid crystal elastomer by combining the aza Michael addition reaction of dopamine-liquid crystal monomer with the mercapto-ene Michael addition reaction is simpler and more convenient.

[0029] The liquid crystal elastomer of the present invention is composed of Fe 3+ - The double dynamic cross-linking of catechol coordination bonds and disulfide bonds can form a dynamic cross-linking network that can undergo network structure reorganization when heated to the dynamic exchange temperature, so that the cross-linked liquid crystal elastomer can be reprocessed and recycled. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is the structural formula and H NMR spectrum of EDTSP, a chain extender containing thiolactone groups;

[0031] Figure 2 It is a temperature-responsive reversible stretching and deformation of a double dynamic bond cross-linked liquid crystal elastomer;

[0032] Figure 3 It is the reversible bending deformation of the double dynamic bond cross-linked liquid crystal elastomer under the control of near-infrared light irradiation;

[0033] Figure 4 It is the tensile curve of the double dynamic bond cross-linked liquid crystal elastomer before and after hot pressing and reprocessing. DETAILED DESCRIPTION

[0034] The present invention is further described below in conjunction with specific embodiments, but it should be understood that the embodiments listed are only for facilitating understanding of the core method and application field of the present invention, but the scope of the present invention is not limited thereto.

[0035] The object of the present invention is to provide a near-infrared light-responsive liquid crystal elastomer with double dynamic bond crosslinking. 3+ -catechol coordination to form a dynamic cross-linking network to achieve pre-cross-linking of liquid crystal elastomers and introduce photothermal effect, avoiding the problem of poor dispersibility of traditional doped or added materials in liquid crystal elastomers and affecting the stability of liquid crystal elastomer performance. At the same time, the present invention provides a method for preparing a near-infrared light-responsive liquid crystal elastomer with double dynamic bond cross-linking, firstly by Fe 3+ -Catechol coordination interaction forms a dynamic cross-linking network to achieve pre-cross-linking of the liquid crystal elastomer, and then a solution of cystamine containing disulfide bonds is used for secondary cross-linking to fix the orientation of the liquid crystal unit. This double dynamic bond cross-linked liquid crystal elastomer can be processed and recycled many times.

[0036] The first aspect of the present invention provides a near-infrared light-responsive liquid crystal elastomer with double dynamic bond crosslinking, wherein the liquid crystal elastomer is polymerized by a liquid crystal monomer, a dopamine hydrochloride monomer, a chain extender and a crosslinking agent under the action of triethylamine through a Michael addition reaction to obtain a main chain liquid crystal polymer containing catechol and thiolactone side groups, and the liquid crystal polymer is crosslinked by Fe 3+ - Liquid crystal elastomers that form dynamic cross-linked networks through catechol coordination interactions;

[0037] The liquid crystal monomer is 2-methyl-1,4-phenylene bis-(4-((6-(acryloyloxy)hexyl)oxy)benzoate and / or 2-methyl-1,4-phenylene bis-(4-((3-(acryloyloxy)propyl)oxy)benzoate.

[0038] The structural formula of the 2-methyl-1,4-phenylenebis-(4-((6-(acryloyloxy)hexyl)oxy)benzoate is as follows:

[0039]

[0040] The structural formula of the 2-methyl-1,4-phenylenebis-(4-((3-(acryloyloxy)propyl)oxy)benzoate is as follows:

[0041] The dopamine hydrochloride monomer is 2-(3,4-dihydroxyphenyl)ethylamine hydrochloride.

[0042] The chain extender is 2,2'-(1,2-ethylenedioxy)bisethanethiol and / or 3-mercaptopropionic acid-2-ethyl-5,11-dioxo-11-[(2-oxotetrahydrothiophene-3-yl)amino]-2-{[(3-mercaptopropionyl)oxy]methyl}-4-oxa-8-thiaundecane-1-yl ester;

[0043] The crosslinking agent is trimethylolpropane tris(3-mercaptopropionate) or pentaerythritol tetrakis(3-mercaptopropionate).

[0044] The molar ratio of the liquid crystal monomer, dopamine hydrochloride monomer, chain extender and triethylamine is (80-130):(5-15):(95-135):(30-65).

