A dual-dynamic bond crosslinked near-infrared light responsive liquid crystal elastomer and a preparation method thereof

Abstract

The present application relates to a kind of dual dynamic key crosslinking near-infrared light response liquid crystal elastomer and its preparation method, belong to liquid crystal elastomer technical field.The liquid crystal elastomer is by liquid crystal monomer, dopamine hydrochloride monomer, chain extender and crosslinking agent under the action of triethylamine by Michael addition polymerization, obtain the main chain type liquid crystal polymer containing catechol and thiolactone side group, liquid crystal polymer is by Fe 3+ The liquid crystal elastomer with dynamic crosslinking network formed by catechol coordination interaction.The present application realizes the pre-crosslinking of liquid crystal elastomer by Fe 3+ Catechol coordination interaction realizes the pre-crosslinking of liquid crystal elastomer while introducing photo-thermal effect, and the photo-thermal effect is excellent, and can enhance the mechanical properties of liquid crystal elastomer;Thiolactone side group is fixed by ring-opening crosslinking reaction with di-functional primary amine and the single-domain structure of liquid crystal elastomer, and the programming preparation method is simple and efficient.

Description

Technical Field

[0001] This invention belongs to the field of liquid crystal elastomer technology, specifically relating to a near-infrared light-responsive liquid crystal elastomer with dual dynamic bond crosslinking and its preparation method. Background Technology

[0002] Liquid crystal elastomers (LCEs) have attracted increasing attention in the development and application of smart materials due to their flexible programming and large reversible deformation. Among them, photoresponsive LCEs offer advantages such as remote control, precise operation, and clean stimulus sources, making them ideal materials for fabricating intelligent biomimetic soft machines. Currently, most photoresponsive LCEs are ultraviolet (UV) responsive, achieving reversible deformation primarily through the photoisomerization of azobenzene. However, UV light is harmful to human tissue and has difficulty penetrating azobenzene, thus significantly limiting their application. Near-infrared (NIIR) light, with its excellent biocompatibility, lower damage, and higher tissue penetration, has made NIIR photoresponsive LCEs a key focus and research area in LCE materials. Furthermore, with increasing awareness of energy conservation and emission reduction, developing LCEs with reprocessable and recyclable properties aligns better with the concept of sustainable development.

[0003] Traditional methods for preparing near-infrared responsive liquid crystal elastomers (LCEs) primarily involve physical doping. This typically involves incorporating inorganic / organic upconversion materials into UV-responsive LCEs, converting near-infrared light into UV light to achieve the near-infrared response. Alternatively, photothermal conversion agents such as carbon nanotubes, gold nanoparticles, or graphene can be added to the LCE to convert light energy into heat energy via photothermal effects, thus achieving a near-infrared response. However, these dopants or added photothermal agents can exhibit aggregation and migration issues, affecting the performance of the LCE material. Introducing photothermal conversion groups as crosslinking points into LCEs via covalent bonding can effectively maintain material stability; however, the introduction of non-dynamic covalent bonds prevents the material from being repeatedly processed and used.

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

[0005] To address the shortcomings of existing technologies, this invention provides a near-infrared light-responsive liquid crystal elastomer with dual dynamic bond crosslinking and its preparation method. This invention utilizes Fe... 3+ - The coordination interaction of catechol enables the pre-crosslinking of liquid crystal elastomers while introducing photothermal effects, resulting in excellent photothermal performance and enhanced mechanical properties of the liquid crystal elastomers; the thiolactone side group fixes the single-domain structure of the liquid crystal elastomers through a ring-opening crosslinking reaction with the bifunctional primary amine, making the programming preparation method simple and efficient.