[0045] In one embodiment, a near-infrared light-responsive liquid crystal elastomer with double dynamic bond crosslinking is provided. The liquid crystal elastomer is polymerized by a liquid crystal monomer, a dopamine hydrochloride monomer, and a chain extender under the action of triethylamine through a Michael addition reaction, and a main chain liquid crystal polymer containing catechol and thiolactone side groups is obtained after polymerization. 3+ -Catechol coordination interactions form a dynamic cross-linked network and introduce photothermal effects. After mechanical stretching and orientation of the molecular chains, cystamine solution is used for cross-linking and fixation. Therefore, it can be driven by near-infrared light and has the characteristics of near-infrared light-responsive reversible deformation and reprocessability.

[0046] The liquid crystal monomer is any one of 2-methyl-1,4-phenylene bis-(4-((6-(acryloyloxy)hexyl)oxy)benzoate (RM82 for short) and 2-methyl-1,4-phenylene bis-(4-((3-(acryloyloxy)propyl)oxy)benzoate (RM257 for short) or a combination thereof;

[0047] The dopamine hydrochloride monomer is 2-(3,4-dihydroxyphenyl)ethylamine hydrochloride, and the structural formula is as follows:

[0048]

[0049] The chain extender is a mixture of 2,2'-(1,2-ethylenedioxy)bis(ethylenethiol) (abbreviated as EDDT) and 3-mercaptopropionic acid-2-ethyl-5,11-dioxo-11-[(2-oxotetrahydrothiophene-3-yl)amino]-2-{[(3-mercaptopropionyl)oxy]methyl}-4-oxa-8-thiaundecane-1-yl ester (abbreviated as EDTSP), and the structural formula is as follows:

[0050]

[0051] The catalyst is triethylamine, and the structural formula is as follows:

[0052]

[0053] The cystamine structural formula is as follows:

[0054]

[0055] The molar ratio of the liquid crystal monomer, dopamine hydrochloride monomer, chain extender and triethylamine is: liquid crystal monomer: dopamine hydrochloride monomer: chain extender: triethylamine = 130-80: 15-5: 135-95: 65-30.

[0056] The cystamine solution is formed by dissolving cystamine in water or ethanol.

[0057] The second aspect of the present invention provides a method for preparing a near-infrared light-responsive liquid crystal elastomer with dual dynamic bond crosslinking, comprising the following steps:

[0058] The liquid crystal monomer, dopamine hydrochloride and triethylamine are dissolved in DMF, reacted at 60-80°C in a nitrogen atmosphere for 5-12 hours, then a chain extender and triethylamine are added, reacted at 75-85°C for 24-48 hours to obtain a mixture, the mixture is poured into a mixed solution of water and methanol to precipitate, and filtered to obtain a main chain liquid crystal polymer containing catechol and thiolactone side groups;

[0059] Dissolve the liquid crystal polymer in a polar solvent and add Fe 3+ solution, and add triethylamine to adjust the pH value to 8-9, evaporate the solvent to obtain Fe 3+ -Catechol coordination interactions form a dynamic cross-linked network of liquid crystal elastomers.

[0060] The chain extender includes 2,2'-(1,2-ethylenedioxy)bisethanethiol and 3-mercaptopropionic acid-2-ethyl-5,11-dioxo-11-[(2-oxotetrahydrothiophen-3-yl)amino]-2-{[(3-mercaptopropionyl)oxy]methyl}-4-oxa-8-thiaundecane-1-yl ester, and the molar ratio thereof is 80-100:15-35;

[0061] The polar solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dichloromethane and acetone.

[0062] The Fe 3+ The solution is a 1,4-dioxane solution of ferric chloride and / or a 1,4-dioxane solution of ferric nitrate;

[0063] A third aspect of the present invention provides a method for preparing an oriented liquid crystal elastomer, comprising:

[0064] The liquid crystal elastomer is placed in a polytetrafluoroethylene mold, and then transferred to a hot press for hot pressing to obtain a liquid crystal elastomer film;

[0065] The liquid crystal elastomer film is stretched 100%-400% or programmed into a desired shape, cross-linked and fixed with a cystamine solution with a molar concentration of 0.1 to 0.5 mol / L, and then placed for 0.5 to 6 hours to obtain a liquid crystal elastomer with double dynamic bond cross-linking and near-infrared light responsiveness.

[0066] In one embodiment, a near-infrared light-responsive liquid crystal elastomer with dual dynamic bond crosslinking and a preparation method thereof are provided, which comprises the following preparation steps:

[0067] Step 1, weighing the reaction components in proportion: including liquid crystal monomer, dopamine hydrochloride, chain extender and triethylamine; the molar ratio of the liquid crystal monomer, dopamine hydrochloride monomer, chain extender and triethylamine is: 130-80:15-5:135-95:65-30.

[0068] Step 2, preparation of EDTSP, one of the chain extenders: trimethylolpropane tris(3-mercaptopropionate) and N-(2-oxyylidene tetrahydrothiophene-3-yl) prop-2-enamide are dissolved in acetone, triethylamine is added and reacted at room temperature for 6-12 hours, then the solvent is removed by rotary evaporation and the oily product EDTSP is obtained by silica gel column chromatography; the molar ratio of trimethylolpropane tris(3-mercaptopropionate) and N-(2-oxyylidene tetrahydrothiophene-3-yl) prop-2-enamide is 1.2-0.9:1.1-0.8. The mass ratio of the sum of the mass of trimethylolpropane tris(3-mercaptopropionate) and N-(2-oxyylidene tetrahydrothiophene-3-yl) prop-2-enamide to acetone is 0.3-0.4, of which triethylamine is 0.2% of the total mass of the system;

[0069] Step 3, preparation of liquid crystal polymer: liquid crystal monomer, dopamine hydrochloride and triethylamine are dissolved in DMF, stirred under nitrogen protection until completely dissolved, heated to 60-80°C, reacted for 5-12 hours under nitrogen atmosphere to obtain a uniform transparent solution, then chain extenders EDTSP and EDDT, and triethylamine are added, reacted at 80°C for 24-48 hours to obtain a mixture, then the mixture is poured into a mixed solution of water and methanol to precipitate, filtered and dried to obtain a main chain liquid crystal polymer containing catechol and thiolactone side groups; the molar ratio of chain extender EDDT to chain extender EDTSP is 100-80:35-15.

[0070] Step 4: Pre-crosslinking of liquid crystal elastomer: Dissolve the main chain liquid crystal polymer obtained in step 3 in a polar solvent, and add 0.5 mmol / g Fe 3+ The solution was prepared by making the molar ratio of the number of moles of the solution to the number of moles of catechol in the solution to be 1-3:9, and triethylamine was added to adjust the pH value to 8-9, and the solvent was evaporated to obtain Fe 3+ -catechol coordination interaction forms a main chain liquid crystal elastomer film with a dynamic cross-linking network. 3+ -Catechol coordination interactions form a dynamic cross-linked network while introducing a photothermal effect, which has the functional characteristics of near-infrared light response.

[0071] Step 5, preparation of liquid crystal elastomer film: put the above liquid crystal elastomer into a polytetrafluoroethylene mold, then transfer it to a hot press, hot press it at 150°C and 5MPa for 15 minutes, and then cool it to room temperature to obtain a liquid crystal elastomer film; the thickness of the polytetrafluoroethylene mold is 0.2mm.

[0072] Step 6, programming of liquid crystal elastomer: stretch the main chain liquid crystal elastomer film obtained in step 5 by 100%-400% or program it into a desired shape, and then cross-link and fix the film with a cystamine solution with a molar concentration of 0.1-0.5 mol / L as required, and then place it for 0.5-6 hours to finally obtain a liquid crystal elastomer with near-infrared light responsiveness.

[0073] The invention synthesizes the required monomer 3-mercaptopropionic acid-2-ethyl-5,11-dioxo-11-[(2-oxotetrahydrothiophene-3-yl)amino]-2-{[(3-mercaptopropionyl)oxy]methyl}-4-oxa-8-thiaundecane-1-yl ester by using trimethylolpropane tris(3-mercaptopropionate) and N-(2-oxyylidenetetrahydrothiophene-3-yl)prop-2-enamide.