[0006] The first objective of this invention is to provide a near-infrared light-responsive liquid crystal elastomer with dual dynamic bond crosslinking. This liquid crystal elastomer is polymerized by a Michael addition reaction of liquid crystal monomers, dopamine hydrochloride monomers, chain extenders, and crosslinking agents under the action of triethylamine to obtain a main-chain liquid crystal polymer containing catechol and thiolactone side groups. The liquid crystal polymer is then subjected to Fe... 3+ -Liquid crystal elastomers that form a dynamic cross-linked network through coordination interactions with catechol;

[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-phenylene bis-(4-((6-(acryloyloxy)hexyl)oxy)benzoate is as follows:

[0009]

[0010] The structural formula of the 2-methyl-1,4-phenylene bis-(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)bis(ethyl)thiol and / or 3-mercaptopropionic acid-2-ethyl-5,11-dioxo-11-[(2-oxotetrahydrothiophene-3-yl)amino]-2-{[(3-mercaptopropionyl)oxy]methyl}-4-oxa-8-thia-undecan-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 objective of this 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] Liquid crystal monomers, dopamine hydrochloride, and triethylamine were dissolved in DMF and reacted at 60–80 °C for 5–12 h under a nitrogen atmosphere. Then, a chain extender and triethylamine were added, and the mixture was reacted at 75–85 °C for 24–48 h to obtain a mixture. The mixture was poured into a mixed solution of water and methanol to precipitate the precipitate. After filtration, a main-chain liquid crystal polymer containing catechol and thiolactone side groups was obtained.

[0017] The liquid crystal polymer was dissolved in a polar solvent, and Fe was added. 3+ The solution was prepared by adding triethylamine to adjust the pH to 8-9, and the solvent was evaporated to obtain the product composed of Fe. 3+ Liquid crystal elastomers that form a dynamic cross-linked network through coordination interactions with catechol.

[0018] Preferably, the chain extender comprises 2,2'-(1,2-ethylenedioxy)diethylthiol and 3-mercaptopropionic acid-2-ethyl-5,11-dioxo-11-[(2-oxotetrahydrothiophene-3-yl)amino]-2-{[(3-mercaptopropionyl)oxy]methyl}-4-oxa-8-thia-undecane-1-yl ester, in a molar ratio of 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] A third objective of this invention is to provide a method for preparing an oriented liquid crystal elastomer, comprising:

[0022] The liquid crystal elastomer described above is placed into 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 by 100%–400% or programmed into the desired shape, crosslinked and fixed with a cystamine solution with a molar concentration of 0.1–0.5 mol / L, and then left to stand for 0.5–6 hours to obtain a liquid crystal elastomer with double dynamic bond crosslinking and near-infrared light responsiveness.

[0024] The fourth objective of this invention is to provide an application of a near-infrared light-responsive liquid crystal elastomer with dual dynamic bond crosslinking in biomimetic materials.

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

[0026] This invention provides a near-infrared photoresponsive liquid crystal elastomer with dual dynamic bond crosslinking, which is a main-chain type liquid crystal elastomer with dual dynamic bond crosslinking. This invention also provides a method for preparing the dual dynamic bond crosslinked near-infrared photoresponsive liquid crystal elastomer, which involves first performing a Michael addition reaction between the amino group in dopamine and a liquid crystal monomer, then adding 2,2'-(1,2-ethylenedioxy)diethylthiol and a dithiol chain extender containing a thiolactone group for chain extension via a thiol-olefin reaction, and finally introducing Fe... 3+ Fe 3+ - Catechol coordination interactions form a dynamic crosslinked network, while simultaneously introducing a photothermal effect. Finally, the above crosslinked network is stretched and oriented, and a solution containing disulfide bonds of cystamine is used for secondary crosslinking. This invention prepares a main-chain liquid crystal polymer containing catechol and thiolactone side groups using aza-Michael addition and mercapto-ene click reaction method. Through Fe... 3+ - Catechol complexes to form a dynamic cross-linked network and introduces a photothermal effect. After mechanically stretching and oriented molecular chains, cross-linking is fixed using cystamine solution. 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 obtained by passing Fe 3+ - The coordination interaction of catechol enables the pre-crosslinking of liquid crystal elastomers while introducing photothermal effects, resulting in excellent photothermal performance and enhanced mechanical properties of the liquid crystal elastomers; the thiolactone side group fixes the single-domain structure of the liquid crystal elastomers through a ring-opening crosslinking reaction with the bifunctional primary amine, making the programming preparation method simple and efficient.