[0074] The polar solvent is any one of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), dichloromethane (DCM), acetone (AC) or a combination thereof.

[0075] The main chain liquid crystal monomer is any one of 2-methyl-1,4-phenylenebis(4-((6-(acryloyloxy)hexyl)oxy)benzoate) (RM82) and 2-methyl-1,4-phenylenebis(4-(3-(acryloyloxy)propoxy)benzoate (RM257) or a combination thereof.

[0076] Main-chain liquid crystal polymers with catechol and thiolactone side chains were synthesized through two reactions: aza-Michael addition of dopamine and thiol-ene click reaction.

[0077] The Fe3+ The solution is any one of ferric chloride and ferric nitrate in 1,4-dioxane solution or a combination thereof.

[0078] A fourth aspect of the present invention provides an application of a near-infrared light-responsive liquid crystal elastomer with double dynamic bond cross-linking in a bionic material.

[0079] The present invention provides a method for preparing a near-infrared light-responsive liquid crystal elastomer with dual dynamic bond crosslinking. The liquid crystal elastomer introduces dopamine into the liquid crystal elastomer through aza-Michael addition. 3+ -catechol interaction realizes pre-crosslinking of liquid crystal elastomers and introduces photothermal effect, and the orientation of liquid crystal elastomers is cross-linked and fixed by thiolactone chemical post-functionalization method, providing a new idea for the two-step preparation of dynamically cross-linked liquid crystal elastomers.

[0080] The experimental methods and detection methods described in the following embodiments are conventional methods unless otherwise specified; the reagents and materials are commercially available unless otherwise specified.

[0081] It should be noted that the brand of liquid crystal monomer purchased in this application is Adamas.

[0082] Example 1

[0083] A preparation method of a near-infrared light-responsive liquid crystal elastomer with double dynamic bond crosslinking, the specific steps are as follows:

[0084] Step 1, preparation of chain extender EDTSP containing thiolactone group: weigh trimethylolpropane tris(3-mercaptopropionate) (7.9710 g, 20 mmol) and N-(2-oxyylidenetetrahydrothiophen-3-yl)prop-2-enamide (3.4242 g, 20 mmol) and dissolve them in acetone (25 ml), add triethylamine, react at room temperature for 12 h, remove the solvent by rotary evaporation, and then obtain oily EDTSP by silica gel column chromatography;

[0085] Step 2, preparation of liquid crystal polymer: liquid crystal monomer RM82 (1.6146 mg, 2.4 mmol), dopamine hydrochloride (0.0304 g, 0.16 mmol) and triethylamine (16 mg, 0.16 mmol) were dissolved in DMF (6 ml), stirred under nitrogen protection until completely dissolved, and then heated to 80° C., reacted under nitrogen atmosphere for 5 h to obtain a uniform transparent solution.

[0086] Step 3, adding chain extender EDTSP (0.2734 g, 0.48 mmol) and EDDT (0.2946 g, 1.6 mmol) and triethylamine (51 mg, 0.5 mmol) to the above uniform transparent solution, reacting at 80° C. for 48 h to obtain a mixture, then pouring the mixture into a mixed solution of water and methanol to precipitate, filtering and drying to obtain a main chain liquid crystal polymer containing catechol and thiolactone side groups;

[0087] Step 4: Preparation of pre-crosslinked liquid crystal elastomer: Dissolve the main chain liquid crystal polymer obtained in step 3 in a polar solvent, and add Fe 3+ solution, making Fe 3+ The molar ratio of Fe to the molar ratio of catechol in the solution was 1:3, and triethylamine was added to adjust the pH value to 8-9. After evaporating the solvent, Fe 3+ -Main chain liquid crystal elastomer dynamically cross-linked by catechol coordination bonds;

[0088] Step 5, preparation of liquid crystal elastomer film: weigh the above pre-crosslinked liquid crystal elastomer and put it into a polytetrafluoroethylene mold, then transfer it to a hot press, hot press it at 150° C. and 5 MPa for 15 minutes, and then cool it to room temperature to obtain a liquid crystal elastomer film;

[0089] Step 6, programming of liquid crystal elastomer: stretch the main chain liquid crystal elastomer film obtained in step 5 by 200%, then cross-link and fix it with 0.4 mol / L cystamine solution and leave it for 0.5 h to finally obtain a near-infrared light-responsive liquid crystal elastomer with double dynamic bond cross-linking.

[0090] Example 2

[0091] A preparation method of a near-infrared light-responsive liquid crystal elastomer with double dynamic bond crosslinking, the specific steps are as follows:

[0092] Step 1, preparation of chain extender EDTSP containing thiolactone group: weigh trimethylolpropane tris(3-mercaptopropionate) (9.9638 g, 25 mmol) and N-(2-oxyylidenetetrahydrothiophen-3-yl)prop-2-enamide (3.4242 g, 20 mmol) and dissolve them in acetone (30 ml), add triethylamine, react at room temperature for 6 h, remove the solvent by rotary evaporation, and then obtain oily EDTSP by silica gel column chromatography;

[0093] Step 2, preparation of liquid crystal polymer: liquid crystal monomer RM257 (1.4127 mg, 2.4 mmol), dopamine hydrochloride (0.0304 g, 0.16 mmol) and triethylamine (16 mg, 0.16 mmol) were dissolved in DMF (5 ml), stirred under nitrogen protection until completely dissolved, heated to 80° C., and reacted for 5 h under nitrogen atmosphere to obtain a uniform transparent solution;

[0094] Step 3, adding chain extender EDTSP (0.2734 g, 0.48 mmol) and EDDT (0.2946 g, 1.6 mmol) and triethylamine (51 mg, 0.5 mmol) to the above uniform transparent solution, reacting at 80° C. for 36 h to obtain a mixture, then pouring the mixture into a mixed solution of water and methanol to precipitate, filtering and drying to obtain a main chain liquid crystal polymer containing catechol and thiolactone side groups;

[0095] Step 4: Preparation of pre-crosslinked liquid crystal elastomer: Dissolve the main chain liquid crystal polymer obtained in step 3 in a polar solvent, and add Fe 3+ solution, making Fe 3+ The molar ratio of Fe to the molar ratio of catechol in the solution was 1:3, and triethylamine was added to adjust the pH value to 8-9. After evaporating the solvent, Fe 3+ -Main chain liquid crystal elastomer dynamically cross-linked by catechol coordination bonds;

[0096] Step 5, preparation of liquid crystal elastomer film: weigh the pre-crosslinked liquid crystal elastomer and put it into a polytetrafluoroethylene mold, then transfer it to a hot press, hot press it at 150° C. and 5 MPa for 15 minutes, and then cool it to room temperature to obtain a liquid crystal elastomer film;

[0097] Step 6, programming of liquid crystal elastomer: stretch the main chain liquid crystal elastomer film obtained in step 5 by 100%, then cross-link and fix it with a 0.5 mol / L cystamine solution and leave it for 1 hour to finally obtain a near-infrared light-responsive liquid crystal elastomer with double dynamic bond cross-linking.

[0098] Example 3

[0099] A preparation method of a near-infrared light-responsive liquid crystal elastomer with double dynamic bond crosslinking, the specific steps are as follows:

[0100] Step 1, preparation of chain extender EDTSP containing thiolactone group: weigh trimethylolpropane tris(3-mercaptopropionate) (9.1667 g, 23 mmol) and N-(2-oxyylidenetetrahydrothiophen-3-yl)prop-2-enamide (3.4242 g, 20 mmol) and dissolve them in acetone (28 ml), add triethylamine, react at room temperature for 12 h, remove the solvent by rotary evaporation, and then obtain oily EDTSP by silica gel column chromatography;

[0101] Step 2, preparation of liquid crystal polymer: liquid crystal monomer RM82 (0.8073 mg, 1.2 mmol), liquid crystal monomer RM257 (0.7064 mg, 1.2 mmol), dopamine hydrochloride (0.0304 g, 0.16 mmol) and triethylamine (16 mg, 0.16 mmol) were dissolved in DMF (6 ml), stirred under nitrogen protection until completely dissolved, heated to 80° C., and reacted for 5 h under nitrogen atmosphere to obtain a uniform and transparent solution;