[0028] The present invention provides a simpler and more convenient method for synthesizing liquid crystal elastomers by combining the aza-Michael addition reaction of dopamine-liquid crystal monomers with the Michael addition reaction of thiol-ene.

[0029] The liquid crystal elastomer of the present invention is made of Fe 3+ The dynamic cross-linking network formed by the dual dynamic bonds of catechol coordination and disulfide bonds can undergo network structure recombination when heated to the dynamic exchange temperature, so that the cross-linked liquid crystal elastomer can be reprocessed and recycled. Attached Figure Description

[0030] Figure 1 The structural formula and 1H 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-dynamically cross-linked liquid crystal elastomer;

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

[0033] Figure 4 These are the stretch curves of the double dynamic bond crosslinked liquid crystal elastomer before and after hot pressing reprocessing. Detailed Implementation

[0034] The present invention will be further described below with reference to specific embodiments. However, it should be understood that the listed embodiments are only for the purpose of understanding the core methods and application fields of the present invention, but the scope of the present invention is not limited thereto.

[0035] The purpose of this invention is to provide a near-infrared light-responsive liquid crystal elastomer with dual dynamic bond crosslinking, wherein the liquid crystal elastomer is crosslinked by Fe 3+ - The coordination of catechol forms a dynamic cross-linking network, achieving pre-cross-linking of the liquid crystal elastomer and introducing a photothermal effect. This avoids the problems of poor dispersion and instability of traditional doped or added materials in liquid crystal elastomers. Simultaneously, this invention provides a method for preparing a near-infrared light-responsive liquid crystal elastomer with dual dynamic bond cross-linking, firstly through Fe... 3+ - The coordination interaction of catechol forms a dynamic cross-linking network to achieve pre-cross-linking of the liquid crystal elastomer. Then, a secondary cross-linking is performed through a solution of cystamine containing disulfide bonds to fix the orientation of the liquid crystal units. This double-dynamic cross-linked liquid crystal elastomer can be processed and recycled multiple times.

[0036] The first aspect of this invention provides a near-infrared light-responsive liquid crystal elastomer with dual dynamic bond crosslinking. The liquid crystal elastomer is polymerized by a Michael addition reaction of liquid crystal monomers, dopamine hydrochloride monomers, chain extenders, and crosslinking agents under the action of triethylamine to obtain a main-chain liquid crystal polymer containing catechol and thiolactone side groups. The liquid crystal polymer is then subjected to Fe... 3+ -Liquid crystal elastomers that form a dynamic cross-linked network through coordination interactions with catechol;

[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-phenylene bis-(4-((6-(acryloyloxy)hexyl)oxy)benzoate is as follows:

[0039]

[0040] The structural formula of the 2-methyl-1,4-phenylene bis-(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)bis(ethyl mercapto) mercapto and / or 3-mercaptopropionic acid-2-ethyl-5,11-dioxo-11-[(2-oxotetrahydrothiophen-3-yl)amino]-2-{[(3-mercaptopropionyl)oxy]methyl}-4-oxa-8-thia-undecane-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 dual dynamic bond crosslinking is provided. The liquid crystal elastomer is polymerized by a Michael addition reaction of liquid crystal monomers, dopamine hydrochloride monomers, and a chain extender under the action of triethylamine. After polymerization, a main-chain liquid crystal polymer containing catechol and thiolactone side groups is obtained, which is then further processed by Fe... 3+ - The coordination interaction of catechol forms a dynamic cross-linked network and introduces a photothermal effect. After mechanical stretching and orientation of the molecular chains, cross-linking and fixation are performed using cystamine solution. Therefore, it can be driven by near-infrared light and has the characteristics of reversible deformation and reprocessability in response to near-infrared light.

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

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

[0048]

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

[0050]

[0051] The catalyst is triethylamine, with the following structural formula:

[0052]

[0053] The cystamine structure is as follows:

[0054]

[0055] The molar ratio of the above 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] A 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] Liquid crystal monomers, dopamine hydrochloride, and triethylamine were dissolved in DMF and reacted at 60–80 °C for 5–12 h under a nitrogen atmosphere. Then, a chain extender and triethylamine were added, and the mixture was reacted at 75–85 °C for 24–48 h to obtain a mixture. The mixture was poured into a mixed solution of water and methanol to precipitate the precipitate. After filtration, a main-chain liquid crystal polymer containing catechol and thiolactone side groups was obtained.