[0102] Step 3, adding chain extender EDTSP (0.2734 g, 0.48 mmol) and EDDT (0.2946 g, 1.6 mmol) and triethylamine (51 mg, 0.5 mmol) to the above uniform transparent solution, reacting at 80° C. for 24 h to obtain a mixture, then pouring the mixture into a mixed solution of water and methanol to precipitate, filtering and drying to obtain a main chain liquid crystal polymer containing catechol and thiolactone side groups;

[0103] Step 4: Preparation of pre-crosslinked liquid crystal elastomer: Dissolve the main chain liquid crystal polymer obtained in step 3 in a polar solvent, and add Fe 3+ solution, making Fe 3+ The molar ratio of Fe to the molar ratio of catechol in the solution was 1:3, and triethylamine was added to adjust the pH value to 8-9. After evaporating the solvent, Fe 3+ -Main chain liquid crystal elastomer dynamically cross-linked by catechol coordination bonds;

[0104] Step 5, preparation of liquid crystal elastomer film: placing the pre-crosslinked liquid crystal elastomer into a polytetrafluoroethylene mold, and then transferring it to a hot press, hot pressing it at 150° C. and 5 MPa for 15 min, and then cooling it to room temperature to obtain a liquid crystal elastomer film;

[0105] Step 6, programming of liquid crystal elastomer: stretch the main chain liquid crystal elastomer film obtained in step 5 by 200%, then cross-link and fix it with a cystamine solution with a molar concentration of 0.4 mol / L and leave it for 3 hours to finally obtain a liquid crystal elastomer with near infrared response.

[0106] In order to illustrate the relevant properties of the liquid crystal elastomer provided by the present invention, corresponding descriptions are given in conjunction with the accompanying drawings.

[0107] Figure 1 It is the structural formula and H-NMR spectrum of chain extender EDTSP; Figure 1 It is the chain extender EDTSP provided by Example 1. It can be seen from the hydrogen nuclear magnetic resonance spectrum that the number of hydrogens is consistent with that of EDTSP, proving that the synthesis was successful.

[0108] Figure 2 It is a temperature-responsive reversible stretching and deformation of a double dynamic bond cross-linked liquid crystal elastomer; Figure 2 The liquid crystal elastomer provided in Example 1 is cross-linked by cystamine to obtain a liquid crystal elastomer that can undergo reversible deformation by heating and cooling.

[0109] Figure 3 It is the reversible bending deformation of the double dynamic bond cross-linked liquid crystal elastomer under the control of near-infrared light irradiation; Figure 3 The liquid crystal elastomer provided in Example 1 is driven to deform by near-infrared light irradiation.

[0110] Figure 4 It is the tensile curve of the double dynamic bond cross-linked liquid crystal elastomer before and after hot pressing and reprocessing; Figure 4 It is the liquid crystal elastomer provided by Example 1. R-LCE3-FE-3 is obtained by cutting LCE3-FE-3 into pieces and hot pressing them again. It can be found from the figure and Table 1 that the material strength has not been significantly reduced, and the elongation at break has been slightly reduced.

[0111] Table 1 Mechanical properties data of double dynamic bond crosslinking and liquid crystal elastomer before and after hot pressing reprocessing

[0112]

[0113] The above embodiments are only some embodiments listed for facilitating understanding of the synthesis and application methods of the materials of the present invention, and are not intended to limit the present invention. It is understood that relevant practitioners can easily make appropriate modifications to this structure, so any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A near-infrared light-responsive liquid crystal elastomer with double dynamic bond crosslinking, characterized in that: The liquid crystal elastomer is prepared by polymerizing a liquid crystal monomer, a dopamine hydrochloride monomer, a chain extender and a crosslinking agent through a Michael addition reaction under the action of triethylamine to obtain a main chain liquid crystal polymer containing catechol and thiolactone side groups. 3+ - Liquid crystal elastomers that form dynamic cross-linked networks through catechol coordination interactions; The liquid crystal monomer is 2-methyl-1,4-phenylene bis-(4-((6-(acryloyloxy)hexyl)oxy)benzoate and / or 2-methyl-1,4-phenylene bis-(4-((3-(acryloyloxy)propyl)oxy)benzoate.