[0059] The liquid crystal polymer was dissolved in a polar solvent, and Fe was added. 3+ The solution was prepared by adding triethylamine to adjust the pH to 8-9, and the solvent was evaporated to obtain the product composed of Fe. 3+ Liquid crystal elastomers that form a dynamic cross-linked network through coordination interactions with catechol.

[0060] The chain extender comprises 2,2'-(1,2-ethylenedioxy)diethylthiol and 3-mercaptopropionic acid-2-ethyl-5,11-dioxo-11-[(2-oxotetrahydrothiophen-3-yl)amino]-2-{[(3-mercaptopropionyl)oxy]methyl}-4-oxa-8-thia-undecane-1-yl ester, in a molar ratio of 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 was placed into 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 by 100%–400% or programmed into the desired shape, crosslinked and fixed with a cystamine solution with a molar concentration of 0.1–0.5 mol / L, and then left to stand for 0.5–6 hours to obtain a liquid crystal elastomer with double dynamic bond crosslinking and near-infrared light responsiveness.

[0066] In one embodiment, a near-infrared photoresponsive liquid crystal elastomer with dual dynamic bond crosslinking and its preparation method are provided, comprising the following preparation steps:

[0067] Step 1: Weigh each reaction component according to the proportion: including liquid crystal monomer, dopamine hydrochloride, chain extender and triethylamine; the molar ratio of 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-oxoylidenetetrahydrothiophene-3-yl)prop-2-enamide were dissolved in acetone. Triethylamine was added, and the mixture was reacted at room temperature for 6–12 h. The solvent was then removed by rotary evaporation, and the oily product EDTSP was obtained by silica gel column chromatography. The molar ratio of trimethylolpropane tris(3-mercaptopropionate) and N-(2-oxoylidenetetrahydrothiophene-3-yl)prop-2-enamide was 1.2–0.9:1.1–0.8. The total mass of trimethylolpropane tris(3-mercaptopropionate) and N-(2-oxoylidenetetrahydrothiophene-3-yl)prop-2-enamide to the mass ratio of acetone was 0.3–0.4, wherein triethylamine accounted for 0.2% of the total mass of the system.

[0069] Step 3, Preparation of liquid crystal polymer: Liquid crystal monomers, dopamine hydrochloride and triethylamine are dissolved in DMF and stirred until completely dissolved under nitrogen protection. The solution is heated to 60–80°C and reacted under nitrogen atmosphere for 5–12 hours to obtain a uniform and transparent solution. Then chain extenders EDTSP and EDDT and triethylamine are added and reacted at 80°C for 24–48 hours to obtain a mixture. The mixture is then poured into a mixed solution of water and methanol to precipitate the precipitate. After filtration and drying, a main-chain liquid crystal polymer containing catechol and thiolactone side groups is obtained. 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 to the resulting solution. 3+ A solution was prepared to achieve a molar ratio of catechol to 1–3:9, and triethylamine was added to adjust the pH to 8–9. The solvent was then evaporated to obtain a solution composed of Fe. 3+ -Catechol coordination interactions form a dynamic cross-linked network in the main-chain liquid crystal elastomer film. This liquid crystal elastomer is produced by Fe... 3+ - The coordination interaction of catechol forms a dynamic cross-linked network, which introduces a photothermal effect and has the functional characteristics of near-infrared light response.

[0071] Step 5: Preparation of liquid crystal elastomer film: The above liquid crystal elastomer is placed in a polytetrafluoroethylene mold, and then transferred to a hot press. It is hot-pressed at 150°C and 5MPa for 15 minutes, and then cooled to room temperature to obtain a liquid crystal elastomer film. The thickness of the polytetrafluoroethylene mold is 0.2 mm.

[0072] Step 6, Programming of the liquid crystal elastomer: Stretch the main chain liquid crystal elastomer film obtained in step 5 by 100%–400% or program it into the required shape. Then, crosslink and fix the film with a cystamine solution with a molar concentration of 0.1–0.5 mol / L as needed, and leave it for 0.5–6 h to finally obtain a liquid crystal elastomer with near-infrared light responsiveness.

[0073] This invention synthesizes the desired monomer 3-mercaptopropionic acid-2-ethyl-5,11-dioxo-11-[(2-oxotetrahydrothiophene-3-yl)amino]-2-{[(3-mercaptopropionyl)oxy]methyl}-4-oxa-8-thiadecane-1-yl ester via trimethylolpropane tri(3-mercaptopropionate)amino]-2-{[(3-mercaptopropionyl)oxy]methyl}-4-oxa-8-thiadecane-1-yl ester.

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

[0075] The main-chain liquid crystal monomer is any one or a combination 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).

[0076] A main-chain liquid crystal polymer with catechol and thiolactone side chains was synthesized by two reactions: the aza-Michael addition of dopamine and the click reaction of mercaptoene.

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

[0078] The fourth aspect of this invention provides the application of a near-infrared light-responsive liquid crystal elastomer with dual dynamic bond crosslinking in biomimetic materials.

[0079] This invention proposes a method for preparing a near-infrared light-responsive liquid crystal elastomer with dual dynamic bond crosslinking. This liquid crystal elastomer incorporates dopamine through aza-Michael addition and Fe... 3+ - The interaction between catechol and hydroxyl groups enables the pre-crosslinking of liquid crystal elastomers and introduces a photothermal effect. The orientation of the liquid crystal elastomers is fixed by the chemical post-functionalization method of thiolactone, which provides a new approach for the two-step preparation of dynamically crosslinked liquid crystal elastomers.

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

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

[0082] Example 1

[0083] The preparation steps of a near-infrared photoresponsive liquid crystal elastomer with dual dynamic bond crosslinking are as follows:

[0084] Step 1, Preparation of chain extender EDTSP containing thiolactone group: Trimethylolpropane tris(3-mercaptopropionate) (7.9710 g, 20 mmol) and N-(2-oxoylidetetrahydrothiophene-3-yl)prop-2-enamide (3.4242 g, 20 mmol) were weighed and dissolved in acetone (25 ml), triethylamine was added, and the reaction was carried out at room temperature for 12 h. The solvent was removed by rotary evaporation, and then the oily EDTSP was obtained 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). The solution was stirred until completely dissolved under nitrogen protection, then heated to 80 °C and reacted for 5 hours under a nitrogen atmosphere to obtain a homogeneous and transparent solution.

[0086] Step 3: Add 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. After reacting at 80 °C for 48 h, a mixture is obtained. Then, the mixture is poured into a mixed solution of water and methanol to precipitate the precipitate. After filtration and drying, a main-chain liquid crystal polymer containing catechol and thiolactone side groups is obtained.

[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 to the resulting solution. 3+ Solution, making Fe 3+ The ratio of the molar amount of Fe to the molar amount of catechol in the solution was 1:3, and triethylamine was added to adjust the pH to 8–9. After evaporating the dry solvent, the product was obtained. 3+ -A main-chain liquid crystal elastomer with dynamic cross-linking via catechol coordination bonds;

[0088] Step 5: Preparation of liquid crystal elastomer film: Weigh the above pre-crosslinked liquid crystal elastomer and place it into a polytetrafluoroethylene mold, then transfer it to a hot press and hot press it at 150℃ and 5MPa for 15 minutes, then cool it to room temperature to obtain a liquid crystal elastomer film.

[0089] Step 6, Programming of liquid crystal elastomer: The main chain type liquid crystal elastomer film obtained in step 5 is stretched and deformed by 200%, then crosslinked and fixed with 0.4 mol / L cystamine solution and left for 0.5 h to finally obtain a near-infrared light-responsive liquid crystal elastomer with double dynamic bond crosslinking.