2. The near-infrared light-responsive liquid crystal elastomer with dual dynamic bond crosslinking according to claim 1, characterized in that: The structural formula of the 2-methyl-1,4-phenylenebis-(4-((6-(acryloyloxy)hexyl)oxy)benzoate is as follows: The structural formula of the 2-methyl-1,4-phenylenebis-(4-((3-(acryloyloxy)propyl)oxy)benzoate is as follows:

3. The near-infrared light-responsive liquid crystal elastomer with dual dynamic bond crosslinking according to claim 1, characterized in that: The dopamine hydrochloride monomer is 2-(3,4-dihydroxyphenyl)ethylamine hydrochloride.

4. The near-infrared light-responsive liquid crystal elastomer with dual dynamic bond crosslinking according to claim 1, characterized in that: The chain extender is 2,2'-(1,2-ethylenedioxy)bisethanethiol and / or 3-mercaptopropionic acid-2-ethyl-5,11-dioxo-11-[(2-oxotetrahydrothiophene-3-yl)amino]-2-{[(3-mercaptopropionyl)oxy]methyl}-4-oxa-8-thiaundecane-1-yl ester; The crosslinking agent is trimethylolpropane tris(3-mercaptopropionate) or pentaerythritol tetrakis(3-mercaptopropionate).

5. The near-infrared light-responsive liquid crystal elastomer with dual dynamic bond crosslinking according to claim 1, characterized in that: The molar ratio of the liquid crystal monomer, dopamine hydrochloride monomer, chain extender and triethylamine is (80-130):(5-15):(95-135):(30-65).

6. A method for preparing the near-infrared light-responsive liquid crystal elastomer with double dynamic bond crosslinking according to any one of claims 1 to 5, characterized in that: The following steps are involved: The liquid crystal monomer, dopamine hydrochloride and triethylamine are dissolved in DMF, reacted at 60-80°C in a nitrogen atmosphere for 5-12 hours, then a chain extender and triethylamine are added, reacted at 75-85°C for 24-48 hours to obtain a mixture, the mixture is poured into a mixed solution of water and methanol to precipitate, and filtered to obtain a main chain liquid crystal polymer containing catechol and thiolactone side groups; Dissolve the liquid crystal polymer in a polar solvent and add Fe 3+ solution, and add triethylamine to adjust the pH value to 8-9, evaporate the solvent to obtain Fe 3+ -Catechol coordination interactions form a dynamic cross-linked network of liquid crystal elastomers.

7. The method for preparing a near-infrared light-responsive liquid crystal elastomer with dual dynamic bond crosslinking according to claim 6, characterized in that: The chain extender includes 2,2'-(1,2-ethylenedioxy)bisethanethiol and 3-mercaptopropionic acid-2-ethyl-5,11-dioxo-11-[(2-oxotetrahydrothiophen-3-yl)amino]-2-{[(3-mercaptopropionyl)oxy]methyl}-4-oxa-8-thiaundecane-1-yl ester, and the molar ratio thereof is 80-100:15-35; The polar solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dichloromethane and acetone.

8. The method for preparing a near-infrared light-responsive liquid crystal elastomer with dual dynamic bond crosslinking according to claim 6, characterized in that: The Fe 3+ The solution is a 1,4-dioxane solution of ferric chloride and / or a 1,4-dioxane solution of ferric nitrate.

9. A method for preparing an oriented liquid crystal elastomer, characterized in that: include: Putting the liquid crystal elastomer according to any one of claims 1 to 5 into a polytetrafluoroethylene mold, and then transferring it to a hot press for hot pressing to obtain a liquid crystal elastomer film; The liquid crystal elastomer film is stretched 100%-400% or programmed into a desired shape, cross-linked and fixed with a cystamine solution with a molar concentration of 0.1-0.5 mol / L, and then placed for 0.5-6 hours to obtain a liquid crystal elastomer with double dynamic bond cross-linking and near-infrared light responsiveness.

10. Use of the near-infrared light-responsive liquid crystal elastomer with double dynamic bonds cross-linked according to any one of claims 1 to 5 in bionic materials.

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