[0090] Example 2

[0091] The preparation steps of a near-infrared photoresponsive liquid crystal elastomer with dual dynamic bond crosslinking are as follows:

[0092] Step 1, Preparation of chain extender EDTSP containing thiolactone group: Trimethylolpropane tris(3-mercaptopropionate) (9.9638 g, 25 mmol) and N-(2-oxoylidetetrahydrothiophene-3-yl)prop-2-enamide (3.4242 g, 20 mmol) were weighed and dissolved in acetone (30 ml), triethylamine was added, and the reaction was carried out at room temperature for 6 h. The solvent was removed by rotary evaporation, and then the oily EDTSP was obtained by silica gel column chromatography.

[0093] Step 2, Preparation of liquid crystal polymer: Dissolve 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) in DMF (5 ml), stir until completely dissolved under nitrogen protection, heat to 80 °C, and react for 5 h under nitrogen atmosphere to obtain a uniform and transparent solution;

[0094] Step 3: Add 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. After reacting at 80 °C for 36 h, a mixture is obtained. Then, the mixture is poured into a mixed solution of water and methanol to precipitate the precipitate. After filtration and drying, a main-chain liquid crystal polymer containing catechol and thiolactone side groups is obtained.

[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 to the resulting solution. 3+ Solution, making Fe 3+ The ratio of the molar amount of Fe to the molar amount of catechol in the solution was 1:3, and triethylamine was added to adjust the pH to 8–9. After evaporating the dry solvent, the product was obtained. 3+ -A main-chain liquid crystal elastomer with dynamic cross-linking via catechol coordination bonds;

[0096] Step 5: Preparation of liquid crystal elastomer film: Weigh the above pre-crosslinked liquid crystal elastomer and place it into a polytetrafluoroethylene mold, then transfer it to a hot press and hot press it at 150℃ and 5MPa for 15 minutes, 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 crosslink and fix it with a 0.5 mol / L cystamine solution and let it stand for 1 hour to finally obtain a near-infrared light-responsive liquid crystal elastomer with double dynamic bond crosslinking.

[0098] Example 3

[0099] The preparation steps of a near-infrared photoresponsive liquid crystal elastomer with dual dynamic bond crosslinking are as follows:

[0100] Step 1, Preparation of chain extender EDTSP containing thiolactone group: Trimethylolpropane tris(3-mercaptopropionate) (9.1667 g, 23 mmol) and N-(2-oxoylidetetrahydrothiophene-3-yl)prop-2-enamide (3.4242 g, 20 mmol) were weighed and dissolved in acetone (28 ml). Triethylamine was added, and the mixture was reacted at room temperature for 12 h. The solvent was removed by rotary evaporation, and then the oily EDTSP was obtained by silica gel column chromatography.

[0101] Step 2, Preparation of liquid crystal polymer: Liquid crystal monomers RM82 (0.8073 mg, 1.2 mmol), 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 until completely dissolved under nitrogen protection, heated to 80 °C, and reacted for 5 h under nitrogen atmosphere to obtain a uniform and transparent solution;

[0102] Step 3: Add 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. After reacting at 80 °C for 24 h, a mixture is obtained. Then, the mixture is poured into a mixed solution of water and methanol to precipitate the precipitate. After filtration and drying, a main-chain liquid crystal polymer containing catechol and thiolactone side groups is obtained.

[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 to the resulting solution. 3+ Solution, making Fe 3+ The ratio of the molar amount of Fe to the molar amount of catechol in the solution was 1:3, and triethylamine was added to adjust the pH to 8–9. After evaporating the dry solvent, the product was obtained. 3+ -A main-chain liquid crystal elastomer with dynamic cross-linking via catechol coordination bonds;

[0104] Step 5: Preparation of liquid crystal elastomer film: The pre-crosslinked liquid crystal elastomer is placed in a polytetrafluoroethylene mold and then transferred to a hot press. It is hot-pressed at 150°C and 5MPa for 15 minutes and then cooled 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 crosslink and fix it with cystamine solution with a molar concentration of 0.4 mol / L and let it stand for 3 hours to finally obtain a liquid crystal elastomer with near-infrared response.

[0106] To illustrate the relevant properties of the liquid crystal elastomer provided by the present invention, the description is provided in conjunction with the accompanying drawings.

[0107] Figure 1 Here is the structural formula and 1H NMR spectrum of the chain extender EDTSP; Figure 1 The chain extender EDTSP provided in Example 1 was synthesized successfully. The hydrogen NMR spectrum showed that the number of hydrogen atoms was consistent with that of EDTSP.

[0108] Figure 2 It is a temperature-responsive reversible stretching and deformation of a double-dynamically cross-linked liquid crystal elastomer; Figure 2 The liquid crystal elastomer provided in Example 1 was crosslinked with 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 a double-dynamically cross-linked liquid crystal elastomer under near-infrared light irradiation; Figure 3 The liquid crystal elastomer provided in Example 1 is deformed by near-infrared light irradiation.

[0110] Figure 4 These are the stretch curves of the double dynamic bond crosslinked liquid crystal elastomer before and after hot pressing reprocessing; Figure 4 The liquid crystal elastomer provided in Example 1, R-LCE3-FE-3, is obtained by cutting LCE3-FE-3 into pieces and then hot-pressing it. As can be seen from the figure and Table 1, the material strength is not significantly reduced, but the elongation at break is slightly reduced.

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

[0112]

[0113] The above embodiments are merely some examples listed to facilitate 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 those skilled in the art can easily make appropriate modifications to this structure; therefore, any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A near-infrared light-responsive liquid crystal elastomer with dual dynamic bond crosslinking, characterized in that, The liquid crystal elastomer is polymerized from liquid crystal monomers, dopamine hydrochloride monomers, chain extenders, and crosslinking agents via a Michael addition reaction under the action of triethylamine to obtain a main-chain liquid crystal polymer containing catechol and thiolactone side groups. The liquid crystal polymer is then subjected to Fe... 3+ -Liquid crystal elastomers that form a dynamic cross-linked network through coordination interactions with catechol; 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-phenylene bis-(4-((6-(acryloyloxy)hexyl)oxy)benzoate is as follows: The structural formula of the 2-methyl-1,4-phenylene bis-(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)bis(ethyl mercapto) mercapto and / or 3-mercaptopropionic acid-2-ethyl-5,11-dioxo-11-[(2-oxotetrahydrothiophen-3-yl)amino]-2-{[(3-mercaptopropionyl)oxy]methyl}-4-oxa-8-thia-undecane-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 a near-infrared photoresponsive liquid crystal elastomer with double dynamic bond crosslinking as described in any one of claims 1 to 5, characterized in that, Includes the following steps: Liquid crystal monomers, dopamine hydrochloride, and triethylamine were dissolved in DMF and reacted at 60–80 °C for 5–12 h under a nitrogen atmosphere. Then, a chain extender and triethylamine were added, and the mixture was reacted at 75–85 °C for 24–48 h to obtain a mixture. The mixture was poured into a mixed solution of water and methanol to precipitate the precipitate. After filtration, a main-chain liquid crystal polymer containing catechol and thiolactone side groups was obtained. The liquid crystal polymer was dissolved in a polar solvent, and Fe was added. 3+ The solution was prepared by adding triethylamine to adjust the pH to 8-9, and the solvent was evaporated to obtain the product composed of Fe. 3+ Liquid crystal elastomers that form a dynamic cross-linked network through coordination interactions with catechol.

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 comprises 2,2'-(1,2-ethylenedioxy)diethylthiol and 3-mercaptopropionic acid-2-ethyl-5,11-dioxo-11-[(2-oxotetrahydrothiophen-3-yl)amino]-2-{[(3-mercaptopropionyl)oxy]methyl}-4-oxa-8-thia-undecane-1-yl ester, in a molar ratio of 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: The liquid crystal elastomer according to any one of claims 1 to 5 is placed in a polytetrafluoroethylene mold and then transferred to a hot press for hot pressing to obtain a liquid crystal elastomer film. The liquid crystal elastomer film is stretched by 100%-400% or programmed into the required shape, crosslinked and fixed with a cystamine solution with a molar concentration of 0.1-0.5 mol / L, and then left to stand for 0.5-6 hours to obtain a liquid crystal elastomer with double dynamic bond crosslinking and near-infrared light responsiveness.

10. The application of a near-infrared light-responsive liquid crystal elastomer with dual dynamic bond crosslinking as described in any one of claims 1 to 5 in biomimetic materials.

Images